behaviour and shear strength of screw connections in high

School of Science and Engineering

Department of Civil & Construction Engineering

Behaviour and Shear Strength of Screw Connections in High

Strength Cold-Formed Steel Structures

Siti Fairuz Sapiee

This thesis is presented for the Degree of

Master of Philosophy

of

Curtin University

November 2013

‘To the best of my knowledge and belief this thesis contains no material previously

published by any other person except where due acknowledgement has been made.

This thesis contains no material which has been accepted for the award of any other

degree or diploma in any university.’

Signature : Date :25th

November 2013

Behaviour and Shear Strength of Screw Connections in High Strength Cold-Formed Steel Structures

i

ABSTRACT

Self-drilling screws are the primary means of fastening cold-formed steel members in

cold-formed thin-gauge steel construction. The fabrication of connections is the most

labour intensive aspect of the cold-formed thin-gauge steel construction process, thus

a better understanding of the behaviour of screw connections could lead to optimum

connection design and reduce the cost of fabrication. This study was carried out to

investigate the behaviour and strength of single-shear connections formed with self-

drilling screws. The objectives of the study are to determine the influence of the

number of screws, screw spacing and screw patterns on the strength of the self-

drilling screw connections. The screw patterns take the diagonal shapes, diamond

shapes or box shapes of screws arrangement in screw connection. The failure loads

of the specimens were recorded and the failure modes were observed from the tests

carried out in the laboratory. The nominal shear strength per screw was calculated

using the American Iron and Steel Institute Specification (AISI 2007) design

equations. The calculated results were compared with the experimental results, which

correlate well with the calculated results using the AISI Specification (2007) design

equations. The results showed that the screw connection strength increased as the

number of screws increased. It was also found that the connection strength of screw

for the specimens with screw spacing more than 3d is greater than the specimens

with screw spacing less than 3d. Thus, the numbers of screws and screw spacing

affect the performance of the screw connection significantly as compared to screw

patterns.


ii

TABLE OF CONTENTS

ABSTRACT ................................................................................ i

TABLE OF CONTENTS ......................................................... ii

NOTATIONS ............................................................................. v

LIST OF FIGURES ................................................................ vii

LIST OF TABLES ................................................................... xi

ACKNOWLEDGDEMENTS ...............................................xiii

1 INTRODUCTION ......................................................................... 1

1.1 Background ................................................................................................ 1

1.1.1 Cold-Formed Steel ............................................................................. 1

1.1.2 Screw Connections ............................................................................. 1

1.1.3 Self-Drilling Screw ............................................................................ 2

1.1.4 Standard Tests for Screw .................................................................... 3

1.2 Objectives .................................................................................................. 6

1.3 Scopes of Study ......................................................................................... 6

1.4 Methodology .............................................................................................. 9

1.5 Report Outlines ........................................................................................ 11

2 LITERATURE REVIEW ........................................................... 12

2.1 Introduction.............................................................................................. 12

2.2 Design Standard for Screw ...................................................................... 12

2.2.1 Ultimate Strength Under Shear ........................................................ 13

2.2.2 Reduction Factor of 0.75 Fu ............................................................. 14

2.3 Screw Connection Behaviour .................................................................. 18

2.3.1 Effect of Steel Sheet Thickness ........................................................ 21

2.3.2 Effect of Number of Screws ............................................................. 23

2.4 Screw Connection Strength ..................................................................... 28

2.4.1 Effect of Number of Screws on Connection Strength ...................... 28

2.4.2 Effect of Screw Spacing on Connection Strength ............................ 39


iii

2.4.3 Effect of Screw Patterns on Connection Strength ............................ 42

2.5 Research Gaps ......................................................................................... 50

2.6 Conclusions ............................................................................................. 53

3 LABORATORY PROGRAMME .............................................. 54

3.1 Introduction.............................................................................................. 54

3.2 Self-Drilling Screw Properties ................................................................. 54

3.3 Cold-Formed Steel Properties.................................................................. 55

3.4 Test Assemblies and Setup ...................................................................... 56

3.5 Conclusions ............................................................................................. 64

4 DESIGN EVALUATIONS ......................................................... 65

4.1 Introduction.............................................................................................. 65

4.2 Design Evaluation for Number of Screws (N) Series .............................. 65

4.3 Design Evaluation for Screw Spacing (S) Series .................................... 67

4.4 Design Evaluation for Screw Patterns (P) Series .................................... 69

4.5 Conclusions ............................................................................................. 74

5 RESULTS AND DISCUSSIONS ............................................... 75

5.1 Introduction.............................................................................................. 75

5.2 Number of Screw (N) .............................................................................. 75

5.2.1 Experimental Results ........................................................................ 75

5.2.2 Load against Displacement Graphs for N Series Specimens ........... 76

5.2.3 Comparison of Experimental and Calculated Results for N Series

Specimens ....................................................................................................... 82

5.2.4 Effect of Number of Screws ............................................................. 84

5.2.5 Failure Modes ................................................................................... 86

5.3 Screw Spacing (S).................................................................................... 92

5.3.1 Experimental Results ........................................................................ 92

5.3.2 Load against Displacement Graphs for S Series Specimens ............ 93

5.3.3 Comparison of Experimental and Calculated Results for S Series

Specimens ....................................................................................................... 98

5.3.4 Effect of Screw Spacing ................................................................. 100

5.3.5 Failure Modes ................................................................................. 102

5.4 Screw Pattern (P) ................................................................................... 106

5.4.1 Experimental Results ...................................................................... 106


iv

5.4.2 Load against Displacement Graphs for P Series Specimens .......... 107

5.4.3 Comparison of Experimental and Calculated Results for P Series

Specimens ..................................................................................................... 113

5.4.4 Effect of Screw Pattern .................................................................. 114

5.4.5 Failure Modes ................................................................................. 120

6 CONCLUSIONS ........................................................................ 127

6.1 Number of Screws (N) ........................................................................... 127

6.2 Screw Spacing (S).................................................................................. 128

6.3 Screw Patterns (P).................................................................................. 128

6.4 Recommendations for Future Works ..................................................... 129

REFERENCES ...................................................................... 130

BIBLIOGRAPHY ................................................................. 136

Appendix A: Stress-Strain Graph for Coupon Test ......... 142

Appendix B: Specimen’s Measured Dimensions ............... 145

Appendix C: Pn Calculation for N Series Specimen .......... 151

Appendix D: Pn Calculation for S Series Specimen .......... 154

Appendix E: Pn Calculation for P Series Specimen .......... 157

Appendix F: Calculation Spread Sheets ............................. 165

Appendix G: Load against Displacement Data ................. 174

Appendix H: Published Paper ............................................. 222


v

NOTATIONS

The following symbols are used throughout this thesis. The symbols are defined

when they appear for the first time. Occasionally a symbol is used for more than one

parameter for reasons of common practice. Where this applies, the exact meaning of

the symbol is made clear when it appears in the text.

Ag = gross area of the member

An = net area of the connected part

d = nominal screw diameter

Ft = nominal tensile stress in the flat sheet

Fu = ultimate strength of the connected part

Fu1 = tensile strength of the member in contact with the screw head

Fu2 = tensile strength of the member not in contact with the screw head

Fy = yield strength of the connected part

g = transverse centre-to-centre spacing between fastener gage lines

L1 = steel sheet length in contact with the screw head

L2 = steel sheet length not in contact with the screw head

n = number of screws in a connection

N1 = number of screw in line 1



nb = number of screw holes in the cross section being analyzed

Pns = nominal shear strength per screw

Pn =nominal tensile strength

P = shear connection strength

s = sheet width divided by the number of screw holes in the cross section being

analysed when evaluating Ft

s’

= longitudinal centre-to-centre spacing of any two consecutive holes

t1 = thickness of the member in contact with the screw head

t2 = thickness of the member not in contact with the screw head

w1 = steel sheet width in contact with the screw head

w2 = steel sheet width not in contact with the screw head


vi

= Mean

Greek Symbols

η = Deviation

σ = Standard Deviation


vii

LIST OF FIGURES

Figure 1-1: Screw Loaded in Shear or Tension (Serrette and Peyton 2009) ............... 2

Figure 1-2: Standard Lap-Joint Shear –units mm (AISI 2008b) .................................. 5

Figure 1-3: Screw Patterns for Three Screws Connection ........................................... 8

Figure 1-4: Screw Patterns for Four Screws Connection ............................................. 8

Figure 2-1: Screwed Connection Specimens (Roger and Hancock 1997, 1999) ....... 16

Figure 2-2: Tilting Mode (Serrette and Peyton 2009)................................................ 19

Figure 2-3: Bearing and Tilting Failure Modes (Roger and Hancock 1997) ............. 19

Figure 2-4: Bearing Failure Mode (Roger and Hancock 1997) ................................. 20

Figure 2-5: Piling of the Steel Sheet .......................................................................... 20

Figure 2-6: Bearing and Pull through or Pull-over (Serrette and Peyton 2009) ........ 20

Figure 2-7: Screw Shear (Yan and Young 2012) ....................................................... 21

Figure 2-8: Test Specimens Layout (Rodriguez-Ferran et al. 2006) ......................... 24

Figure 2-9: Mode of Failure (a) Tilting and Pull-out (b) Tilting and Net Section

Failure (Rodriguez-Ferran et al. 2006) ...................................................................... 25

Figure 2-10: F-d Curve of a T+N Failure (Rodriguez-Ferran et al. 2006) ................ 26

Figure 2-11: F-d Curve of a T+B+PO Failure (Rodriguez-Ferran et al. 2006) ......... 26

Figure 2-12: Steel sheet fracture (Li, Ma and Yao 2010) .......................................... 27

Figure 2-13: Screw Configurations (Serrette and Lopez 1996) ................................. 30

Figure 2-14: Specimen Dimensions (Serrette and Lopez 1996) ................................ 30

Figure 2-15: Effect of Number of Screws on Connection Strength for 0.76 mm Steel

SheetThickness-No.12 Screws-3d Spacing (LaBoube and Sokol 2002) ................... 32

Figure 2-16: Group Effect-Number of Screws Graph for 1.35 mm Steel Sheet

Thickness-No.10 Screws-3d Spacing (LaBoube and Sokol 2002) ............................ 32

Figure 2-17: Arrangement of Screw (Koka, Yu and LaBoube 1997) ........................ 35

Figure 2-18: Load Versus Number of Screws for Single Screw Connection (Koka,

Yu and LaBoube 1997) .............................................................................................. 35

Figure 2-19: Joint Layout (Rodriguez-Ferran et al. 2006) ......................................... 37

Figure 2-20: Put/Put2screws against Number of crews (Rodriguez-Ferran et al. 2006) .. 37

Figure 2-21: Test Specimen (Carril, LaBoube and Yu 1994) .................................... 38

Figure 2-22: General Test Setup for Connection Tests (Sokol, LaBoube and Yu

1998) .......................................................................................................................... 40


viii

Figure 2-23: Effect of Screw Spacing on Connection Strength (Sokol, LaBoube and

Yu 1998) .................................................................................................................... 41

Figure 2-24: Effect of Screw Spacing (Li, Ma, and Yao 2010) ................................. 41

Figure 2-25: Screw Patterns for Four Screws (Sokol, LaBoube and Yu 1998) ......... 43

Figure 2-26: Screw Patterns for Two Screws (Sokol, LaBoube and Yu 1998) ......... 44

Figure 2-27: Design Details (Yan and Young 2012) ................................................. 47

Figure 2-28: Layout for different bolt arrangement (Noorashikin 2006) .................. 49

Figure 3-1: Self-drilling Screw .................................................................................. 54

Figure 3-2: Number of Screw Series Labelling ......................................................... 56

Figure 3-3: S2-15 Specimen ...................................................................................... 57

Figure 3-4: Screw Spacing Series Labelling .............................................................. 58

Figure 3-5: Screw Pattern Series Labelling ............................................................... 58

Figure 3-6: N Series Test Specimens (mm) ............................................................... 59

Figure 3-7: S Series Test Specimens (mm) ................................................................ 59

Figure 3-8: P Series Test Specimens (mm) ................................................................ 60

Figure 3-9: Specimen with Centreline ....................................................................... 61

Figure 3-10: Universal Testing Machine GOTECH .................................................. 62

Figure 3-11: Front and Side View of the Specimen in the UTM Machine ................ 63

Figure 4-1: Thicker Member Contact with Screw Head ............................................ 65

Figure 4-2: Arrangement of S Series Specimens ....................................................... 67

Figure 4-3: Screws arrangement for S Series Test Specimens .................................. 68

Figure 4-4: P Series Screw Arrangement ................................................................... 70

Figure 4-5: N Series Specimen (N3-ST) compared with P Series specimen (P3-DG

and P3-DM) ............................................................................................................... 73

Figure 4-6: N Series Specimen (N4-ST) compared with P Series Specimen (P4-DM

and P4-BX) ................................................................................................................ 73

Figure 5-1: Load against Displacement Graph for N1 Series Specimens.................. 77


Figure 5-3 : Load against Displacement Graph for N3 Series Specimens................. 79


Figure 5-5: Load against Number of Screw Graph for N Series Specimens ............. 84

Figure 5-6: Effect of Number of Screw ..................................................................... 85

Figure 5-7: Tilting of Screws Occurred at the Beginning of Test (N1-ST-4 specimen)

.................................................................................................................................... 87


ix

Figure 5-8: Tilting of the Screw and Bearing of the Steel Sheet (N1-ST-4 tested

specimen) ................................................................................................................... 88

Figure 5-9: Screw Shear Off when Tested to Destruction (N1-ST-4 tested specimen)

.................................................................................................................................... 88

Figure 5-10: Screw Shear Off (N1-ST-4 tested specimen) ........................................ 89

Figure 5-11: Tilting and Bearing Failure (N1-ST-1 tested specimen) ....................... 89

Figure 5-12: Magnified View of Failure of Screw Threads of Tilting Failure Mode 90

Figure 5-13 : End Section of Specimen curls out of Plane (N3-ST-1 specimen) ...... 91



Figure 5-16: Load against Displacement Graph for S2-15 Series Specimens ........... 94

Figure 5-17 : Load against Displacement Graph for S2-40 Series Specimens .......... 95

Figure 5-18 : Load against Displacement Graph for S3-15 Series Specimens .......... 96

Figure 5-19: Load against Displacement Graph for S3-25 Series Specimens ........... 97

Figure 5-20: Load against Number of Screw Graph for S Series Specimens .......... 101

Figure 5-21: Initial Stage of Test (S3-15-1 specimen) ............................................ 103

Figure 5-22: Test Specimen Before Fail (S3-15-1 specimen) ................................. 103

Figure 5-23: Screw sheared off (S3-15-1 specimen) ............................................... 104

Figure 5-24: Screw shear off (S3-15-1 specimen) ................................................... 104

Figure 5-25 : Tilting and Bearing Failure (S3-15-3 specimen) ............................... 105

Figure 5-26: Failure Mode of Combination of Tilting and Bearing (S3-25-3

specimen) ................................................................................................................. 105

Figure 5-27: P Series Specimens Screw Arrangement ............................................ 106

Figure 5-28: Load against Displacement Graph for P3-DG Series Specimens ....... 108

Figure 5-29: Load against Displacement Graph for P3-DM Series Specimens ...... 109

Figure 5-30: Load against Displacement Graph for P4-DM Series Specimens ...... 110

Figure 5-31: Load against Displacement Graph for P4-BX Series Specimens ....... 111

Figure 5-32: Different Shape of Three Screws Connections ................................... 115

Figure 5-33: Symmetrical Axis ................................................................................ 117

Figure 5-34: Non-Uniform Stress Redistribution .................................................... 118

Figure 5-35: Different Shape of Four Screws Connections ..................................... 119

Figure 5-36: Initial of Test (P3-DG) ........................................................................ 121

Figure 5-37: Initial Tear of Steel Sheets (P3-DM specimen) .................................. 122

Figure 5-38: Stage 1 of Testing (P4-DM-3 specimen) ............................................ 123


x

Figure 5-39: Stage 2 of Test (P4-DM-3 specimen) ................................................. 124

Figure 5-40 : Screw Head Pushed Toward Sheet .................................................... 124

Figure 5-41: Sheet Curl out of Plane (P4-BX-4 specimen) ..................................... 125

Figure 5-42: Tilting and Bearing Failure Mode (P4-BX-4 specimen) .................... 126


xi

LIST OF TABLES

Table 1-1: Screw Number and Screw Diameter (ITW Buildex 2012) ........................ 3

Table 1-2: Recommended Geometrical Proportions for Standard Lap-Joint

Connection Tests (AISI 2008b) ................................................................................... 5

Table 1-3: Specimen Descriptions ............................................................................... 9

Table 2-1: Comparison of Maximum Load Capacities (per Screw) for 2-screw and 4-

screw connections (Serrette and Lopez 1996) ........................................................... 31

Table 2-2: Effect of Number of Screws on Shear Strength (Li, Ma and Yao 2010) . 34

Table 2-3: Steel Mechanical Properties (Rodriguez-Ferran et al. 2006) ................... 36

Table 2-4: Test Results (Carril, LaBoube and Yu 1994) ........................................... 38

Table 2-5 : Results for Four Screw Patterns (Sokol, LaBoube and Yu 1998) ........... 44

Table 2-6 : Effect of Number of Rows on Connection Strength (Sokol, LaBoube and

Yu1998) ..................................................................................................................... 45

Table 2-7 : Effect of Number of Rows on Connection Strength of No.2 screw with

0.76 mm Sheet Thickness (Sokol, LaBoube and Yu 1998) ....................................... 45

Table 2-8 : Effect of Number of Rows on Connection Strength No.2 screw with 1.35

mm Sheet Thickness (Sokol, LaBoube and Yu 1998) ............................................... 45

Table 2-9: Single Shear Connection Results (Yan and Young 2012)........................ 48

Table 2-10: Summaries of Relevant Literatures ........................................................ 50

Table 3-1: Technical Properties of Screw (ASTEKS 2009) ...................................... 55

Table 3-2: Yield Strength and Ultimate Strength for Cold-formed Steel Sheets....... 55

Table 3-3: Screw Spacing for S Series Specimen ...................................................... 57

Table 4-1: Calculated Results for N Series Specimens.............................................. 66

Table 4-2 : Calculated Results of Screw Spacing(S) Series ...................................... 69

Table 4-3: Nominal Shear Strength, P of P Series ..................................................... 72

Table 5-1: Experimental Results for N Series Specimens ......................................... 76

Table 5-2: Experimental Results for N series Specimens .......................................... 82

Table 5-3: Comparison of Experimental and Calculated Results for N Series

Specimens .................................................................................................................. 83

Table 5-4: Group Effect for N Series Specimens ...................................................... 86

Table 5-5: Experimental Results for S Series Specimens .......................................... 93

Table 5-6 : Experimental Results for S series Specimens ......................................... 99


xii

Table 5-7: Comparison of Experimental and Calculated Results for S series

Specimens ................................................................................................................ 100

Table 5-8: Experimental Results for P Series Specimens ........................................ 107

Table 5-9 : Experimental Results of P series ........................................................... 113

Table 5-10: Experimental Results and Calculated Results for P series ................... 114

Table 5-11: Effect of Screw Patterns for Three Screws Connections ..................... 116

Table 5-12: Effect of Screw Patterns for Four Screws Connections ....................... 120


xiii

ACKNOWLEDGDEMENTS

I would like to express my appreciation to my supervisor Associate Professor Ir Lau

Hieng Ho for his advice, guidance, encouragement, support and endless motivation

throughout this research work.

I am also grateful to Ecosteel Sdn. Bhd. for providing me all the test specimens and

staff at Department of Civil and Construction Engineering for giving me kind

assistances and advices especially Mr. George ak Edmund Dingun, a lab technician

at Curtin Sarawak University.

I would like to express my heartful thanks to my friend, Ms Tang Su Yii for assisting

me with the test data collection and laboratory work.

Lastly, I would like to express my greatest gratitude to my family, especially my

parents for their understanding and unending support.


1

1 INTRODUCTION

1.1 Background

1.1.1 Cold-Formed Steel

Cold-formed steel is one of the commonly used building materials in light-weight

steel construction because of its lightness, high strength and stiffness, recyclability

and most importantly ease in transportation and handling. Cold-formed steel also has

a high strength to weight ratio and is an excellent alternative to timber in the areas

that are prone to termite infestation. Historically, cold-formed steel was only used for

sheeting and decking. Recently it has been used on structural members such as roof

trusses and stud walls of steel framed houses. This is due to its enhanced corrosion

resistance, ease of maintenance and pleasing appearance.

The cold-formed steel structural members are made from thin steel sheets, strip, plate

or flat bar through cold-rolling or brake-pressing process. Normally, the thicknesses

of cold-formed steel sheet or strip come in various thicknesses, ranging from 0.378

mm to 6.35 mm (Yu and LaBoube 2010). The cold-rolling or brake-pressing process

increases the strength and hardness, as well as produces an accurate thickness of steel

sheets and other steel products (Rogers and Hancock 1998). The cold-formed steel is

also capable of achieving a high strength with stress grade of G550 e.g. 550 MPa

nominal yield and tensile strength but it is less ductile. According to Daulet and

LaBoube (1996), G550 is considered as low ductility steel as the % of elongation is

low roughly about 8%.

1.1.2 Screw Connections

Connection is an important structural element that functions to transfer load from one

member to another. The fabrication of connections is the most labour-intensive

aspect of the construction process, thus a better understanding of the behaviour of

screw connections could lead to optimum connection design, and may also reduce

the cost of the fabrication.


2

A screw connection is defined as the link between structural elements through

screws. Screw connections are said to be loaded in tension if the direction of the

forces on the connections are more or less parallel to the axis of the screw. The screw

connections are said to be loaded in shear if the direction of the external loads or

forces acting on the connections are more or less perpendicular to the axis of the

screw. Figure 1-1 shows the screws loaded in shear or in tension.

Figure 1-1: Screw Loaded in Shear or Tension (Serrette and Peyton 2009)

The loading conditions of screw connections are depending on the application of the

connecting structural elements. Screw connections in thin-walled members are used

for (Toma, Sedlacek and Weynand 1993):

1. Connecting steel sheets to the supporting structure, e.g. to a purlin

2. Interconnecting two or more sheets, e.g. longitudinal seams of sheets

3. Assembling linear cold-formed sections, e.g. in storage racking.

1.1.3 Self-Drilling Screw

Fasteners that are commonly used in construction with cold-formed steel are bolts

and nuts, screws, rivets, pin and other special devices such as adhesive bonding. In

order to fasten sheet metal cladding and roofing to framing members and to make

joints in cladding and roofing, self-drilling screws are the most commonly used

fasteners. Self-drilling screws are externally threaded fasteners with the ability to

drill their own hole and form their own internal threads.The use of self-drilling


3

screws is effective because two or more thin steel sheets can be clamped in one easy

operation with self-drilling screws. The usage of self-drilling screws ensures correct

hole size, resulting in better thread engagement and tighter clamp. It could reduce the

fabrication time by eliminating the task of alignment and pre-drilling hole during the

assembly.The use of self-drilling screws is also economic as the fastening process

does not require power drills and drill bits, costly press tools, machine taps and

maintenance. Thus, self-drilling screws can provide a rapid, effective and economical

means to fasten thin-walled steel members such as cold-formed steel structural

members.

Self-drilling screws are made either by carbon steel plated with zinc for corrosion

protection or stainless steel with carbon steel drill point. Self-drilling screws come in

a variety of lengths, diameters, strengths and coatings. Screw diameter selection is

based on the required connection capacity. As the screw diameter increases, the

capacity of the screw also increases. The gauge of a screw is determined by the basic

size of the thread outside diameter. Table 1-1 shows the generic gauge number and

screw diameter according to screw manufacturers.

Table 1-1: Screw Number and Screw Diameter (ITW Buildex 2012)

Screw Number Screw Diameter (mm)

6 3.5

8 4.2

10 4.8

12 5.5

1.1.4 Standard Tests for Screw

Currently, the standard test methods for determining shear strength of screws are

stated in the American Iron and Steel Institute’s Cold-Formed Steel Design Manual

(AISI 2008a). AISI Manual (2008a) provides procedures for conducting tests to

determine the shear strength of carbon steel screws connections. The test is intended

to determine the ability of a screw to withstand a load applied transversely to the axis

of screw.


4

In this research, the experimental procedures are adopted from AISI Manual section

AISI S905-08 (2008b) for mechanically fastened cold-formed steel connections.

Table 1-2 shows the recommended geometrical proportions for single shear

connections. Figure 1-2 shows the standard shear-test specimen recommended by

AISI Manual (2008b). The single-lap joint is using two flat straps connected with

two fasteners e.g. screws to prevent under-torquing, over-torquing and limits lap

shear connection distortion of flat unformed members.


5

Table 1-2: Recommended Geometrical Proportions for Standard Lap-Joint Connection

Tests (AISI 2008b)

Fastener Diameter Specimen Dimensions (mm)

d (mm) w Ls e1 p lg

≤ 6.5 60 260 30 60 150

Tolerance +2 +5 +1 +1 +5

Figure 1-2: Standard Lap-Joint Shear –units mm (AISI 2008b)


6

1.2 Objectives

The aim of this study is to enhance the understanding of the behaviour of self-drilling

screws connections used in cold-formed steel structures. The objectives of the study

are:

to evaluate the behaviour and shear strength of screw connection for high

strength cold-formed steel with low ductility.

to determine the effects of number of screws, screw spacing and screw patterns

on the screw connection shear strength.

1.3 Scopes of Study

This study determines the effects of number of screw, screw spacing and screw

patterns on the connection shear strength for self-drilling screw of cold-formed thin-

gauge steel construction. A total set of 48 specimens comprising of number of screws

series specimens i.e. N series, screw spacing series specimens i.e. S series, and screw

patterns series specimens i.e. P series were tested in the laboratory. The failure

modes were observed and the test data collected were analyzed. The experimental

results were compared with the calculated results using the equations from American

Iron and Steel Institute Specification (AISI 2007).

In design calculations, the connection strength is calculated by considering all

different failure modes and the lowest connection strength is taken as the design

load. The nominal shear strength P of the specimens is calculated by using the AISI

Specification (2007) design equations. From literature review, the ultimate tensile

strength Fu of steel sheets, is used in the calculation to determine the nominal tensile

strength per screw Pns. Previous studies also showed that when screw connections

with G550 steel sheets have same steel sheet thickness, 0.75 Fu reduction factor is

unemployed in the calculation to determine the connection strength of screw (Rogers

and Hancock 1997, 1999, Seleim and LaBoube 1996). Thus, 0.75 Fu reduction factor

is not applied in the design equation to determine the connection strength of screws

in this study. The calculated results of P are compared with the experimental results

obtained from the testing.


7

For N series specimens, the effect of increasing number of screws on connection

strength was studied. The load against number of screw graph is plotted to show the

relationship between the increasing number of screws and the connection strength of

screw. From design calculation, the connection strength of multiple screws is

multiplied by the connection strength of single screw connection. For example, the

connection strength of four screws is four times as strong as the connection strength

of single screw. The reduction in connection strength per screw as the increasing

number of screws in normal ductility screw connection is called “Group Effect”

reduction (LaBoube and Sokol 2002). Thus, this study is carried out to investigate

the effect of multiple screws connection on the connection strength per screw when

low ductility steel sheet is used in screw connections.

AISI Specification (2007) design guidelines limit the screw spacing to not less than

3d, where d is the nominal screw diameter. For S series specimens, the effect of

screw spacing on connection strength is determined in this study. The screw spacing

is oriented perpendicular to the applied force and the screw spacings are varied from

less than 3d to more than 3d. The calculated results using the AISI Specification

(2007) design equations are compared with the experimental results for specimens

with less than 3d and more than 3d. The effect of screw spacings on the calculated

results was determined in this study. The effect of screw spacing on the connection

strength of screws was also investigated in this study.

Screw patterns in screw connections are occurred in many shapes, such as a

staggered, and they can be categorized by a number of rows and a number of

columns in the specimens. A row is defined as a line of screws arranged

perpendicular i.e. transverse to the direction of loading where a column is a line of

screws arranged parallel i.e. longitudinal to the direction of loading. This study is

carried out to investigate the effect of screw patterns when the screws are not

arranged in symmetrical shape e.g. three screw connections specimens as shown in

Figure 1-3. The effect of number of rows when the screws are arranged in a

symmetrical pattern is also investigated in this study e.g. four screws connections as

shown inFigure 1-4. The connection strength of P series specimens is also compared

with the connection strength of N series specimens that act as a control specimen e.g.

P3-DG series specimens and P3-DM series specimens are compared with N3-ST


8

series specimens, whereas P4-DM series specimens and P4-BX series specimens are

compared with N4-ST series specimens.

Figure 1-3: Screw Patterns for Three Screws Connection

Figure 1-4: Screw Patterns for Four Screws Connection


9

1.4 Methodology

The specimens are made of low ductility steel sheets with grade G550 and connected

with self-drilling screw of 5.35 mm diameter. The steel sheets have identical

thickness of 1.2 mm. All the specimens are categorised into three series according to

the parameters determined, such as, number of screws with “N” series, screw spacing

with “S” series, and screw pattern with “P” series. For N series specimens, the

number of screws varied from one to four screws connections. For S series

specimens, the screw spacings varied from less than 3d to more than 3d where d is

the outer diameter of screw. The screw spacing is a distance between the centre of

screws. For P series specimens, the screws are arranged in a diamond (DM) and a

diagonal (DG) patterns for three screws connection and the screws are arranged in a

diamond (DM) and a box (BX) patterns for four screws connections. The

descriptions of the specimen series are shown in Table 1-3.

