Structural Design Calculation Sample

Doc. No :

UPD-BC-G4-CS-DR-6003

DESIGN OF JACKET STRAND JACK SUPPORT

Doc. Class : Document type:

Disciplin Discipline e : Error! Unknown Unknown Revision : D1

System/Subsystem :

Contractor Job No : 365

Rev. Date :

document property name.

Contract No : 4600006595

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UJUNG PANGKAH DEVELOPMENT OFFSHORE PHASE II (WHP-B EPCC)

HESS (INDONESIA-PANGKAH) LTD

Strandjack Bracket Design For Jacket and Topside

D1

22-July-09

Issued For Approval

DBES

HK M

MARK

A

18-May-09

Issued for Review

DBES

HKM

MARK

By

Check

App

Rev.

Date

Description

Cont Contra ract ctor or Appr Approv oval al

By

Date

Comp Compan any y Appr Approv oval al

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TABULA TABULATION TION OF REVISE REVISED D PA PAGES GES REVISIONS

SHEET B1 1

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TABLE OF CONTENTS

CHAPTER

PAGE

1.0

INTRODUCTION

4

2.0

SCOPE OF WORK

4

3.0

DESIGN SPECIFICATION

4

4.0

DESIGN APPROACH

5

5.0

DESIGN OF STRAND JACK SUPPORT

6

6.0

MANUAL DESIGN VERIFICATION

11

APPENDICES APPENDIX – A STRAND JACK SPECIFICATION SPECIFICATION APPENDIX – B WEIGHT CONTROL SUMMARY & ESTIMATION ESTIMATION OF REQUIRED PULL FORCE APPENDIX APPENDIX – C STRAND STRAND JACK SUPPORT SUPPORT DRAWINGS DRAWINGS APPENDIX APPENDIX – D FEM INPUT & OUTPUT OUTPUT FILES









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1.0 INTRODUCTION This This docume document nt presen presents ts the analy analysis sis and and struc structura turall design design of strand strand jack jack suppor supportt for loadin loading g out WHP-B Jacket Structure at Bakrie Fabrication Yard. Yard. The WHP-B Jacket Structure will be skidded out from its fabrication position onto the transportation barge using hydraulic strand jack system. These strand jacks will be mounted on the existing skid frame temporary support structures that support the entire weight of the WHP-B Jacket Structure. A. For typical strand jack specification and details, refer to Appendix – A.

2.0 SCOPE OF WORK Design checks are limited to global and local strength of the strand jack support and its attachments where the strand jack supports are to be mounted and maximum pull forces are supported. Detai Detailed led skid skid frame, frame, tie back back syste system m and jacket jacket member member struct structura urall integr integrity ity streng strength th check checkss are beyond the scope of this report.

3.0 DESIGN SPECIFICATION st

(1) API RP 2A 21 Edition – Recommended Practice fo Planning, Designing and Constructing Fixed Offshore Platforms (WSD) by American Petroleum Institute (2) AISC Manual of Steel Construction (Allowable Stress Design) – by American Institute of Steel Construction Generally, increases in basic allowable stresses ARE NOT allowed for load out condition. The follow following ing basic basic and combi combined ned allow allowabl ablee stresse stressed d criter criteria ia are adopte adopted d (Fy is materia materiall yield yield strength): Axial Tension, Fat Axia Axiall Comp Compre ress ssio ion, n, Fac Fac Bending Stress, Fby Shear Stress, Fv Von Mises Mises Stress Stress,, Fvm Fvm

= 0.60Fy = Max Max 0.60 0.60Fy Fy = 0.66Fy = 0.40Fy = 0.80Fy 0.80Fy for combin combined ed axial, axial, bendi bending ng and and shear shear stres stresses ses









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4.0 DESIGN APPROACH

(a) Strand Jack Support Arrangement The Strand Jack Support System are to be arranged in such the manner that the induced forces due to skidding operation will be adequately transferred to the existing temporary support structures and skid frame system.

