API RP 2A 21st 2007 - Joint Only

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    Comparisons on API

    RP 2A - WSD 21st edition2000 Publication vs. 2007 Publication

    Strength of Tubular Joints

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    All right reserved. No part of this document may be reproduced in any form withoutprior written permission of Engineering Dynamics, Inc.

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    OverviewThe old (we will call it API 2000):API RP 2A - WSD 21st edition 2000PublicationRecommended Practice forPlanning, Designing and

    Constructing Fixed OffshorePlatforms Working Stress Design

    Upstream Segment

    API RECOMMENDED PRACTICE 2A-WSD

    (RP 2A-WSD)TWENTY-FIRST EDITION, DECEMEBER 2000

    And the latest (we will call it API 2007):API RP 2A - WSD 21st edition 2007Publication (API 2007)Recommended Practice for Planning,Designing and Constructing Fixed Offshore

    Platforms Working Stress Design

    Upstream Segment

    API RECOMMENDED PRACTICE 2A-WSD (RP 2A-WSD)

    TWENTY-FIRST EDITION, DECEMEBER 2000ERRATA AND SUPPLEMENT 1, DECEMBER 2002ERRATA AND SUPPLEMENT 2, SEMPTEMBER 2005ERRATA AND SUPPLEMENT 3, AUGUST 2007

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    Conclusions1. The latest. The new API RP 2A - WSD 21 st edition with Errata andSupplement 1, 2 an 3 has made wide ranging changes on tubularconnections, fatigue and foundations over the 2000 publication. The newcode should be used if the API RP 2A WSD 21 st edition is selected as designcode.

    2. One stop solution, no interface handling. Based on 35+ yearsexperience in supplying offshore structure software system, EDI is theleading 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

    editionwith Errata and Supplement 1, 2 and 3 is now an essential part in the mostcomprehensive offshore package in the world.

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    Strength of Tubular Joints

    Code ContentsAPI 20004 Connections

    4.1 Connections of Tension and CompressionMembers4.2 Restraint and Shrinkage4.3 Tubular Joints

    API 20074 Strength of Tubular Joints

    4.1 Application4.2 Design Considerations4.3 Simple Joints4.4 Overlapping Joints4.5 Grouted Joints4.6 Internally Ring-stiffened Joints4.7 Cast Joints4.8 Other Circular Joint Types4.9 Damaged Joints4.10 Non-circular Joints

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    Fact:Last major update to joint strength provisionswas 14 th edition. The guidance essentiallyremained unchanged for all editions up to21 st .

    Strength of Tubular JointsBackground

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    Fact:Much further knowledge, including both experimentaldata and numerical studies, has been gained on thebehavior of joints since 14 th edition issued. Over theperiod 1994 to 1996 MSL engineering, under theauspices of a joint industry project, undertook anupdate to the tubular joint database and guidance. This

    work had more recent studies, notably by API/EWI andthe University of Illinois, have formed the basis of thetubular joint strength provisions of ISO.

    Strength of Tubular JointsBackground

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    Fact:The ISO drafting committee took, as a starting

    point for drafting, the relevant provisions fromAPI RP 2A LRFD 1st edition (similar to API RP 2AWSD 20 th edition) because ISO is in LRFD format.For the purpose of the supplement to the 21 st edition of API RP 2A, the draft ISO provisions, inturn, have been used as a starting basis.

    Strength of Tubular JointsBackground

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    Strength of Tubular JointsMajor Update

    API 2007

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    Minimum Capacity Check Revised

    API 2000

    In which Pa is calculated as follows with FS = 1.0

    In SACS program the following equation is used:

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    API 2000

    SF = 1.7 Corresponded to an LRFDresistance factor of 0.95.

    Strength of Tubular JointsMajor Update

    Safety Factor Recalibrated

    API 2007

    SF = 1.6 Corresponded to an LRFDresistance factor of 1.0

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    API 2000

    Section 4.1Fyc the yield strength of the chord

    member at the joint (or 2/3 of thetensile strength if less)

    Strength of Tubular JointsMajor Update

    The 2/3 limits on tensile strength relaxed

    API 2007

    Section 4.2.1The value of yield stress for the chord,in the calculation of joint capacity,should be limited to 0.8 times thetensile strength of the chord formaterials with a yield stress of 72 ksi(500 MPa) or less.

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    API 2000

    Strength of Tubular JointsMajor Update

    Additional guidance on detailing practice

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    Strength of Tubular JointsMajor Update

    Additional guidance on detailing practice - continued

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    API 2000The adequacy of the joint may bedetermined on the basis of (a)punching shear or (b) nominal loads inthe brace.

    Strength of Tubular JointsMajor Update

    Punching shear approach removed

    API 2007The joint interaction ratio, IR, for axialloads and/or bending moments in thebrace should be calculated using thefollowing expression,

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    API 2000

    Strength of Tubular JointsMajor Update

    New Strength factor Q u formulations

    API 2007

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    API 2000

    Strength of Tubular JointsMajor Update

    New chord load factor Q f formulations

    API 2007

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    API 2000N/A

    Strength of Tubular JointsMajor Update

    Strength for axially loaded Y and X joints with short can lengths reduced

    API 2007For simple, axially loaded Y and X joints where athickened joint can is specified, the joint

    allowable capacity may be calculated as follows,

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    Simple T joint:

    Brace 3-4: 16x0.375 5.0ftChord 1-3 & 3-2: 24x0.375 8.25ft

    Can: 24x0.625 1.75ft

    All Fy = 36 ksiLoad at brace joint 4:

    Fx = 10.0 kipFy = 7.5 kipFz = -50.0 kip

    Load at connecting joint 3:Fx = -400.0 kip

    Fy = 50.0 kip

    Strength of Tubular JointsExample

    Member Length shown in ft

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    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 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 11.51 -1.63 3.84 5.12 3.66 6.65 11.15 0.974

    Strength of Tubular JointsExample Results Compared

    API 2007 Brace loads interaction check with final unity check ratio = 1.168

    * * J O I N T C A N D E T A I L R E P O R T * *(UNITY CHECK ORDER)

    EFFT. CHORD * ACTING STRESSES * *** PUNCHING SHEAR ***

    COMM CHRD BRCE ****** CHORD **** CHORD JNT GAP *** BRACE ** BRACE LOAD *CHORD** BRACE * ALLOWABLE STRESSES UNITYJNT 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 -11.51 -2.72 6.40 8.54 7 .20 10.16 21.30 1.168

    Joint Can Length

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    Figure 2.3.1-1 Procedure for Calculation of Wave Plus Current Forces for Static Analysis

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