Table 1-3: Specimen Descriptions

Specimen

Series Parameter Number of Screw

Specimen

Series

Labelling

N Number of

screws

1 N1-ST

2 N2-ST

3 N3-ST

4 N4-ST

S Screw

spacing

2 <3d S2-15

>3d S2-40

3 <3d S3-15

>3d S3-25

P Screw

patterns

3 Diagonal (DG) P3-DG

Diamond (DM) P3-DM

4 Diamond (DM) P4-DM

Box (BX) P4-BX


10

The specimens are tested by the Universal Testing Machine in the structural

laboratory at Curtin Sarawak University. The failure modes of screw connection for

the specimens with low ductility steel sheet e.g. G550 are observed in this study. The

effect of number of screws in connection and the effect of different screw patterns on

the behaviour of screw connection are also observed in this study. The maximum

loads are recorded after the test specimens failed.


11

1.5 Report Outlines

Brief descriptions of each chapter in the thesis are as follow;

Chapter 2 reviews and summaries all the literatures on connections used in cold-

formed steel structures especially screw connection. It reviewed previous works on

the behaviors and strength of screw connection, the factors that affect the screw

connection strength and the design equations for screw connections.

Chapter 3 illustrates the laboratory programme of single-lap shear test to determine

the screw connection strength. A test programme was setup for 48 numbers of

specimens from three different parameters investigated e.g. number of screws, screw

spacing and screw patterns. The preparation of the test specimens is also described in

this chapter.

Chapter 4 demonstrates the design calculations for all the specimens tested. The

design calculations were based on the design equations from American Iron and

Steel Institute Specification (AISI 2007) to calculate the nominal tensile strength per

screw Pns.

Chapter 5 discusses both the experimental results and failure modes of the screw

connections obtained from this study. The experimental results were recorded and

compared with the calculated results using AISI Specification (2007) design

equations.

Finally, Chapter 6 concludes the findings of this study and provides

recommendations for future research.


12

2 LITERATURE REVIEW

2.1 Introduction

This chapter presents previous research work on the use of self-drilling screws in

connections for cold-formed steel structures. Many studies have looked at the

behavior of the connections and at the factors that affect the connection strength of

the screws. These factors include the number of screws, screw spacing and screw

patterns. However, unlike the first two factors, there are still a limited number of

studies that look at the effects of screw patterns on the screw connections. Further

study is therefore needed to enhance the understanding of the effects that the patterns

may have on the screw connections and the advancement of screw connections.

2.2 Design Standard for Screw

The American Iron and Steel Institute Specification (AISI) outlines the design

guidelines for cold-formed steel connections in "Specification for the Design of

Cold-Formed Steel Structural Members" (AISI 2007).

In this specification, the design standards for bolted connections, screwed

connections and welded connections are provided. These design standards are based

primarily on experimental data obtained from previous test programmes. The design

equations for screwed connections in the AISI Specification (2007) Specification are

used to determine the nominal shear strength, the nominal tensile strength and shear

fracture of both the connected parts and screws. The nominal shear strengths are

calculated based on the failure in tilting or bearing. These design requirements are

used for screws with diameters range from 2.03 mm to 6.35 mm e.g. screw No. 6 to

No. 12 (AISI 2007).

As mentioned above, there are also provisions for design equations for the nominal

shear strength per screw Pns of screw connections. The provisions include the

employment of the yield strength, Fy and ultimate strength, Fu in design equations for

tilting and bearing failure. Also included in these provisions is the application of


13

reduction factor 0.75 Fu for low ductility steel i.e. yield stress greater than 380 MPa,

to determine the nominal shear strength per screw, Pns in AISI Specification (2007)

design standard.

2.2.1 Ultimate Strength Under Shear

Previously, there were no design guidelines for screw connections in the American

Iron and Steel Institute (AISI) Specification for the Design of Cold-Formed Steel

Structural Members (Pekoz 1990). In 1990s, many of the national specifications were

based on the European Convention for Constructional Steelwork (ECCS)

recommendations (ECCS 1987 quoted in Pekoz 1990, 575). The design equations for

nominal shear strength per screw, Pns for tilting and bearing failure mode as stated in

the European Recommendations (1987) are as follows:

1. for t2/t1 = 1.0, the smallest of

Equation 2-1

Equation 2-2

2. for t2/t1 ≥ 2.5

Equation 2-3

3. for 1.0 < t2/t1< 2.5

Pns is taken by linear interpolation between above two cases.

In the above equations, t1 is the thickness of steel sheet member in contact with the

screw head, t2 is the thickness of steel sheet member not in contact with the screw

head and d is the nominal screw diameter.

The above equations were investigated by Pekoz (1990) through this analysis of

more than 3500 connection test data from United States, Canada, Sweeden, Britain

and Netherlands. From his analysis, Pekoz found that the provisions by the ECCS

recommendations for shear design did not correlate well when yield strength Fy was

used. He then introduced the application of the ultimate strength, Fu into the

equations and the results from the design calculations correlate well with the


14

experimental results. The coefficients were also modified in order to ensure that the

ratio of the calculated results to the experimental results is closer to 1. The above

equations by the European Recommendations were modified by Pekoz as follows:

1. for t2/t1 = 1.0, the smallest of

Equation 2-4

Equation 2-5

2. for t2/t1 ≥ 2.5

Equation 2-2

3. for 1.0 < t2/t1< 2.5

Pns is taken by linear interpolation between two cases.

Therefore, a new set of design equations for estimating the strength of cold-formed

steel-to-steel connections by Pekoz (1990) was recommended and introduced into the

1996 AISI Specification for the Design of Cold-Formed Steel Structural Members

(AISI 1996). Based on Pekoz’s study, the 1996’s AISI (1996) introduces provisions

for the estimation of the connection strength which is based on the failure in the

connected elements, e.g. tilting or bearing. Thus, in this study, the AISI Specification

design equations as proposed by Pekoz (1990) were used to calculate the strength of

screw connections. The ultimate tensile strength, Fu of steel sheets was used in the

calculation to determine the Pns.

2.2.2 Reduction Factor of 0.75 Fu

Currently, there are a number of design equations available for the prediction of

connection strength for cold-formed steel members such as design equations

provided by the Australia Standards/New Zealand Standards 4600 (AS/NZS 2005),

Canadian Standards Association (CSA 2012), American Iron and Steel Institute

(AISI 2007) and European Committee for Standardisation (ECS 2005). According to

all of them, cold-formed steel design standards allow the use of thin, high strength

steel sheets e.g. Fy = 550 MPa, but the yield strength, Fy and ultimate strength, Fu has


15

to be reduced to 0.75 of their minimum specified values. This is due to the low

ductility exhibited by steel sheets which were cold-reduced in thickness.

Rogers and Hancock (1997, 1999) carried out tests on 150 single overlap screw

connection specimens with multiple-point fasteners at the University of Sydney. The

various number and arrangements of screws in the specimens are as shown in Figure

2-1.The steel sheets used for the specimens were the 0.42 mm and 0.60 mm thick

G550 steel type. There were two categories of screw connection specimens

investigated,

(1) screw connections with the same steel sheets thickness,

(2) screw connections with different steel sheets thicknesses.


16

Figure 2-1: Screwed Connection Specimens (Roger and Hancock 1997, 1999)

The strength of screw connections in their study were calculated using AISI

Specification design equations. The 0.75 Fu reduction factor was applied to the AISI

design equations for the connection strength of screws connections. According to

them, the screw connection strength with the same steel sheet thickness was

accurately calculated using AISI Specification design equations when 0.75 Fu

reduction factor was not applied in the equations. However, the calculated results

without the 0.75 Fu reduction factor became unconservative when the sheets used


17

were of different thicknesses. Thus, this study was carried out to determine the

calculated results of connection strength of screws when the 0.75 Fu reduction factor

was not applied in the design equations for connections with G550 steel sheets of the

same thickness for 1.2 mm.

Roger and Hancock’s (1999) also reviewed the Australia Commonwealth Scientific

and Industrial Research Organisation (CSIRO) Division of Building, Construction

and Engineering screw connection test results (Macindoe and Pham 1995, 1996,

quoted in Roger and Hancock 1999, 132). In the test, single overlap screwed

connection specimens, composed of G550 steel sheets with varying thickness of 0.42

mm, 0.60 mm, 0.75 mm, 0.80 mm, 0.95 mm and 1.00 mm were examined. The screw

connections specimens were connected by different and identical steel sheets

thickness. The strength of screw connections were calculated using AISI (1997) and

AS/ZN (1996) design equations without 0.75 Fu reduction factor applied. They found

that the calculated results without 0.75 Fu reduction factor became conservative

when G550 steel sheets with identical steel sheets thickness were used in the

connections. The test results show that the experimental results-to-calculated results

were found to be above or only slightly less than one when 0.75 Fu reduction factor

were not applied in AISI Specification (1997) and AS/ZN (1996) design equations.

These results indicate that if Fu is not reduced by 0.75, the current design standards

can be used to provide a reasonable estimate of screw connection for G550 steel

sheets of the same thickness. In other words, the reduction of 0.75 Fu is not required

in the design equations when the steel sheets in the single-overlap screwed

connections are of the same thickness.

AISI Specification (2007) also provides design equations to calculate the connection

strength of bolts. Seleim and LaBoube (1996) carried out an experiment to study

single lap bolted connections. In his research, low ductility steel sheets of ultimate

strength between 488 MPa to 535 MPa were used. Each bolted connection consists

of two identical steel sheets thickness. The design equations in AISI Specification

were used to calculate the nominal strength capacity Pn of the bolted connections and

0.75 Fu reduction factor was not utilized in the calculations. The nominal strength

capacity Pn, as calculated by the AISI specification was compared to the ultimate test

load, Pu. The nominal strength capacity Pn was calculated according to the predicted


18

failure modes such as bearing and net section failure. For bearing failure mode, the

ratio of Pu/Pn ranged from 0.89 to 1.16, with a mean of 1.01. For net section failure

mode, the ratio of Pu/Pn ranged from 0.94 to 1.19 and a mean of 1.07. In his research,

AISI design equations yielded good predictions of the connection strength of bolts

even without the 0.75 Fu reduction factor in the calculations. Thus, for low-ductility

steel sheets in connections, the Pn calculation for bolted connections can be omitted

the 0.75 Fu reduction factor. Thus, Seleim and LaBoube’s research shows that the

design equations to calculate the connection strength of bolts for low ductility steel

sheet with identical steel sheets thickness does not require 0.75 Fu reduction factor.

Therefore in this study, in order to calculate the connection strength of screw for low

ductility steel with 1.2 mm identical steel sheets thickness, the 0.75 Fu reduction

factor was not employed in the AISI Specification (2007) design equations.

2.3 Screw Connection Behaviour

Screw connections are designed with the aid of applicable design standards, for

example, North American Specification for the Design of Cold-Formed Steel

Structural Members (AISI 2007) and Australia/New Zealand Standard, AS/NZ 4600

(AS/NZ 2005). American Iron and Steel Institution (AISI) released its first edition of

the Specification for the Design of Light Gage Steel Structural Members in 1946

(AISI 1946). Since the 1946 edition of the Specification, AISI has updated its data

and added information for designers. The screw connection strength equations in the

1996 edition is based on the European Convention for Constructional Steelwork

(ECCS 1987 quoted in Pekoz 1990, 575) Recommendations which are derived from

the results of 3500 tests from the United States, Canada, Sweden, United Kingdom,

and the Netherlands. The most recent edition of the North American Specification for

the Design of Cold-formed Steel Structural Members was released in 2007.

According to AISI Specification (2007), screw connections loaded in shear failed in

one mode or in combination of several modes. These modes are screw shear, edge

tearing, tilting and subsequent pull-out of the screw, hole bearing of the joined

materials and tensile fracture at the net section of the connected part elements.


19

The tilting failure mode is categorized into screw failure type. Tilting action occurred

because of inherent eccentricity associated with the lap connection. The tilting failure

of the screw is followed by the threads tearing out of the lower sheet. The tilting

failure mode as illustrated in Figure 2-2 shows the end section of steel sheet curls out

of plane. Some of the screws will show pull-out action after significant tilting. In

some cases, the failure is caused by a combined failure mode of tilting and bearing as

shown in Figure 2-3.

Figure 2-2: Tilting Mode (Serrette and Peyton 2009)

Figure 2-3: Bearing and Tilting Failure Modes (Roger and Hancock 1997)

Bearing failure mode generally refers to failure in the connected element or

component resulting from local deformation at the loaded face of the fastener. The

screws remain perpendicular to the steel sheets and show an initial pull-out tear in

the direction of load (Figure 2-4). The steel sheets will also exhibit some piling in

front of the screws as shown in Figure 2-5. Consequently, failure can potentially

result from some combination of bearing and pull through or pull-over in either

connected element as shown by Figure 2-6. Finally, fastener failure in a shear


20

connection may result from fracture of the fastener. The fracture of the fastener is

illustrated in Figure 2-7.

Figure 2-4: Bearing Failure Mode (Roger and Hancock 1997)

Figure 2-5: Piling of the Steel Sheet

Figure 2-6: Bearing and Pull through or Pull-over (Serrette and Peyton 2009)


21

Figure 2-7: Screw Shear (Yan and Young 2012)

AISI Specification (2007) design equations that are used to calculate the nominal

shear strength per screw are focus on the tilting and bearing failure modes. The

design equations depend on the thickness of the connected members. When the head

of the screw is connected with the thinner steel sheet, the bearing failure mode is

considered in the calculation of nominal shear strength per screw. When both steel

sheets are the same thickness, or when the thicker member is in contact with the

screw head, tilting failure mode must also be considered in the calculation of

nominal shear strength per screw. Instead of sheet thickness used in the connections,

the number of screws in the connections may also affect the failure mode in screw

connections. The effect of steel sheet thickness and number of screws are discussed

in Section 2.3.1. and Section 2.3.2.

2.3.1 Effect of Steel Sheet Thickness

The thicknesses of steel sheets affect the failure mode of screw connections where a

thick steel sheet may cause failure by shearing, whereas a thin steel sheet may cause

failure by tilting and bearing.

Daulet and LaBoube (1996) carried out a study on 264 shear test specimens. The two

steel sheets were connected with self-drilling screws No.10 and No.12 e.g. screw

diameter of 4.8 mm and 5.5 mm. The thicknesses of the steel sheets used were 0.74

mm, 1.04 mm, 1.35 mm, 1.83 mm and 2.49 mm. The study involved tests carried out

for a single screw in single shear, two screws in single shear and single screw in

double shear. They observed that steel sheets with thicknesses of 0.74 mm, 1.04 mm

and 1.35 mm caused tilting and bearing failure of the screws. The second failure

mode, screw shearing, occurred when the 1.83 mm and 2.49 mm thick steel sheets


22

were used. In other words, according to their study, the thinner steel sheets such as

0.74 mm, 1.04 mm and 1.35 mm would experience a tilting failure of the screws in

combination with bearing failure of the screw holes. Meanwhile, with the thicker

steel sheets which were greater than or equal to 1.83 mm, the screws would

experience failure by screw shearing. These results are applied to predict the

connection behaviour of self-drilling screws with 1.2 mm steel sheets for this study.

This is because 1.2 mm is still in the range of a thinner steel sheet and thus, the

expected failure would be a combination of tilting and bearing.

Rogers and Hancock (1997, 1999) later conducted a research to study the failure

modes in self-drilling screw connections when the arrangement of screw lines were

perpendicular and parallel to the applied force as shown in Figure 2-1. Tilting of the

screws and bearing were the failure modes observed when the same extremely thin

G550 steel sheets, ranging from 0.41 mm to 0.6 mm thick, were used. On the other

hand, when two steel sheets of different thickness were utilised, bearing distress in

the thinner connected element was observed. They further stated that the

combination of bearing and tilting failure modes also occurred due to the use of

screw fasteners with threads that did not extend up to the base of the screw heads. In

other words, the threaded shank was not located directly below the screw heads due

to limitations in the manufacturing. Thus their research concludes that the identical

thinner steel sheets may fail in tilting and bearing failure mode for both screw lines

perpendicular and parallel to the applied force. However, further study is needed to

determine the effect of thinner steel sheets on the failure mode when different screw

patterns are arranged in the connections.

The effects of steel sheet thickness on the failure mode of screw connections were

also investigated by Rodriguez-Ferran et al. (2006). The single shear tests were

carried out on steel sheets grade G350 or G250 with the thickness of the sheets

varied from 0.85 mm to 3.0 mm, and its width is 100 mm. They found that when

both steel sheets were of the same thickness e.g. varied at 1.0 mm and 1.5 mm, tilting

always occurred at the beginning of the test. After a period of joint elongation, the

final failure mode that took place was either pull-out or net section failure. On the

other hand, when the steel sheets were of different thicknesses, different failure

modes were observed. When the sheet in contact with the screw head was thinner


23

than the one not in contact with the head, bearing failure occurred in the thinner sheet

was as significant as the tilting during the first step of loading. The joints that were

more prone to bearing were those with small diameter screws and great differences

between t1 and t2. However, Rodriguez-Ferran et al.’s research carried out single

shear test on normal ductility steel sheets with grade G350 and G250. The failure

mode results on the connection strength behaviour of screw connection with 1.2mm

steel sheet thickness of low ductility steel with Grade G550 is required to be

investigated in this study.

2.3.2 Effect of Number of Screws

The numbers of screws are varied in screw connections to determine the effect of

increasing the number of screw on the failure modes of screw connections.

Daulet and LaBoube (1996) furthered their research to investigate the failure modes

in screw connections by varying the number of screws for single and double screws

in connections. The screws were arranged parallel i.e. longitudinal to the applied

force. The results of the research revealed that both single and double screws in

single shear connections experienced tilting or bearing failure. However, this

conclusion was solely based on single and double screws in connections. In the case

where multiple screws are employed in the connections, the failure modes are still

debateable. Therefore, this study will provide further investigation on the types of

failure mode that occurs when multiple screws are used in connections.

Koka, Yu and LaBoube (1997), carried out a research on the behaviour of screw

connections with more than two screws. In their research, the screws were also

arranged parallel i.e. longitudinal to the applied force. The same steel sheet thickness

of 0.74 mm and 0.43 mm were used in their study. The first row suffered a greater

amount of deformation compared to the subsequent rows. All the tested specimens

failed in a combination of screw tilting and bearing in the steel sheets. According to

their observation, the screws started to tilt at about 75% of the ultimate capacity.

Then, at 85% of the ultimate capacity, the screws exhibited significant tilting and

after 90% of the ultimate capacity, sheet separation began. The sheet separation was

due to the drill tip end of the screw slipping out of the enlarged hole. This occurred


24

thread by thread until the screw could no longer hold the load. From their findings, it

can be concluded that the number of screws in connections does not influence the

failure mode of the screw connections. However, these results were mainly for the

specimens with the same steel sheet thickness of 0.43 mm and 0.74 mm. For the

thickness more than 0.74 mm e.g. 1.2 mm, further research is required to study the

effects of number of screws to the behaviour of screw connections.

Rodriguez-Ferran et al. (2006) conducted an experiment to identify the various

failure modes of screw connections by varying the number of screws in the screwed

connections and the thickness of the steel sheets. The number of screws in his test

specimens was arranged in columns, as shown by Figure 2-8. Each column consisted

of a line of screws perpendicular to the applied forces. The number of screws in each

connection was varied in order to determine the effect of increasing the number of

screws to the failure modes of screw connections.

Figure 2-8: Test Specimens Layout (Rodriguez-Ferran et al. 2006)

According to their research, the failure modes depended on the number of screw

columns. In their research, column is the line of screws perpendicular to the applied

force. If the number of screws was small e.g. four columns or less, tilting and pull-

out of screws would occur. If the number of screws was large e.g. six columns, tilting

and net section failure would occur on the steel sheets. All of these failures occurred

when the steel sheets of the specimens were of identical thicknesses. Figure 2-9

shows the failure modes of screw specimens that connected steel sheets with the

same thickness of 1.0 mm. The screws experienced tilting and pull-out failure, and

tilting and net section failure. The final modes of failure were either pull-out and

pull-through or net section failure depending on the number of columns. The joints


25

with 6 columns would always experience net section failure. The failure modes

affected by number of screws reported in their research were less comparative with

this study. This is because the arrangement of screws in Rodriguez-Ferran et al.’s

research was different to the screw arrangement of this study. In Rodriguez-Ferran et

al.’s research, the screws were arranged in two lines parallel to the applied force

whereas in this study, the screws were arranged in a single line parallel to the applied

force.

Figure 2-9: Mode of Failure (a) Tilting and Pull-out (b) Tilting and Net Section Failure

(Rodriguez-Ferran et al. 2006)

Other than physical characteristics as described and shown above, the failure modes

were also observed from the Force against Displacement i.e. F-d curve. The

connections which failed in tilting and net section i.e. T+N are different from the

connections failed in tilting, bearing and pull-out i.e. T+B+PO as shown by the Force

against Displacement curves. Figure 2-10 shows the F-d curve of a T+N section

failure and Figure 2-11 shows the F-d curve of a T+B+PO failure. Figure 2-10 shows

the curve has three stages e.g. elastic behaviour, hardening and failure stages while

Figure 2-11 shows the curve also has three stages but these stages are not apparent as

T+N section failure joints because both yielding and failure occurred gradually in

T+B+PO failure. Thus, the connection behaviour is not only visible on steel sheet

(a) (b)


26

specimens affected by the number of screws, but can also be shown in the graph

plotted using data recorded by data lodger during the test.

Figure 2-10: F-d Curve of a T+N Failure (Rodriguez-Ferran et al. 2006)

Figure 2-11: F-d Curve of a T+B+PO Failure (Rodriguez-Ferran et al. 2006)


27

Similar conclusion was made from Li, Ma and Yao (2010) study. In their study, the

specimens were all made from normal ductility steel sheets with thickness of 1.0

mm. They stated that tilting and bearing failure or a combination of several failure

modes usually occurred when the connections were made with less number of

screws. On the other hand, if the connections were made of a large number of

screws, the steel sheets would fracture. In their study, the failure mode of a large

number of screws connections was represented by the specimen with nine screws in a

connection and the screws were arranged in three rows and three columns. The tilting

failure mode occurred when a small number of screws, e.g. specimen with five

screws, and were arranged parallel i.e. longitudinal to the applied force. In their

study, it was also observed that the failures almost always occurred in a row closest

to the jaws of the testing machine. And when the steel sheets fractured, it always

occurred in the sheet that had the screw threads exposed as shown by Figure 2-12.

According to the researchers, although different failure modes were sometimes

observed for certain specimens with the same details, their strengths were still

similar.

Figure 2-12: Steel sheet fracture (Li, Ma and Yao 2010)


28

2.4 Screw Connection Strength

The connection strength of screws is affected by a number of factors such as number

of screw, screw spacing, screw patterns, stripped screws and so forth. In order to

investigate these factors, shear tests can be carried out in a study. The effect of

number of screws on connection strength can be investigated by carrying out shear

tests on specimens with screws arranged a line parallel to the applied force and

varying number from one to multiple numbers of screws.

The American and Iron Steel Institute (AISI 2007) design specification limits the

spacing of screws in a connection to not less than 3d, where d is the nominal

diameter of screw. The spacing is measured from centre-to-centre distance of screws,

parallel i.e. longitudinally or perpendicular i.e. transversely to the applied force.

The screws can be arranged in various patterns. The effect of screw patterns on screw

connections have been investigated by a number of previous studies. It is found that,

on the one hand, screw connection strength affected by number of screws and screw

spacing. On the other hand, screw patterns have no significant effect on the

connection strength of screws. This will be further discussed in the subsequent

sections.

2.4.1 Effect of Number of Screws on Connection Strength

Normally, in a cold-formed steel structure, more than one screw is applied to the

connection. The number of screws used in a connection will affect the connection

strength. An increased in the number of screws will increase the connection strength

of the screws. However, several studies found that the screw connection strength

does not increase proportional to the number of screws in a connection. Instead, the

connection strength per screw in a connection reduces as the number of screws in a

connection increases.

Daulet and LaBoube (1996) further their research on the effect of number of screws

on the connection strength. The screws were arranged parallel i.e. longitudinal to the

applied force. The steel sheets used were of the low and normal ductility steel. The


29

results of the tests for normal ductility steel specimens indicated that the connection

strength of two screws in single shear connections did not necessarily produce twice

the connection strength of a single screw in a single shear connection. Normal

ductility steel sheets achieved only 90% of expected capacity compared to low

ductility steel sheets which achieved an average of 99% of expected capacity. Daulet

and LaBoube (1996) explained that connection deformation might have produced

secondary stresses on the connections where more screws were used, resulting in a

reduction of performance in the connection. They observed that during testing, the

reduction of performance in normal ductility steel sheets was due to greater sheet

separation of the tested specimens. The increased of sheet separation in normal

ductility materials might have produced more secondary effects which led to slightly

premature failures and in turn reduced the connection strength. On the other hand,

when low ductility steel sheets were used, reduction in connection strength per screw

for connections with two screws was not observed. In other words, reduction in

connection strength did not occur when low ductility steel sheets were used in

screwed connections. The researchers also claimed that low ductility steel sheets

have lower Fu/Fy ratio and this was why they performed better than normal ductility

steel sheets. When the Fu/Fy ratio was lower, they experienced less stress distribution

capacity, thus increased their performance. However their conclusion was not

conclusive enough for multiple screws in connections because the experiment was

carried out only for single and double screws. Thus, study is important to determine

the effects of multiple screws on the of connection strength per screw for low

ductility steel. In the study, single lap shear tests on specimen with one to four

screws using low ductility steel will be carried out.

Another study on the performance of self-tapping screws in lap-shear metal-to-metal

connections was carried out by Serrette and Lopez (1996). All of the connections

tested used the same nominally specified screw, No.12 e.g. diameter 5.5 mm but with

different head and thread styles. The head styles used included Pancake head: Type

A, Hexagon Washer Head: Type B, and Hexagon Washer Head with large washer:

Type C as shown in Figure 2-13.


30

Figure 2-13: Screw Configurations (Serrette and Lopez 1996)

The screw patterns such as the end, edge, and centre-to-centre dimensions were

determined based on the AISI recommendations (CCFSS 1993) for 20 gauge

coupons prior to failure in bearing as shown in Figure 2-14. The results of the

research showed that the connection strength per screw decreased as the number of

screws in a connection increased. Table 2-1 shows the comparison of maximum load

capacities per screw for 2-screws and 4-screws connections by using 3 types of

screws; Type A, Type B and Type C.

Figure 2-14: Specimen Dimensions (Serrette and Lopez 1996)


31

Table 2-1: Comparison of Maximum Load Capacities (per Screw) for 2-screw and 4-

screw connections (Serrette and Lopez 1996)

Screw Type Maximum Load Ratio X2/X4 Maximum Load Ratio X2S/X4S

A 1.02 1.03

B 1.07 1.04

C 1.10 1.04

Table 2-1 shows that the connection strength per screw for 2-screw connection was

higher than the connection strength per screw for 4-screw connection in all screw

types. This is because the value for both connection strength ratio for normal screw

e.g. X2/X4 and stripped screw e.g. X2S/X4S is more than 1. The maximum load

ratio of X2/X4 is more than one and this indicates that the maximum load per screw

for X2 (two screws connection) is more than the maximum load per screw for X4

(four screws connections). This means that, when the number of screws in screw

connections increases, the connection strength per screw decreases. In other words,

there is a reduction in connection strength per screw when the number of screws in

the connection is increased. In their study, Serrette and Lopez investigated the effects

of screw types on the connection strength per screw for 2-screw and 4-screw metal-

to-metal connections. However, the grade of steel used in their research was not

revealed, and as a result, the causes of the reduction in maximum load capacities per

screw as the numbers of screws increased are still unclear.

LaBoube and Sokol (2002) used steel sheets of the same thickness in their test on the

strength of screw connections of normal ductility steel sheets. Their test revealed that

the connection strength of specimen with four screws was less than the connection

strength of four times a single screw connection.

Figure 2-15 shows the constant slope of the trend line of 0.76 mm steel sheet

thickness, connected with No.12 screw e.g. 5.5 mm diameter. The graph indicates

that although there is a constant increase in the connection strength of screws, the

connection strength does not double when the number of screws is doubled. This

shows that the connection strength per screw in a connection decreases as the number

of screws in the connection increases. The decreasing in connection strength is


32

defined as the “Group Effect” reduction. The “Group Effect” is defined as the ratio

of the connection strength per screw to the average strength for a single screw

connection of the same sheet thickness and screw size. The relationship between the

“Group Effect” and the number of screws is shown in Figure 2-16.

Figure 2-15: Effect of Number of Screws on Connection Strength for 0.76 mm Steel

SheetThickness-No.12 Screws-3d Spacing (LaBoube and Sokol 2002)

Figure 2-16: Group Effect-Number of Screws Graph for 1.35 mm Steel Sheet

Thickness-No.10 Screws-3d Spacing (LaBoube and Sokol 2002)


33

Figure 2-16 shows the Group Effect of steel sheet with 1.35 mm thickness and 3d

spacing of No.10 screw which is 4.8 mm in diameter. The graph shows that the

connection strength per screw diminishes as the number of screws increases. The

diminishing of connection strength was due to the use of normal ductility steel sheets

in the connections. Normal ductility steel sheets, as claimed by Daulet and LaBoube

(1996), only achieve 90% of the expected connection strength. However, a study is

required to determine the effect of multiple screws on the connection strength per

screw for low ductility steel.

