The document compares the 2000 and 2007 editions of API RP 2A - WSD 21st edition recommended practice for planning, designing and constructing fixed offshore platforms. Major updates in the 2007 edition include expanded guidance on strength of tubular joints, including new formulations for joint capacity factors and relaxed limits on chord material properties. The 2007 edition also overhauls the fatigue provisions, including changing the S-N curves for tubular connections to bilinear curves without an endurance limit and updating the recommended stress concentration factor equations. These changes are fully implemented in the SACS offshore structural analysis software.

1. Comparisons on API
Comparisons on API
RP 2A ‐ WSD 21st edition
2000 Publication vs. 2007 Publication
Strength of Tubular Joints
And
Fatigue
g
Prepared for Shell reference only. All right reserved. No part of this document may be
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Prepared for Shell reference only. All right reserved. No part of this document may be
reproduced in any form without prior written permission of Engineering Dynamics, Inc.

2. Overview
Overview
The old (we will call it API 2000):
API RP 2A WSD 21st diti 2000
And the latest (we will call it API 2007):
API RP 2A WSD 21st diti 2007
API RP 2A ‐ WSD 21st edition 2000
Publication
Recommended Practice for
Planning Designing and
API RP 2A ‐ WSD 21st edition 2007
Publication (API 2007)
Recommended Practice for Planning,
Designing and Constructing Fixed Offshore
Planning, Designing and
Constructing Fixed Offshore
Platforms – Working Stress Design
Designing and Constructing Fixed Offshore
Platforms – Working Stress Design
Upstream Segment
Upstream Segment
API RECOMMENDED PRACTICE 2A-WSD
(RP 2A-WSD)
API RECOMMENDED PRACTICE 2A-WSD (RP 2A-
WSD)
TWENTY-FIRST EDITION, DECEMEBER 2000
TWENTY-FIRST EDITION, DECEMEBER 2000 ERRATA AND SUPPLEMENT 1, DECEMBER 2002
ERRATA AND SUPPLEMENT 2, SEMPTEMBER 2005
ERRATA AND SUPPLEMENT 3, AUGUST 2007
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3. Conclusions
Conclusions
1. The latest. The new API RP 2A ‐ WSD 21st edition with Errata and
Supplement 1, 2 an 3 has made wide ranging changes on tubular
Supplement 1, 2 an 3 has made wide ranging changes on tubular
connections, fatigue and foundations over the 2000 publication. The new
code should be used if the API RP 2A – WSD 21st edition is selected as design
code.
2. One stop solution, no interface handling. Based on 35+ years
experience in supplying offshore structure software system, EDI is the
leading software company with integrated graphics modeling, pre‐
processing, solving and graphics post‐processing capabilities.
3. Demand the best. Fully implemented in post processor, joint can and
fatigue programs in SACS 5.3 release, the new API RP 2A – WSD 21st edition
with Errata and Supplement 1, 2 and 3 is now an essential part in the most
comprehensive offshore package in the world.
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4. Strength of Tubular Joints
g
Code Contents
API 2000
4 Connections
API 2007
4 Strength of Tubular Joints
4 Connections
4.1 Connections of Tension and Compression
Members
4.2 Restraint and Shrinkage
4 3 Tubular Joints
4 Strength of Tubular Joints
4.1 Application
4.2 Design Considerations
4.3 Simple Joints
4 4 Overlapping Joints
4.3 Tubular Joints 4.4 Overlapping Joints
4.5 Grouted Joints
4.6 Internally Ring-stiffened Joints
4.7 Cast Joints
4 8 Oth Ci l J i t T
4.8 Other Circular Joint Types
4.9 Damaged Joints
4.10 Non-circular Joints
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5. Strength of Tubular Joints
Background
Fact:
Last major update to joint strength provisions
Last major update to joint strength provisions
was 14th edition. The guidance essentially
remained unchanged for all editions up to
remained unchanged for all editions up to
21st.
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6. Strength of Tubular Joints
Background
Fact:
Much further knowledge, including both experimental
data and numerical studies has been gained on the
data and numerical studies, has been gained on the
behavior of joints since 14th edition issued. Over the
period 1994 to 1996 MSL engineering, under the
auspices of a joint industry project, undertook an
update to the tubular joint database and guidance. This
work had more recent studies, notably by API/EWI and
work had more recent studies, notably by API/EWI and
the University of Illinois, have formed the basis of the
tubular joint strength provisions of ISO.
