fatigue in concrete.pdf

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European Union Brite EuRam III

Fatigue of normal weight concrete

and lightweight concrete

EuroLightCon

Economic Design and Construction with

Light Weight Aggregate Concrete

Document BE96-3942/R34, June 2000

Project funded by the European Union

under the Industrial & Materials Technologies Programme (BriteEuRamIII)

Contract BRPR-CT97-0381, Project BE96-3942


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The European Union Brite EuRam III

Fatigue of normal weight concrete and

lightweight concrete

EuroLightCon






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Information on the project and the partners on the internet:: http://www.sintef.no/bygg/sement/elcon

ISBN 90 376 02 78 9


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The European Union Brite EuRam III

Fatigue of normal weight concrete and

lightweight concrete

Euro-LightCon





Selmer ASA, NO

SINTEF, the Foundation for Scientific and Industrial Research at the

Norwegian Institute of Technology, NO

NTNU, University of Technology and Science, NO

ExClay International, NO

Beton Son B.V., NL

B.V. VASIM, NL

CUR, Centre for Civil Engineering Research and Codes, NL

Smals B.V., NL

Delft University of Technology, NL

IceConsult, Lnuhnnun hf., IS

The Icelandic Building Research Institute, IS

Taywood Engineering Limited, GB

Lias-Franken Leichtbaustoffe GmbH & Co KG, DE

Dragados y Construcciones S.A., ESEindhoven University of Technology, NL

Spanbeton B.V., NL


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Fatigue of normal weight and lightweight concrete

BE96-3942 EuroLightCon 5

Table of Contents

PREFACE 9

SUMMARY 12

SYMBOLS 14

1. INTRODUCTION 17

2. THEORIES 18

2.1 Miners hypothesis 18

2.2 Other hypothesises of damage development 19

2.2.1 Marco and Starkey 19

2.2.2 Manson, Nachtigall and Freche 19

2.2.3 Freudenthal and Heller 19

2.2.4 Haibach 19

2.2.5 Corten and Dolan 20

2.2.6 Shanley 20

2.2.7 Cornelissen and Reinhardt 202.3 Methods for counting 20

2.3.1 Peak count 21

2.3.2 Mean crossing peak count 21

2.3.3 Range count 22

2.3.4 Range mean count 22

2.3.5 Range pair count 23

2.3.6 Level crossing count 24

2.3.7 Fatigue meter count 24

2.3.8 Rain-flow count 25

2.3.9 TNO method for counting cycles 25

2.3.10Summary of methods for counting 26

3. EXPERIMENTAL RESEARCH 27

3.1 Factors influencing fatigue 27

3.1.1 Aggregates 27

3.1.2 Concrete strength 27

3.1.3 Water penetration 31

3.1.4 Frequency 31

3.1.5 Humidity 31


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3.1.6 Wave forms 32

3.1.7 Stress gradients 36

3.1.8 Rest periods 36

3.1.9 Two axial loads 37

3.2 Remnant strength and stiffness 38

3.3 Deformations 38

3.3.1 Deformations under cyclic compression 38

3.3.2 Deformations under cyclic tension 40

3.4 Fatigue under tension 41

3.4.1 Results of tests under cyclic tension 41

3.5 Fatigue under shear 41

3.6 Fatigue of reinforcement 42

3.7 Test set-up in previous tests 42

3.7.1 Experimental loads [2, p5] 42

3.7.2 CUR research 42

3.7.3 Research at Trondheim University 43

4. FATIGUE IN SOME STANDARDS 44

4.1 Dutch Code (VBB1995) 44

4.1.1 Modulus of elasticity of concrete 44

4.1.2 Fatigue of concrete under compression 44

4.1.3 Fatigue of concrete under tension 45

4.1.4 Material check concrete 464.1.5 Material check reinforcement 47

4.1.6 Material check pre-stressing steel 48

4.2 Euro Code 2, part 2 49


4.2.2 Fatigue of concrete under shear 51

4.2.3 Fatigue verification for reinforcement and pre-stressing steel 52

4.2.4 Fatigue of concrete 53

4.2.5 Material check pre-stressing steel 54

4.3 Model Code 1990 564.3.1 Modulus of elasticity of concrete 56


4.3.3 Fatigue of concrete under tension 58

4.3.4 Fatigue of concrete under shear 58

4.3.5 Fatigue of reinforcement 59

4.3.6 Fatigue of pre-stressing steel 59

4.4 Comparison of the codes 60

4.4.1 Loading and material factors 60

4.4.2 Modulus of elasticity 60

4.4.3 Ultimate fatigue compressive stresses 61


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4.4.4 Hypothesises of damage development and methods for counting 62