(b) Design Loadings / Assumptions The following design loadings are considered: Weight Control Report No: Factored Weight

UPD-BC-W2-WC-RP-0002, Rev 3

= 403.7MT

Assumed vertical static load on support can = 73MT per leg Assumed Assumed coefficien coefficientt of friction friction = 20% during initial skidding stage, Nos of Strand jack, N

= 2 Nos

Estim Estimat ated ed pull pull forc forcee per per jack jack

= 43.4MT / jack

Appe pend ndix ix – B for (Refer (Refer to Ap for Weig Weight ht Cont Contro roll Summ Summar ary y & Estim Estimat atio ion n of Requ Requir ired ed Pull Pull Capacity)

(c) Analysis and Design Methodology Analysis and design are performed using SAP2000 Finite Element Software (FEM) and verified by manual calculation.

(d) Materials All plate materials shall be of ASTM 36 (Min. Yield Strength = 248MPa) or equivalent, unless specified otherwise. All welding shall comply with AWS1.1 and shall be of full penetration welds, unless specified otherwise.









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5.0 DESIGN OF STRAND STRAND JACK SUPPORT SUPPORT

5.1 GENERAL ARRANGEMENT

The Strand Jack Support System are to be arranged in such the manner that the induced forces due to skidding operation will be adequately transferred to the existing temporary support structures and skid frame system. It shall be ensured that the all the strands are clash-free with jacket or other temporary structures. For detail strand jack support drawings, refer to Appendix – C.

SAP2000 Ver.10 software is used for structural modelling and analysis of the strand jack support system. The temporary support can and strand jack supports are modelled as finite element (shell element) with appropriate restraint conditions (fixed-supported).

The following presents the isometric view of the simplified structural model of strand jack support system:

Temporary Support Can Dia1181x32thk

Strand Jack Support (Typ)

Top FLG/Ring FLG/Ring Plate PL25

Exist'g Bottom FLG/Ring PL25











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5.2 ELEMENT PROPERTIES

The following table summarizes the element and material properties assumed in the analysis:

S/N

Description

Element Type

Shell Grp

Shell Thk

Material Yield Strength

[mm]

[Mpa]

1

Strand Jack Support

Shell

PL25

25

248

2

Support Can Dia1181mm

Shell

PL32

32

248

3

Exist'g Bottom Flange Plate

Shell

PL25

25

248

4

Additional Top Flange/Stiff Plate

Shell

PL25

25

248

5.3 LOAD COMBINATION

The following table summarizes all the basic load cases, associated load factors and combined load condition: Basic Load Case

Load

Combined Load Condition

Case

1000

Jacket Weight = 73MT* per leg

STA1

1.00

Stand Jack Pull Force = 44MT per leg

PUL2

1.00

Note *Assumed max static vertical load on each leg for design purpose only.

-









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5.4 ANALYSIS RESULT

The following following presen presents ts the Finite Finite Elemen Elementt Model Model Analys Analysis is results results – Max Von Mises Mises Stres Stresses ses (Combined Axial, bending, and shear stresses) of the proposed strand jack design:

(a) Von Mises Stress – Overall

(b) Von Mises Stress – Support Can (32mm thk Pipe Wall)









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(c) Von Mises Stress – Strand Jack Support Bottom Flange / Skid Frame Top Flange Plate

(d) Von Mises Stress – Strand Jack Support Support Top Flange Plate (with additional flange plate)









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Findings

Generally, the overall stress level (Von Mises Stress) is less than 105MPa. High stress zones (i.e. 186MPa) are limited to areas such as the strand jack bearing surface, mainly attributed to modelling technique using point load at strand jack supporting joint locations. Stress levels on Temporary Support Can are also less than 90MPa (at interface between strand jack support and support can). For detailed FEM Input & Output Files, refer to Appendix – D .

Summary

Conserva Conservatively tively,, max Von Mises Stress Stress is found found to be 186.7MPa, 186.7MPa, which is within the allowable stress (0.80Fy = 0.80 x 248 = 198MPa) as specified in Section 3.0. Therefore, the strand jack design appears to be structurally fit.









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6.0 MANUAL DESIGN VERIFICATION

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APPENDIX – A STRAND JACK SPECIFICATION

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APPENDIX – B WEIGHT CONTROL SUMMARY AND ESTIMATION ESTIMATION OF REQUIRED REQUIRED PULL FORCE FORCE









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APPENDIX – C STRAND JACK SUPPORT DRAWINGS











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APPENDIX – D

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Structural Design Calculation Sample

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