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7. Strength of Tubular Joints
Background
Fact:
The ISO drafting committee took, as a starting
point for drafting, the relevant provisions from
API RP 2A LRFD 1st edition (similar to API RP 2A
WSD 20th di i ) b ISO i i LRFD f
WSD 20th edition) because ISO is in LRFD format.
For the purpose of the supplement to the 21st
edition of API RP 2A the draft ISO provisions in
edition of API RP 2A, the draft ISO provisions, in
turn, have been used as a starting basis.
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8. Strength of Tubular Joints
Major Update
API 2000
Safety Factor Recalibrated
API 2007
API 2000
SF = 1.7 Corresponded to an LRFD
resistance factor of 0 95
API 2007
SF = 1.6 Corresponded to an LRFD
resistance factor of 1 0
resistance factor of 0.95. resistance factor of 1.0
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9. Strength of Tubular Joints
Major Update
Th 2/3 li it t il t th l d
API 2000
The 2/3 limits on tensile strength relaxed
API 2007
Section 4.1
Fyc – the yield strength of the chord
Section 4.2.1
The value of yield stress for the chord,
yc y g
member at the joint (or 2/3 of the
tensile strength if less)
y ,
in the calculation of joint capacity,
should be limited to 0.8 times the
tensile strength of the chord for
materials with a yield stress of 72 ksi
materials with a yield stress of 72 ksi
(500 MPa) or less.
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10. Strength of Tubular Joints
Major Update
Additional guidance on detailing practice
API 2000
API 2000
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11. Strength of Tubular Joints
Major Update
Additional guidance on detailing practice ‐ continued
API 2007
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12. Strength of Tubular Joints
Major Update
Punching shear approach removed
API 2000
h d f h b
Punching shear approach removed
API 2007
h f l
The adequacy of the joint may be
determined on the basis of (a)
punching shear or (b) nominal loads in
the brace.
The joint interaction ratio, IR, for axial
loads and/or bending moments in the
brace should be calculated using the
following expression,
g p ,
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13. Strength of Tubular Joints
Major Update
New Strength factor Qu formulations
API 2000
API 2007
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14. Strength of Tubular Joints
Major Update
New chord load factor Qf formulations
API 2000
f
API 2007
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15. Strength of Tubular Joints
Major Update
Strength for axially loaded Y and X joints with short can lengths reduced
API 2000
N/A
API 2007
For simple, axially loaded Y and X joints where a
thi k d j i t i ifi d th j i t
thickened joint can is specified, the joint
allowable capacity may be calculated as follows,
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16. Strength of Tubular Joints
Major Update
API 2000
Implementation into SACS joint can program
API 2007
API 2000
Fully implemented
API 2007
Fully implemented
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17. Strength of Tubular Joints
Simple T joint:
Example
p j
Brace 3‐4: φ16x0.375” – 5.0ft
Chord 1‐3 & 3‐2: φ24x0.375” – 8.25ft
Can: φ24x0.625” – 1.75ft
φ
All Fy = 36 ksi
Load at brace joint 4:
Fx = 10.0 kip
p
Fy = 7.5 kip
Fz = ‐50.0 kip
Load at connecting joint 3:
Fx = ‐400.0 kip
Fy = 50.0 kip
Member Length shown in ft
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18. Strength of Tubular Joints
API 2000 – Punching shear joint check with final unity check ratio = 0.98
g
Example Results Compared
* * J O I N T C A N D E T A I L R E P O R T * *
(JOINT ORDER)
CHORD * ACTING STRESSES * *** PUNCHING SHEAR ***
COMMON CHORD BRACE ****** CHORD ***** JOINT GAP *** BRACE ** BRACE LOAD *CHORD** BRACE * ALLOWABLE STRESSES UNITY
JOINT JOINT JOINT O.D. WT FY TYPE O.D. WT ANGLE CASE SRSS FA OPB IPB FA OPB IPB CHECK