Similar results were also obtained from a research carried out by Li, Ma, and Yao

(2010) on shear behavior of screw connections for cold-formed steel. They

conducted a test on 75 steel-to-steel single lap screw connections. They used screws

with diameter of 4.2 mm and arranged them in 3 different ways: in a line parallel to

the force i.e. L-Longitudinal, a row perpendicular to the force i.e. T-Transverse, and

interlacing or in several lines by several rows i.e. I-Interlacing. The screw row is

defined as a line of screws perpendicular to the applied force. They also varied the

number of screws in the connections from two to five. All of the specimens were

made from normal ductility steel sheets with the ultimate strength, Fu mean value of

366 MPa and thickness of 1.0 mm. Table 2-2 shows the effect of number of screws

on shear strength of specimens arranged in a line parallel to the applied force. The

label, for example, SC2-3D-L, represents the number and arrangement of screws in a

connection. In this case, there are two screws in the connection, with the spacing 3d

and arranged parallel i.e. longitudinal to applied force. Table 2-2 shows the results

for mean shear strength, P and the ratio of mean shear strength per screw to single

screw connection shear strength (P per screw/P1). P1 is the mean strength of single

shear connection strength specimens. The researchers discovered that, the strength

per screw in a connection diminished as the number of screws increased. The

decrease in connection strength per screw was possibly due to the low performance

of normal ductility steel sheets used in the tests. In order to substantiate this finding,

the current study intends to further the investigation by looking at the connection

strength per screw with low ductility steel sheets and determine if the reduction in

connection strength do happen to low ductility steel.


34

Table 2-2: Effect of Number of Screws on Shear Strength (Li, Ma and Yao 2010)

Specimen P (kN) P/P1 P per screw/P1

Longitudinal

SC2-3D-L 5.468 1.77 0.885

SC3-3D-L 7.731 2.51 0.837

SC4-3D-L 10.286 3.34 0.835

SC5-3D-L 11.810 3.83 0.766

Koka, Yu and LaBoube (1997), tested 21 specimens of single shear screw

connections with low ductility steel sheets, such as Structural Grade 80 of A635 steel

sheets. The screws were arranged parallel i.e. longitudinal to the applied force as

shown in Figure 2-17. The thickness of the steel sheets ranged from 0.43 mm to 0.74

mm. The graph load against number of screws in Figure 2-18 shows that the curve

almost flattens at the top for a specimen with four screws. This means that the load

distribution on a screw group was not linear and also the load was not distributed

equally when the number of screws was equal to four. However, the screw

connection strength increased proportionally when the numbers of screws were one

to three. It can be deduced that low ductility steel sheets probably do not decrease the

strength per screw in connection unless a large number of screws are used. However,

in their study, the steel sheets used were limited to low ductility steel of A635 with

the above mentioned with tensile strength of 799 MPa and 743 MPa respectively.

Thus, the effects of number of screws on low ductility steel with grade G550 e.g.

tensile strength of 590 MPa and 1.2 mm thickness are still unknown. Thus, this study

also determines the impact of more than three numbers of screws used in the

connections on the connection strength with low ductility steel sheets when the load

distribution on a screw group is linear and the load can be distributed equally

between them.


35

Figure 2-17: Arrangement of Screw (Koka, Yu and LaBoube 1997)

Figure 2-18: Load Versus Number of Screws for Single Screw Connection (Koka, Yu

and LaBoube 1997)


36

Rodriguez-Ferran et al. (2006) carried out experiment on screwed joints in straps.

The grades of steels used were S350 GD+Z or S250 GD+Z with steel mechanical

properties shown in Table 2-3. Based on the steel sheet mechanical properties used

as shown in Table 2-3, measured ultimate stress, Fut for both steel types are between

345 MPa to 520 MPa and thickness ranges from 0.85 mm to 3.0 mm. They have low

ductility in mechanical properties because the high Fut. The results obtained were

based on the entire single lap shear testing including the specimens with identical

steel sheets thickness and different steel sheet thickness.

Table 2-3: Steel Mechanical Properties (Rodriguez-Ferran et al. 2006)

Figure 2-19 shows the arrangement of the screws on the specimens. The spacing and

the longitudinal and transverse edge distances are also shown in Figure 2-19. There

are two lines of screws that were arranged parallel to the applied force is labelled as

row whereas the lines of screws that were arranged perpendicular to the applied force

is the column. The row is constant at two whereas the number of columns is varied

from one to six. Therefore one column with two rows has two screws and two

columns with two rows have four screws. The connection strengths of the specimens

with six screws e.g. three columns and eight screws e.g. four columns were

compared to the strength of the specimens with two screws e.g. one column. Figure

2-20 shows the graph of ratio of tested ultimate load to tested ultimate load of 2

screws i.e. Put/Put 2screws against number of screws in the connections i.e. n. The figure

shows that an increase in the number of screws does not cause a decrease in the

strength per screw. For instance, the strength of eight screw joints is similar to the


37

strength of four times of two-screw joints. The results obtained in their research

shows that there was no group effect in single lap shear testing. Therefore, the results

of Rodriguez-Ferran et al.’s research suggest that the connection strength per screw

for multiple screws in connection does not decrease when low ductility steel sheets

are used. However, the effects of number of screws in connection on the group effect

when single line of screws parallel to the applied force in low ductility steel are still

unknown and unclear.

Figure 2-19: Joint Layout (Rodriguez-Ferran et al. 2006)

Figure 2-20: Put/Put2screws against Number of crews (Rodriguez-Ferran et al. 2006)

Other than screwed connections, the results of study by Carril, LaBoube and Yu

(1994) showed that bolted connections also showed similar results when the number


38

of bolts in a connection was increased. In their study, the bolts were arranged in a

line parallel i.e. longitudinal to the applied force as shown in Figure 2-21. They used

low ductility steel for the specimens and the thicknesses of the steel sheets were

1.067 mm, 1.78 mm and 3.048 mm. The diameter of bolts used was 12.7 mm. The

specimens were categorized with Type A, Type B and Type C. Type A was for

single bolt connections, Type B was for two bolts connections and Type C was for

three bolts connections. The test results of the study for the steel sheet thickness at

3.048 mm are as tabulated in Table 2-4. The table shows that the connection strength

of bolts increases as the number of bolts increases.

Figure 2-21: Test Specimen (Carril, LaBoube and Yu 1994)

Table 2-4: Test Results (Carril, LaBoube and Yu 1994)

Spacing

(inch)

Pattern Specimen Number of

Screw

Strength (kips)

1.625

A AN31-2 1 6.58

A AN31-3 1 6.54

B BN31-1 2 6.60

B BN31-2 2 6.60

C CN31-2 3 6.92

C CN31-3 3 6.75

3.250

A AN32-1 1 8.09

A AN32-2 1 8.20

B BN32-1 2 14.46

B BN32-2 2 14.69

C CN32-1 3 16.00

C CN32-2 3 15.83


39

2.4.2 Effect of Screw Spacing on Connection Strength

AISI Design Specification (2007) provides a guideline for spacing of a fastener in a

connection to not less than 3d, where d is the nominal screw diameter. The spacing

less than 3d is impractical as the head of the screws coming very close to each other.

The screw spacing also affects the strength of a connection especially when spacing

is less than 3d, the connection strength of screws is expected to decrease.

Sokol, LaBoube and Yu (1998) conducted total of 200 a single lap connection tests

on normal ductility steel sheets with three different thicknesses of 0.76 mm, 1.02 mm

and 1.35 mm and three self-drilling screw sizes of No.8, No.10 and No. 12 e.g. 4.2

mm, 4.8 mm and 5.5 mm in diameter. The effect of screw spacing was investigated

for 1, 2, 4, 6, and 8 screws in a connection. The screw spacing was measured by the

distance perpendicular i.e. transverse to the applied force and parallel i.e.

longitudinal to the applied force as shown in Figure 2-22. The results of this research

show that specimens with 3d screw spacing has greater connection strength than the

specimens with 2d screw spacing as shown in Figure 2-23. The figure shows the

results for specimens with N16 steel sheet e.g. 1.35 mm thickness and using No.8

screw. Thus, screw spacing has a direct influence on the connection strength of

screws. In Sokol, Laboube and Yu’s research, the calculated results of nominal shear

strength of screw connection is yet to be compared to the experimental results of

specimens with spacing less than 3d and more than 3d. Thus, this study sets out to

determine the effects of screw spacing less than 3d on nominal shear strength design

equations.


40

Figure 2-22: General Test Setup for Connection Tests (Sokol, LaBoube and Yu 1998)


41

Figure 2-23: Effect of Screw Spacing on Connection Strength (Sokol, LaBoube and Yu

1998)

Li, Ma, and Yao (2010) furthered their study by looking at the effect of an indefinite

increase in screw spacing on the screws connection strength. Their study was carried

out on six different spacings including 3d, 4d, 5d, 10d, 15d and 20d. For each

connection, five screws were used and they were arranged parallel i.e. longitudinal to

the applied force. The effects of these screw spacings are shown in Figure 2-24.

Figure 2-24: Effect of Screw Spacing (Li, Ma, and Yao 2010)


42

The graph connection strength against screw spacings shows that the connection

strength increases as the screw spacing increases within a certain range but only up

to 5d. When the screw spacing exceeded 5d, the shear strength seemed to be

unaffected by the increase of spacing. In addition, the graph also shows no linear

correlation between the spacing of screws and connection strength especially when d

was increased more than 5d. Although, the results of the study revealed the effect of

increasing screw spacing beyond 5d, they did not investigate what would happen to

the connection strength when the screw spacing is less than 3d. The behavior of

screw connection for screw spacing less than 3d is critical because it could happen in

a congested connection area. Furthermore, their research only focused on the screw

spacing that was parallel i.e. longitudinally to the applied force. Further study is

needed to determine the effects of screw spacing when the spacing is oriented

perpendicular i.e. transversely to the applied force. This study extended these

research on the effects of screw spacing by investigating the effect of screw spacing

less than 3d on connection strength and the screw spacing perpendicular to the

applied force.

2.4.3 Effect of Screw Patterns on Connection Strength

Screw in screw connections can be arranged in many shapes, such as staggered

shape, diamond shape and they can be categorized by number of rows and number of

columns in specimens. A row is defined as a line of screws arranged perpendicular

i.e. transverse to the direction of loading where a column is a line of screws arranged

parallel i.e. longitudinal to the direction of loading.

The common understanding is that, the pattern of screws in a connection does not

significantly affect the connection strength but the number of rows in the connection

does. In other words, an increased in the number of rows will increase the connection

strength of the screws. Other than looking at the effects of number of screws and

screw spacing, Sokol, LaBoube, and Yu (1998) also looked at the effects of screw

pattern on connection strength.Their study used steel sheets N20 e.g. 0.76 mm thick

and screws No.8. Figure 2-25 shows how the screws were arranged.


43

Figure 2-25: Screw Patterns for Four Screws (Sokol, LaBoube and Yu 1998)

According to them, screw patterns did not significantly influence the strength of the

connectionbut the trend of rows does. The more rows of the screwed connection had,

the higher was the strength of the connection. Table 2-5 shows the connection

strength results of the different screw patterns. The results in Table 2-5 show that the

connection strength of the screws, except for specimen 4E, increases as the number

of row increases. Specimen 4E consisted of 2 rows but the connection strength is

higher than the specimen with 3 rows. Based on these overall results, the researchers

conclude that the number of rows affects the connection strength of screw

connections.


44

Table 2-5 : Results for Four Screw Patterns (Sokol, LaBoube and Yu 1998)

Pattern Number of

Row

Connection

Strength (lbs)

Connection Strength

per Screw

(lbs)

Group Effect

4C 1 1492 373 0.71

4A 2 1506 377 0.72

4A 2 1524 381 0.72

4B 3 1559 390 0.74

4B 3 1563 391 0.74

4E 2 1583 396 0.75

4D 4 1663 416 0.79

Note: N20 (0.76 mm thick), No.8 Screw, 3d Spacing

Furthermore, according to Sokol, LaBoube, and Yu (1998), the same effect was also

observed on the column pattern with two screws in connections. As shown by Figure

2-26, the screws arranged perpendicularly to the applied force were in single row

whereas the screws arranged parallel to the applied force were in double rows. The

connection strength results for single row and double rows are compared in Table

2-6.

Figure 2-26: Screw Patterns for Two Screws (Sokol, LaBoube and Yu 1998)

According to the results shown in Table 2-6, the connection strength of screws

arranged in double rows is higher if compared to the connection strength of screws

arranged in single rows. These results are based on a study with 1.02 mm thick steel

sheets and screw types No.8 e.g. 4.2 mm diameter.


45

Table 2-6 : Effect of Number of Rows on Connection Strength (Sokol, LaBoube and

Yu1998)

Pattern Number of Row Strength (lbs) Strength per

Screw (lbs)

Group Effect

2A 1 1146 573 0.83

2A 1 1197 599 0.87

2B 2 1188 594 0.86

2B 2 1281 641 0.93

Note: N18 (1.02 mm thick), No.8 Screw, 3d Spacing

The same results were also obtained for steel sheets with thicknesses of 0.76 mm and

1.35 mm and screw type No.8 and No.10 e.g. 4.2 mm and 4.8 mm diameter

respectively as shown in Table 2-7 and Table 2-8.

Table 2-7 : Effect of Number of Rows on Connection Strength of No.2 screw with 0.76

mm Sheet Thickness (Sokol, LaBoube and Yu 1998)


Screw (lbs)

Group Effect

2A 1 749 375 0.71

2A 1 789 395 0.75

2B 2 900 450 0.85

2B 2 844 422 0.80

Note: N20 (0.76 mm), No.8 Screw, 3d Spacing

Table 2-8 : Effect of Number of Rows on Connection Strength No.2 screw with 1.35 mm

Sheet Thickness (Sokol, LaBoube and Yu 1998)


Screw (lbs)

Group Effect

2A 1 2652 1326 0.87

2A 1 2697 1349 0.89

2B 2 2835 1418 0.93

2B 2 2812 1406 0.92

Note: N16 (1.35 mm), No.10 Screw, 3d Spacing

The researchers explained that the connection strength of screws arranged in double

rows was higher because this arrangement increased the rotational stability of the

connection and thus offered more resistance to rotation. As a result, the double row

screw patterns developed better structural performance if compared to single row

screws in connections. They explained that as the connection was loaded, the sheets

lapped each other and caused eccentricity in loading. The eccentricity then caused


46

the connection to rotate and this resulted in screw tilting. Thus, the screws were put

into tension and sheared instead of only shear. This phenomenon gives less strength

to the connection with fewer rows because the screws tend to pull out of the sheets

rather than bear on them. However in their research, except 4E specimen, all the

screws in the specimens were arranged in symmetrical. Thus, the increase in the

number of rows would increase the connection strength of the screws. Further study

is required in order to investigate the effect of screws patterns that are not arranged

symmetrically. In Sokol, LaBoube and Yu’s research, the calculated results of

nominal shear strength of screw connection for patterns specimens are yet to be

compared to the experimental results of pattern specimens. Thus, this study sets out

to determine the effects of screw patterns on nominal shear strength design

equations.

The experimental single shear screwed results obtained by Yan and Young (2012)

for two screws with different number of rows were similar to the Sokol, LaBoube

and Yu’s (1998) experimental results. Figure 2-27 shows that the arrangement of the

screws in the specimens. This finding was based on the specimens consisted of G550

steel sheets with the same thickness at 0.42 mm, G500 1.20 mm and G450 1.90 mm.

Yan and Young’s results were based on the effects of screwed connections of thin

steel sheets at elevated temperatures.

Table 2-9 shows that the results of shear connection for specimen with two screws

arranged in a line parallel to applied force e.g. S2-P was higher than the shear

connection for specimen with two screws arranged in a line perpendicular to applied

force e.g. S2-V. The specimens consisted of 1.2 mm thick G500 steel sheets also

shows similar results. The results for the test on the specimens with four screws e.g.

S4-S and S4-D were similar. There was no huge difference between the connection

strength of both four screws specimens with different patterns even though they had

different number of rows. The screw arrangement in their study seems similar with

this study. However, Yan and Young (2012) results were based on the effects of

screwed connections of thin steel sheets at elevated temperatures. Thus, this study is

important because it will investigate the effects of screw patterns on connection

strength.


47

;

Figure 2-27: Design Details (Yan and Young 2012)


48

Table 2-9: Single Shear Connection Results (Yan and Young 2012)

Steel

Type

Thickness

(mm)

Number

of Screw

Pattern Number

of Row

Strength (kN)

G550 0.42

2 S2-V 1 2.57

S2-P 2 3.31

4 S4-S 2 6.17

S4-D 3 6.12

G500 1.2 2 S2-V 1 15.09

S2-P 2 16.96

In addition to look at the effect of number of rows on screwed connections, Li, Ma

and Yao (2010) extended their study to look at the effects of screw patterns on the

connections. Their study was carried out on twelve different geometric screw

patterns, on 36 shear strength test specimens.They found that, the connections with

screws arranged parallel i.e. longitudinally to the applied force and in multiple rows

perpendicular to applied force had more strength than those with a line of screws

arranged perpendicular i.e. transversely to the applied force. This phenomenon only

occurred for connections with two and three screws, and spacing that was equal to

3d. A different results were obtained when the number of screws were increased to

four and five and the spacing was more than 3d. In other words, the results obtained

for four screws connections were not substantial and thus unable to support the

hypothesis that if the number of rows in a connection is increased, the connection

strength of the screws would also increase. Therefore, this study will further the

investigation on the effects of screw pattern on connection strength especially for

three and four screws connection and spacing more than 3d.

Previously, not as much research had been done on the effects of screw patterns on

connection strength if compared to the studies on bolt patterns. Noorashikin (2006)

investigated the effects of six different patterns of 6 bolts as shown in Figure 2-28. In

her study, the row indicates a line of screws perpendicular to the applied force. Her

results showed that the connection strength of the specimens with the patterns of

bolts that had more rows as in Arrangement 1 was higher if compared to patterns

with fewer rows. The same result was also observed with Arrangements 4 and 5.

Arrangement 5 with 3 rows was stronger than Arrangement 4 with 2 rows. Based on

these observations, Noorashikin concluded that if the number of rows in a pattern is


49

increased, the shear effects of the pattern can be minimised. According to her, this is

because, once the loading is applied, the first bolt will receive higher stress than the

rest of the bolts. A staggered pattern, such as Arrangement 3 and 6, would cause zig-

zag failure pattern due to the very short distance between the bolts. Even though

Noorashikin’s (2006) experiment was on the effects of number of rows on bolted

connection, the concluding results were similar to those of the experiment on the

effects of number of rows on screwed connections. In other words, in both cases, an

increase in the number of rows causes an increased in the connection strength.

Figure 2-28: Layout for different bolt arrangement (Noorashikin 2006)


50

2.5 Research Gaps

The summaries of relevant literatures are tabulated in Table 2-10.

Table 2-10: Summaries of Relevant Literatures

Previous Studies Research Gaps

Rodriquez-Ferran et al (2006)

The results of the research showed that

the thinner steel sheets would experience

a tilting failure of the screws in

combination with bearing failure of the

screw holes.

This conclusion solely applied to normal

ductility steel sheets with Grade G350

and G250. The failure modes of steel

sheets for low ductility steel with Grade

G550 still unknown. Thus, further study

is needed to investigate the screw

connection behaviour for steel sheets

with Grade 550 for low ductility steel.

Daulet and LaBoube (1996)

The results of the research revealed that

both single and double screws in single

shear connections experienced tilting and

bearing failure.

This conclusion was solely based on

single and double screws in connections.

In the case where multiple screws are

employed in the connections, the failure

modes are still unknown and debateable.

Daulet and LaBoube (1996)

The connection strength of screws with

low ductility steel increase directly with

the number of screws.

However their conclusion was not

conclusive enough for multiple screws in

connections because the experiment was

carried out only for single and double

screws. Thus, further study is important

to determine the effects of multiple

screws on the connection strength per

screw for low ductility steel.

Serrette and Lopez (1996)

The results showed that when the number

of screws in screw connections increases,

The grade of steel used in their research

was not revealed, and as a result, the


51

the connection strength per screw

decreases.

causes of the reduction in maximum load

capacities per screw as the numbers of

screws increased are still unclear.

LaBoube and Sokol (2002)

Researchers found that the connection

strength per screw diminished as the

number of screws increased.

The diminishing of connection strength

was due to the use of normal ductility

steel sheets in the connections. A study is

required to determine the effect of

multiple screws on the connection

strength per screw for low ductility steel.

Li, Ma, and Yao (2010)

The researchers discovered that, the

strength per screw in a connection

diminished as the number of screws

increased.

The decrease in connection strength per

screw was possibly due to the low

performance of normal ductility steel

sheets used in the tests. In order to

substantiate this finding, the current

study intends to further the investigation

by looking at the connection strength per

screw with low ductility steel sheets and

determine if the reduction in connection

strength do happen to the screw

connection with low ductility steel.

Sokol, LaBoube and Yu (1998)

The results of this research show that

specimens with 3d screw spacing has

greater connection strength than the

specimens with 2d screw spacing. Thus,

screw spacing has a direct influence on

the connection strength of screws.

The calculated results of nominal shear

strength of screw connection is yet to be

compared to the experimental results of

specimens with spacing less than 3d and

more than 3d. Thus, this study sets out to

determine the effects of screw spacing

less than 3d and more than 3d on

nominal shear strength design equations.


52

Li, Ma, and Yao (2010)

Researchers found that the connection

strength increases as the screw spacing

increases.

Their study was carried out on six

different spacings including 3d, 4d, 5d,

10d, 15d and 20d. They did not

investigate what would happen to the

connection strength when the screw

spacing is less than 3d. The behavior of

screw connection for screw spacing less

than 3d is critical because it could

happen in a congested connection area.

Furthermore, their research only focused

on the screw spacing that was parallel i.e.

longitudinally to the applied force. The

effect of screw spacing perpendicular to

the applied force is still unknown.

Sokol, LaBoube and Yu (1998)

Researchers found that the screw patterns

did not significantly influence the

strength of the connectionbut the trend of

rows does.

This conclusion is based on the screws in

the specimens that were arranged in

symmetrical patterns. Further study is

required in order to investigate the effect

of screws patterns that are not arranged

symmetrically.


53

2.6 Conclusions

A review on the literature shows that the failure modes of screw connections depend

on the thickness of steel sheets. In order to study the failure mode of screw

connections to tilting and bearing failures, same thickness of steel sheets which are

1.2 mm, was used in this study.

A review of previous research also shows that multiple screw connection strength is

not directly proportional to multiple of single screw connection strength. This is due

to “Group Effect” that is observed from connections with normal ductility steel

members only. Hence, this study determines the effects of a number of screws on

connections with low ductility steel sheets.

Due to the limited research on the effects of screw spacing, further study on this is

highly desired. In addition, this study also investigates the effects of screw spacing

more than 3d and less than 3d based on the design guideline provided by AISI

Specification (2007) on screw connections.

The studies on the effects of screw patterns in screwed connection are still limited if

compared to those on bolted connections. Thus, further research is needed to study

the effects of screw patterns and number of rows in screw connections.


54

3 LABORATORY PROGRAMME

3.1 Introduction

A total of 48 specimens of self-drilling screw connections were fabricated. The

samples were tested using the Universal Testing Machine GOTECH GT-7001-L060

in the Structural Laboratory at Curtin Sarawak University. The tests were carried out

to determine the shear strength and behaviour of self-drilling screw connection.

3.2 Self-Drilling Screw Properties

The mechanical properties of the screws were provided by the manufacturer. The

type of screws used in this study is the ASTEKS, type AT2 screws as shown in

Figure 3-1. This type of screws used in this study because it is commonly available

from the market in Malaysia. The technical properties of the screws are shown in

Table 3-1.

Figure 3-1: Self-drilling Screw


55

Table 3-1: Technical Properties of Screw (ASTEKS 2009)

Fastener Description 12-14×20 mm

Diameter, d Gauge #12 (5.35 mm)

Thread Form 14 TPI (threads per inch)

Drive Hex Head 5/16 inch

Length 20.00 ± 0.75 mm

Drill Point 7.00 -7.50 mm length

4.35 – 4.45 mm diameter

Type of steel AISI C 1022 Steel, Hardened heat treated

Mechanical Properties

- Single Shear

9.0 kN

Corrosion Classification AS 3566.2 – 2002 Class 2, with minimum 12

µ zinc (98% Purity ) electroplating

3.3 Cold-Formed Steel Properties

The cold-formed steel sheets used in this study were ZINCALUME steel (Zinc

Aluminium Alloy), AZ150 coating, with Grade of G550. The steel sheets were high-

tensile steel with thickness 1.20 mm. Zincalume steel sheets have minimum coating

requirements, which complies with AS1397 i.e. Steel Sheet and Strip-Hot-Dip Zinc

Coated or Alimunium/Zinc Coated. Coupon test have been done in Structural

Laboratory, Curtin Sarawak University to obtain the yield strength, Fy and ultimate

strength, Fu of the steel sheets. The average yield strength, Fy for the steel sheet is

561.50 MPa and the average ultimate strength, Fu, for the steel sheet is 590.32 MPa

as shown in Table 3-2. The graphs of Stress (MPa) against Strain (%) for cold-

formed steel sheets are shown in Appendix A.

Table 3-2: Yield Strength and Ultimate Strength for Cold-formed Steel Sheets

Coupon Average

Thickness (mm)

Fy (MPa) Fu (MPa)

TC-75-1 1.204 563 591.62 1.05

TC-90-2 1.195 560 589.02 1.05

Average 561.50 590.32 1.05


56

3.4 Test Assemblies and Setup

The test specimens consisted of two overlapping 1.2 mm thick, flat steel sheets and

connected using self-drilling screws. The steel sheet thickness 1.2 mm is used

because it is readily available and common section size for local industry. The size

for each steel sheet was 450 mm length and 70 mm width. Two packing shims with

the length of 130 mm, 1.2 mm thickness and 70 mm width were attached to both

ends of the specimens. The packing shims were provided to allow for centric loading

across the lap joint.

All the specimens are categorized into three series according to the parameters

determined, such as, number of screws, with “N” series, screw spacing, with “S”

series, and screw pattern, with “P” series.

The specimens are labelled in the manner as shown in Figure 3-2, where the number

stated after series category, “N” is the number of screws in connection whereas, “ST”

indicates the arrangement of the screws in the connection e.g. the screws are

arranged parallel to the applied force in standard arrangement. The last number

recorded in the label is the serial number of specimens with similar details as shown

in Figure 3-2.

Figure 3-2: Number of Screw Series Labelling

According to American Iron and Steel Institute Cold-Formed Steel Design

Specification (AISI 2007), the minimum spacing recommended by the standard is

not less than 3d, where d is the outer diameter of the screw. Thus, in this study, the

effect of screw spacing in the connections are studied by varying the screw spacing


57

more than 3d and also less than 3d. This was done for both two and three screw

connections. The spacings studied are stated in Table 3-3.

Table 3-3: Screw Spacing for S Series Specimen

Number of

Screw

Outer Diameter

of Screw, d

(mm)

3d (mm)

Spacing less

than 3d

studied(mm)

Spacing more

than 3d

studied(mm)

2 5.35 16.05 15 40

3 5.35 16.05 15 25

The screw spacing for specimens less than 3d are chosen at 15 mm because it is a

minimum distance that can prevent the screw heads from overlapping each other on

the test specimens as shown in Figure 3-3. The screw spacing more than 3d

specimens are chosen at 40 mm and 25 mm for two and three screws respectively.

These dimensions are chosen to allow the minimum edge distance for screw

connection in the specimen. According to AISI (2007) design rule for screw

connections, the minimum edge distance is not less than 1.5d.

Figure 3-3: S2-15 Specimen

For screw spacing series, the specimens are labelled as shown in Figure 3-4. The

number denoted after series category “S” is the number of screws in the connection.

The number such as “15” indicates the screw spacing, which covers the spacing, less

than 3d e.g. 15 mm and more than 3d e.g. 25 mm and 40 mm. The last number

recorded in the label is the serial number of specimens with similar details.

Small Gap Screw Head

15 mm


58

Figure 3-4: Screw Spacing Series Labelling

For screw pattern series, the specimens are labelled as shown in Figure 3-5. The

number denoted after series category “P” is the number of screws in the connection.

The two letters in the middle indicate the pattern of screws, “DM” for diamond

shape, “BX” for box shape and “DG” for diagonal shape. The last number recorded

in the label is the serial number of specimens with similar details.

Figure 3-5: Screw Pattern Series Labelling

The layouts for all specimens are shown in Figure 3-6 to Figure 3-8. For these

specimens, the screws were arranged either in parallel or perpendicular to the applied

force. For N series specimens, the steel sheets overlapped each other and are

connected by one, two, three or four screws at the centre of the specimens as shown

in Figure 3-6. The screw spacing, longitudinal and transverse edge distances are the

same for all the specimens. The only difference was in the number of screws, which

varied from one to four screws for the N series. The details of each N series

specimen are shown in Appendix B.


59

Figure 3-6: N Series Test Specimens (mm)

S series test specimens are shown in Figure 3-7. The steel sheets overlapped each

other and are connected by two and three screws at the centre of the specimens. The

screws are arranged in a line perpendicular to the applied force. The screw spacings

are varied to less than 3d and more than 3d for the connections. The details of each S

series specimen are shown in Appendix B.

Figure 3-7: S Series Test Specimens (mm)


60

Three different patterns are studied and compared with the standard arrangement of

screws. There are diamond (DM) and diagonal (DG) patterns for three screws

connections whereas diamond (DM) and box (BX) patterns are used for four screws

connections as shown in Figure 3-8. The longitudinal spacing of the screws is 60

mm. A centreline was drawn on each of the specimen to ensure the specimens are

arranged concentrically during the experiment setup as shown inFigure 3-9.