4.4.5 Stress gradient 62

4.4.6 Frequency 62

4.4.7 Maximum number of cycles under compression 63

4.4.8 Diameter of the reinforcement 63

4.4.9 Couplers of reinforcement 63

4.4.10Bending diameter of reinforcement 63

5. PROPOSAL FOR TESTS ON LWAC 64

5.1 Shape and dimensions 64

5.2 Storage/testing conditions 64

5.3 Age of specimens 64

5.4 Concrete Quality 64

5.5 Test set-up 65

5.5.1Type of tests 655.5.2 Method for counting 65

5.5.3 Stress gradient 65

5.5.4 Frequency 65

5.5.5 Stress levels 65

5.6 Additional research 66

6. REFERENCES 67

7. NOMENCLATURE 70


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PREFACEThe lower density and higher insulating capacity are the most obvious characteristics of Light-

Weight Aggregate Concrete (LWAC) by which it distinguishes itself from ordinary Normal

Weight Concrete (NWC). However, these are by no means the only characteristics, which jus-

tify the increasing attention for this (construction) material. If that were the case most of the

design, production and execution rules would apply for LWAC as for normal weight concrete,

without any amendments.

LightWeight Aggregate (LWA) and LightWeight Aggregate Concrete are not new materials.

LWAC has been known since the early days of the Roman Empire: both the Colosseum and thePantheon were partly constructed with materials that can be characterised as lightweight aggre-

gate concrete (aggregates of crushed lava, crushed brick and pumice). In the United States, over

100 World War II ships were built in LWAC, ranging in capacity from 3000 to 140000 tons and

their successful performance led, at that time, to an extended use of structural LWAC in build-

ings and bridges.

It is the objective of the EuroLightCon-project to develop a reliable and cost effective design and

construction methodology for structural concrete with LWA. The project addresses LWA manu-

factured from geological sources (clay, pumice etc.) as well as from waste/secondary materials

(fly-ash etc.). The methodology shall enable the European concrete and construction industry toenhance its capabilities in terms of cost-effective and environmentally friendly construction,

combining the building of lightweight structures with the utilisation of secondary aggregate

sources.

The major research tasks are:

Lightweight aggregates: The identification and evaluation of new and unexploited sources spe-

cifically addressing the environmental issue by utilising alternative materials from waste. Further

the development of more generally applicable classification and quality assurance systems for

aggregates and aggregate production.

Lightweight aggregate concrete production: The development of a mix design methodology toaccount for all relevant materials and concrete production and in-use properties. This will include

assessment of test methods and quality assurance for production.

Lightweight aggregate concrete properties: The establishing of basic materials relations, the

influence of materials characteristics on mechanical properties and durability.

Lightweight aggregate concrete structures: The development of design criteria and -rules

with special emphasis on high performance structures. The identification of new areas for

application.

The project is being carried out in five technical tasks and a task for co-ordination/management

and dissemination and exploitation. The objectives of all technical tasks are summarised below.


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Starting point of the project, the project baseline, are the results of international research work

combined with the experience of the partners in the project whilst using LWAC.

This subject is dealt with in the first task.

Tasks 2-5 address the respective research tasks as mentioned above: the LWA itself, production

of LWAC, properties of LWAC and LWAC structures.

Sixteen partners from six European countries, representing aggregate manufacturers and suppli-

ers, contractors, consultants research organisations and universities are involved in the Eu-

roLightCon-project. In addition, the project established co-operation with national clusters and

European working groups on guidelines and standards to increase the benefit, dissemination and

exploitation.

At the time the project is being performed, a Working Group under the international concrete

association fib (the former CEB and FIP) is preparing an addendum to the CEB-FIP Model

Code 1990, to make the Model Code applicable for LWAC. Basis for this work is a state-of-the-

art report referring mainly to European and North-American Standards and Codes. Partners in

the project are also active in the fibWorking Group.

General information on the EuroLightCon-project, including links to the individual project part-

ners, is available through the web site of the project:

http://www.sintef.no/bygg/sement/elcon/

At the time of publication of this report, following EuroLightCon-reports have been published:

R1 Definitions and International Consensus Report. April 1998

R1a LightWeight Aggregates Datasheets. Update September 1998

R2 LWAC Material Properties State-of-the-Art. December 1998

R3 Chloride penetration into concrete with lightweight aggregates. March 1999

R4 Methods for testing fresh lightweight aggregate concrete, December 1999

R5 A rational mix design method for lightweight aggregate concrete using typical UK mate-

rials, January 2000

R6 Properties of Lytag-based concrete mixtures strength class B15-B55, January 2000