(IN) (IN) (KSI) (IN) (IN) (IN) (DEG) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI)
( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )
3 1 4 24.00 0.625 36.0 T 16.00 0.375 90.00 1 11.68 -1.63 3.84 5.12 3.64 6.62 11.03 0.981
API 2007 Brace loads interaction check with final unity check ratio = 1 25
API 2007 – Brace loads interaction check with final unity check ratio = 1.25
* * J O I N T C A N D E T A I L R E P O R T * *
(JOINT ORDER)
EFFT. CHORD * ACTING STRESSES * *** PUNCHING SHEAR ***
COMM CHRD BRCE ****** CHORD **** CHORD JNT GAP *** BRACE ** BRACE LOAD *CHORD** BRACE * ALLOWABLE STRESSES UNITY
JNT JNT JNT O D WT FY LNGTH TYP O D WT ANGLE CASE STRESS FA OPB IPB FA OPB IPB CHECK
JNT JNT JNT O.D. WT FY LNGTH TYP O.D. WT ANGLE CASE STRESS FA OPB IPB FA OPB IPB CHECK
(IN) (IN) (KSI) (FT) (IN) (IN) (IN) (DEG) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI)
3 1 4 24.00 0.625 36.0 3.5 T 16.00 0.375 90.00 1 -15.13 -2.72 6.40 8.54 6.61 9.67 20.27 1.251
Joint Can Length
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19. Fatigue
Fatigue
Code Contents
API 2000
5 F i
API 2007
5 F i
5 Fatigue
5.1 Fatigue Design
5.2 Fatigue Analysis
5.3 S-N curves for all members and
5 Fatigue
5.1 Fatigue Design
5.2 Fatigue Analysis
5.3 Stress concentration factors
connections, except tubular connections
5.4 S-N curves for tubular connections
5.5 Stress concentration factors
5.4 S-N curves for all members and
connections, except tubular connections
5.5 S-N curves for tubular connections
5.6 Fracture mechanics
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20. Fatigue
Background
Fact:
Th API S N f t b l ti d i d th b i f
The new API S‐N curves for tubular connections are derived on the basis of
the proposed ISO hotspot design approach. The new API “WJ” curves are
bilinear, with slope exponents of m = 3 and m = 5, and no endurance limit.
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21. Fatigue
Background
Fact:
Th i l i f th EWI t d th t th Efth i ti
The main conclusion from the EWI study was that the Efthymiou equations
and the Lloyd’s design equations have considerable advantages in
consistency and coverage in comparison with other available equations.
Use of Efthymiou SCF equations is recommended because this set of
Use of Efthymiou SCF equations is recommended because this set of
equations is considered to offer the best option for all joint types and load
types.
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22. Fatigue ‐ Major Update
API 2000
g j p
S‐N curves for tubular connections changed
API 2007
API 2000
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23. Fatigue ‐ Major Update
S N curves for tubular connections changed ti d
API 2000
Basic Curves:
Profile control 11 1 3d: X curve
S-N curves for tubular connections changed - continued
API 2007
Basic Curves:
Profile control – 11.1.3d: X curve
Non‐profiled Joints ‐ X’ curve
Endurance Limit: Yes
Profiling – 11.1.3d: WJ1 curve
Burr Grinding – WJ2 curve
Hammer Peening – WJ3 curve
Non‐profiled Joints ‐ WJ curve
API S N C API X' API X Non profiled Joints WJ curve
Cast Joints – CJ curve
Endurance Limit: No
100
ss
s
(ksi)
API S-N Curves API X API X
API WJT in Water API WJT in Air
10
Stres
1
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10,000 100,000 1,000,000 10,000,000 100,000,000 1,000,000,000
Cycles

24. Fatigue ‐ Major Update
API 2000
g j p
Thickness effect corrections are now dependent on weld improvement techniques
API 2007
API 2000 API 2007
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25. Fatigue ‐ Major Update
API 2000
g j p
Recommended SCF formulations in unstiffened tubular joints changed
API 2007
API 2000
No specific requirement. C5.4 listed
empirical formulas to estimate hot
API 2007
For unstiffened welded tubular joints,
SCFs should be evaluated using the
spot SCF:
1) The Kuang formulas;
2) SCF formulas based on the
K ll f l
Efthymiou equations.