Figure 3-8: P Series Test Specimens (mm)


61

Figure 3-9: Specimen with Centreline

A total of 48 specimens were tested. The single lap shear test method was adopted

from the American Iron and Steel Manual (2008b) e.g. AISI S905-08 “Test Methods

for Mechanically Fastened Cold-Formed Steel Connections” . The testing was

conducted using the Universal Testing Machine (UTM), GOTECH GT-7001-L060

with GT-U55 operating software as shown in Figure 3-10.The experimental tests of

the specimens were conducted at Curtin University Structural Laboratory in

Sarawak, Malaysia.


62

Figure 3-10: Universal Testing Machine GOTECH

According to AISI Manual Section 8.2.2 (2008b), the standard test for single shear

specimen consists of two flat steel components connected using two fasteners e.g.

screws to prevent under-torquing, over-torquing and limit lap shear connection

distortion of flat unformed members. However, one screw connection specimens

were tested in this study to determine the single screw strength and the mode of

failure as the control specimens.

The locations of the screws were marked on the steel sheets according to the design

and the steel sheets were screwed together by using a screw gun. The specimen

dimensions were checked and measured to ensure the specimens comply with the

AISI Manual (2008b) testing standard.


63

The connection test specimens were mounted onto the Universal Testing Machine

(UTM) by inserting them into the top and bottom grip of the machine as shown in

Figure 3-11. The gripped end of each test specimen is at 130 mm where the packing

are attached to the specimens. An initial load was applied to eliminate the gaps and

slip occurred during testing. Specimens were aligned using the laser marker to ensure

the specimens were placed in the centre of the grips to avoid any eccentricity.

Axial load was applied at a constant rate that is not more than 2 kN per minute. At

least four specimens of each series were carried out. Overall specimen deformation

was recorded every second during the test using a data logger. The screw failures

were observed and recorded. Failure was defined by the inability of the connection to

carry additional loading.

Figure 3-11: Front and Side View of the Specimen in the UTM Machine


64

3.5 Conclusions

A total of 48 screw connection specimens were designed according to recommended

geometry by AISI Manual (2008b). The specimens were labelled according to the

series category. All the specimens were tested using the Universal Testing Machine

(UTM) and the experimental testing was conducted at Curtin University Structural

Laboratory in Sarawak, Malaysia. The specimens were tested until the maximum

load was taken as the ultimate connection strength of the screws and the screw

failure modes were observed.


65

4 DESIGN EVALUATIONS

4.1 Introduction

The design evaluation in this study is based on the American Iron and Steel Institutes

Specification (AISI 2007).

4.2 Design Evaluation for Number of Screws (N) Series

In this study, the thickness of both steel sheet members is 1.2 mm. The width of the

steel sheet is constant at 70 mm whereas the nominal diameter of screw is 5.35 mm

i.e. Type #12. The ultimate tensile strength, Fu for the steel sheet is 590.32 MPa

without any 0.75 reduction factor applied. There are one to four screws arranged in a

line parallel to the applied force for the N series specimens.

There are three equations in AISI Specification (2007) that are used to calculate the

nominal shear strength per screw, Pns that failed in either tilting or bearing. For

members that have the same steel sheet thickness or a thicker steel sheet member that

is in contact with the screw head as shown in Figure 4-1, Pns based on different

failure modes are calculated according to the equations below:

Figure 4-1: Thicker Member Contact with Screw Head


66

Tilting or Equation 4-1

Bearing or Equation 4-2

Bearing Equation 4-3

In the above equations, t1 is the thickness of steel sheet member in contact with the

screw head, t2 is the thickness of steel sheet member not in contact with the screw

head, d is the nominal screw diameter, Fu1 is the tensile strength of the steel sheet

member in contact with the screw head and Fu2 is the tensile strength of member not

in contact with the screw head.

The shear strength of a connection with more than one screw P, is calculated as

follows:

Equation 4-4

Where n is the number of screws in connections.

The calculated results for nominal shear strength as specified by AISI Specification

(2007) for one to four screws connections are tabulated in Table 4-1. The full

calculations are shown in Appendix C-1 to Appendix C-4.

Table 4-1: Calculated Results for N Series Specimens

Specimen n P Tilting (kN) P Bearing (kN)

N1-ST-1 1 7.54 10.23

N2-ST-2 2 15.08 20.46

N3-ST-3 3 22.62 30.69

N4-ST-4 4 30.16 40.96

According to AISI Specification (2007) design rules, P is taken as the smaller value

when comparing between tilting and bearing failure.From the calculations, the

calculated results of P by tilting failure are smaller than the calculated results of P by

bearing failure as shown in Table 4-1. Thus, N series specimens are predicted to fail

by tilting in the screw connection. The calculated results of P are compared with the

experimental results in Section 5.2.3.


67

4.3 Design Evaluation for Screw Spacing (S) Series

AISI Specification (2007) recommended that the minimum screw spacing is not less

than 3d, where d is the outer diameter of the screw. Thus, in this study, the effect of

screw spacing in connections are studied by varying the screw spacing more than 3d

and also less than 3d. This was done for both two and three screws connections. The

screws were arranged in a line perpendicular to the applied force as shown in Figure

4-2.

Figure 4-2: Arrangement of S Series Specimens

There are three equations in AISI Specification (2007) that are used to calculate the

nominal shear strength, P of two and three screws in connections that failed either by

tilting or bearing as shown by Equation 4-1 to Equation 4-3. The calculated results of

nominal shear strength for two and three screws connections are shown in Table 4-2.

According to the AISI Specification (2007) design standard for bolts, the failure of

rupture in net section may also occur when a single row of bolts are arranged

perpendicular to the applied force. The nominal tensile strength, Pn is calculated as

follows:


68

Equation 4-5

Equation 4-6

In the above equations, An is the net area of connected part, Ft is the nominal tensile

stress in flat sheet, Fu is the tensile strength of the connected part, d is the nominal

bolt diameter and s is the sheet width divided by the number of bolt holes in the cross

section being analysed when evaluating Ft.

For S series specimens, the screws are arranged in a line perpendicular to the applied

force as shown in Figure 4-3. When a single row of screws are arranged

perpendicular to the applied force, the failure of rupture in net section may also occur

in the connections. Instead of tilting and bearing failure modes, the screw

connections are also predicted to fail by rupture in net section. Since there is no

design equations for screw failed by rupture in net section failure, thus, the nominal

tensile strength, Pn by rupture in net section failure of the bolted connections are used

to calculate Pn by rupture in net section failure for screw connections. The full

calculations are shown in Appendix D-1 to D-2.

Figure 4-3: Screws arrangement for S Series Test Specimens


69

Table 4-2 shows the calculated results of P for S series specimens that failed either

by tilting, bearing or rupture in net section.

Table 4-2 : Calculated Results of Screw Spacing(S) Series

Specimen n P (kN)

Tilting

P (kN)

Bearing

Pn(kN)

Rupture in Net Section

S2 2 15.08 20.46 16.05

S3 3 22.62 30.69 21.91

From the calculations, the calculated results of P by bearing failure show greater

value compared with the calculated results of P by tilting failure and rupture in net

section as shown inTable 4-1. The calculated result of P by tilting failure is less than

calculated result of P by rupture in net section failure for two screws connections,

whereas for three screws connection, the calculated result of P by rupture in net

section failure is less than the calculated result of P by tilting failure. Thus, S series

specimens are predicted to fail by tilting for two screws connections and predicted to

fail by rupture in net section for three screws connections in this study. The

experimental results of S series specimens are compared with calculated results in

Section 5.3.3.

4.4 Design Evaluation for Screw Patterns (P) Series

The number of screws used for P series specimens were grouped into three and four

screws connections and arranged in two different patterns. The screws are arranged

in a staggered shape. For three screws in connections, the screws are arranged in a

diamond (DM) and a diagonal (DG) patterns whereas for four screws in connections,

the screws are arranged in a diamond (DM) and a box (BX) patterns as shown in

Figure 4-4.


70

Figure 4-4: P Series Screw Arrangement

AISI Specification (2007) design equations are also used to calculate the nominal

shear strength P that failed in either tilting or bearing. The nominal shear strength, P

for P series specimens are compared with the N series specimens which act as the

control specimens e.g. P3-DG and P3-DM specimens are compared with N3-ST

specimens whereas P4-DM and P4-BX specimens are compared with N4-ST

specimens.

The calculated results of nominal shear strength, P for P3-DG and P3-DM specimens

are similar with the calculated results of nominal shear strength, P for N3-ST

specimen whereas the calculated results of nominal shear strength, P for P4-DM and

P4-BX specimens are similar with the calculated results of nominal shear strength, P

for N4-ST specimen as shown in Table 4-3.

According to AISI Specification (2007) design equations for bolts, the failure of

rupture in net section may also occur when the bolts are arranged in a staggered

pattern. The nominal tensile strength, Pn when the bolts are arranged in a staggered

pattern is calculated as follows:


71

Equation 4-6

In the above equation, An is the net area of connected part. Ft is the nominal tensile

stress in flat sheet. When the line of screws is in a staggered pattern, An is calculated

according to Equation 4-7. For a single bolt, or a single row of bolts perpendicular to

the applied force, Ft is calculated according to Equation 4-8. For multiple bolts in a

line parallel to the applied force, Ft is equal to the ultimate tensile stress, Fu.

Equation 4-7

Equation 4-8

In the above equations Ag is the gross area of the member, nb is the number of bolt

holes in the cross section being analyzed, d is the nominal bolt diameter and s is the

sheet width divided by the number of bolt holes in the cross section being analyzed

when evaluating Ft, t is the steel sheet thickness, s’ is the longitudinal centre-to-

centre spacing of any two conservatives holes, g is transverse centre-to-centre

spacing between fastener gage lines and Fu is the tensile strength of connected part.

For P series specimens, the screws are arranged in a staggered screw pattern. When

the screws are arranged in a staggered pattern, failure of rupture in net section may

also occur in the connections. Instead of tilting and bearing failure modes, the screw

connections for P series specimens may also fail by rupture in net section. Since

there is no design equations for screw failed by rupture in net section failure, thus,

the nominal tensile strength, Pn by rupture in net section failure of the bolted

connections are used to calculate Pn by rupture in net section failure for screw

connections. Hence, the nominal tensile strength, Pn of the screw connections are

also calculated using the AISI Specification (2007) design equations of rupture in net

section failure. The full calculations are shown in Appendix E.


72

Table 4-3: Nominal Shear Strength, P of P Series

Specimen n Corresponding

N Series

P Tilting (kN)

N Series

P Bearing (kN)

N Series

P Rupture in

Net Section

(kN)

P3-DG 3 N3-ST 22.62 30.69 26.25

P3-DM 3 N3-ST 22.62 30.69 24.08

P4-DM 4 N4-ST 30.16 40.96 42.01

P4-BX 4 N4-ST 30.16 40.96 42.01

In design evaluation of P series specimens, the possible failure modes are tilting,

bearing and rupture in net section. P is taken as the smaller value when comparing

between failure by tilting, bearing and rupture in net section. From the calculations,

all the calculated results of P by tilting failure show the smaller values compared

with the calculated results of P by bearing failure and rupture in net section as shown

in Table 4-3. Thus, all P series specimens are predicted to fail by tilting in the screw

connections. The calculated results of Pare compared with the experimental results in

Section 5.4.3. The experimental results for P series specimens are also compared

with experimental results for N series specimens which act as the control specimens

e.g. P3-DG and P3-DM compared with N3-ST whereas P4-DM and P4-BX

compared with N4-ST. Figure 4-5 and Figure 4-6 show the comparison of screw

arrangements between the N series specimens with P series specimens.


73

Figure 4-5: N Series Specimen (N3-ST) compared with P Series specimen (P3-DG and

P3-DM)

Figure 4-6: N Series Specimen (N4-ST) compared with P Series Specimen (P4-DM and

P4-BX)


74

4.5 Conclusions

The nominal shear strength, P of the specimens are calculated using AISI

Specification (2007) design equations. In design calculations, the connection strength

is calculated by considering all the different failure modes and the lowest connection

strength is taken as the failed load.

For N series specimens, the screws are arranged in a line parallel to the applied force.

N series specimens are predicted to fail by tilting in the screw connection. This is

because the calculated results of P by tilting failure are smaller than the calculated

results of P by bearing failure.

According to AISI Specification (2007) design standard, the screws that are arranged

in a line perpendicular to the applied force may fail by tilting, bearing or rupture in

net section. The screws in S series specimens are arranged in a line perpendicular to

the applied force. S series specimens are predicted to fail by tilting for two screws

connections and predicted to fail by rupture in net section for three screws

connections. This is because the calculated results of P failed by tilting failure are

smaller than the calculated results of P by bearing failure and net section failure for

two screws connections. However, the calculated results of P by rupture in net

section failure are smaller than the calculated results of P by tilting failure and

bearing failure for three screws connections.

The screws in P series specimens are arranged in a staggered pattern. The connection

strength of P series specimens are calculated by considering three different failure

modes e.g. tilting, bearing and rupture in net section failure. P series specimens are

predicted to fail by tilting in the screw connections because the calculated results of

P by tilting failure are smaller than the calculated results of P by bearing failure and

rupture in net section failure.


75

5 RESULTS AND DISCUSSIONS

5.1 Introduction

A total of 48 specimens were tested in the Structural Laboratory at Curtin Sarawak

University. The experimental programme categorized the test specimens to three test

series according to the parameterdetermined, such as, number of screws, with “N”

series, screw spacing, with “S” series, and screw pattern, with “P” series. In this

chapter, all the experimental results and the failure modes of the specimens were

presented and discussed. The experimental results were tabulated and plotted and

then compared with the calculated results using the American Iron and Steel Institute

Specification (AISI 2007) design equations. The critical factors that influenced the

connection strength are also discussed.

5.2 Number of Screw (N)

A total of 16 specimens with screws are arranged in a line parallel to the applied

force, were tested. The numbers of screws on the specimens are varied from one to

four screws in a connection. In this chapter, the calculated results according to the

American Iron and Steel Institute Specification (AISI 2007) design equations are

compared with the experimental results. The effects of number of screws on the

connection strength are investigated.

5.2.1 Experimental Results

The experimental results for N series specimens were recorded and tabulated in

Table 5-1. The experimental results showed that the screw connection strength

increased as the number of screw in the connection increased. The failure modes

were observed and the maximum loads were recorded as the strength of screw

connection. The maximum loads were achieved when the test specimens failed to

carry any additional load. All failed specimens showed the similar failure modes

which are tilting and bearing failure modes. However some of the screws in one and

two screws connection specimens were shear off, but it was only occurred after the

maximum value was achieved and the specimens are tested to destruction.


76

Table 5-1: Experimental Results for N Series Specimens

Number

of screw Specimen

Experimental

Results (kN) Failure Modes

1

N1-ST-1 7.26 Tilting + Bearing



N1-ST-4 7.15 Tilting + Bearing (1 Screw shear off)

2





3





4





5.2.2 Load against Displacement Graphs for N Series Specimens

The experimental results of the N series specimens were plotted from the test data

collected by the Universal Testing Machine (UTM). Figure 5-1 to Figure 5-4 show

the Load against Displacement graphs for N1-ST, N2-ST, N3-ST and N4-ST

specimens. The full test data of the Load against Displacement graph from the single

shear testing are shown in Appendix G-1.


77

Figure 5-1: Load against Displacement Graph for N1 Series Specimens

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

Load

(kN

)

Displacement (mm)

N1-ST-1

N1-ST-2

N1-ST-3

N1-ST-4

7.26 7.15

8.14 8.14


78


0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14

Load

(kN

)

Displacement (mm)

N2-ST-1

N2-ST-2

N2-ST-3

N2-ST-4

16.66

14.67

16.65 16.24


79

Figure 5-3 : Load against Displacement Graph for N3 Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 2 4 6 8 10 12 14

Load

(kN

)

Displacement (mm)

N3-ST-1

N3-ST-2

N3-ST-3

N3-ST-4

24.03

22.15

24.41 23.27


80


0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

0 2 4 6 8 10 12 14

Load

(kN

)

Displacement (mm)

N4-ST-1

N4-ST-2

N4-ST-3

N4-ST-4

32.69

28.91

31.32 32.01


81

The connection strength of each specimen is taken as the highest load in each of the

curve. The graphs show that at the beginning of each test, a curve was linear until

maximum load was achieved. The linear curve implies that the specimens remain

elastic at the beginning of the testing and followed by a plastic deformation formed in

the tested specimen. The peaks of the curve represent the points at which the threads

of the screw were pulled through the hole. The peaks of the curve are obvious in

specimens with one and two screws in connections as shown in Figure 5-1 and

Figure 5-2. The Load against Displacement curves for N3 and N4 specimens

remained smooth throughout the whole experiment testing as shown in Figure 5-3

and Figure 5-4; no peaks of the curve are observed in the graph of N3 and N4

specimens because none of the screws were pulled out from the hole during testing.

Load against Displacement curves for N3-ST test specimens show that the gradient

of the slopes for N3-ST-3 and N3-ST-4 specimens are different from the gradient of

the slope for N3-ST-1 and N3-ST-2 specimen as shown in Figure 5-3. This is

because they went through different loading rates. The loading rates for the N3-ST-3

and N3-ST4 specimens were higher than the loading rates of the N3-ST-1 and N3-

ST-2 specimens. The loading rate is controlled manually and the loading rate at the

beginning of the test was generally larger as it is controlled by the control valve

manually. However the loading rate for all the testing was kept to below 0.5 kN per

minutes where it is accordance with loading rate stated in AISI (2008b) standard. In

AISI (2008b), axial load was applied at a constant rate that is not more than 2 kN per

minute.

All the curves of N series specimens show that the specimens actually failed in a

ductile manner although low ductility steel with Grade 550 used in this experiments.

The screws did shear off at the end of the experiment but it occurred only after the

screw connection had effectively failed in a combination of tilting and bearing

failure modes and the test specimens were tested to destruction.


82

5.2.3 Comparison of Experimental and Calculated Results for N

Series Specimens

In this section, the experimental results are compared with the calculated results

obtained using the American Iron and Steel Institute Specification (2007) design

equations. Some of the outliners are disregarded from the experimental results. The

experimental results from each category are shown in Table 5-1. According to AISI

Manual (2008b), the preferable value of deviation η is less than ± 15%. The

deviation η and standard deviation σ are calculated according to Equation 5-1 and

Equation 5-3. Table 5-2 shows that the deviation is less than 15% for all specimens.

Thus the results are used in this study. The low values of standard deviation σ

indicate that the data tend to be very close to the mean. Thus the experimental

results stated in Table 5-2 are used in comparing the experimental results and

calculated results in this study.

Deviation

Equation 5-1

Mean

Equation 5-2

Standard Deviation

Equation 5-3

Where x is the experimental result and n is the number of specimens.

Table 5-2: Experimental Results for N series Specimens

Specimen x (kN) (kN)

N1-ST-1 7.26 -7.52

0.51 N1-ST-2 8.14 7.85 3.69

N1-ST-3 8.14 3.69

N2-ST-1 16.65 0.12

0.38 N2-ST-2 16.99 16.63 2.16

N2-ST-3 16.24 -2.35

N3-ST-2 24.41 2.13

0.58 N3-ST-3 23.27 23.90 -2.64

N3-ST-4 24.03 0.54

N4-ST-2 32.01 0

0.69 N4-ST-3 32.69 32.01 2.12

N4-ST-4 31.32 -2.16


83

According to the AISI Specification (2007) design rules, the nominal tensile strength

P is taken as the smaller value when comparing between tilting and bearing

failure.The AISI Specification (2007) design equations also used the ultimate

strength Fu instead of the yield strength Fy to calculate the nominal tensile strength

P. There is no 0.75 Fu reduction factor applied in the design calculation in this study.

N series specimens are predicted to fail by tilting in the screw connection. This is

because the calculated results of P by tilting failure showed the smaller value

compared with the calculated results of P by bearing failure. The experimental

results also showed that the tested specimens were failed in combination of tilting

and bearing failure mode. Table 5-3 shows that the ratio of experimental results to

calculated results are as low as 0.96 and as high as 1.13. In general, the ratios of the

experimental results to the calculated results for N series specimens are more than

one. Figure 5-5 shows that the experimental results are generally higher compared

with the calculated results. It is found that the AISI Specification (2007) design

equations without 0.75 Fu reduction factor correlate well with the experimental

results for screw connection of low ductility steel with the same steel sheets

thickness (1.2 mm).

Table 5-3: Comparison of Experimental and Calculated Results for N Series

Specimens

Specimen P Exp (kN) P Cal Tilting (kN)

N1-ST-1 7.26

7.54

0.96

N1-ST-2 8.14 1.08

N1-ST-3 8.14 1.08

N2-ST-1 16.65

15.08

1.10

N2-ST-2 16.99 1.13

N2-ST-3 16.24 1.08

N3-ST-2 24.41

22.62

1.08

N3-ST-3 23.27 1.03

N3-ST-4 24.03 1.06

N4-ST-2 32.01

30.16

1.06

N4-ST-3 32.69 1.08

N4-ST-4 31.32 1.04


84

Figure 5-5: Load against Number of Screw Graph for N Series Specimens

5.2.4 Effect of Number of Screws

The experimental results for N series specimens show that the connection strength of

screws increased with the number of screw in connection. Figure 5-6 shows the

relationship between the connection strength and the number of screws. As shown in

Figure 5-6, linear slope of the curve indicates that the number of screw has a direct

relation with the connection strength. The connection strength of multiple screws is

multiple of the connection strength for single screw connection. For example, the

connection strength of four screws is four times stronger than the connection

strength of single screw.

0

5

10

15

20

25

30

35

0 1 2 3 4

Load

(kN

)

Number of Screw

Experimental Results

Calculated Results


85

Figure 5-6: Effect of Number of Screw

LaBoube and Sokol (2002) found that there is a diminishing in connection strength

per screw as the number of screw is increasing for normal ductility steel

connections. In his study, the diminishing in connection strength per screw is shown

by the “Group Effect”, where the Group Effect is reducing as the number of screw in

connection is increasing. The "Group Effect" is defined as the ratio of the

connection strength per screw to the average strength for a single screw connection

of the same sheet thickness and screw size (LaBoube and Sokol 2002). The "Group

Effect" provides an indication of the ability of the fastener group to share the load

(LaBoube and Sokol 2002). Table 5-4and Figure 5-6 show that there is no

decreasing in the strength for multiple screws in screw connections. The “Group

Effect” reduction found by LaBoube and Sokol (2002) are not observed in this

study. Table 5-4 shows that the connection strength per screw is close to the average

strength of a single screw connection and the Group Effect is close to one.

Therefore, there is no Group Effect reduction occurred in multiple screws

connections for the low ductility steel sheet in this study. This is because low

ductility steel sheets have lower Fu/Fy ratio and this was why they performed better

0

5

10

15

20

25

30

35

0 1 2 3 4

Load

(kN

)

Number of Screws


86

than normal ductility steel sheets. When the Fu/Fy ratio was lower, they experienced

less stress distribution capacity, thus increased their performance.

Table 5-4: Group Effect for N Series Specimens

Specimen

name

n PExp

(kN)

(kN)

Group

Effect

N1-ST-1 7.26 7.26 1

N1-ST-2 1 8.14 8.14 1

N1-ST-3 8.14 8.14 1

N2-ST-1 16.65 8.33 1.06

N2-ST-2 2 16.99 8.50 1.08

N2-ST-3 16.24 8.13 1.04

N3-ST-2 24.41 8.14 1.04

N3-ST-3 3 23.27 7.76 0.99

N3-ST-4 24.03 8.01 1.02

N4-ST-2 32.01 8.00 1.02

N4-ST-3 4 32.69 8.17 1.04

N4-ST-4 31.32 8.83 1.12

In conclusion, the increment number of screws increases the connection strength of

screw connection in this study. The experimental results of N series specimens also

show that the multiple screws in connection did not reduce the connection strength

per screws when the low ductility steel is used.

5.2.5 Failure Modes

All tested specimens showed that the specimens failed in combination of tilting and

bearing failure. Tilting of the screws generally observed from the beginning of the

test as shown in Figure 5-7. After the load was applied, tilting of the screws occurred

and bearing of the steel sheet was observed as shown in Figure 5-8. Figure 5-9 shows

the screw head shearing off after the maximum load was achieved and the specimen

was tested to destruction. Figure 5-10 also shows the screw sheared off and initial

tear at the edge of piled steel sheet in the direction of loading. Although many

specimens experienced screw shearing, they occurred only after the connection had

failed due to tilting and bearing failure and the specimens are not carrying any further

load. Figure 5-11 shows tilting and bearing failure with pull-out action of screw after


87

significant tilting for N1-ST-1 specimens. The steel sheet also exhibited some piling

in front of the screw and the failure in screw threads is shown in Figure 5-12.

Figure 5-7: Tilting of Screws Occurred at the Beginning of Test (N1-ST-4 specimen)


88

Figure 5-8: Tilting of the Screw and Bearing of the Steel Sheet (N1-ST-4 tested

specimen)

Figure 5-9: Screw Shear Off when Tested to Destruction (N1-ST-4 tested specimen)


89

Figure 5-10: Screw Shear Off (N1-ST-4 tested specimen)

Figure 5-11: Tilting and Bearing Failure (N1-ST-1 tested specimen)

Initial tear


90

Figure 5-12: Magnified View of Failure of Screw Threads of Tilting Failure Mode

For N3-ST and N4-ST series specimens, the tested specimens showed that the steel

sheet curls out of the plane at the end of the section. The edge curling effect was

mainly obvious in the three and four screws connections. Figure 5-13 shows the end

section of the specimen curls out of plane for N3-ST-1 specimen during testing.

Figure 5-14 and Figure 5-15 show the combination of tilting and bearing failure for

three and four screw connections. There are no screws shear off happened during the

testing for N3-ST and N4-ST series specimens. The first row suffered a greater

amount of deformation on the steel sheet compared to the steel sheet at subsequent

rows. It was consider that the increasing number of row can minimise the shear

effect because the first screw will receive the higher stress and others experience less

stress once the loading was applied.

From the observations of N series tested specimens, it is found that all N series

specimens failed in a combination of tilting and bearing failure modes. Thus

increasing number of screws in connections did not affect the failure mode of screw

connections. It is also observed that, the screw connections with the low ductility

steel e.g. grade G550 are failed in a combination of tilting and bearing failure mode.


91

Figure 5-13 : End Section of Specimen curls out of Plane (N3-ST-1 specimen)


Steel sheet

curls out of

plane

Steel sheet

curls out of

plane

Piling of the steel sheet

Steel sheet curls out of plane

1st 2

nd 3

rd


92


5.3 Screw Spacing (S)

A total of 16S series specimens were tested. The screws are arranged in a line

perpendicular to the applied force. The screw spacings are varied from less than 3d

to more than 3d in a connection. In this section, the calculated results using the

American Iron and Steel Institute Specification (AISI 2007) design equations are

compared with the experimental results. The effects of screw spacing in a

connection are also discussed.


The maximum load that achieved in the experimental testing was recorded as the

connection strength of screw connection. The maximum load was achieved when the

test specimen failed to carry any additional load. The failure modes and the

connection strength are tabulated in Table 5-5. All S series specimens failed in a

combination of tilting and bearing failure modes, even the screw spacing of the

specimens are different. Specimen S3-15-2 was excluded from the test because the

specimen was found damage before the test.

The experimental results for both S2 and S3 series specimens are shown in Table

5-5. The connection strength of the tested specimens with screw spacing more than

3d are higher than the connection strength of the tested specimens with spacing less

than 3d. This is occurred for both S2 and S3 series specimens.

Piling of the steel sheet

Curls out of plane

1st 2

nd 3

rd 4

th


93

Table 5-5: Experimental Results for S Series Specimens

Number

of screw Specimen

Screw

Spacing

Experimental


2

S2-15-1 12.44 Tilting + Bearing

S2-15-2 < 3d 11.59 Tilting + Bearing



2


S2-40-2 > 3d 15.99 Tilting + Bearing



3


S3-15-2 < 3d N/A -



3


S3-25-2 > 3d 21.53 Tilting + Bearing



5.3.2 Load against Displacement Graphs for S Series Specimens

The experimental results of the S series specimens were plotted from the test data

collected by the Universal Testing Machine (UTM). Figure 5-16 to Figure 5-19

show the Load against Displacement curves for S2-15, S2-40, S3-15 and S3-25

specimens. The full test data of the Load against Displacement for single shear

testing are shown in Appendix G-2.


94

Figure 5-16: Load against Displacement Graph for S2-15 Series Specimens

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

S2-15-1

S2-15-2

S2-15-3

S2-15-4

14.22

11.59 12.44 12.56


95

Figure 5-17 : Load against Displacement Graph for S2-40 Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

S2-40-1

S2-40-2

S2-40-3

S2-40-4

22.51

15.47 15.25

15.99


96

Figure 5-18 : Load against Displacement Graph for S3-15 Series Specimens

0

2

4

6

8

10

12

14

16

18

20

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

S3-15-1

S3-15-3

S3-15-4

18.98

14.53

16.77


97

Figure 5-19: Load against Displacement Graph for S3-25 Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

S3-25-1

S3-25-2

S3-25-3

S3-25-4

27.98

22.95

21.53

24.08


98

Figure 5-16 to Figure 5-19 show the Load against Displacement curves for S series

specimens. The highest load in each of the curves is taken as the connection strength

of each specimen. The graphs show that at the beginning of each test, a curve was

linear until the maximum load was achieved. The linear curve implies that the

specimens remain elastic at the beginning of the testing and followed by a plastic

deformation formed in the tested specimen. However, some of the curves have some

peaks before it achieved maximum load as shown in Figure 5-18 and Figure 5-19for

S3-15-3 and S3-25-4 specimens’ curve. The peaks of the curve represent the points

at which the threads of the screw were pulled through the hole.