R7 Grading and composition of the aggregate, March 2000

R8 Properties of lightweight concretes containing Lytag and Liapor, March 2000

R9 Technical and economic mixture optimisation of high strength lightweight aggregate con-

crete, March 2000

R10 Paste optimisation based on flow properties and compressive strength, March 2000

R11 Pumping of LWAC based on expanded clay in Europe, March 2000

R12 Applicability of the particle-matrix model to LWAC, March 2000

R13 Large-scale chloride penetration test on LWAC-beams exposed to thermal and hygral

cycles, March 2000

R14 Structural LWAC. Specification and guideline for materials and production, June 200

R15 Light Weight Aggregates, June 200

R16 In-situ tests on existing lightweight aggregate concrete structures, June 200

R17 Properties of LWAC made with natural lightweight aggregates, June 2000

R18 Durability of LWAC made with natural lightweight aggregates, June 2000


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R19 Evaluation of the early age cracking of lightweight aggregate concrete, June 2000

R20 The effect of the moisture history on the water absorption of lightweight aggregates,

June 2000

R21 Stability and pumpability of lightweight aggregate concrete. Test methods, June 2000

R22 The economic potential of lightweight aggregate concrete in c.i.p. concrete bridges, June

2000

R23 Mechanical properties of lightweight aggregate concrete, June 2000

R24 Prefabricated bridges, June 2000

R25 Chemical stability, wear resistance and freeze-thaw resistance of lightweight aggregate

concrete, June 2000

R26 Recycling lightweight aggregate concrete, June 2000

R27 Mechanical properties of LWAC compared with both NWC and HSC, June 2000

R28 Prestressed beams loaded with shear force and/or torsional moment, June 2000

R29 A prestressed steel-LWAconcrete bridge system under fatigue loading

R30 Creep properties of LWAC, June 2000

R31 Long-term effects in LWAC: Strength under sustained loading; Shrinkage of High

Strength LWAC, June 2000

R32 Tensile strength as design parameter, June 2000

R33 Structural and economical comparison of bridges made of inverted T-beams with top-

ping, June 2000

R34 Fatigue of normal weight concrete and lightweight concrete, June 2000

R35 Composite models for short- and long-term strength and deformation properties of

LWAC, June 2000

R36 High strength LWAC in construction elements, June 2000

R37 Comparison of bridges made of NWC and LWAC. Part 1: Steel concrete composite

bridges, June 2000

R38 Comparing high strength LWAC and HSC with the aid of a computer model, June 2000

R39 Proposal for a Recommendation on design rules for high strength LWAC, June 2000

R40 Comparison of bridges made of NWC and LWAC. Part 2: Bridges made of box beams

post-tensioned in transversal direction, June 2000

R41 LWA concrete under fatigue loading. A literature survey and a number of conducted

fatigue tests, June 2000

R42 The shear capacity of prestressed beams, June 2000

R43 A prestressed steel-LWA concrete bridge system under fatigue loading, June 2000


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SUMMARYThis report is part of the European Brite Euram III project on economic design and construction

with lightweight aggregate concrete. It is a desk study on fatigue of lightweight aggregate con-

crete (LWAC).

The proposals for the test set-up are based, structurally on the stress levels in the bridges made

of inverted T beams and theoretically on the known theories used in the fatigue test of NDC.

Some end results are presented below:

the Miner hypothesis is sufficient to be used by explaining of fatigue behaviour of LWAC and

in the concrete in general. humidity has large influence on fatigue life of the concrete. Most tests on fatigue are done inall wet and very dry conditions. Generally the fatigue tests on the LWAC should be done in

the condition close to outside average humidity.

because no significant differences have been found different amplitude tests it is best to useconstant amplitude tests. The sinusoidal loading cycle's best describe (fatigue) loading in

practice.

Using proposed test set-up some additional research on LWAC is recommended:

What is the influence of the fatigue on the modulus of elasticity of LWAC?

What happens with time dependent characteristics of LWAC exposed on the cycle loading? How big is the influence of the various stress levels on LWAC and HSLWAC? How much influence have various humidity on the fatigue life of LWAC and HSLWAC?


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Keywords

Light weight aggregate (LWA); light weight aggregate concrete (LWAC); fatigue; fatigue in

codes; research on fatigue


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min minimum normal shear stress under frequent combination of actions at the sec-tion where max occurs;

sfat shear capacity of the reinforcement;u;fat total ultimate shear capacity for fatigue;u;fat maximum shear capacity when shear reinforcement is used; efficiency factor;1 adjusted ration to bond strength taking into account the different diameters of

prestressing and reinforcing steel.

ratio of bond strength of prestressing steel and high bond reinforcing steel.