Kellogg formula;
3) SCF formulas developed by
Lloyds Register;
4) Other more recent works by
4) Other more recent works by
Gibstein, Buitrago and Tebbett.
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26. Fatigue ‐ Major Update
API 2000
Implementation into SACS fatigue program
API 2007
API 2000
Fully implemented
API 2007
Fully implemented
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27. Fatigue ‐ Example
Example frame:
Two bay frame with 10m x 10m
g p
Two bay frame with 10m x 10m
for each bay.
Two basic load cases:
own
Load case 1:
Fx = 60.0 kN at joint 3, 4, 5 and 6
ckness
in
cm
sho
Load case 2:
Fx = ‐60.0 kN at joint 3, 4, 5 and 6
Diameter
by
thic
Fx 60.0 kN at joint 3, 4, 5 and 6
D
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28. Fatigue ‐ Example
API 2000
Fatigue parameters
g p
API 2007
Fatigue parameters
Fatigue parameters
Design fatigue life = 20 yrs
Period for cycle data 20 yrs
Fatigue parameters
Period for cycle data = 20 yrs
Life safety factor = 1.0
Number of occurrences = 250000
D i lifi ti f t 1 5
Same as left hand side
Dynamic amplification factor = 1.5
Stress range determined by max/min
search on load cases.
S‐N curve: API X’ curve with
thickness correction.
S‐N curve: API standard WJ curve
with thickness correction.
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29. Fatigue – Example
g p
Results Compared
API 2000 fatigue Results for joint 3 and 4
* * * M E M B E R F A T I G U E R E P O R T * * *
(DAMAGE ORDER)
ORIGINAL
JOINT MEMBER GRUP TYPE OD WT JNT MEM FATIGUE RESULTS
API 2007 fatigue Results for joint 3 and 4
* * * M E M B E R F A T I G U E R E P O R T * * *
(DAMAGE ORDER)
ORIGINAL
JOINT MEMBER GRUP TYPE OD WT JNT MEM FATIGUE RESULTS
JOINT MEMBER GRUP TYPE OD WT JNT MEM FATIGUE RESULTS
ID ID (CM) (CM) TYP TYP DAMAGE LOC SVC LIFE
3 3- 2 D01 TUB 36.00 1.250 TK BRC 2.495754 T 8.013609
3 1- 3 COL TUB 60.00 3.000 TK CHD 2.198595 T 9.096718
3 3- 6 D01 TUB 36.00 1.250 TK BRC .6093029 T 32.82439
3 3- 5 COL TUB 60 00 3 000 TK CHD 3792182 T 52 74008
JOINT MEMBER GRUP TYPE OD WT JNT MEM FATIGUE RESULTS
ID ID (CM) (CM) TYP TYP DAMAGE LOC SVC LIFE
3 3- 2 D01 TUB 36.00 1.250 TK BRC .4588493 T 43.58730
3 1- 3 COL TUB 60.00 3.000 TK CHD .6680558 T 29.93762
3 3- 6 D01 TUB 36.00 1.250 TK BRC .1480694 T 135.0718
3 3- 5 COL TUB 60 00 3 000 TK CHD 1631456 T 122 5899
3 3 5 COL TUB 60.00 3.000 TK CHD .3792182 T 52.74008
3 3- 4 H01 TUB 48.00 1.750 TK BRC .2284094 B 87.56207
3 1- 3 COL TUB 60.00 3.000 TK CHD .2344230 B 85.31586
4 3- 4 H01 TUB 48.00 1.750 T BRC .1258805 T 158.8809
4 2- 4 COL TUB 60.00 3.000 T CHD .2057996 T 97.18193
3 3 5 COL TUB 60.00 3.000 TK CHD .1631456 T 122.5899
3 3- 4 H01 TUB 48.00 1.750 TK BRC .0673998 B 296.7369
3 1- 3 COL TUB 60.00 3.000 TK CHD .1031036 B 193.9796
4 3- 4 H01 TUB 48.00 1.750 T BRC .0417927 T 478.5526
4 2- 4 COL TUB 60.00 3.000 T CHD .0928771 T 215.3383
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30. This is the end of this report.
p
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