All the S2 series specimens failed in a combination of tilting and bearing failure

modes. Throughout the Load against Displacement curves as shown in Figure 5-17

for S2-40 series specimens, it shows that the gradient of the slope of S2-40-4

specimen is different from other S2-40 specimens. This is because they went through

different loading rates. The loading rate for S2-40-4 specimen is higher than other

S2-40 specimens. As mentioned, the loading rate is controlled by the control valve

manually and generally larger at the beginning of the test. It is also found that, the

gradient of the slopes of S3-25-1 and S3-25-2 specimens are different from S3-25-3

and S3-25-4 specimens as shown in Figure 5-19. This is because, the loading rate for

S3-25-1 and S3-25-2 specimen are higher than the loading rate of the S3-25-3 and

S3-25-4 specimens.

5.3.3 Comparison of Experimental and Calculated Results for S

Series Specimens

The experimental results for the S series specimens are compared with the calculated

results using the American Iron and Steel Institute Specification (AISI 2007) design

equations. Some of the outliners are disregarded from the experimental results. The

experimental results are shown in Table 5-6. According to the AISI Manual (2008b),

the deviation η is calculated and the value is preferable at ± 15%. Table 5-6 shows

that the deviation η is less than 15% for all S series specimens. Since the deviation η

is less than 15%, thus, the results are used in this study. The results also have a low

value of standard deviation σ as shown in Table 5-6. The low value of σ indicates


99

that the data points tend to be very close to the mean. Thus the experimental results

stated in Table 5-6 are used to compare with the calculated results in this study.

Table 5-6 : Experimental Results for S series Specimens

Number

of Screw Specimen Spacing x (kN)

(kN)

2

S2-15-1 12.44

12.20

1.97

0.53 S2-15-2 < 3d 11.59 -5.00

S2-15-3 12.56 2.95

S2-40-1 15.25

15.57

-2.06

0.38 S2-40-2 > 3d 15.99 2.70

S2-40-3 15.47 -0.64

3

S3-15-1 16.77

16.76

0.06

2.23 S3-15-3 < 3d 14.53 -13.31

S3-15-4 18.98 13.24

S3-25-1 24.08

22.85

5.38

1.28 S3-25-2 > 3d 21.53 -5.78

S3-25-4 22.95 0.44

For S series specimens, the specimens with two screws connection are predicted to

fail by tilting failure. However, the specimens with three screws connections are

predicted to fail by rupture in net section failure. This is because the calculated

results using the AISI Specification (2007) design equations for nominal tensile

strength P by rupture in net section failure is smaller than the calculated results of P

by tilting failure for three screws connections. All S series tested specimens failed in

combination of tilting and bearing failure in the testing and no rupture in net section

failure occurred on the tested specimens. Thus, AISI Specification (2007) design

equations of P by tilting failure are used to calculate P for the screws arranged a line

perpendicular to the applied force in this study.

Table 5-7 shows the experimental results for the specimens with spacing less than 3d

are lesser than the calculated results using the AISI Specification (2007) design

equations.This is shown by the ratio of P experimental results to P calculated results

(P exp/P cal) in Table 5-7. The value of P exp/P cal ratio for specimens with screw

spacing less than 3d is less than one, whereas the P exp/P cal ratio for specimens

with screw spacing more than 3d is more than one. This happens in both two and

three screws connections. It shows that the calculated results using the AISI


100

Specification (2007) design equations are conservative for the specimens with screw

spacing more than 3d compared with the specimens with screw spacing less than 3d.

The specimens with screw spacing less than 3d has connection strength lesser than

the predicted results.

Table 5-7: Comparison of Experimental and Calculated Results for S series Specimens

Specimen Spacing P Exp (kN) P Cal Tilting

(kN)

S2-15-1 12.44 0.82

S2-15-2 <3d 11.59 15.08 0.77

S2-15-3 12.56 0.83

S2-40-1 15.25 1.01

S2-40-2 >3d 15.99 15.08 1.06

S2-40-3 15.47 1.02

S3-15-1 16.77 0.74

S3-15-3 <3d 14.53 22.62 0.64

S3-15-4 18.98 0.84

S3-25-1 24.08 1.06

S3-25-2 >3d 21.53 22.62 0.95

S3-25-4 22.95 1.01

In conclusion, the calculated results using the AISI Specification (2007) design

equations correlate well with the experimental results for screw connection with

screw spacing more than 3d when the screws are arranged in a line perpendicular to

the applied force.

5.3.4 Effect of Screw Spacing

The effect of screw spacing was determined using different screw spacings. The

screw spacing is oriented perpendicular to the applied force. The screw spacings are

varied from spacing less than 3dtospacing more than 3d. The experimental results

show that the specimens with spacing more than 3d have higher connection strength

compared with the specimens with screw spacing less than 3d as shown in Figure

5-20.


101

Figure 5-20: Load against Number of Screw Graph for S Series Specimens

Figure 5-20 also shows that the experimental results of the specimens with screw

spacing more than 3d are more than the calculated results, whereas the experimental

results of specimens with screw spacing less than 3dareless than the calculated

results. Thus, it is noted that the specimens with spacing less than 3d did not


equations. The use of screw spacing more than 3d is preferable in screw connections

as recommended by AISI Specification (2007).

It is concluded that, the screw spacing affects the connection strength of screw

connection when the screws are arranged in a line perpendicular to the applied force.

The connection strength of specimens with screw spacing more than 3d is higher

than the connection strength of specimens with screw spacing less than 3d. The AISI

Specification (2007) design equations correlate well with the experimental results for

screw connection with screw spacing more than 3d.

0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 1 2 3 4

Load

(kN

)

Number of Screws

P Exp : < 3d Spacing

P Exp : > 3d Spacing

P Cal (AISI 2007)


102

5.3.5 Failure Modes

The failure modes for the S series specimens are similar to those for N series

specimens. The screws failed in a combined failure of tilting and bearing failure

modes and some failed specimens demonstrated the screws being shear off at the end

of the testing after the specimens had failed in tilting and bearing failure modes and

tested to destruction.

Figure 5-21 shows the specimen with screw spacing less than 3d for three screws

connection during testing. Initially when the load was applied during testing, the

edge of steel sheets curls out of plane. The curling effect became more obvious as the

load was applied continuously to the specimen as shown in Figure 5-22. The screws

would then shear off at the end of the testing after the specimens failed due to tilting

and bearing failure as shown in Figure 5-23. Figure 5-24 shows the screw sheared off

and initial tear in the direction of loading was observed. There is no piling in front of

the screws was observed when both edge of the steel sheet curl out of plane. Figure

5-25 shows the failed specimen with screw spacing less than 3dwhere there is no

screw being shear off. Figure 5-25 also shows that when both edge of the steel sheet

curl out of plane, the steel sheet was in contact with screw head and did not exhibit

any piling in front of the screws head.


103

Figure 5-21: Initial Stage of Test (S3-15-1 specimen)

Figure 5-22: Test Specimen Before Fail (S3-15-1 specimen)


104

Figure 5-23: Screw sheared off (S3-15-1 specimen)

Figure 5-24: Screw shear off (S3-15-1 specimen)


105

Figure 5-25 : Tilting and Bearing Failure (S3-15-3 specimen)

Figure 5-26 shows the failed specimen with screw spacing more than 3d for three

screws connection. It was observed that the screw tilted and the steel sheet that was

not in contact with screw head was curling out of plane. The steel sheet that was in

contact with screw head was not exhibit any steel sheet curl out of plane but some

piling in front of the screws was exhibited.

Figure 5-26: Failure Mode of Combination of Tilting and Bearing (S3-25-3 specimen)

Even the screw spacing of the specimens are varied from less than 3d to more than

3d in this study, all the specimens were failed in the same failure modes i.e. a

combined of tilting and bearing failure modes. Thus, the screw spacing does not

affect the failure mode of the specimens.


106

5.4 Screw Pattern (P)

All P series specimens with different screw patterns were tested using the Universal

Testing Machine (UTM). The numbers of screws used in a connection were three

and four. The specimens with three screws were arranged in a diagonal (DG) and a

diamond (DM) shape and the specimens with four screws were arranged in a

diamond (DM) and a box (BX) shape as shown in Figure 5-27. In this section, the

calculated results using the American Iron and Steel Institute Specification (AISI

2007) design equations are compared with the experimental results. The connection

strength of P series specimens are also compared with the connection strength of N

series specimens which act as the control specimens.

Figure 5-27: P Series Specimens Screw Arrangement


Table 5-8shows the experimental results of 16 test specimens carried out in a

laboratory at Curtin Sarawak University. The failure modes for all screw pattern

tested specimens are similar. All tested specimens showed failure in a combination of

tilting and bearing failure modes. Some of the screws in the specimens sheared off,

but only after the maximum load achieved and the specimens are tested to

destruction.


107

Table 5-8: Experimental Results for P Series Specimens

Number

of Screw Specimen

Experimental


3

P3-DG-1 22.83 Tilting + Bearing (2 screw shear off)



P3-DG-4 24.79 Tilting + Bearing

P3-DM-1 23.47 Tilting + Bearing

P3-DM-2 24.03 Tilting + Bearing (2 screw shear off)



4





P4-BX-1 31.08 Tilting + Bearing (1 screw shear off)



P4-BX-4 31.65 Tilting + Bearing

5.4.2 Load against Displacement Graphs for P Series Specimens

The experimental results of P series specimens were plotted from the test data

collected by the Universal Testing Machine (UTM). Figure 5-28 to Figure 5-31

shows the Load against Displacement curve for P3-DG, P3-DM, P4-DM and P3-BX

specimens. All the series of the test data are shown in Appendix G-3


108

Figure 5-28: Load against Displacement Graph for P3-DG Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

P3-DG-1

P3-DG-2

P3-DG-3

P3-DG-4

24.79

22.10

24.83 22.79


109

Figure 5-29: Load against Displacement Graph for P3-DM Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 2 4 6 8 10 12

Load

(m

m)

Displacement (mm)

P3-DM-1

P3-DM-2

P3-DM-3

P3-DM-4

24.79

23.30

23.47 24.03


110

Figure 5-30: Load against Displacement Graph for P4-DM Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

P4-DM-1

P4-DM-2

P4-DM-3

P4-DM-4

32.49

27.48

28.68

31.81


111

Figure 5-31: Load against Displacement Graph for P4-BX Series Specimens

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

0 2 4 6 8 10 12

Load

(kN

)

Displacement (mm)

P4-BX-1

P4-BX-2

P4-BX-3

P4-BX-4

31.65

28.58 30.41

31.08


112

Figure 5-28 to Figure 5-31 show the Load against Displacement curves for P series

specimens. The shapes of the curves for every P series specimens are consistence.

The maximum load achieved in the experimental testing was recorded as the

connection strength of the screw connection. Similar to N series and S series tested

specimens, all P series tested specimens failed in a combination of tilting and bearing

failure modes.

Figure 5-28 and Figure 5-29 show the Load against Displacement curves for P3-DG

and P3-DM series specimens with three screws connections. Figure 5-28 show that

the Load against Displacement curves for P3-DG-1, P3-DG-2 and P3-DG-3

specimens demonstrated sudden dropping in load. The sudden dropping in load

happened as the screws were sheared off after maximum load had achieved and the

specimens had failed in combination of tilting and bearing. However, there is no

sudden dropping in load demonstrated in Load against Displacement curve was

found in P3-DG-4 specimens since there was no screw shear off occurred in the

specimens. Thus, it was noted in this study that the sudden dropping in load shown in

the Load against Displacement curves are the sign of screw shear off during testing.

The sudden droppings in load also are found in the Load-against Displacement

curves for P3-DM-3 specimens as shown in Figure 5-29. The curve for P3-DM-3

specimen shows that the load is suddenly dropping after maximum load had achieved

and the specimen had failed in combination of tilting and bearing. It is also observed

that the sudden dropping in load for Load against Displacement curve demonstrated

that the screws were shear off during testing.

Figure 5-30 and Figure 5-31 show the Load against Displacement curves for P4-DM

and P4-BX. All the curves for both P4-DM and P4-BX specimens are found

consistence in its Load against Displacement curves. Some peaks are observed

before the maximum load had achieved in Load against Displacement curve for P4-

DM-2 specimens. The peaks of the curve represent the points at which the threads of

the screws in P4-DM-2 specimens were pulled through the hole. The peaks of the

curve before the maximum load had achieved are also obvious in Load against

Displacement curves for P3-DG-3 and P3-DG-4 specimens as shown in Figure 5-28.


113

The peaks also represent that the point at which the threads of the screws in P3-DG-3

and P3-DG-4 specimens were also being pull through the hole during testing.

5.4.3 Comparison of Experimental and Calculated Results for P

Series Specimens

The experimental results for P series specimens are compared with the calculated

results using the American Iron and Steel Institute Specification (AISI 2007) design

equations. Some of the outliner results are disregarded from this study. The

experimental results are shown in Table 5-9. Similar to N series and S series, the

deviation η is less than 15% for all P series specimens as shown in Table 5-9. Thus,

the experimental results are used in this study as the preferable value of deviation η is

± 15% (AISI 2008b). The low values of standard deviation, σ shown in Table 5-9

also show that the experimental results tend to be very close to the mean. Thus the

experimental results are used in comparing the experimental results and calculated

results in this study.

Table 5-9 : Experimental Results of P series

Number

of Screw

Specimen x (kN)

(kN)

3

P3-DG-1 22.83 1.15

P3-DG-2 22.79 22.57 0.97 0.41

P3-DG-3 22.10 -2.08

P3-DM-1 23.47 -0.55

P3-DM-2 24.03 23.60 1.82 0.38

P3-DM-3 23.30 -1.27

4

P4-DM-1 31.81 2.65

P4-DM-2 32.49 30.99 4.84 2.03

P4-DM-3 28.68 -7.45

P4-BX-1 31.08 0.10

P4-BX-2 30.41 31.05 -2.06 0.62

P4-BX-4 31.65 1.93

In the design evaluation of P series specimens, the possible failure modes are tilting,

bearing and rupture in net section.From the calculations, all the calculated results of

nominal tensile strength P by tilting failure show the smallest values compared with

the calculated results of P by bearing failure and rupture in net section failure. Thus,

all P series specimens are predicted to fail in tilting failure. After the tests were


114

conducted, all P series specimens failed in a combination of tilting and bearing

failure modes. Thus, the calculated results of P by tilting failure using the AISI

Specification (2007) design equations for P series are used to compare with the

experimental results in this study. The comparison of the experimental results and the

calculated results are shown in Table 5-10.

Table 5-10: Experimental Results and Calculated Results for P series

Number

of Screw

Specimen P Exp

(kN)

P Cal Tilting

(kN) Percentage

Difference (%)

3

P3-DG-1 22.83 1.01 1

P3-DG-2 22.79 22.62 1.01 1

P3-DG-3 22.10 0.98 2

P3-DM-1 23.47 1.04 4

P3-DM-2 24.03 22.62 1.06 6

P3-DM-3 23.30 1.03 3

4

P4-DM-1 31.81 1.05 5

P4-DM-2 32.49 30.16 1.08 8

P4-DM-3 28.68 0.95 5

P4-BX-1 31.08 1.03 3

P4-BX-2 30.41 30.16 1.01 1

P4-BX-4 31.65 1.05 5

Table 5-10 shows that the experimental results for the P series specimens are

generally higher than the calculated results using the AISI Specification (2007)

design equations. This is shown by the ratio of P by experimental results to P by

calculated results (P exp/P cal) in Table 5-10. Most of the values of P exp/P cal ratio

for the specimens are more than one. Thus the calculated results of P failed by tilting

using AISI Specification (2007) design equations correlate well with the

experimental results for P series specimens. The percentage difference between the

experimental results and the calculated results also low which is less than 8% as

shown in Table 5-10. Thus, it shows that the calculated results using the AISI

Specification (2007) design equations for P series specimens correlate well with the

experimental results even the specimens have different screw patterns.

5.4.4 Effect of Screw Pattern

The effect of screw patterns was determined by rearranged the screws in different

shapes or patterns. For three screws connections, the screws are arranged in a


115

diagonal (DG) and a diamond (DM) shape. For four screws connection, the screws

are arranged in a diamond (DM) and a box (BX) shape. The connection strength for

P series specimens are compared with the connection strength of N series specimens

which act as a control specimens. The comparisons are corresponding to the number

of screws in the connection.

The screws in N series specimens are arranged in a line parallel i.e. longitudinally to

the applied force, whereas, the screws in P3-DG specimens are arranged in a

staggered shape and the screws in P3-DM specimens are arranged in a diamond

shape as shown in Figure 5-32.Table 5-11 shows the comparison of the experimental

results for N series specimen and the experimental results of P series specimens.

Figure 5-32: Different Shape of Three Screws Connections

Table 5-11 shows the experimental results for three screws connections with

different screw patterns. The experimental results are arranged in an increasing order

of an average strength e.g. N3-ST specimens are the highest connection strength and

followed by P3-DM and P3-DG specimens. The results show that the connection

strength of N series specimens are similar to the connection strength of P3-DM

specimens. The connection strength of N3-ST specimens is only 1.3% higher than

the connection strength of P3-DM specimens as shown in Table 5-11. However the

connection strength of N series specimens is5.6% higher than the connection strength


116

of P3-DG specimens as shown in Table 5-11.Since the percentage difference is less

than 10%, thus, screw patterns have minimal effect on the connection strength of

screw.

Table 5-11: Effect of Screw Patterns for Three Screws Connections

Specimen Experimental Results

(kN)

Percentage

Different (%)

N3-ST-1 24.41

N3-ST-3 23.27

N3-ST-4 24.03

Average 23.90 -

P3-DM-1 23.47

P3-DM-2 24.03

P3-DM-3 23.30

Average 23.60 -1.3

P3-DG-1 22.83

P3-DG-2 22.79

P3-DG-3 22.10

Average 22.57 -5.6

Low ductility steels were used in this study. The low ductility steel possessed lower

Fu/Fy ratio, therefore it has less stress redistribution capacity (Daulet and LaBoube

1996). When low ductility steels has less stress redistribution capacity, the stress

redistribution was uneven throughout the section.

In this study, the connection strength of P3-DG specimens is slightly lower than the

connection strength of N3-ST specimens. The minimum difference found in the

connection strength between N3-ST specimens and P3-DG specimens was because

of the different in a screw pattern. Figure 5-33 shows that both N3-ST and P3-DG

specimens have same number of screw rows. However, the screw pattern for P3-DG

specimens is arranged in an unsymmetrical pattern if compared with the screw

pattern for N3-ST specimens. The screws in N3-ST specimens are arranged in a

symmetrical pattern for both x-axis and y-axis as shown in Figure 5-33.


117

Figure 5-33: Symmetrical Axis

It is mentioned that stress redistribution was uneven due to low ductility steels. The

unsymmetrical screws arrangement in P3-DG specimens increased the uneven stress

redistribution over the section. The combination of unsymmetrical screw

arrangement and low ductility steels used leaded to even more non-uniform stress

redistribution over the section. Hence, more stress concentrated at the screw-hole

region as shown in Figure 5-34 due to the secondary stresses caused by

unsymmetrical screw arrangement which subsequently reduced the connection

performance in P3-DG specimens in this study. Thus, it is found in this study that the

connection strengths of P3-DG specimens are slightly less than the connection

strength of N3-ST specimens because of the unsymmetrical screw pattern of P3-DG

specimens. The percentage difference in connection strength between P3-DG and

N3-ST specimens is only 5.6% as shown in Table 5-11. Therefore, the

unsymmetrical screw patterns and symmetrical screw patterns have minimal effect

on the connection strength of screws in this study.

x

y

y

Row 1

Row 2

Row 3


118

Figure 5-34: Non-Uniform Stress Redistribution

For specimens with four screws in connections, the screws in P4-DM specimens are

arranged in a diamond shape whereas the screws in P4-BX specimens are arranged in

a box shape. All the screws patterns have different number of rows of screws, e.g.

N4-ST specimens have four rows of screws, P4-DM specimens have three rows of

screws and P4-BX specimens have two rows of screws as shown in Figure 5-35. A

row is defined as a line of screws perpendicular to the direction of loading. The

screws for all screw patterns are arranged symmetrically for both x-axis and y-axis as

shown in Figure 5-3.

Stress

Concentration


119

Figure 5-35: Different Shape of Four Screws Connections

Table 5-12 shows the experimental results of N4-ST as a control specimen compared

with the experimental results of P4-DM and P4-BX specimens. The results are

arranged in an increasing order of an average strength e.g. N4-ST specimens are the

highest connection strength and followed by P4-BX and P4-DM specimens. The

connection strength of N4-ST specimens is 3% higher than the connection strength

of P4-DM and P4-BX specimens even though all the specimens have different

number of rows of screws. The connection strength of P4-DM specimens and P4-BX

specimens did not have any significant difference as shown in Table 5-12. Thus, the

minimum percentage difference in connection strength between N4-ST specimens

with P4-DM and P4-BX specimens showed that the number of rows have minimal

effect on the connection strength of screw when low ductility steels used in this

study.

Row 1

Row 2

Row 3

Row 4


120

Table 5-12: Effect of Screw Patterns for Four Screws Connections

Specimen Experimental

Results (kN)

Percentage

Difference (%)

N4-ST-2 32.01

N4-ST-3 32.69

N4-ST-4 31.32

Average 32.01 -

P4-BX-1 31.08

P4-BX-2 30.41

P4-BX-4 31.65

Average 31.05 -3.0

P4-DM-1 31.81

P4-DM-2 32.49

P4-DM-3 28.68

Average 30.99 -3.2

In conclusion, the numbers of rows and the symmetrical and unsymmetrical screw

patterns show some minimal effect on the connection strength of the screws in this

study.

5.4.5 Failure Modes

All P series specimens failed in a combination of tilting and bearing failure mode.

The failure modes observed for P series specimens were similar to the failure modes

for N series specimens and S series specimens.Figure 5-36 shows the screw tilted at

the beginning of testing for P3-DG specimen. Bearing of the steel sheets and tilting

of the screws occurred during the testing. For P3-DM specimen, initial tear in the

direction of loading on the steel sheets not in contact with screw head occurred

during testing as shown in Figure 5-37. Even though both P3-DG and P3-DM

specimens have different screw patterns, both of the specimens failed in the same

failure modes.


121

Figure 5-36: Initial of Test (P3-DG)


122

Figure 5-37: Initial Tear of Steel Sheets (P3-DM specimen)

Figure 5-38 shows the initial stage of testing for P4-DM-3 specimens. The screws

start to tilt after the tensile force was applied. Tilting of the screws and bearing of the

steel sheets occurred after the load continuing applied to the specimen as shown in

Figure 5-39. The screw-heads pushed toward the steel as shown in Figure 5-40. For

P4-BX specimens, Figure 5-42 shows the steel sheets of P4-BX-4 specimen was

curled out of plane at the end of the sections during testing. As the screws were

subjected to higher tensile force, the curling effect became more obvious as shown in

Figure 5-42. It was also observed that P4-DM and P4-BX tested specimens have

same basic pattern of failures even both specimens have different patterns. Thus, it is

found in this study that the same pattern of failures lead to similar connection

strength achieved in screw connections. From observations, it is also found that all P

series tested specimens failed in combination of tilting and bearing failure mode.

Thus, the screw patterns did not affect the failure modes of the screw connection.


123

Figure 5-38: Stage 1 of Testing (P4-DM-3 specimen)


124

Figure 5-39: Stage 2 of Test (P4-DM-3 specimen)

Figure 5-40 : Screw Head Pushed Toward Sheet


125

Figure 5-41: Sheet Curl out of Plane (P4-BX-4 specimen)


126

Figure 5-42: Tilting and Bearing Failure Mode (P4-BX-4 specimen)


127

6 CONCLUSIONS

The objectives of this study are to evaluate the behaviour and strength of screw

connection for high strength cold-formed steel and determine the effects of number

of screws, screw spacing and screw patterns on the connection strength of screws. A

total of 48 specimens comprising of two low ductility steel sheets that are connected

using self-drilling screws were designed, fabricated and tested. The specimens are

categorized into three series according to the parameters determined such as number

of screws, with “N” series, screw spacing, with “S” series, and screw pattern, with

“P” series. N series specimens are varied from one to four screws connection. The

screws are arranged in a line parallel to the applied force. S series specimens are

varied from screw spacing less than 3d to more than 3d where d is the nominal

diameter of the screws. The screws are arranged in a line perpendicular to the applied

force in S series specimens. P series specimens are varied with different screw

patterns e.g. three screws connections with a diagonal (DG) screw pattern and a

diamond (DM) screw pattern, whereas four screws connections with a diamond

(DM) screw pattern and a box (BX) screw pattern. The effects of number of screws,

screw spacing and screw patterns were studied and reviewed. All experimental

results were compared with the calculated results using the American Iron and Steel

Institute Specification (AISI 2007) design equations.

6.1 Number of Screws (N)

AISI Specification (2007) design equations provide a prediction of connection

strength for single shear connection that failed in tilting or bearing failures. The

calculated results in this study are calculated without considering the 0.75 Fu

reduction factors. Based on the experimental results, it can be concluded that the

calculated results correlate well with the experimental results when 0.75 Fu reduction

factor is unemployed in the design equations to which low ductility steels are used in

screw connections. The connection strength increased proportionally to the number

of screws in a connection. The connection strength of four screws, e.g. an average of

32.01 kN, is almost four times the connection strength of single screw, e.g. an

average of 7.84 kN. Thus, there is no Group Effect reduction occurred although


128

multiple screws, e.g. 4 screws, are used in the connections. This is due to the usage

of low ductility steel sheet that is incapable of redistributing stress. The less stress

distribution capacity of low ductility steel caused the experimental results to achieve

almost 100% of the calculated results. As a conclusion, the increases number of

screws increases the connection strength of screw. Thus the objective of this study

which is to determine the effect of number of screws on connection strength of

screws is met by evaluating the experimental results obtained in this study.

6.2 Screw Spacing (S)

The screw spacing varied from more than 3d to less than 3d in this study. The

experimental results of S series specimens show that the screw spacing affects the

connection strength of screw. The specimens with screw spacing more than 3d

achieved higher connection strength compared with the specimens with screw

spacing less than 3d. For two screws connections, the connection strength for

specimens with screw spacing more than 3d is an average of 15.57 kN whereas the

connection strength for specimens with screw spacing less than 3d is an average of

12.20 kN. For three screws connections, the connection strength for specimens with

screw spacing more than 3d is an average of 22.85 kN whereas the connection

strength for specimens with screw spacing less than 3d is an average of 16.76 kN.

Besides, the experimental results of specimens with screw spacing more than 3d


equations compared with the experimental results of specimens with screw spacing

less than 3d. Thus, it is concluded that the screw spacing affect the connection

strength of screw where the connection strength of the specimens with spacing more

than 3d is higher than the connection strength of the specimens with screw spacing

less than 3d. The objective of the study which is to investigate the effect of screw

spacing is achieved.

6.3 Screw Patterns (P)

The screws are arranged in a diagonal (DG) and a diamond (DM) pattern for three

screws connections. The diagonal pattern specimens have three rows of screws

whereas the diamond pattern specimens have two rows of screws. A row is a line of


129

screws perpendicular to the loading. For four screws connection, the screws are

arranged in a box (BX) and a diamond (DM) patterns. The box pattern specimens

have two rows of screws whereas the diamond pattern specimens have three rows of

screws. The experimental results of control specimens from N series specimens are

compared with the experimental results of P series specimens with respect to the

number of screws. The experimental results showed that screw pattern have minimal

effect on the connection strength as the different between the P series to N series is

only less than 5.6% different. The calculated results of P series are calculated based

on the N series specimens using the AISI Specification (2007) design equations. The

experimental results of P series correlate well with the calculated results. As a

conclusion, screw patterns have minimal effect on connection strength of screws,

thus, the objective of this study to investigate the effect of screw patterns on

connection strength of screws is achieved.

6.4 Recommendations for Future Works

This research studied the effect of number of screws, screw spacing and screw

patterns on the screw connection strength for low ductility steel.

The study on the effect of increasing the screw spacing on connection strength of

screw should be investigated further. The specimens with screw spacing larger than

3d such as 4d, 5d should be considered to investigate the limit of screw spacing in

connection strength.

In screw patterns used, the more number of rows i.e. the more lines of screws

perpendicular to applied force give more rotational stability on the specimens. This

rotational stability offers more resistance to rotation. Thus, more screw patterns with

more numbers of screws is needed to show the effect of patterns on the connection

strength of screw. The patterns of screws could be arranged with more number of

rows i.e. lines of screws perpendicular to the applied force and more number of

columns i.e. lines of screw parallel to the applied force to determine the effect of

number of row and columns on self-drilling screws strength under tensile force.


130

REFERENCES

AISI (American Iron and Steel Institute). 1946. Specification for the Design of Light

Gage Steel Structural Members. New York.

AISI (American Iron and Steel Institute). 1996. Specification for the Design of Cold-

Formed Steel Structural Members.

AISI (American Iron and Steel Institute). 1997. Commentary on the 1996 Edition of

the Specification for the Design of Cold-Formed Steel Structural Members.

