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Comparison of AS 3990 and AS 4100 Design Provisions for...
Transcript of 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.
Slide 2 of 21 © Structural Integrity Engineering Pty Ltd 2016
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.
Slide 3 of 21 © Structural Integrity Engineering Pty Ltd 2016
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
Slide 4 of 21 © Structural Integrity Engineering Pty Ltd 2016
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.
Slide 5 of 21 © Structural Integrity Engineering Pty Ltd 2016
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.
Slide 6 of 21 © Structural Integrity Engineering Pty Ltd 2016
Slide 7 of 21
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
Slide 8 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)
© Structural Integrity Engineering Pty Ltd 2016
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%)
© Structural Integrity Engineering Pty Ltd 2016
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
© Structural Integrity Engineering Pty Ltd 2016
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.
© Structural Integrity Engineering Pty Ltd 2016
APPROACH TO PRACTICAL COMPARISON (CASE STUDY)
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
4 2 Stacker 400t D 270
5 1 Shiploader 1000t D 280
6 3 Stacker 500t D 380
© Structural Integrity Engineering Pty Ltd 2016
APPROACH TO PRACTICAL COMPARISON (CASE STUDY)
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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.
© Structural Integrity Engineering Pty Ltd 2016
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)
© Structural Integrity Engineering Pty Ltd 2016
AS 3990 vs AS 4100 PRACTICAL COMPARISON (CASE STUDY)
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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
© Structural Integrity Engineering Pty Ltd 2016
AS 3990 vs AS 4100 PRACTICAL COMPARISON (CASE STUDY)
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
© Structural Integrity Engineering Pty Ltd 2016
AS 4324.1-1995 vs AS 4324.1-REVISION PRACTICAL COMPARISON (CASE STUDY)
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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%)
© Structural Integrity Engineering Pty Ltd 2016
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%)
© Structural Integrity Engineering Pty Ltd 2016
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.
© Structural Integrity Engineering Pty Ltd 2016
Slide 20 of 21
THANK YOU
QUESTIONS?
Structural Integrity Engineering Pty Ltd
www.siepl.com.au
© Structural Integrity Engineering Pty Ltd 2016