Comparisons on API RP 2A ‐ WSD 21st edition 2000 Publication vs. 2007 Publication Strength of Tubular Joints
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Overview The old (we will call it API 2000): API RP 2A ‐ WSD 21st edition 2000 Publication
And the latest (we will call it API 2007): API RP 2A ‐ WSD 21st edition 2007 Publication (API 2007)
Recommended Practice for Planning, Recommended Practice for Planning, Designing and Constructing Fixed Designing and Constructing Fixed Offshore Offshore Platforms – Working Stress Platforms – Working Stress Design Design Upstream Segment Upstream Segment API RECOMMENDED PRACTICE 2A-WSD (RP 2A-WSD) API RECOMMENDED PRACTICE 2A-WSD (RP TWENTY-FIRST EDITION, DECEMEBER 2000 2A-WSD) ERRATA AND SUPPLEMENT 1, DECEMBER 2002 TWENTY-FIRST EDITION, DECEMEBER 2000 ERRATA AND SUPPLEMENT 2, SEMPTEMBER 2005 ERRATA AND SUPPLEMENT 3, AUGUST 2007
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Conclusions 1.
2.
3.
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 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. 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. 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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Strength of Tubular Joints Code Contents API 2000
API 2007
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 4.5 Grouted Joints 4.6 Internally Ring-stiffened Joints 4.7 Cast Joints 4.8 Other Circular Joint Types 4.9 Damaged Joints 4.10 Non-circular Joints
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Strength of Tubular Joints Background Fact: Last major update to joint strength provisions was 14th edition. The guidance essentially remained unchanged for all editions up to 21st.
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Strength of Tubular Joints Background Fact: Much further knowledge, including both experimental 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 the University of Illinois, have formed the basis of the tubular joint strength provisions of ISO. 6/24/2010
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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 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 turn, have been used as a starting basis. 6/24/2010
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Strength of Tubular Joints Major Update Minimum Capacity Check Revised
API 2000
API 2007
In SACS program the following equation is used:
In which Pa is calculated as follows with FS = 1.0
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Strength of Tubular Joints Major Update Safety Factor Recalibrated
API 2000
API 2007
SF = 1.7 Corresponded to an LRFD resistance factor of 0.95.
SF = 1.6 Corresponded to an LRFD resistance factor of 1.0
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Strength of Tubular Joints Major Update The 2/3 limits on tensile strength relaxed
API 2000
API 2007
Section 4.1 Fyc – the yield strength of the chord member at the joint (or 2/3 of the tensile strength if less)
Section 4.2.1 The value of yield stress for the chord, 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 (500 MPa) or less.
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Strength of Tubular Joints Major Update Additional guidance on detailing practice
API 2000
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Strength of Tubular Joints Major Update Additional guidance on detailing practice ‐ continued
API 2007 6/24/2010
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Strength of Tubular Joints Major Update Punching shear approach removed
API 2000
API 2007
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,
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Strength of Tubular Joints Major Update New Strength factor Qu formulations
API 2000 API 2007
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Strength of Tubular Joints Major Update New chord load factor Qf formulations
API 2000
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API 2007
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Strength of Tubular Joints Major Update Strength for axially loaded Y and X joints with short can lengths reduced
API 2000
API 2007
N/A
For simple, axially loaded Y and X joints where a thickened joint can is specified, the joint allowable capacity may be calculated as follows,
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Strength of Tubular Joints Major Update Implementation into SACS joint can program
API 2000
API 2007
Fully implemented
Fully implemented
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Strength of Tubular Joints Example Simple T joint: Brace 3‐4: φ16x0.375” – 5.0ft Chord 1‐3 & 3‐2: φ24x0.375” – 8.25ft Can: φ24x0.625” – 1.75ft All Fy = 36 ksi Load at brace joint 4: Fx = 10.0 kip 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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Strength of Tubular Joints Example Results Compared API 2000 – Punching shear joint check with final unity check ratio = 0.974 * * J O I N T
C A N D E T A I L (JOINT ORDER)
COMMON CHORD BRACE ****** CHORD ***** JOINT GAP *** BRACE ** JOINT JOINT JOINT O.D. WT FY TYPE O.D. WT (IN) (IN) (KSI) (IN) (IN) (IN) 3
1
4
24.00 0.625
36.0
T
16.00 0.375
R E P O R T * *
CHORD * ACTING STRESSES * *** PUNCHING SHEAR BRACE LOAD *CHORD** BRACE * ALLOWABLE STRESSES ANGLE CASE SRSS FA OPB IPB FA OPB IPB (DEG) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI)
*** UNITY CHECK
90.00
0.974
1
11.51
-1.63
3.84
5.12
3.66
6.65
11.15
API 2007 – Brace loads interaction check with final unity check ratio = 1.168 * * J O I N T
EFFT. COMM CHRD BRCE ****** CHORD **** CHORD JNT JNT JNT JNT O.D. WT FY LNGTH TYP IN IN KSI FT 3
1
4
24.00 0.625
36.0
3.5
T
GAP IN
C A N D E T A I L (UNITY CHECK ORDER)
CHORD *** BRACE ** O.D. WT IN IN 16.00 0.375
R E P O R T * *
* ACTING STRESSES BRACE LOAD *CHORD** BRACE ANGLE CASE STRESS FA OPB DEG KSI KSI KSI
* *** PUNCHING SHEAR * ALLOWABLE STRESSES IPB FA OPB IPB KSI KSI KSI KSI
*** UNITY CHECK
90.00
8.54
1.168
1 -11.51
-2.72
6.40
7.20
10.16
21.30
Joint Can Length 6/24/2010
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