comparison of as 3990 and as 4100 design provisions for...

Comparison of AS 3990 and AS 4100

Design Provisions for Application to

Bulk Handling Machinery

Simon Edgar – Senior Structural Engineer

Structural Integrity Engineering Pty Ltd

www.siepl.com.au

Slide 1 of 21 © Structural Integrity Engineering Pty Ltd 2016

DISCLAIMER AND COPYRIGHT ACKNOWLEDGEMENT

1. Material presented may be covered by copyright and should not be reproduced without

permission.

2. These notes are intended to provide general information only, across a range of matters. They

should not be relied or acted upon.

3. The authors, contributors and presenters of these notes do not accept any responsibility

whatsoever for any actions or omissions, by any party, arising out of use of these notes or the

material presented.


BACKGROUND

1. AS 4324.1-1995 is the standard for structural design of continuous bulk handling machinery.

2. AS 4324.1-1995 is currently being revised.

3. Both the 1995 version and the proposed revision of AS 4324.1 offer the designer a choice

between limit state design or permissible stress design.

4. Key changes to the proposed revision of AS 4324.1 are the prescription of different

(conventional) limit state partial load factors and a change to the minimum permissible stress

design safety factors.


AGENDA

1. Theoretical comparisons between AS4100 and AS3990.

2. Practical comparisons/case studies for actual machine designs between:

a) AS 4100 vs AS 3990,

b) AS 4324.1-1995 vs AS 4324.1-Revision

3. Conclusions and Questions


AS 4100 vs AS 3990 THEORETICAL COMPARISON APPROACH

1. Desktop comparison of main member strength design provisions of AS 3990 and AS 4100.

2. Considers key differences in strength design limitations only.

a) No consideration of other theoretical aspects such as stiffness, serviceability, fatigue etc.

b) No consideration of practical aspects such as fabrication methods, constructability, steelwork availability,

member rationalisation etc.

3. Limit state load factors and ɸ factors set to provide a total theoretical ‘safety factor’ comparable

with the ‘safety factor’ achieved by compliance with AS 3990.

4. Differences are a direct comparison of member ‘stress ratio’ or member ‘design utilisation’

expressed as a percentage.


AS 4100 vs AS 3990 THEORETICAL COMPARISON – BENDING CAPACITY

1. Slenderness limits for slender sections are similar.

2. Section capacity for compact sections:

a) Basis of design provisions for compact sections similar, but AS 3990 provisions simplified based on ratio of

S/Z ~ 1.1.

b) Minimal difference for I-beams with bending about the major axis (S/Z ~ 1.1).

c) Possible for ~ 20-40% difference with bending about the minor axis (or for sections where S/Z > 1.1).

d) Extreme example - up to 60% difference for tee section.

3. Section capacity for non-compact sections:

a) Standards use similar approach.

b) Differences are possible due to AS3990 simplifying assumptions.


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AS 4100 vs AS 3990 THEORETICAL COMPARISON – BENDING CAPACITY

4. Bending member capacity:

a) Capacity based on reference buckling moment

for both standards.

b) Reference buckling moment differences

possible, due to AS 3990 simplifications.

c) Additional differences in ‘slenderness reduction

factor’ calculation.

d) Practical differences in ‘slenderness reduction

factor’ ~ 10%

e) Larger differences possible where reduction

factor < 0.60.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10

‘Sle

nder

ness

Red

uctio

n F

acto

r’

Fs/Fob (AS3990) or Ms/Mo (AS4100)

AS4100

AS3990

© Structural Integrity Engineering Pty Ltd 2016

of 21

AS 4100 vs AS 3990 THEORETICAL COMPARISON – COMPRESSION CAPACITY

1. Local plate buckling slenderness limits are

similar.

2. Section (yield) capacity for stocky sections

are similar.

3. Member buckling capacity:

a) Single buckling curve provided for AS 3990.

b) 5x buckling curves provided for AS 4100.

c) Extreme differences is the order of 20-25%.

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400

Buc

klin

g R

educ

tion

Fac

tor

l/r Ratio

AS3990

AS4100 (αb -1.0)

AS4100 (αb -0.5)

AS4100 (αb 0.0)

AS4100 (αb 0.5)

AS4100 (αb 1.0)


AS 4100 vs AS 3990 THEORETICAL COMPARISON – TENSION CAPACITY

Slide 9 of 21

1. Yield capacity similar for concentrically

connected members with no holes.