AISI (American Iron and Steel Institute). 2007. North American Specification for the

Design of Cold-Formed Steel Structural Members.

AISI (American Iron and Steel Institute). 2008a. "S904-08 Standard Test Methods

for Determining the Tensile and Shear Strength of Screws." In AISI Manual

Cold-Formed Steel Design. American Iron and Steel Institute.

AISI (American Iron and Steel Institute). 2008b. "S905-08 Test Methods for

Mechanically Fastened Cold-Formed Steel Connections." In AISI Manual

Cold-Formed Steel Design. American Iron and Steel Institute.

AS/NZS (Australia/New Zealand Standard). 1996. Cold-Formed Steel Structures

4600.

AS/NZS (Australia/New Zealand Standard). 2005. Cold-Formed Steel Structures

4600.

ASTEKS. 2009. Product Data Sheet. Australia: ASTEKS Corp Pte Ltd.

http://asteks.com.au/pdf2/ASTeks-

XTSeal%20Product%20Specification/XT%2012%20-

%2014%20x%2020%20HxW.pdf

http://asteks.com.au/pdf2/ASTeks-XTSeal%20Product%20Specification/XT%2012%20-%2014%20x%2020%20HxW.pdf




131

CCFSS (Centre for Cold-Formed Steel Structures). 1993. “AISI Specification

Provisions for Screw Connection.” CCFSS Technical Bulletin, Vol. 2, No. 1,

University of Missouri-Rolla, Rolla, MO, February.

CSA (Canadian Standards Association). 2012. North American Specification for the

Design of Cold-Formed Steel Structural Members CSA-S136.

Carril,L. Jeffrey, Roger A. Laboube, Wei-Wen Yu. 1994. “Tensile and Bearing

Capacities of Bolted Connections.” University of Missouri-Rolla.

https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/25290/Civil_94

1.pdf?sequence=1.

Daudet, L. Randy and Roger A. LaBoube. 1996. “Shear Behavior of Self Drilllng

Screws Used in Low Ductility Steel.”In International Specialty Conference

on Cold-Formed Steel Structures: Recent Research and Developments in

Cold-Formed Steel Design and Construction Held in St. Louis, Missouri

U.S.A,. 17-18 October 1996, 595-613.

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=

&title=International%20Specialty%20Conference%20on%20Cold-

Formed%20Steel%20Structures%3A%20Recent%20Research%20and%20D

evelopments%20in%20Cold-

Formed%20Steel%20Design%20and%20Construction&date=1996&volume=

&issue=&spage=595&epage=613&aulast=Daudet&aufirst=L.%20Randy&ati

tle=Shear%20behavior%20of%20self%20drilllng%20screws%20used%20in

%20low%20ductility%20steel.

ECS (European Committee for Standardisation). 2005. Eurocode 3: Design of Steel

Structures.

ITW Buildex. 2012. Self-Drilling Screws. Australia: ITW Buildex.

http://www.buildex.com.au/pdf/pages/Corporate/SelfDrilling.pdf.

https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/25290/Civil_941.pdf?sequence=1


http://www.buildex.com.au/pdf/pages/Corporate/SelfDrilling.pdf


132

Koka, Exaud N., Wen-Wen Yu and Roger A. Laboube. 1997. “Screw and Welded

Connection Behaviour Using Structural Grade 80 of A653 Steel.” Fourth

Progress Report, University of Missouri-Rolla.

https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/25302/Civil_97

4.pdf?sequence=1.

LaBoube, Roger A. and M. A. Sokol. 2002. "Behavior of Screw Connections in

Residential Construction." Journal of Structural Engineering 128 (1): 115-

118.

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=0

7339445&title=Journal%20of%20Structural%20Engineering&date=2002&v

olume=128&issue=1&spage=115&epage=118&aulast=LaBoube&aufirst=R.

A.&atitle=Behavior%20of%20screw%20connections%20in%20residential%

20construction.

Li,Yuanqi, Rongkui Ma, and Xingyou Yao. 2010. "Shear Behavior of Screw

Connections for Cold-Formed Thin-Walled Steel Structures" In 20th

International Specialty Conference on Cold-Formed Steel Structures - Recent

Research and Developments in Cold-Formed Steel Design and Construction,

November 3, 2010 - November 4, 2010, St. Louis, MO, United States, 493-

503.

Noorashikin, M. J. 2006. "Effect of Bolt Arrangement and Size to the Capacity of

Splice Connection." Final Year Thesis, Faculty of Civil Engineering,

University Teknologi Malaysia, Johor, Malaysia.

http://www.efka.utm.my/thesis/IMAGES/3PSM/2006/1JSB/PART4/noorashi

kinca020041d06ttt.pdf.

Pekoz, Teoman. 1990. "Design of Cold-Formed Steel Screw Connections" In 10th

International Specialty Conference on Cold-Formed Steel Structures, St.

Louis, MO, United States, 23-24 October 1990, 575-587.



Formed%20Steel%20Structures&date=1990&volume=&issue=&spage=575



http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=07339445&title=Journal%20of%20Structural%20Engineering&date=2002&volume=128&issue=1&spage=115&epage=118&aulast=LaBoube&aufirst=R.A.&atitle=Behavior%20of%20screw%20connections%20in%20residential%20construction





http://www.efka.utm.my/thesis/IMAGES/3PSM/2006/1JSB/PART4/noorashikinca020041d06ttt.pdf

http://www.efka.utm.my/thesis/IMAGES/3PSM/2006/1JSB/PART4/noorashikinca020041d06ttt.pdf


133

&epage=587&aulast=Pekoz&aufirst=Teoman&atitle=Design%20of%20cold-

formed%20steel%20screw%20connections.

Rodriguez-Ferran, Antonio, MiquelCasafont, Alfredo Arnedo, FrancescRoure. 2006.

"Experimental Testing of Joints for Seismic Design of Lightweight

Structures. Part 1. Screwed Joints in Straps. "Thin-walled structures 44 (2):

197-210. doi:10.1016/j.tws.2006.01.002.

Rogers, A. Colin and Gregory J. Hancock. 1997. “Screwed Connection Tests of Thin

G550 and G300 Sheet Steels.” Sydney: Centre for Advanced Structural

Engineering, University of Sydney.

http://sydney.edu.au/engineering/civil/publications/1997/r761.pdf.

Rogers, A. Colin and Gregory J. Hancock. 1999. "Screwed Connection Tests of Thin

G550 and G300 Sheet Steels." Journal of Structural Engineering 125 (2):

128-136.


7339445&title=Journal%20of%20structural%20engineering%20New%20Yo

rk%2C%20N.Y.&date=1999&volume=125&issue=2&spage=128&epage=13

6&aulast=ogers&aufirst=Colin%20A.&atitle=Screwed%20connection%20tes

ts%20of%20thin%20G550%20and%2G300%20sheet%20steels.

Seleim, S. and R. LaBoube.1996."Behavior of Low Ductility Steels in Cold-Formed

Steel Connections." Thin-walled structures 25 (2): 135-151.


2638231&title=Thin-

Walled%20Structures&date=1996&volume=25&issue=2&spage=135&epage

=151&aulast=Seleim&aufirst=S.&atitle=Behavior%20of%20low%20ductilit

y%20steels%20in%20cold-formed%20steel%20connections.

Serrette, Reynaud and Victor Lopez. 1996. “Performance of Self-Tapping Screws in

Lap-Shear Metal-to-Metal Connections.” In International Specialty

Conference on Cold-Formed Steel Structures: Recent Research and

http://sydney.edu.au/engineering/civil/publications/1997/r761.pdf

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=07339445&title=Journal%20of%20structural%20engineering%20New%20York%2C%20N.Y.&date=1999&volume=125&issue=2&spage=128&epage=136&aulast=ogers&aufirst=Colin%20A.&atitle=Screwed%20connection%20tests%20of%20thin%20G550%20and%252G300%20sheet%20steels





http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=02638231&title=Thin-Walled%20Structures&date=1996&volume=25&issue=2&spage=135&epage=151&aulast=Seleim&aufirst=S.&atitle=Behavior%20of%20low%20ductility%20steels%20in%20cold-formed%20steel%20connections






134

Developments in Cold-Formed Steel Design and Construction, Missouri

U.S.A






&issue=&spage=615&epage=622&aulast=Serrette&aufirst=Reynaud&atitle=

Performance%20of%20self-tapping%20screws%20in%20lap-

shear%20metal-to-metal%20connections.

Serrette, Reynaud and Dean Peyton. 2009. "Strength of Screw Connections in Cold-

Formed Steel Construction." Journal of Structural Engineering 135 (8): 951-

958.



olume=135&issue=8&spage=951&epage=958&aulast=Serrette&aufirst=Rey

naud&atitle=Strength%20of%20screw%20connections%20in%20cold-

formed%20steel%20construction.

Sokol, Marc Allen, Roger A. LaBoube and Wen WenYu.1998.“Determination of the

Tensile and Shear Strengths of Screws and the Effect of Screw Patterns on

Cold-Formed Steel Connections.” Civil Engineering Study 98-3, Cold-

Formed Steel Series, Department of Civil Engineering, University of

Missouri-Rolla.

Toma, A., G. Sedlacek and K. Weynand. 1993. "Connections in Cold-Formed Steel."

Thin-walled structures 16 (1): 219-237.


2638231&title=Thin-

Walled%20Structures&date=1993&volume=16&issue=1&spage=219&epage

=237&aulast=Toma&aufirst=A.&atitle=Connections%20in%20cold-

formed%20steel.

ttp://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=

ttp://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=02638231&title=Thin-Walled%20Structures&date=1993&volume=16&issue=1&spage=219&epage=237&aulast=Toma&aufirst=A.&atitle=Connections%20in%20cold-formed%20steel






135

Yu, Wen-Wen and Roger A. Laboube. 2010. "Introduction." In Cold-Formed Steel

Design. New Jersey: John Wiley & Sons, Inc.

Yan, Shu, and Ben Young. 2012. "Screwed Connections of Thin Sheet Steels at

Elevated Temperatures – Part I: Steady State Tests." Engineering Structures

35 (0): 234-243. doi: http://dx.doi.org/10.1016/j.engstruct.2011.10.030.

http://dx.doi.org/10.1016/j.engstruct.2011.10.030


136

BIBLIOGRAPHY

Acharya, R. Sandesh and K.S. Sivakumaran. 2012. “Finite element Models for Thin-

Walled Steel Member Connections.” International Scholarly Research

Network ISRN Civil Engineering 2012.doi: 10.5402/2012/197170.

Babalola, R. Michael, Roger A. LaBoube. 2004. “Strength of Screw Connections

Subject to Shear Force.” Final Report, University of Missouri-Rolla.

http://www.smdisteel.org/~/media/Files/SMDI/Construction/CFSD%20-

%20Report%20-%20RP04-2.pdf.

Bambach, R. Michael, and Kim J. R. Rasmussen. 2007. "Behavior of Self-Drilling

Screws in Light-Gauge Steel Construction." Journal of Structural

Engineering 133 (Compendex): 895-898.

http://dx.doi.org/10.1061/(ASCE)0733-9445(2007)133:6(895).

Bayan, A, Sariffuddin, S and Hanim, O. 2011. "Cold-Formed Steel Joints and

Structures-a Review." International Journal of Civil and Structural

Engineering 2 (2): 621-634.doi: 10.6088/ijcser.00202010137.

Couchaux, Mael, Mohammed Hjiaj, Ivor Ryan and A.Bureau. 2009. "Effect of

Contact on the Elastic Behaviour of Bolted Connections" Nordic Steel

Construction Conference Sweden.

http://www.nordicsteel2009.se/pdf/157.pdf.

Epstein, H. I., and B. H. Thacker. 1991. "The Effect of Bolt Stagger for Block Shear

Tension Failures in Angles." Computers & Structures 39 (5): 571-576. doi:

http://dx.doi.org/10.1016/0045-7949(91)90065-T.

Franca, Ryan Michael. 2009. "Screw Connections Subject to Tension Pull-out and

Shear Forces." Master’s thesis, University of Science and Technology,

Missouri.

http://www.smdisteel.org/~/media/Files/SMDI/Construction/CFSD%20-%20Report%20-%20RP04-2.pdf

http://www.smdisteel.org/~/media/Files/SMDI/Construction/CFSD%20-%20Report%20-%20RP04-2.pdf

http://dx.doi.org/10.1061/(ASCE)0733-9445(2007)133:6(895)

http://www.nordicsteel2009.se/pdf/157.pdf

http://dx.doi.org/10.1016/0045-7949(91)90065-T


137

https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/34544/2026%2

0Screw%20connections%20subject%20to%20tension%20pull-

out%20and%20shear%20forces.pdf?sequence=1.

Francka, Ryan Michael and Roger A. LaBoube. 2010. "Screw Connections Subject

to Tension Pull-out and Shear Forces" 20th International Specialty

Conference on Cold-Formed Steel Structures - Recent Research and

Developments in Cold-Formed Steel Design and Construction, 3-4 November

2010, St. Louis, MO, United States, 635-651.

LaBoube, R. A. 1996. “Additional Design Considerations for Bolted Connections.”

In International Specialty Conference on Cold-Formed Steel Structures:

Recent Research and Developments in Cold-Formed Steel Design and

Construction, Held in St. Louis, Missouri U.S.A., 17-18 October 1996, 575-

593.

Lin, Shin-Hua, Wei-Wen Yu, Theodore V. Galambos, and Edward Wang. 2005.

"Revised Asce Specification for the Design of Cold-Formed Stainless Steel

Structural Members." Engineering Structures 27 (9): 1365-1372. doi:

http://dx.doi.org/10.1016/j.engstruct.2005.03.007.

Lu, Wei, Pentti Mäkeläinen, Jyri Outinen, and Zhongcheng Ma. 2011. "Design of

Screwed Steel Sheeting Connection at Ambient and Elevated Temperatures."

Thin-Walled Structures 49 (12): 1526-1533. doi:

http://dx.doi.org/10.1016/j.tws.2011.07.014.

Mael Couchaux , Mohammed Hjiaj, Ivor Ryan, A.Bureau. 2009. "Effect of Contact

on the Elastic Behaviour of Bolted Connections" Nordic Steel Construction

Conference Sweden,

Moe, Primo. 2011. "Investigation of High Strength Steel Connections with Several

Bolts in Double Shear." Journal of constructional steel research 67 (3): 333-

347.


https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/34544/2026%20Screw%20connections%20subject%20to%20tension%20pull-out%20and%20shear%20forces.pdf?sequence=1



http://dx.doi.org/10.1016/j.engstruct.2005.03.007

http://dx.doi.org/10.1016/j.tws.2011.07.014

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=0143974X&title=Journal%20of%20Constructional%20Steel%20Research&date=2011&volume=67&issue=3&spage=333&epage=347&aulast=Moe&aufirst=Primo&atitle=Investigation%20of%20high%20strength%20steel%20connections%20with%20several%20bolts%20in%20double%20shear


138

143974X&title=Journal%20of%20Constructional%20Steel%20Research&da

te=2011&volume=67&issue=3&spage=333&epage=347&aulast=Moe&aufir

st=Primo&atitle=Investigation%20of%20high%20strength%20steel%20conn

ections%20with%20several%20bolts%20in%20double%20shear.

Moss, Stephen and Mahen Mahendran. 2002. “Structural Behaviour of Self-Piercing

Riveted Connections in Steel Framed Housing.” In International Specialty

Conference on Cold-Formed Steel Structures: Recent Research and

Developments in Cold-Formed Steel Design and Construction Held in

Orlando, Florida U.S.A., 17-18 October 2002. 748-762.






&issue=&spage=748&epage=762&aulast=Moss&aufirst=Stephen&atitle=Str

uctural%20behaviour%20of%20self-

piercing%20riveted%20connections%20in%20steel%20framed%20housing.

Pedreschi, Remo. and Brajraman Sinha. 1996. "Potential of Press-Joining in Cold-

Formed Steel Structures." Construction & Building Materials 10 (4): 243-

250.


9500618&title=Construction%20and%20Building%20Materials&date=1996

&volume=10&issue=4&spage=243&epage=250&aulast=Pedreschi&aufirst=

R.F.&atitle=Potential%20of%20press-joining%20in%20cold-

formed%20steel%20structures

Rogers, A. Colin, Gregory J. Hancock. 1998. “Failure Modes of Bolted-Sheet-Steel

Connections Loaded in Shear.” Research Report, Centre for Advanced

Structural Engineering, University of Sydney, Australia.








http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=&title=International%20Specialty%20Conference%20on%20Cold-Formed%20Steel%20Structures%3A%20Recent%20Research%20and%20Developments%20in%20Cold-Formed%20Steel%20Design%20and%20Construction&date=2002&volume=&issue=&spage=748&epage=762&aulast=Moss&aufirst=Stephen&atitle=Structural%20behaviour%20of%20self-piercing%20riveted%20connections%20in%20steel%20framed%20housing








http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=09500618&title=Construction%20and%20Building%20Materials&date=1996&volume=10&issue=4&spage=243&epage=250&aulast=Pedreschi&aufirst=R.F.&atitle=Potential%20of%20press-joining%20in%20cold-formed%20steel%20structures






139

6&aulast=Rogers&aufirst=Colin%20A.&atitle=Failure%20modes%20of%20

bolted-sheet-steel%20connections%20loaded%20in%20shear.

Rogers, A. Colin. 2000. "Failure Modes of Bolted-Sheet-Steel Connections Loaded

in Shear." Journal of structural engineering 126 (3): 288-296.




6&aulast=Rogers&aufirst=Colin%20A.&atitle=Failure%20modes%20of%20

bolted-sheet-steel%20connections%20loaded%20in%20shear.

Rogers, A. Colin, D. Yang and Gregory J. Hancock. 2003. "Stability and Ductility of

Thin High Strength G550 Steel Members and Connections." Thin-walled

structures 41 (2): 149-166.doi:10.1016/S0263-8231(02)00084-8.

Teh, H. Lip and Drew D. A. Clements. 2012. "Block Shear Capacity of Bolted

Connections in Cold-Reduced Steel Sheets." Journal of structural

engineering 138 (4): 459-467.



olume=138&issue=4&spage=459&epage=467&aulast=Teh&aufirst=Lip%20

H.&atitle=Block%20shear%20capacity%20of%20bolted%20connections%20

in%20cold-reduced%20steel%20sheets.

Teh, H. Lip and Drew D. A. Clements. 2012. "Tension Capacity of Staggered Bolted


engineering 138 (6): 769-776.


7339445&title=Journal%20of%20Structural%20Engineering%20%28United

%20States%29&date=2012&volume=138&issue=6&spage=769&epage=776

&aulast=Teh&aufirst=Lip%20H.&atitle=Tension%20capacity%20of%20stag

gered%20bolted%20connections%20in%20cold-reduced%20steel%20sheets.

http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=07339445&title=Journal%20of%20Structural%20Engineering&date=2012&volume=138&issue=4&spage=459&epage=467&aulast=Teh&aufirst=Lip%20H.&atitle=Block%20shear%20capacity%20of%20bolted%20connections%20in%20cold-reduced%20steel%20sheets





http://sfx.lis.curtin.edu.au/sfx_local?sid=EI%3ACompendex&genre=&issn=07339445&title=Journal%20of%20Structural%20Engineering%20%28United%20States%29&date=2012&volume=138&issue=6&spage=769&epage=776&aulast=Teh&aufirst=Lip%20H.&atitle=Tension%20capacity%20of%20staggered%20bolted%20connections%20in%20cold-reduced%20steel%20sheets






140

Teh, Lip and Benoit P. Gilbert. 2012. "Net Section Tension Capacity of Bolted


engineering 138 (3): 337-344.


7339445&title=Journal%20of%20Structural%20Engineering%20%28United

%20States%29&date=2012&volume=138&issue=3&spage=337&epage=344

&aulast=Teh&aufirst=Lip%20H.&atitle=Net%20section%20tension%20capa

city%20of%20bolted%20connections%20in%20cold-

reduced%20steel%20sheets.

Yuanqi, Li. 2013. "Experimental Investigation and Design Method Research on

Low-Rise Cold-Formed Thin-Walled Steel Framing Buildings." Journal of

structural engineering 139 (5): 818-36.



olume=139&issue=5&spage=818&epage=36&aulast=Yuanqi&aufirst=Li&at

itle=Experimental%20Investigation%20and%20Design%20Method%20Rese

arch%20on%20Low-Rise%20Cold-Formed%20Thin-

Walled%20Steel%20Framing%20Buildings.

“Every reasonable effort has been made to acknowledge the owners of copyright

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or incorrectly acknowledged.”


141

APPENDIX A


142

Appendix A: Stress-Strain Graph for Coupon Test

Sheet Average

Thickness

(mm)

%

Elongation

Fy

(MPa)

Fu

(MPa)

TC-75-1 1.204 1.500 563 591.62 1.05

TC-90-2 1.195 3.632 560 589.02 1.05

Average 561.50 590.32 1.05

0

100

200

300

400

500

600

700

0 0.5 1 1.5 2

Str

ess (

MP

a)

Strain (%)

Stress-Strain Graph ( TC-75-1)

Fy = 563Mpa

Fu = 591.62Mpa


143

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6 7 8

Str

ess (

MP

a)

Strain (%)

Stress-Strain Graph (TC-90-2)

Final Strain

Moderated

E1

E2

E3

E4

Fu = 589.02MPa

Fy = 560MPa


144

APPENDIX B


145

Appendix B: Specimen’s Measured Dimensions

Dimensions and Specifications of Specimens

No. Parameter Specimen Number

of screw

Length

(mm)

Width

(mm)

Thickness

(mm)

Number

of

specimen

1 Number of

screw

N1-ST 1 450 70 1.2 4

2 N2-ST 2 450 70 1.2 4

3 N3-ST 3 450 70 1.2 4

4 N4-ST 4 450 70 1.2 4

5 Screw

Spacing

S2-15 2 450 70 1.2 4

6 S2-40 2 450 70 1.2 4

7 S3-15 3 450 70 1.2 4

8 S3-25 3 450 70 1.2 4

9

Screw

Pattern

P3-DG 3 450 70 1.2 4

10 P3-DM 3 450 70 1.2 4

11 P4-DM 4 450 70 1.2 4

12 P4-BX 4 450 70 1.2 4

*All measurements in unit mm.

Measured dimensions for N1-ST

Specimen T1 T2 W1 W2 L1 L2

N1-ST-1 1.25 1.25 70 70 451 451

N1-ST-2 1.24 1.24 70 70 450 449

N1-ST-3 1.24 1.24 71 70 451 450

N1-ST-4 1.24 1.24 69 69 449 449

Average

N1-ST 1.24 1.24 70 70 450 450



N2-ST-1 1.23 1.23 70 70 449 449

N2-ST-2 1.23 1.21 70 70 448 449

N2-ST-3 1.21 1.21 70 70 449 449

N2-ST-4 1.21 1.21 70 70 449 449

Average


146

N2-ST 1.22 1.22 70 70 449 449



N3-ST-1 1.19 1.20 70 70 449 449

N3-ST-2 1.23 1.22 70 70 449 449

N3-ST-3 1.21 1.21 70 70 450 449

N3-ST-4 1.21 1.21 70 70 449 449

Average

N3-ST 1.21 1.21 70 70 449 449



N4-ST-1 1.20 1.21 70 70 448 449

N4-ST-2 1.18 1.21 70 71 448 448

N4-ST-3 1.19 1.21 70 70 450 449

N4-ST-4 1.19 1.21 70 70 448 448

Average

N4-ST 1.19 1.21 70 70 449 449

Measured dimensions for S2-15


S2-15-1 1.22 1.20 71 71 448 449

S2-15-2 1.22 1.21 70 70 448 448

S2-15-3 1.22 1.20 70 70 450 449

S2-15-4 1.22 1.22 71 70 448 448

Average

S2-15 1.22 1.21 71 70 449 449


147



S2-40-1 1.22 1.22 70 70 450 450

S2-40-2 1.22 1.22 70 70 449 446

S2-40-3 1.22 1.23 70 70 449 449

S2-40-4 1.23 1.21 69 69 449 450

Average

S2-40 1.22 1.22 70 70 449 449



S3-15-1 1.23 1.20 71 70 449 448

S3-15-2 1.23 1.23 70 70 449 448

S3-15-3 1.22 1.22 70 70 450 449

S3-15-4 1.23 1.23 71 70 449 448

Average

S3-15 1.23 1.22 71 70 449 448



S3-25-1 1.22 1.21 69 69 449 449

S3-25-2 1.22 1.22 70 70 449 449

S3-25-3 1.22 1.21 69 70 449 449

S3-25-4 1.21 1.20 70 70 450 449

Average

S3-25 1.22 1.21 70 70 449 449


148

Measured dimensions for P3-DG


P3-DG-1 1.22 1.21 70 69 448 450

P3-DG-2 1.22 1.22 70 69 450 449

P3-DG-3 1.22 1.21 70 69 449 450

P3-DG-4 1.21 1.21 70 70 449 449

Average

P3-DG 1.22 1.21 70 69 449 450

Measured dimensions for P3-DM


P3-DM-1 1.22 1.21 69 70 450 450

P3-DM-2 1.20 1.22 70 70 448 448

P3-DM-3 1.21 1.23 71 69 450 449

P3-DM-4 1.21 1.22 69 69 448 450

Average

P3-DM 1.21 1.22 70 70 449 449

Measured dimensions for P4-BX


P4-BX-1 1.22 1.22 70 69 449 449

P4-BX-2 1.22 1.23 70 69 448 448

P4-BX-3 1.23 1.22 70 70 448 449

P4-BX-4 1.23 1.22 70 69 450 459

Average

P4-BX 1.23 1.22 70 69 449 449


149

Measured dimensions for P4-DM


P4-DM-1 1.23 1.23 70 70 449 449

P4-DM-2 1.22 1.22 70 70 449 449

P4-DM-3 1.22 1.22 70 70 448 449

P4-DM-4 1.22 1.22 70 70 450 450

Average

P4-DM 1.22 1.22 70 70 449 449


150

APPENDIX C


151

Appendix C: Pn Calculation for N Series Specimen

The calculated results of Pns for N series specimens are calculated using the

American Iron and Steel Institute Specification (AISI, 2007) design equations.

Appendix C-1: N1-ST Specimen

According to the Equation 4-1, the nominal shear strength Pns for tilting failure is

calculated as follows:

Pns=7.54 kN

According to theEquation 4-2, the nominal shear strength Pns for bearing failure is


Pns= 10.23N


According to the Equation 4-4, P for two screws connection of tilting failure is


P = 15.08kN

The nominal shear strength P of two screw connection of bearing failure is calculated

as follows:

P = 20.46kN


152


According to the Equation 4-4, P for three screws connection of tilting failure is


P = 22.62kN

The nominal shear strength P for three screws connection of bearing failure is


P = 30.69kN


According to the Equation 4-4, P for four screws connection of tilting failure is


P = 30.16kN

The nominal shear strength P for four screws connection of bearing failure is


P = 40.96kN


153

APPENDIX D


154

Appendix D: Pn Calculation for S Series Specimen

The calculations in this section are according to the American Iron and Steel

Specification (AISI, 2007) design equations.

According totheEquation 4-5, nominal tensile strengthPnof two and three number of

screws in a connection is determined as follows:

For a single row of screws perpendicular to the force, nominal tensile stressFtis

determine according to the Equation 4-6 as follows:

Where s is the sheet width divided by the number of the screw holes in the cross

section being analyzedwhen evaluating Ft.

Appendix D-1: S2 Specimen

For two screws connection in S series specimens, a net area Anis determine as

follows:

An= 71.16 mm2

Ft = 225.59Mpa

Pn= 16.05kN


155

Appendix D-2: S3 Specimen

For three screws connections, a net area Anis determine as follows:

An= 64.74mm2

Ft = 338.37Mpa

Pn= 21.91kN


156

APPENDIX E


157

Appendix E: Pn Calculation for P Series Specimen

The calculations in this section are according to the American Iron and Steel

Specification (AISI, 2007) design equations.

Appendix E-1

Three Number of Screws

1. Diagonal Shape

There are two possible fracture lines for a diagonal screws pattern e.g. line ABC and

line ABDEF. The fracture of steel can occur at a screw location which has smaller

cross sectional area.

The calculation of the net area for both line ABC and line ABDEF are as follows:

Net area for line ABC:

An = 77.58 mm2


158

Net area for line ABDEF was determined according to the Equation 4-7because the

line is in a staggered pattern.

An = 187.87mm2

Since the net area, An for the line ABC is smaller than the line ABDEF, thus, the

possible failure will occur at the line ABC. An for the line ABC was chosen in the

calculation of Pn.

The nominal tensile stress, FtforlineABC was determined according to the Equation

4-8 as follows:

Ft = 338.38Mpa

Pn= 26.25kN


159

2. Diamond Shape

There are two possible fracture lines for a diamond screws pattern e.g. line ABCDE

and line ABDE. The fracture of steel can occur at a screw location which has smaller


The calculation of the net area for both line ABDE and line ABCDE are as follows:

Net Area for line ABDE:

An = 71.16 mm2

The net area for line ABCDE was determined according totheEquation 4-7because

the line is in a staggered pattern.

An = 187.87mm2

Since the net area, An for line ABDE is smaller than the line ABCDE, thus, the

possible failure will occur at the line ABDE. An for the line ABDE was chosen in the

calculation of Pn.