Latin lower case symbols

c total number of variations during life;

fc;c characteristic compressive cube strength of concrete at 28 days;

fcd design value of concrete cylinder compressive strength;fcd;fat design compressive strength under fatigue;

fctd;fat design tensile strength under fatigue;

fc;k characteristic compressive cylinder strength of concrete at 28 days;

fc;max maximum stress to prevent failure on fatigue;

fc;rep;fat representative compressive strength under fatigue;

fc;t;fat design tensile strength under fatigue;

fc;t;k characteristic axial tensile strength of concrete;

fc;t;m mean value of axial tensile strength of concrete;

fc;u;fat(n) design value of the tensile strength at n cycles;

k1 slope of the appropriate S-N line to be taken from Table 4 or Table 5;k2 slope of the appropriate S-N line to be taken from Table 4 or Table 5;

n number of cycles;

ni number of cycles at the same stress level;

p number of different stresslevels during life;

Latin upper case symbols

Ecd normal modulus of elasticity.

Ec;fat modulus of elasticity under fatigue;

Ms Miner sum;

Ni number of cycles at stresslevel when fatigue failure would occur at constantlevel cyclic loading;

Nobs number of lorries per year according to ENV 1991-3, table 4.5 in million;

Nobs;i number of lorries expected on lane i per year;

Nobs;1 number of lorries on the slow lane per year;

Nyears design working life of the bridge (to be specified, if different from 100 years);

Q factor for traffic type;

R ratio of minimum and maximum relative stress (R = c;min / c;max );Sc;d;max general fatigue quantity;

Su(n) design value of the material strength at fatigue at n cycles;

Vrep;max maximum representative shear force due to dead load, pretentiousness and


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maximum of the variable actions;

VRd1 design shear resistance according to equation 4.18 in ENV 1992-1-1;

Vref shear resistance.


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1. INTRODUCTIONThis report on fatigue of lightweight aggregate concrete (LWAC) is meant as a study to come to

a universal test set-up. Therefore all kinds of publications on fatigue are studied mainly on nor-

mal dense concrete (NDC) but some also on light weight aggregate concrete (LWAC). Also

different codes are studied on regulations on fatigue.

Chapter 1 is this introduction.

Chapter 2 describes some theories about fatigue and methods for counting cycles. Best known

method for fatigue is the Miner hypothesis.

Chapter 3 deals with the results of earlier experimental research. This research is mainly onNDC, some however also compare the results of tests on LWAC.

In chapter 4 fatigue in some standards is described. Used are Dutch code, Euro Code and FIP

Model Code.

And finally, in chapter 5, is proposed a test set-up for tests on fatigue. This set up is based on a

structural behaviour and stress level in the bridge decks made of inverted T beams with struc-

tural topping.


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The Miner hypothesis assumes hypothetical damaging units. Therefore verification of the validity

is necessary. For verification variable amplitude tests and tests with programmed loading are

executed. Validity of Miners hypothesis is sufficiently guaranteed. However, some obje ctions to

Miners hypothesis can be raised when used on concrete. Main reason is the simple use. In addi-

tion, it has never been proven that the hypothesis would not be valid. [1, p8]

2.2 Other hypothesises of damage developmentSome less used hypothesises of damage development are described in CUR report 163 [7]. Most

of these hypothesises are based on crack development. Other hypothesises of damage develop-

ment, like Miner, are phenomenological. Some of these hypothesises of damage development

and their backgrounds will be discussed. [7]

2.2.1 Marco and Starkey

By constant amplitude tests on steel Marco and Starkey proved that damage varies within every

cycle. In other words, damage contribution is not linear. Damage Dc+1 at stress level Sc+2 can be

expressed as function of Miner sum, or total damage appearance:

D f M f N N

c Scii

c

i

cxc

+= =

= =

=

+

11 11

1 11

( )

Where

xc+1 depends on stress level sc+2.

The sequence of the cycles is important because MSc is based on a not linear damage function.

2.2.2 Manson, Nachtigall and Freche

Manson, Nachtigall and Freche publish a hypothesis of damage development based on modified

results of constant amplitude tests. The authors start from the principle that in a programmed

loading, after a block of constant amplitude stress cycles, the damage in the next block will be

larger than according to Miners hypothesis expected.

2.2.3 Freudenthal and Heller

Freudenthal and Heller introduced interaction ratio wi in Miners hypothesis:

MN

w

si

i

i

c

= 1).

2.2.4 Haibach

Haibach adjusted Miners hypothesis with ns:

MN n

si si

c

=

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