2. At holes, AS 4100 considers fu where

AS 3990 considers fy. Differences vary from

39% (Gr 250 steel) to 9% (Gr 350 steel).

3. Eccentric Connections:

a) Both require reduction factor.

b) AS 3990 based on proportions of connected vs

unconnected.

c) AS 4100 simplified for common sections.

d) Differences in range of 0-15%

0.0

0.2

0.4

0.6

0.8

1.0

0 1 2 3 4

Non

-Uni

form

Str

ess

Red

uctio

n F

acto

r

Ratio of Connected Part (A1) / Unconnected Part (A2)

AS3990

AS4100

UA (~9%)

EA (~3%)

UA (~11%)


AS 4100 vs AS 3990 THEORETICAL COMPARISON – COMBINED ACTIONS

Slide 10 of 21

1. Uniaxial bending:

a) Generally both standards consider linear

addition of utilisations.

b) For specific members, AS 4100 provides

alternative, less conservative provisions.

c) Using less conservative provisions of AS 4100

results in ~ 15% difference for major axis bending.

2. Biaxial bending:

a) AS 3990 based on linear addition of utilisations.

b) AS 4100 similar, except for specific sections

where AS 4100 uses a ‘power law’.

c) Using ‘power law’ ~ 20% difference at 100% total utilisation.

BIAXIAL BENDING

UTILISATION COMPARISON

Axi

al F

orce

Util

isat

ion

(%)

AS 3990 Combined

Actions utilisation

AS 4100 Combined

Actions utilisation

~ 20% Difference


APPROACH TO PRACTICAL COMPARISON (CASE STUDY)

Slide 11 of 21

1. AS 3990 vs AS 4100 case studies:

a) AS 3990 vs AS 4100 using minimum AS 4324.1-1995 requirements.

b) AS 3990 vs AS 4100 using AS 4324.1-1995 per common industry practice.

c) AS 3990 vs AS 4100 using AS 4324.1-Revision requirements.

2. AS4324.1-1995 vs AS4324.1-Revision case studies:

a) AS 4324.1-1995 vs AS 4324.1-Revision using limit state design to AS 4100.

b) AS 4324.1-1995 vs AS 4324.1-Revision using PSD to AS 3990.

c) AS 4324.1-1995 vs AS 4324.1-Revision using PSD to AS 3990, based on current common industry practice.

3. Comparisons made between:

a) Load / Capacity Ratio for the limit state design approach.

b) Stress ratios for the permissible stress design approach.



Slide 12 of 21

4. Some 2100 individual members assessed for 6 actual / existing machine designs.

5. Sample main, additional and special load combinations considered (Generally 6x load

combinations per machine).

Case Study

No.

Machine

SupplierMachine Type Approx. Mass

AS1170.2 Wind

RegionNo. Members

1 1 Reclaimer 2000t D 600

2 1 Stacker 400t D 240

3 2 Reclaimer 2000t D 360


5 1 Shiploader 1000t D 280




Slide 13 of 21

6. Differences are presented as the magnitude of difference in design utilisation or stress ratio

(expressed as a percentage), calculated as:

a) For AS 3990 vs AS 4100 comparisons, differences are calculated as:

Difference (%) = Member Design Stress

AS 3990 Permissible Stress−

Limit State Design ActionAS 4100 Design Capacity

×100

Negative results indicate AS 4100 is more conservative than AS 3990.

b) For AS 4324.1-1995 vs AS 4324.1-Revision Comparisons:

Difference (%) = (AS 4324.1−1995 Utilisation (%)) − (AS 4324.1−Revision Utilisation (%))

Negative results indicate AS 4324.1-Revision is more conservative than AS 4324.1-1995.

7. These comparisons are made to the member capacity limit and not to each other.


AS 3990 vs AS 4100 PRACTICAL COMPARISON (CASE STUDY)

Slide 14 of 21

1. Results for AS 3990 vs AS 4100 comparison of mean differences in utilisation or stress ratio:

a) Results for minimum requirements of AS 4324.1-1995 shown.

b) Case study machine 2 has maximum differences.

c) Case study machine 6 has minimum differences.