160

The nominal tensile stress, Ftforthe line ABDE was determined according to the

Equation 4-8 as follows:

Ft = 338.38Mpa

Pn= 24.08kN


161

Appendix E-2

Four Number of Screws

1. Diamond Pattern

There are two possible fracture lines for a diamond screws pattern e.g. line ABCDE

and line ABDE. The fracture of steel can occur at a screw location which has smaller


The calculation of net area for both line ABDE and line ABCDE are as follows:

Net Area for ABDEline:

An = 71.16 mm2

Net area for line ABCDE was determined according totheEquation 4-7because the

line is in a staggered pattern.

An = 187.87mm2


162

Since the net area An for the line ABDE is smaller than the line ABCDE, thus, the

possible failure will occur at the line ABDE. An for the line ABDE was chosen in the

calculation of Pn.

The nominal tensile stress, Ftfor the line ABDE is equal to Fu, because there are

multiple screws in the line parallel to the applied force.

Ft = 590.32Mpa

Pn = 42.01kN


163

2. Box Pattern

The possible fracture line for box screws pattern is the line ABCD.

Net Area for line ABDE:

An = 71.16 mm2

The nominal tensile stress, Ftfor the line ABCD is equal to Fu, because there are

multiple screws in the line parallel to the applied force.

Ft = 590.32Mpa

Pn = 42.01kN


164

APPENDIX F


165

Appendix F: Calculation Spread Sheets

The numerical calculation is based on American Iron and Steel InstituteSpecification

(AISI, 2007) design equations. These spread sheetsare include the inputs, basic

parameters and output sections.


166

Appendix F-1

Table below shows the calculations for the N seriesspecimens. The number of screw

varied from one to four screws connections. The dimensionsare based on the N1-ST-

2 specimen.

NUMERICAL CALCULATION FOR N SERIES SPECIMEN

INPUT

Reference

(According to AISI

(2007)design

equations)

Width, w = 70 mm

Thickness (Head), t1 = 1.2 mm

Thickness(Body), t2 = 1.2 mm

Screw diameter, d = 5.35 mm

Number of screw, n = 1

Tensile strength (Head), Fu1 = 590.32 Mpa

Tensile strength (Body), Fu2 = 590.32 Mpa

BASIC PARAMETERS

Tilting, Pns = 7.54 kN Pns=4.2 (t2³d) ½ Fu2

Bearing Pns= 10.23 kN Pns=2.7 t1d Fu1

Bearing Pns = 10.23 kN Pns=2.7 t2 d Fu2

OUTPUT

Tilting, Pns = 7.54 kN 1 Screw

Bearing, Pns = 10.23 kN

Tilting, P = 15.08 kN 2 Screws P= 2Pns


Tilting, P= 22.62 kN 3 Screws P= 3Pns


Tilting, P= 30.16 kN 4 Screws P=4Pns

Bearing, P = 40.96 kN


167

Appendix F-2

Table below shows the calculations for the S2 series specimens. The screw spacings

are varied from less than 3dto more than 3d. The screw spacing for less than 3d is

15mm and the screw spacing for more than 3d is 40mm. The dimensions of the S2

series specimenarebased onthe S2-15-1specimen.

NUMERICAL CALCULATION FOR S2 SERIES SPECIMEN

INPUT

Reference

(According to AISI

(2007)

design equations)

Width, w = 70 mm





Transverse spacing (S2-15), g = 15 mm




BASIC PARAMETERS

s = 35 mm S = w/n

Gross area of member, Ag = 84 mm Ag = wt

Net Area ,A = 71.10 mm A = Ag- ndt

Nominal Tensile Stress,Ft = 225.59 MPa Ft = (2.5d/s) Fu ≤Fu

OUTPUT

Rupture in net section, Pn = 16.05 kN Pns= AnFt


Bearing, P= 20.46 kN 2 Screws P= 2Pns


168

Appendix F-3

Table below shows the calculations for the S3 series specimens. The screw spacings

are varied from less than 3dto more than 3d. The screw spacing for less than 3d is

15mm and the screw spacing for more than 3d is 25mm. The dimensions of the S3

series specimen arebased onthe S3-25-4specimen.

NUMERICAL CALCULATION FOR S3 SERIES SPECIMEN

INPUT Reference

(According to AISI

(2007)

design equations)

Width, w = 70 mm









BASIC PARAMETERS

s = 23.33 mm s = w/n

Gross area of member, Ag = 84 mm Ag = wt

Net Area ,A = 64.74 mm A = Ag- ndt


OUTPUT

Rupture in net section, P = 21.91 kN Pns= AnFt


Bearing, P= 30.69 kN 3 Screws P= 3Pns


169

Appendix F-4

Table below shows the calculations for the P3-DG series specimens. The dimensions

of the P3-DG specimen arebased on the P3-DG-4specimen.

NUMERICAL CALCULATION FOR P3-DG

INPUT

Reference

(According

to AISI (2007)

design

equations)

Width, w = 70 mm




Number of screw in connection, n

= 3

Number of screw in LINE 1, n1 = 1


Longitudinal Spacing, s' = 60 mm

Transverse spacing, g = 15 mm



BASIC PARAMETERS

s = 23.33 mm s = w/n

Gross area of member, Ag= 84 mm Ag = wt

Net Area ,An1 = 77.58 mm An1 =Ag - n1dt

Net Area ,An2 = 187.87 mm An2= 0.9 [ Ag - nbdt + ∑(s'²/4g)t ] for

staggered hole

* The less net area is chosen for

nominal shear strength calculation


OUTPUT

Rupture in net section, Pn = 26.25 kN Pns = An1Ft


Bearing, P = 30.69 kN 3 Screws P= 3Pns


170

Appendix F-5

Table below shows the calculations for the P3-DM series specimens. The dimensions

of the P3-DG specimen are based on the P3-DM-2specimen.

NUMERICAL CALCULATION FOR P3-DM

INPUT

Reference (According

to AISI

(2007) design

equations)

Width, w = 70 mm




Number of screw in connection,

n = 3

Number of screw in LINE 1, n1

= 2


= 3





BASIC PARAMETERS

s = 23.33 mm s = w/n




staggered hole

* The less net area is chosen for nominal

shear strength calculation


OUTPUT





171

Appendix F-6

Table below shows the calculations for the P4-BX series specimens. The dimensions

of the P4-BX specimen are based on the P4-BX-1specimen.

NUMERICAL CALCULATION FOR P4-BX

INPUT Reference

(According

to AISI

(2007) design

equations)

Width, w = 70 mm




Number of screw in connection, n = 4


Tensile strength (Head), Fu1= 590.32 Mpa

Tensile strength (Body), Fu2= 590.32 Mpa

BASIC PARAMETERS

s = 17.5 mm s = w/n



Nominal Tensile Stress,Ft = 590.32 MPa

Ft = Fu for multiple screws in

the line parallel to the force

OUTPUT





172

Appendix F-7

Table below shows the calculations for the P4-DM series specimens. The dimensions

of the P4-DM specimen are based on the P4-DM-1specimen.

NUMERICAL CALCULATION FOR P4-DM

INPUT

(According to AISI

(2007)

design equations)

Width, w = 70 mm




Number of screw in

connection, n =

4


=

2


=

4





BASIC PARAMETERS

s = 17.5 mm s = w/n




staggered hole

* The less net area is chosen for

nominal shear strength calculation

Nominal Tensile Stress,Ft = 590.32 MPa Ft = Fu for multiple screws in the line

parallel to the force

OUTPUT





173

APPENDIX G


174

Appendix G: Load against Displacement Data

A values are extracting from the row data provided by the testing.

Appendix G-1 : Number of Screw Specimen

Test Sample : N1-ST-1

Test Date & Time : 12-07-2012

Test Venue : Curtin Sarawak University,

Structural Laboratory

Tested by : Siti Fairuz

Load Displacement Load Displacement Load Displacement

(kN) (mm) (kN) (mm) (kN) (mm)

3.430715 0.2 7.203092 5.4 4.246054 10.6

3.983502 0.4 7.202111 5.6 4.062284 10.8

4.420325 0.6 7.176232 5.8 4.174642 11.0

4.821608 0.8 7.146423 6.0 4.512047 11.2

5.174899 1.0 7.158543 6.2 4.637017 11.4

5.473978 1.2 7.135284 6.4 4.951819 11.6

5.735875 1.4 7.095484 6.6 5.253354 11.8

5.972221 1.6 7.070097 6.8 5.23026 12.0

6.181215 1.8 6.999013 7.0 5.149021 12.2

6.484062 2.0 6.914006 7.2 5.4992 12.4

6.563334 2.2 7.037012 7.4 5.795003 12.6

6.676021 2.4 7.038977 7.6 5.939136 12.8

6.788707 2.6 6.996393 7.8 6.003505 13.0

6.870602 2.8 6.971168 8.0 5.950111 13.2

6.920886 3.0 6.926946 8.2 5.775021 13.4

6.991151 3.2 6.94185 8.4 0.766694 13.6

7.105312 3.4 6.762993 8.6 1.824768 13.8

7.177378 3.6 6.735314 8.8 2.837473 14.0

7.161655 3.8 6.667013 9.0 3.979898 14.2

7.176395 4.0 6.077211 9.2 4.35137 14.4

7.195395 4.2 5.782882 9.4 4.400834 14.6

7.209645 4.4 5.896061 9.6 0.093687 14.8

7.235197 4.6 6.042651 9.8 0.710842 15.0

7.25698 4.8 6.149769 10.0 1.447727 15.2

7.243386 5.0 5.575854 10.2 1.72371 15.4

7.215213 5.2 4.921518 10.4


175








0 0.0 7.442715 4.0 6.782812 8.0

3.360614 0.2 7.536402 4.2 6.391357 8.2

3.879168 0.4 7.637623 4.4 6.358927 8.4

4.317466 0.6 7.696424 4.6 6.193664 8.6

4.815875 0.8 7.784871 4.8 5.968946 8.8

4.991292 1.0 7.841541 5.0 5.832182 9.0

5.229932 1.2 7.920159 5.2 5.683135 9.2

5.4784 1.4 7.994683 5.4 5.618766 9.4

5.685919 1.6 8.031863 5.6 5.45072 9.6

5.856424 1.8 8.087059 5.8 5.245001 9.8

6.053135 2.0 8.117032 6.0 5.19439 10.0

6.229697 2.2 8.113757 6.2 5.217976 10.2

6.412322 2.4 8.123584 6.4 5.238286 10.4

6.542534 2.6 8.067896 6.6 5.301672 10.6

6.678807 2.8 7.98158 6.8 5.070402 10.8

6.794932 3.0 7.897393 7.0 3.770248 11.0

6.909584 3.2 7.822705 7.2 3.656251 11.0

7.034718 3.4 7.745234 7.4

7.269591 3.6 7.637951 7.6

7.352633 3.8 7.362131 7.8


176








0 0.0 7.607323 3.8 7.929005 7.8

3.455775 0.2 7.700191 4.0 7.954718 8.0

4.023465 0.4 7.814024 4.2 8.022854 8.2

4.508444 0.6 7.877247 4.4 8.074119 8.4

4.947397 0.8 7.991408 4.6 8.043001 8.6

5.288405 1.0 8.04513 4.8 7.911315 9.0

5.588301 1.2 8.122603 5.0 7.792568 9.2

5.945525 1.4 8.113757 5.2 7.635986 9.4

6.142562 1.6 8.084438 5.4 7.139707 9.6

6.331738 1.8 8.019252 5.6 6.609032 9.8

6.499457 2.0 7.867912 5.8 6.420183 10.0

6.665048 2.2 7.010642 6.2 6.591179 10.2

6.809509 2.4 6.885015 6.4 6.584136 10.4

6.926126 2.6 7.036193 6.6 5.468245 10.6

7.054209 2.8 7.337727 6.8 4.715309 10.8

7.144294 3.0 7.592582 7.0 4.279959 11.0

7.280729 3.2 7.77668 7.2 4.017406 11.1

7.402425 3.4 7.905255 7.4 7.510688 3.6 7.980434 7.6


177








0 0.0 6.931367 4.4 6.333867 8.8

3.441853 0.2 6.999503 4.6 6.03397 9.0

3.948123 0.4 7.038649 4.8 5.9981 9.2

4.418851 0.6 7.041271 5.0 6.173026 9.4

4.832417 0.8 7.063218 5.2 6.361713 9.6

5.199304 1.0 7.071898 5.4 6.361713 9.8

5.489702 1.2 7.102854 5.6 6.044617 10.0

5.744392 1.4 7.132991 5.8 5.663154 10.2

5.963705 1.6 7.107767 6.0 5.615654 10.4

6.323385 1.8 7.086475 6.2 5.80958 10.6

6.361713 2.0 7.080415 6.4 5.929474 10.8

6.436562 2.2 7.071242 6.6 6.043306 11.0

6.52206 2.4 7.040778 6.8 6.163199 11.2

6.585282 2.6 7.049132 7.0 6.099978 11.4

6.637695 2.8 7.023253 7.2 5.976808 11.6

6.650635 3.0 6.997047 7.4 5.810235 11.8

6.621971 3.2 6.970513 7.6 5.505916 12.0

6.614601 3.4 6.94447 7.8 5.094151 12.2

6.624428 3.6 6.842103 8.0 5.144598 12.4

6.663901 3.8 6.855698 8.2 5.108401 12.6

6.705667 4.0 6.644738 8.4 4.904484 12.8

6.837189 4.2 6.401348 8.6 0.226847 12.9


178








0 0.0 15.36026 4.6 15.89846 9.4

3.772542 0.2 15.56171 4.8 15.40464 9.6

4.515159 0.4 15.73419 5.0 14.91229 9.8

5.389462 0.6 15.89486 5.2 13.98394 10.0

6.296688 0.8 16.01394 5.4 13.07966 10.2

7.131681 1.0 16.13792 5.6 12.97893 10.2

8.03088 1.2 16.26437 5.8 12.84299 10.2

8.836229 1.4 16.38705 6.0 12.01258 10.4

9.55215 1.6 16.44568 6.2 11.8316 10.6

10.36929 1.8 16.55378 6.4 11.86763 10.8

11.10011 2.0 16.60734 6.6 12.0989 11.0

11.8316 2.2 16.63781 6.8 12.17571 11.2

12.1708 2.4 16.29319 7.0 12.59861 11.4

12.63563 2.6 15.73074 7.2 12.61729 11.6

12.80401 2.6 15.19958 7.4 11.94985 11.8

13.1858 2.8 15.09868 7.6 11.36201 12.0

13.49798 3.0 14.98371 7.8 10.50982 12.2

13.7602 3.2 15.07592 8.0 9.608328 12.4

14.03226 3.4 15.25772 8.2 4.931837 12.6

14.36901 3.6 15.5057 8.4 0.886096 12.8

14.54803 3.8 15.7486 8.6 14.6915 4.0 15.91976 8.8 14.95209 4.2 15.97151 9.0 15.17272 4.4 16.01754 9.2


179








0 0.0 13.61607 3.0 16.69218 6.0

4.04181 0.2 13.95102 3.2 16.76638 6.2

5.362273 0.4 14.31709 3.4 16.83517 6.4

6.669634 0.6 14.63189 3.6 16.92624 6.6

7.532143 0.8 14.93637 3.8 16.68449 6.8

8.541738 1.0 15.19925 4.0 16.6455 7.0

9.198693 1.2 15.43249 4.2 16.75377 7.2

9.901344 1.4 15.65327 4.4 16.80503 7.4

10.41859 1.6 15.8264 4.6 16.0593 7.6

11.01331 1.8 16.15201 4.8 8.541738 7.8

11.36578 2.0 16.19443 5.0 8.338148 8.0

11.81309 2.2 16.30024 5.2 8.162403 8.2

12.22583 2.4 16.42341 5.4 7.867419 8.4

12.70688 2.6 16.52414 5.6 13.15664 2.8 16.63011 5.8


180








0 0.0 14.77438 4.2 15.95677 8.4

4.162686 0.2 15.15454 4.4 15.60266 8.6

5.03142 0.4 15.24823 4.6 14.89821 8.8

5.641369 0.6 15.42331 4.8 14.04864 9.0

6.458837 0.8 15.52421 5.0 13.47865 9.2

7.235031 1.0 15.7278 5.2 12.72981 9.4

8.009424 1.2 15.85097 5.4 11.15646 9.6

8.819358 1.4 15.9114 5.6 10.2874 9.8

9.493184 1.6 15.83442 5.8 6.580369 10.0

10.22385 1.8 15.55713 6.0 6.600678 10.2

10.93338 2.0 15.22054 6.2 6.053624 10.4

11.49747 2.2 14.82598 6.4 5.586008 10.6

11.95804 2.4 14.79666 6.6 5.147874 10.8

12.44302 2.6 14.93113 6.8 4.28995 11.0

12.84463 2.8 15.22054 7.0 3.145559 11.2

13.21708 3.0 15.45804 7.2 2.536757 11.4

13.52664 3.2 15.77054 7.4 0.73279 11.6

13.82588 3.4 16.0331 7.6 0.790443 11.8

14.12119 3.6 16.17543 7.8 0.570148 11.6

14.36672 3.8 16.23063 8.0 0.317586 11.5

14.57947 4.0 16.17658 8.2 0.030301 11.3


181








0 0.0 13.73416 5.6 12.01471 11.6

3.932072 0.3 13.78756 5.8 12.30511 11.8

4.747739 0.4 13.93971 6.0 12.42844 12.0

6.123891 0.7 14.1035 6.2 12.37472 12.2

6.402331 0.8 14.21455 6.4 11.95689 12.4

6.832439 0.8 14.33985 6.6 11.19937 12.6

7.652037 1.0 14.41241 6.8 10.44234 12.8

8.755971 1.2 14.4907 7.0 10.48787 13.0

8.904037 1.3 14.5192 7.2 10.51637 13.2

9.346267 1.4 14.53018 7.4 10.64609 13.4

10.09314 1.6 14.56211 7.6 10.86197 13.6

10.72045 1.8 14.5934 7.8 10.71177 13.8

11.25817 2.0 14.61223 8.0 9.854992 14.0

11.67092 2.2 14.64139 8.2 9.728385 14.2

12.13034 2.4 14.68004 8.4 9.630767 14.4

12.45563 2.6 14.67447 8.6 9.269451 14.6

12.80663 2.8 14.6065 8.8 8.138817 14.8

13.09555 3.0 14.52756 9.0 7.378183 15.0

13.32731 3.2 14.37359 9.2 6.963798 15.2

13.52337 3.4 14.14609 9.4 4.239175 15.4

13.73744 3.6 14.04159 9.6 5.436469 15.6

13.81737 3.8 13.73416 9.8 3.14949 15.8

13.79476 4.0 12.45612 10.0 3.262176 16.0

13.81016 4.2 12.17588 10.2 3.212385 16.2

13.83358 4.4 11.59459 10.4 3.381251 16.4

13.79476 4.6 11.32467 10.6 3.587133 16.6

13.6503 4.8 11.27242 10.8 1.532569 16.8

13.35876 5.0 11.34318 11.0 0.029318 17.0

13.33698 5.2 11.45144 11.2 13.47374 5.4 11.68074 11.4


182








0 0.0 17.1141 3.4 21.65923 6.8

3.684752 0.2 17.55519 3.6 21.7485 7.0

4.578218 0.4 17.90258 3.8 21.88903 7.2

5.528191 0.6 18.22311 4.0 21.96945 7.4

6.592654 0.8 18.43194 4.2 22.109 7.6

7.685123 1.0 18.78262 4.4 22.07526 7.8

8.701266 1.2 19.11527 4.6 21.66923 8.0

9.736245 1.4 19.40092 4.8 21.68675 8.2

10.80922 1.6 19.6674 5.0 21.58864 8.4

11.85764 1.8 19.89474 5.2 21.39635 8.6

12.88819 2.0 20.15091 5.4 20.95036 8.8

13.74268 2.2 20.42869 5.6 18.85747 9.0

14.53755 2.4 20.64898 5.8 13.69239 9.2

15.2076 2.6 20.91285 6.0 13.23805 9.4

15.72518 2.8 21.28498 6.2 12.84152 9.6

16.20917 3.0 21.38768 6.4 12.23189 9.8

16.61274 3.2 21.54376 6.6 11.76968 9.8


183








0 0.0 19.18422 4.2 23.73231 8.4

2.609479 0.2 19.44367 4.4 23.99748 8.6

3.540126 0.4 19.83234 4.6 24.25905 8.8

4.481418 0.6 20.15566 4.8 24.34406 9.0

5.622534 0.8 20.46178 5.0 24.38648 9.2

6.649815 1.0 20.81998 5.2 24.34586 9.4

7.657443 1.2 21.1392 5.4 23.91591 9.6

8.564995 1.4 21.4319 5.6 23.61815 9.8

9.491874 1.6 21.73098 5.8 23.65991 10.0

10.49115 1.8 21.95749 6.0 23.17772 10.2

11.58116 2.0 22.18401 6.2 22.61855 10.4

12.60238 2.2 22.43608 6.4 21.48169 10.6

13.61803 2.4 22.53616 6.6 20.83112 10.8

14.54688 2.6 22.36615 6.8 20.61869 11.0

15.37729 2.8 22.16649 7.0 20.15222 11.2

16.13579 3.0 22.27098 7.2 20.14746 11.4

16.78865 3.2 22.47212 7.4 20.08522 11.6

17.32948 3.4 22.71289 7.6 19.85838 11.8

17.79497 3.6 22.96332 7.8 19.71572 12.0

18.21574 3.8 23.23504 8.0 19.709 12.2

18.63717 4.0 23.50022 8.2 19.63596 12.3


184








0 0.0 22.11735 2.4 22.94268 4.8

4.524331 0.2 22.37319 2.6 22.91615 5.0

6.38284 0.4 22.60429 2.8 23.04947 5.2

8.633459 0.6 22.94907 3.0 22.93024 5.4

11.09389 0.8 23.10221 3.2 22.6567 5.6

13.80099 1.0 23.22145 3.4 22.11965 5.8

16.76818 1.2 23.42176 3.6 22.11784 6.0

19.61253 1.4 23.56999 3.8 21.45679 6.2

20.87157 1.6 23.7061 4.0 20.13404 6.4

21.20849 1.8 23.65074 4.2 19.0984 6.6

21.45548 2.0 23.59947 4.4 21.81303 2.2 23.32644 4.6


185








0 0.0 22.4885 1.8 24.00272 3.6

4.283398 0.2 22.80625 2.0 23.98142 3.8

5.760115 0.4 23.04898 2.2 23.35035 4.0

7.613874 0.6 23.1787 2.4 22.63689 4.2

9.813719 0.8 23.40358 2.6 21.81762 4.4

12.35785 1.0 23.56393 2.8 20.03691 4.6

15.09279 1.2 23.74901 3.0 19.57765 4.8

18.01232 1.4 23.86088 3.2 19.62023 5.0

20.97394 1.6 23.97176 3.4 19.30559 5.2


186








0 0.0 23.09877 3.6 28.15279 7.2

4.325001 0.2 23.67122 3.8 28.12249 7.4

5.714583 0.4 24.27641 4.0 27.60607 7.6

7.24404 0.6 24.78072 4.2 27.7656 7.8

8.778576 0.8 25.23753 4.4 28.04748 8.0

10.32589 1.0 25.63946 4.6 28.23208 8.2

11.83405 1.2 26.02338 4.8 28.48758 8.4

13.29897 1.4 26.41287 5.0 28.77912 8.6

14.70952 1.6 26.79024 5.2 28.90754 8.8

16.02016 1.8 27.13763 5.4 28.59945 9.0

17.30557 2.0 27.45735 5.6 28.73458 9.2

17.61857 2.2 27.75675 5.8 28.55653 9.4

18.70826 2.4 27.77002 6.0 27.00398 9.6

19.66626 2.6 27.92398 6.2 26.13476 9.8

20.49846 2.8 28.00768 6.4 24.17339 10.0

21.24256 3.0 28.06698 6.6 23.80601 10.0

21.96535 3.2 28.25254 6.8 22.69208 3.4 28.23027 7.0


187








0 0.0 21.84088 3.6 30.56229 7.2

4.191185 0.2 22.75154 3.8 30.84302 7.4

5.589448 0.4 23.32283 4.0 31.15471 7.6

7.066985 0.6 23.98863 4.2 31.43954 7.8

8.414636 0.8 24.64559 4.4 31.43315 8.0

9.703162 1.0 25.29698 4.6 31.78251 8.2

11.11469 1.2 25.85861 4.8 31.94384 8.4

12.67232 1.4 26.40026 5.0 31.96366 8.6

11.30976 1.6 26.91979 5.2 31.93762 8.8

13.32158 1.8 27.49322 5.4 31.65083 9.0

14.71083 2.0 27.8529 5.6 31.31408 9.2

15.82492 2.2 28.2645 5.8 30.69479 9.4

17.00616 2.4 28.68691 6.0 29.61166 9.6

18.07521 2.6 29.21726 6.2 28.62696 9.8

19.01257 2.8 29.44803 6.4 27.83144 10.0

19.87312 3.0 29.7987 6.6 27.04886 10.2

20.61623 3.2 29.89976 6.8 26.16293 10.4

21.20767 3.4 30.36656 7.0 25.76689 10.5


188








0 0.0 19.49166 3.6 30.78962 7.2

2.382141 0.2 20.57364 3.8 31.18714 7.4

3.662148 0.4 21.76062 4.0 31.54731 7.6

4.726446 0.6 22.67669 4.2 31.9119 7.8

5.766339 0.8 23.63354 4.4 32.15218 8.0

6.544499 1.0 24.50523 4.6 32.37985 8.2

6.614764 1.2 25.26586 4.8 32.58688 8.4

7.589798 1.4 25.97129 5.0 32.67336 8.6

8.554348 1.6 26.63906 5.2 32.665 8.8

9.520373 1.8 27.09488 5.4 32.61014 9.0

10.56731 2.0 27.65045 5.6 32.45699 9.2

11.64029 2.2 28.16197 5.8 32.1969 9.4

12.74226 2.4 28.68216 6.0 31.90764 9.6

13.83653 2.6 29.05249 6.2 31.38106 9.8

14.93015 2.8 29.39481 6.4 31.02925 10.0

16.01492 3.0 29.687 6.6 30.16838 10.2

17.16013 3.2 30.03964 6.8 29.10326 10.2

18.3607 3.4 30.4324 7.0


189








0 0.0 26.47887 3.2 30.73607 6.4

4.419506 0.2 26.99284 3.4 30.80814 6.6

5.998264 0.4 27.40133 3.6 30.82239 6.8

8.027113 0.6 27.59018 3.8 30.96079 7.0

10.367 0.8 27.93004 4.0 31.08822 7.2

12.94634 1.0 28.20553 4.2 31.17306 7.4

15.74696 1.2 28.56702 4.4 31.05807 7.6

17.96416 1.4 28.91687 4.6 31.10246 7.8

19.3847 1.6 29.18597 4.8 31.26052 8.0

20.58183 1.8 29.48259 5.0 31.30278 8.2

21.65743 2.0 29.84441 5.2 31.16405 8.4

22.7237 2.2 30.07649 5.4 30.76506 8.6

23.62716 2.4 30.33888 5.6 29.19629 8.8

24.37321 2.6 30.50496 5.8 27.22444 8.9

25.16464 2.8 30.65745 6.0 25.88924 3.0 30.54558 6.2


190

Appendix G-2 : Screw Spacing Specimen

Test Sample : S2-15-1







0 0.0 11.41197 3.6 8.274434 7.2

4.120429 0.3 11.57313 3.8 7.972407 7.4

4.902847 0.4 11.71186 4.0 7.977485 7.6

6.002032 0.7 11.79982 4.2 7.840886 7.8

6.606412 0.8 11.83864 4.4 7.117104 8.0

7.230119 1.0 11.97638 4.6 5.802538 8.2

7.386373 1.2 12.07629 4.8 4.697783 8.4

7.863816 1.4 12.2242 5.0 4.363982 8.6

8.348959 1.6 12.38045 5.2 4.53334 8.8

8.731567 1.8 12.42303 5.4 4.382982 9.0

9.099601 2.0 12.4114 5.6 3.922736 9.2

9.443884 2.2 12.37996 5.8 3.365691 9.4

9.780469 2.4 12.2789 6.0 2.801767 9.6

10.10297 2.6 12.06581 6.2 2.120734 9.8

10.4163 2.8 11.7687 6.4 1.203027 10.0

10.85181 3.0 11.06948 6.6 1.113271 10.2

10.95991 3.2 9.217202 6.8 0.802728 10.4

11.1748 3.4 8.685215 7.0 0.841382 10.4


191








0 0.0 11.47535 3.6 9.177728 7.2

3.927649 0.2 11.08849 3.8 8.563849 7.4

4.826685 0.4 10.96712 4.0 7.641391 7.6

5.781409 0.6 11.00708 4.2 6.541059 7.8

6.789691 0.8 10.98301 4.4 5.687885 8.0

7.654003 1.0 11.08341 4.6 5.341145 8.2

8.36681 1.2 11.23032 4.8 5.283982 8.4

9.006896 1.4 11.29338 5.0 5.46284 8.6

9.73379 1.6 11.31549 5.2 5.67773 8.8

10.20271 1.8 11.31091 5.4 5.983032 9.0

10.61432 2.0 11.33106 5.6 6.033643 9.2

10.95041 2.2 11.31124 5.8 6.198742 9.4

11.18577 2.4 11.32008 6.0 5.269242 9.6

11.38019 2.6 11.15793 6.2 1.421357 9.8

11.51122 2.8 10.40974 6.4 0.408161 10.0

11.5602 3.0 10.43006 6.6 0.091066 10.1

11.58034 3.2 10.34931 6.8 11.53415 3.4 10.09281 7.0


192








0 0.0 10.737 2.8 12.50067 5.6

4.706955 0.3 11.0536 3.0 12.50182 5.8

4.985233 0.4 11.27635 3.2 12.50689 6.0

5.40666 0.6 11.4426 3.4 12.47446 6.2

6.001704 0.8 11.6 3.6 12.45579 6.4

6.47538 1.0 11.70957 3.8 11.59033 6.6

6.914333 1.2 11.86304 4.0 11.68418 6.8

7.61666 1.4 11.94707 4.2 11.72235 7.0

8.269521 1.6 12.10479 4.4 11.66895 7.2

8.8151 1.8 12.29905 4.6 10.68081 7.4

9.261588 2.0 12.37062 4.8 7.424863 7.6

9.615862 2.2 12.46431 5.0 6.374487 7.7

9.993721 2.4 12.51246 5.2 10.37944 2.6 12.50869 5.4


193








0 0.0 13.41461 3.8 12.4725 7.6

3.872616 0.2 13.7607 4.0 11.48223 7.8

4.936914 0.4 13.80426 4.2 10.64102 8.0

5.941594 0.6 13.86061 4.4 9.686619 8.2

6.690762 0.8 13.85471 4.6 8.706837 8.4

7.369993 1.0 13.87928 4.8 8.609381 8.6

7.94227 1.2 13.94594 5.0 8.89896 8.8

8.720103 1.4 14.01375 5.2 9.441263 9.0

9.329232 1.6 14.09843 5.4 9.787349 9.2

10.06301 1.8 14.11595 5.6 9.989463 9.4

10.73487 2.0 14.20096 5.8 10.21959 9.6

11.25686 2.2 14.14625 6.0 10.04171 9.8

11.49222 2.4 14.15346 6.2 8.71093 10.0

11.76493 2.6 14.12529 6.4 7.52248 10.2

12.15114 2.8 14.0945 6.6 7.368028 10.4

12.4648 3.0 13.86945 6.8 4.520892 10.6

12.72539 3.2 13.46817 7.0 3.055148 10.8

12.95043 3.4 13.26785 7.2 1.779399 11.0

13.2238 3.6 13.0415 7.4 0.691679 11.0


194








0 0.0 13.94004 3.8 14.96127 7.6

3.756655 0.2 14.16886 4.0 14.66808 7.8

4.576416 0.4 14.3867 4.2 14.23142 8.0

5.295119 0.6 14.60699 4.4 13.95315 8.2

5.991548 0.8 14.77045 4.6 13.78854 8.4

6.663082 1.0 14.90116 4.8 13.77511 8.6

7.613547 1.2 15.00434 5.0 13.64817 8.8

8.565323 1.4 15.0715 5.2 13.47456 9.0

9.532657 1.6 15.1891 5.4 13.20168 9.2

10.05481 1.8 15.24102 5.6 12.79205 9.4

10.61088 2.0 15.21563 5.8 12.18652 9.6

11.14614 2.2 15.23168 6.0 9.462883 9.8

11.64995 2.4 15.09983 6.2 8.721413 10.0

12.10823 2.6 15.06314 6.4 5.106926 10.2

12.49919 2.8 14.95291 6.6 4.939863 10.4

12.80712 3.0 14.87724 6.8 5.140505 10.6

13.11111 3.2 14.96176 7.0 4.224271 10.8

13.42476 3.4 15.06707 7.2 1.917473 11.0

13.69288 3.6 15.08607 7.4 1.528147 11.0


195








0 0.0 13.4567 3.0 15.31275 6.0

3.726681 0.2 13.64457 3.2 15.27967 6.2

4.522857 0.4 13.99917 3.4 15.3026 6.4

5.301507 0.6 14.29268 3.6 15.19303 6.6

6.09883 0.8 14.62927 3.8 15.02809 6.8

6.961505 1.0 15.05282 4.0 14.93391 7.0

7.766854 1.2 15.32373 4.2 14.81189 7.2

8.501118 1.4 15.53403 4.4 14.64958 7.4

9.247502 1.6 15.67342 4.6 14.85169 7.6

9.968171 1.8 15.93106 4.8 14.99189 7.8

10.69883 2.0 15.98101 5.0 11.0762 8.0

11.26325 2.2 15.68619 5.2 7.159853 8.2

11.82537 2.4 15.48326 5.4 7.255014 8.4

12.3811 2.6 15.47818 5.6 7.184257 8.6

12.84102 2.8 15.36222 5.8 3.491153 8.7


196








0 0.0 12.97451 3.0 15.15143 6.0

3.724551 0.2 13.27932 3.2 14.84235 6.2

4.703024 0.4 13.50944 3.4 14.78011 6.4

5.508536 0.6 13.8059 3.6 14.55523 6.6

6.144854 0.8 14.08008 3.8 14.51871 6.8

6.916625 1.0 14.45041 4.0 14.57669 7.0

7.616987 1.2 14.55441 4.2 14.82106 7.2

8.46279 1.4 14.72213 4.4 14.86889 7.4

9.18084 1.6 14.9136 4.6 14.8494 7.6

9.947534 1.8 15.06986 4.8 14.83007 7.8

10.64118 2.0 15.16452 5.0 12.28562 8.0

11.2449 2.2 15.29818 5.2 7.375726 8.2

11.87549 2.4 15.38122 5.4 7.22455 8.3

12.20814 2.6 15.44526 5.6 12.60517 2.8 15.41299 5.8


197








0 0.0 18.94473 3.2 21.45743 6.4

8.253753 0.2 19.29941 3.4 21.69776 6.6

8.741116 0.4 19.64263 3.6 21.95912 6.8

9.269327 0.6 19.97594 3.8 22.18782 7.0

9.932675 0.8 20.28429 4.0 22.3318 7.2

10.80558 1.0 20.49867 4.2 22.42258 7.4

11.68822 1.2 20.70911 4.4 22.4365 7.6

12.54254 1.4 20.97661 4.6 22.38583 7.8

13.54689 1.6 21.14 4.8 22.34359 8.0

14.50296 1.8 21.23847 5.0 22.36986 8.2

15.31954 2.0 21.30133 5.2 22.4843 8.4

16.01253 2.2 21.23634 5.4 22.48176 8.6

16.76363 2.4 21.172 5.6 22.3467 8.8

17.43951 2.6 21.13427 5.8 21.67688 9.0

18.01347 2.8 21.23519 6.0 20.3325 9.2

18.48896 3.0 21.19525 6.2 18.58957 9.3


198








0 0.0 13.61836 3.0 14.8453 6.0

3.468059 0.2 14.12251 3.2 14.62812 6.2

3.987923 0.4 14.60257 3.4 14.37769 6.4

3.681311 0.6 14.97732 3.6 14.04208 6.6

4.626371 0.8 15.37663 3.8 13.59167 6.8

5.560294 1.0 15.79659 4.0 13.43852 7.0

6.581188 1.2 16.04604 4.2 13.11569 7.2

7.524282 1.4 16.37607 4.4 12.43778 7.4

8.443136 1.6 16.62699 4.6 11.11633 7.6

9.303518 1.8 16.74067 4.8 8.973975 7.8

10.13638 2.0 16.62093 5.0 6.008256 8.0

10.92568 2.2 16.24717 5.2 4.617363 8.2

11.71383 2.4 16.1312 5.4 4.149747 8.3

12.4191 2.6 15.97708 5.6 13.06623 2.8 15.51864 5.8


199








0 0.0 13.61296 3.4 7.923926 6.8

3.434319 0.2 13.93382 3.6 6.335178 7.0

4.289786 0.4 14.30021 3.8 4.658474 7.2

5.47021 0.6 14.52428 4.0 3.902262 7.4

6.358927 0.8 14.43256 4.2 3.893581 7.6

7.328555 1.0 14.23716 4.4 3.79842 7.8

8.24397 1.2 14.06436 4.6 3.060553 8.0

9.043421 1.4 14.17492 4.8 3.110672 8.2

9.771299 1.6 14.21947 5.0 3.160791 8.4

10.56321 1.8 13.98951 5.2 3.274788 8.6

8.23709 2.0 13.69141 5.4 3.357338 8.8

10.14572 2.2 13.38693 5.6 3.669518 9.0

11.08439 2.4 13.10423 5.8 3.448568 9.2

11.65814 2.6 12.62433 6.0 1.227595 9.4

12.13542 2.8 12.19701 6.2 0.419299 9.6

12.60648 3.0 11.86026 6.4 0.706911 9.8

13.09997 3.2 10.63348 6.6 0.623871 9.9


200








0 0.0 18.64421 3.8 12.95158 7.6

3.958933 0.2 18.81095 4.0 12.15082 7.8

5.142305 0.4 18.88318 4.2 11.56839 8.0

6.315523 0.6 18.87483 4.4 10.53472 8.2

7.345916 0.8 18.97179 4.6 9.691206 8.4

8.264771 1.0 18.80522 4.8 9.393765 8.6

9.144643 1.2 18.63389 5.0 8.22284 8.8

10.17078 1.4 18.69368 5.2 8.427412 9.0

11.28749 1.6 18.68843 5.4 8.814281 9.2

12.35588 1.8 18.75182 5.6 8.416439 9.4

13.35761 2.0 18.70433 5.8 9.276984 9.6

14.2822 2.2 18.74494 6.0 10.25185 9.8

15.14864 2.4 18.67615 6.2 10.71406 10.0

15.97069 2.6 17.91012 6.4 10.5832 10.2

16.6609 2.8 16.48728 6.6 1.331437 10.4

17.30229 3.0 16.10402 6.8 0.605035 10.6

17.6949 3.2 15.05987 7.0 0.475478 10.8

18.04655 3.4 14.2686 7.2 0.001802 11.0

18.36414 3.6 13.68453 7.4


201








0 0.0 21.36425 2.2 23.7798 4.4

5.076299 0.2 21.6974 2.4 23.95981 4.6

7.617642 0.4 22.05511 2.6 24.06169 4.8

9.67974 0.6 22.37303 2.8 23.80896 5.0

12.74521 0.8 22.58873 3.0 23.49268 5.2

15.25838 1.0 22.81886 3.2 23.36427 5.4

17.73011 1.2 23.00804 3.4 23.15888 5.6

19.4417 1.4 23.20343 3.6 22.887 5.8

20.21053 1.6 23.37492 3.8 22.22889 6.0

20.59461 1.8 23.5089 4.0 21.56293 6.2

20.95707 2.0 23.6586 4.2 19.56667 6.3


202








0 0.0 19.13836 2.6 21.20161 5.2

4.345474 0.2 19.58059 2.8 20.97361 5.4

5.623352 0.4 20.03216 3.0 20.14911 5.6

6.245585 0.6 20.32272 3.2 17.9414 5.8

7.361639 0.8 20.48339 3.4 13.30585 6.0

9.021311 1.0 20.82735 3.6 13.13371 6.2

10.75174 1.2 21.03144 3.8 12.26432 6.4

12.47217 1.4 21.17229 4.0 11.97032 6.6

14.08483 1.6 21.4016 4.2 11.14319 6.8

15.61625 1.8 21.39979 4.4 10.83232 7.0

16.41309 2.0 21.45253 4.6 9.533149 7.2

17.4253 2.2 21.50232 4.8 18.51793 2.4 21.47464 5.0


203








0 0.0 19.66446 3.8 27.5833 7.6

3.804316 0.2 20.34417 4.0 27.79377 7.8

4.232951 0.4 20.99212 4.2 27.847 8.0

4.76985 0.6 21.62582 4.4 27.95838 8.2

5.305603 0.8 22.22529 4.6 27.96493 8.4

5.988437 1.0 22.7802 4.8 27.94232 8.6

6.738589 1.2 23.28533 5.0 27.82685 8.8

7.52854 1.4 23.76342 5.2 27.69321 9.0

8.494893 1.6 24.20189 5.4 27.18104 9.2

9.499573 1.8 24.63396 5.6 25.88072 9.4

10.58189 2.0 25.01739 5.8 24.99479 9.6

11.65192 2.2 25.33203 6.0 24.47247 9.8

12.89425 2.4 25.71497 6.2 23.96767 10.0

14.01015 2.6 26.09299 6.4 23.82894 10.2

15.13848 2.8 26.41975 6.6 23.93885 10.4

16.21425 3.0 26.73766 6.8 24.11852 10.6

17.21352 3.2 27.00202 7.0 23.83091 10.8

18.0934 3.4 27.25638 7.2 22.89699 11.0

18.8768 3.6 27.42001 7.4 22.53026 11.1


204








0 0.0 15.8716 3.8 22.27819 7.6

3.73487 0.2 16.5451 4.0 22.43854 7.8

4.466678 0.4 17.09199 4.2 22.60282 8.0

5.230423 0.6 17.70407 4.4 22.73303 8.2

6.26262 0.8 18.20133 4.6 22.85309 8.4

7.171646 1.0 18.85305 4.8 22.94285 8.6

8.178126 1.2 19.28921 5.0 22.74712 8.8

9.167572 1.4 19.83398 5.2 21.88526 9.0

9.979963 1.6 20.22461 5.4 21.06517 9.2

10.82708 1.8 20.56513 5.6 20.91416 9.4

9.052758 2.0 20.88173 5.8 20.21446 9.6

10.55191 2.2 21.08909 6.0 19.59796 9.8

11.67075 2.4 21.4776 6.2 17.4194 10.0

12.39929 2.6 21.48317 6.4 11.93183 10.2

11.44489 2.8 21.48317 6.6 5.71016 10.4

12.69607 3.0 21.55081 6.8 2.505309 10.6

13.46751 3.2 21.83924 7.0 0.705437 10.7

14.27532 3.4 22.03169 7.2 15.09246 3.6 22.17959 7.4


205

Appendix G-3 : Screw Pattern Specimen

Test Sample : P3-DG-1







0 0.0 18.18692 3.0 22.65752 6.2

4.60082 0.2 18.85632 3.2 22.77267 6.4

5.309697 0.4 19.36112 3.4 22.79068 6.6

6.176303 0.6 19.85133 3.6 22.57088 6.8

6.180561 0.6 20.24344 3.8 22.37008 7.0

7.134629 0.8 20.63031 4.0 22.35517 7.2

8.317019 1.0 20.98885 4.2 22.35517 7.4

9.671386 1.2 21.25123 4.4 22.35517 7.6

10.74142 1.4 21.7051 4.6 22.35534 7.8

11.88482 1.6 21.91622 4.8 21.70755 8.0

12.43712 1.8 22.08476 5.0 21.20014 8.2

14.0144 2.0 22.21579 5.2 17.06775 8.4

15.03268 2.2 22.34338 5.4 7.137904 8.6

15.93433 2.4 22.37385 5.6 7.092535 8.7

16.78816 2.6 22.50389 5.8 17.51407 2.8 22.56187 6.0


206








0 0.0 21.30921 3.4 22.7915 6.8

6.384314 0.2 21.55245 3.6 22.7689 7.0

8.601029 0.4 21.71001 3.8 22.49472 7.2

10.3267 0.6 21.77487 4.0 22.36565 7.4

11.72857 0.8 21.86741 4.2 22.20416 7.6

13.1003 1.0 21.79059 4.4 22.03153 7.8

14.28941 1.2 21.71837 4.6 21.69609 8.0

15.18091 1.4 21.52345 4.8 21.01194 8.2

16.16937 1.6 21.59798 5.0 20.42247 8.4

17.13441 1.8 21.86037 5.2 19.80973 8.6

17.71766 2.0 22.14765 5.4 18.88449 8.8

18.50794 2.2 22.37106 5.6 16.24897 9.0

19.11576 2.4 22.30276 5.8 14.85562 9.2

19.66052 2.6 22.30456 6.0 10.1087 9.4

20.25671 2.8 22.52551 6.2 9.228502 9.6

20.66389 3.0 22.79118 6.4 5.795166 9.8

21.0257 3.2 22.79805 6.6 5.25319 9.9


207








0 0.0 17.20992 3.0 20.04198 6.0

3.594176 0.2 17.58565 3.2 20.02004 6.2

4.685172 0.4 18.20821 3.4 20.26114 6.4

5.55931 0.6 18.81685 3.6 20.63162 6.6

6.490776 0.8 19.27857 3.8 20.85077 6.8

7.479732 1.0 19.70704 4.0 21.18589 7.0

8.548616 1.2 20.08932 4.2 21.49446 7.2

9.677611 1.4 20.62114 4.4 21.71968 7.4

10.81479 1.6 20.78673 4.6 21.91048 7.6

12.09939 1.8 21.13167 4.8 22.08836 7.8

13.27539 2.0 21.27368 5.0 21.9688 8.0

14.38293 2.2 21.26975 5.2 21.02341 8.2

15.50603 2.4 21.48922 5.4 13.4757 8.4

16.26126 2.6 21.33543 5.6 13.67405 8.6

15.20957 2.8 20.63097 5.8 13.24673 8.7


208








0 0.0 18.92675 3.4 24.59825 6.8

4.258666 0.2 19.55603 3.6 24.69194 7.0

5.719332 0.4 20.10619 3.8 24.56943 7.2

6.643427 0.6 20.61246 4.0 24.75025 7.4

7.82336 0.8 21.10203 4.2 24.52291 7.6

9.10779 1.0 21.48529 4.4 24.2145 7.8

10.27036 1.2 21.8322 4.6 24.19616 8.0

11.51483 1.4 22.35992 4.8 24.42742 8.2

12.66986 1.6 22.79871 5.0 24.43987 8.4

13.84193 1.8 23.09795 5.2 24.46215 8.6

14.84973 2.0 23.37803 5.4 24.43643 8.8

15.73451 2.2 23.56623 5.6 23.73476 9.0

16.54445 2.4 23.86465 5.8 23.58702 9.2

17.32834 2.6 23.96046 6.0 23.63109 9.4

15.07706 2.8 23.96046 6.2 22.71911 9.6

17.58679 3.0 24.04842 6.4 20.44343 9.7

18.28633 3.2 24.29639 6.6


209

Test Sample : P3-DM-1







0 0.0 17.76303 3.0 23.46435 5.8

3.740603 0.2 18.42179 3.2 23.47483 6.0

4.681241 0.4 19.06433 3.4 23.39048 6.2

5.413703 0.6 19.75748 3.6 23.17444 6.4

6.339929 0.8 20.30667 3.8 23.1674 6.6

7.573255 1.0 20.85176 4.0 22.95791 6.8

8.804944 1.2 21.23797 4.2 22.71649 7.0

10.0255 1.4 21.68872 4.4 22.59414 7.2

11.23786 1.6 21.93669 4.6 22.74466 7.4

12.36849 1.8 22.52895 4.8 22.95791 7.6

13.47194 2.0 22.90927 5.0 23.06765 7.8

15.46426 2.4 23.18951 5.2 22.71813 8.0

16.24095 2.6 23.38573 5.4 21.7313 8.1

17.063 2.8 23.38623 5.6


210








0 0.0 16.8355 2.6 22.20596 5.2

3.686225 0.2 17.72798 2.8 22.36041 5.4

4.497305 0.4 18.61408 3.0 22.56547 5.6

5.468573 0.6 19.33229 3.2 23.03719 5.8

6.506173 0.8 19.95911 3.4 23.3361 6.0

7.631074 1.0 20.50469 3.6 23.59161 6.2

8.776446 1.2 20.9592 3.8 23.96112 6.4

10.06563 1.4 21.44746 4.0 23.98028 6.6

11.30158 1.6 21.83433 4.2 24.03728 6.8

12.44482 1.8 22.11703 4.4 24.01321 7.0

13.55252 2.0 22.15617 4.6 23.43355 7.2

14.71427 2.2 21.92555 4.8 21.96519 7.4

15.87897 2.4 21.99483 5.0 21.10874 7.4


211








0 0.0 19.62809 3.8 23.11712 7.6

3.823971 0.2 20.0071 4.0 21.97584 8.0

5.068273 0.4 20.56169 4.2 12.30068 8.2

6.127494 0.6 20.69222 4.4 12.14312 8.4

7.212757 0.8 21.03455 4.6 12.31035 8.6

8.290484 1.0 21.19948 4.8 12.65643 8.8

9.335455 1.2 21.45237 5.0 13.03708 9.0

10.4448 1.4 21.65284 5.2 13.24132 9.2

11.56789 1.6 21.81664 5.4 13.60624 9.4

12.63547 1.8 22.02596 5.6 13.89205 9.6

13.47587 2.0 22.16354 5.8 13.81081 9.8

14.29841 2.2 22.27803 6.0 13.71352 10.0

14.99206 2.4 22.52338 6.2 13.01841 10.2

15.67817 2.6 22.72222 6.4 5.71966 10.4

16.51988 2.8 23.0765 6.6 5.413048 10.6

17.24071 3.0 23.14283 6.8 4.928561 10.8

18.03476 3.2 23.26273 7.0 4.47372 11.0

18.64749 3.4 23.22391 7.2 4.321233 11.0

19.15622 3.6 23.10828 7.4


212








0 0.0 18.1802 3.0 24.19517 6.0

4.231478 0.2 18.74396 3.2 24.33931 6.2

5.64317 0.4 19.27611 3.4 24.40957 6.4

7.008185 0.6 19.79761 3.6 24.77301 6.6

7.514948 0.8 20.44491 3.8 24.77301 6.8

8.614623 1.0 20.97673 4.0 24.79366 7.0

9.713972 1.2 21.45679 4.2 24.61103 7.2

10.8636 1.4 21.88805 4.4 24.37764 7.4

12.08923 1.6 22.31783 4.6 24.13997 7.6

13.07295 1.8 22.71878 4.8 23.81322 7.8

14.15624 2.0 23.01049 5.0 22.81263 8.0

15.12161 2.2 23.12121 5.2 22.21235 8.2

16.02965 2.4 23.50579 5.4 21.70903 8.4

16.85761 2.6 23.78325 5.6 17.55977 2.8 24.01828 5.8


213

Test Sample : P4-BX-1







0 0.0 20.01824 2.6 29.73172 5.2

5.163107 0.2 21.26287 2.8 29.82098 5.4

6.38546 0.4 22.40103 3.0 30.28123 5.6

7.473672 0.6 23.44535 3.2 30.59357 5.8

8.419386 0.8 24.50752 3.4 30.85728 6.0

9.095834 1.0 25.36249 3.6 30.85728 6.2

10.18421 1.2 26.09201 3.8 30.94637 6.4

11.3892 1.4 26.8985 4.0 31.09428 6.6

12.88918 1.6 27.5286 4.2 30.94637 6.8

14.43534 1.8 28.36981 4.4 30.86694 7.0

15.97462 2.0 28.63351 4.6 30.47204 7.2

17.35585 2.2 29.0253 4.8 29.1791 7.4

18.69482 2.4 29.51617 5.0 28.22879 7.5


214








0 0.0 20.71532 2.6 29.29506 5.2

4.549227 0.2 21.85823 2.8 29.6626 5.4

5.830218 0.4 22.75842 3.0 29.88928 5.6

7.511507 0.6 23.58358 3.2 30.2655 5.8

9.209175 0.8 24.41972 3.4 30.33543 6.0

10.52571 1.0 25.13892 3.6 30.40423 6.2

11.7402 1.2 25.77098 3.8 30.35149 6.4

12.98106 1.4 26.45594 4.0 30.10516 6.6

14.11612 1.6 27.0749 4.2 29.9204 6.8

15.55254 1.8 27.59477 4.4 29.93744 7.0

16.83304 2.0 28.2016 4.6 29.84752 7.2

18.05458 2.2 28.53934 4.8 28.73801 7.4

19.29118 2.4 28.96748 5.0 27.34057 7.5


215








0 0.0 17.55633 2.4 26.90211 4.8

3.700802 0.2 18.67484 2.6 27.44391 5.0

4.772798 0.4 19.72604 2.8 27.87059 5.2

6.00498 0.6 20.71532 3.0 28.23141 5.4

6.913351 0.8 21.61256 3.2 28.5115 5.6

8.082146 1.0 22.42904 3.4 28.30594 5.8

9.30663 1.2 23.2796 3.6 27.60558 6.0

10.61268 1.4 24.05776 3.8 26.76796 6.2

12.04583 1.6 24.77302 4.0 25.296 6.4

13.61394 1.8 25.3086 4.2 23.09124 6.6

14.86856 2.0 25.95033 4.4 22.99542 6.6

16.18149 2.2 26.39649 4.6


216








0 0.0 25.03606 3.4 31.31654 6.8

4.562821 0.2 25.83486 3.6 31.51521 7.0

6.158613 0.4 26.5213 3.8 31.61872 7.2

8.043656 0.6 27.174 4.0 31.65443 7.4

10.01829 0.8 27.7692 4.2 31.58695 7.6

11.54939 1.0 28.26843 4.4 31.09313 7.8

12.49363 1.2 28.71819 4.6 30.29662 8.0

13.75398 1.4 29.20235 4.8 29.64917 8.2

14.87462 1.6 29.62788 5.0 29.33338 8.4

16.28959 1.8 29.93203 5.2 29.18221 8.6

17.40139 2.0 30.08616 5.4 29.02956 8.8

18.82308 2.2 30.36345 5.6 28.49298 9.0

19.82333 2.4 30.52364 5.8 28.11316 9.2

21.02586 2.6 30.65499 6.0 27.08817 9.4

22.06788 2.8 30.9354 6.2 26.38338 9.6

23.18984 3.0 31.14145 6.4 25.42915 9.7

24.12982 3.2 31.24922 6.6


217








0 0.0 25.62734 3.4 31.80413 6.7

4.786884 0.3 26.44891 3.6 31.75811 6.8

6.619023 0.4 27.17105 3.8 31.6677 6.9

7.664812 0.6 27.81441 4.0 31.70029 7.0

8.804617 0.8 28.33935 4.2 31.78038 7.2

10.02681 1.0 28.81286 4.4 31.66541 7.4

11.34285 1.2 29.22135 4.6 31.33782 7.6

12.77682 1.4 29.74564 4.8 31.07855 7.8

14.19097 1.6 30.03898 5.0 30.73344 8.0

15.73762 1.8 30.30531 5.2 30.51496 8.2

17.29378 2.0 30.58555 5.4 29.7078 8.4

18.79129 2.2 30.91984 5.6 29.72566 8.6

20.26556 2.4 31.06053 5.8 30.06306 8.8

21.57898 2.6 31.21826 6.0 30.41275 9.0

22.72615 2.8 31.52831 6.2 30.56769 9.2

23.68415 3.0 31.68014 6.4 28.83301 9.4

24.7491 3.2 31.78874 6.6


218








0 0.0 21.39979 3.2 31.54829 6.8

4.042957 0.2 22.54238 3.4 31.71896 7.0

5.382583 0.4 23.57654 3.6 31.84836 7.2

6.955444 0.6 24.53716 3.8 31.95924 7.4

8.632804 0.8 25.50106 4.0 31.99838 7.6

9.900198 1.0 26.2214 4.2 32.01313 7.8

10.81021 1.2 26.89867 4.4 32.11844 8.0

11.70286 1.4 27.47111 4.6 32.23391 8.2

12.69132 1.6 27.97459 4.8 32.49745 8.4

13.62197 1.8 28.46219 5.0 32.39852 8.6

14.50888 2.0 28.89 5.2 32.077 8.8

15.90141 2.2 29.38432 5.4 30.95636 9.0

17.30901 2.4 30.0421 5.8 30.30269 9.2

18.76919 2.6 30.4478 6.0 29.51748 9.4

18.77345 2.6 30.97111 6.2 28.16049 9.6

18.04065 2.8 31.20434 6.4 26.29494 9.8

20.12634 3.0 31.37844 6.6


219








0 0.0 21.55998 3.0 28.23666 6.0

5.283819 0.2 22.51044 3.2 27.91006 6.2

6.244602 0.4 23.24634 3.4 27.75102 6.4

7.339528 0.6 23.9888 3.6 26.86378 6.8

8.398257 0.8 24.5257 3.8 26.7126 7.0

9.576881 1.0 25.01755 4.0 26.87983 7.2

10.89538 1.2 25.5651 4.2 27.27063 7.4

12.17162 1.4 26.05794 4.4 28.10874 7.8

13.5232 1.6 26.46823 4.6 28.4427 8.0

15.01843 1.8 26.86853 4.8 28.65267 8.2

15.98347 2.0 27.2423 5.0 28.49069 8.4

17.11148 2.2 27.64472 5.2 27.43311 8.6

18.35742 2.4 27.87714 5.4 25.36872 8.8

19.53932 2.6 28.3559 5.6 20.56742 2.8 28.41404 5.8


220








0 0.0 21.78945 3.2 27.25916 6.4

5.422548 0.2 22.65015 3.4 26.94158 6.6

7.002615 0.4 23.34364 3.6 26.53178 6.8

8.208918 0.6 24.23792 3.8 25.82126 7.0

8.445593 0.8 24.6202 4.0 25.58475 7.2

8.580554 1.0 25.06833 4.2 25.74085 7.4

10.28625 1.2 25.52006 4.4 26.0016 7.6

11.68861 1.4 25.86058 4.6 26.38388 7.8

13.06279 1.6 26.17292 4.8 26.77467 8.0

14.39046 1.8 26.46119 5.0 26.89998 8.2

15.6785 2.0 26.77746 5.2 27.09275 8.4

16.93623 2.2 26.77467 5.4 27.09816 8.6

18.15138 2.4 27.16826 5.6 26.97434 8.8

19.22599 2.6 27.3368 5.8 26.87442 9.0

20.18153 2.8 27.44228 6.0 24.37976 9.2

21.02767 3.0 27.47029 6.2 22.35763 9.4


221

APPENDIX H


222

Appendix H: Published Paper


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225

behaviour and shear strength of screw connections in high

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