-2.5%

0.0%

2.5%

5.0%

E I II/1 III/6 III/8 III/10Mea

n D

iffer

ence

in

Des

ign

Util

isat

ion

AS4324.1-1995 Load Combination

Machine 1 (Mean)

Machine 2 (Mean)

Machine 3 (Mean)

Machine 4 (Mean)

Machine 5 (Mean)

Machine 6 (Mean)



Slide 15 of 21

2. Case study machine 2 results (maximum differences in design utilisation or stress ratio):

Governing

standard:

AS 4324.1-1995

Minimum

Requirements

AS 4324.1-1995

Common industry

Practice

AS 4324.1-Revision

Minimum

Requirements

Load Case

Mean

Difference

(%)

Standard

Deviation

(%)

Mean

Difference

(%)

Standard

Deviation

(%)

Mean

Difference

(%)

Standard

Deviation

(%)

E 2.3 6.9 5.5 8.5 5.1 8.3

I 3.0 8.2 7.4 9.9 6.8 9.8

II/1 2.3 7.3 6.2 8.8 6.2 8.7

III/6 1.9 6.3 5.6 7.7 3.3 7.7

III/8 2.3 6.8 6.4 8.1 3.8 7.7

III/10 2.7 6.9 7.7 8.6 -2.5 10



Slide 16 of 21

3. Case study machine 6 results (minimum differences in design utilisation or stress ratio):

Governing

standard:

AS 4324.1-1995

Minimum

Requirements

AS 4324.1-1995

Common industry

Practice

AS 4324.1-Revision

Minimum

Requirements

Load Case

Mean

Difference

(%)

Standard

Deviation

(%)

Mean

Difference

(%)

Standard

Deviation

(%)

Mean

Difference

(%)

Standard

Deviation

(%)

E 0.2 4.0 2.0 4.3 1.8 4.3

I 0.1 5.8 2.6 6.0 2.3 6.0

II/1 0.6 6.8 3.7 7.2 3.7 7.3

III/6 -0.4 6.5 2.1 6.4 0.8 6.4

III/8 0.0 5.7 2.7 5.7 1.5 6.2

III/10 2.1 7.4 6.1 8.4 -3.5 9.7


AS 4324.1-1995 vs AS 4324.1-REVISION PRACTICAL COMPARISON (CASE STUDY)

Slide 17 of 21

1. Results for AS 4324.1-1995 vs AS 4324.1-Revision comparison of mean differences in utilisation

using the limit state design approach. Proposed AS 4324.1-Revision is slightly more

conservative.

-10.0%

-7.5%

-5.0%

-2.5%

0.0%E I II/1 III/6 III/8 III/10

Mea

n D

iffer

ence

in

Des

ign

Util

isat

ion

AS 4324.1 Load Combination

Machine 1 (Mean)

Machine 2 (Mean)

Machine 3 (Mean)

Machine 4 (Mean)

Machine 5 (Mean)

Machine 6 (Mean)

Differences for ‘wind

while idle’ (LC III/10),

differences ~ 5-10%

Differences are small

for operational

loading (< 3%)


AS 4324.1-1995 vs AS 4324.1-REVISION PRACTICAL COMPARISON (CASE STUDY)

Slide 18 of 21

2. Results for AS 4324.1-1995 vs AS 4324.1-Revision comparison of mean differences in stress

ratio using the permissible stress design approach. Proposed AS 4324.1-Revision slightly more

conservative.

-10.0%

-7.5%

-5.0%

-2.5%

0.0%E I II/1 III/6 III/8 III/10

Mea

n D

iffer

ence

in

Str

ess

Rat

io

AS 4324.1 Load Combination

Machine 1 (Mean)

Machine 2 (Mean)

Machine 3 (Mean)

Machine 4 (Mean)

Machine 5 (Mean)

Machine 6 (Mean)

Differences are small

for all load

combinations (< 5%)


CONCLUSIONS

Slide 19 of 21

1. Limit state design vs permissible stress design:

a) The theoretical comparisons show potential for large differences in individual member design.

b) The theoretical differences amount to little practical difference in overall machine design outcomes for typical

‘case study’ machines.

2. AS 4324.1-1995 vs AS 4324.1-Revision:

a) The revision provides slight increase in safety factor / reliability for both design approaches.

b) The slight increase in safety factor / reliability amounts to little practical difference in overall machine design

outcomes for typical ‘case study’ machines.


of 21

THANK YOU

QUESTIONS?

Structural Integrity Engineering Pty Ltd

www.siepl.com.au


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