ABS Standards OS-501

8/22/2019 ABS Standards OS-501

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OFFSHORE STANDARD

DET NORSKE VERITAS

DNV-OS-C501

COMPOSITE COMPONENTS

OCTOBER 2010


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FOREWORD

DET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life,property and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification andconsultancy services relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carriesout research in relation to these functions.

DNV service documents consist of amongst other the following types of documents:

Service Specifications. Procedual requirements.

Standards. Technical requirements. Recommended Practices. Guidance.

The Standards and Recommended Practices are offered within the following areas:

A) Qualification, Quality and Safety Methodology

B) Materials Technology

C) Structures

D) Systems

E) Special Facilities

F) Pipelines and Risers

G) Asset Operation

H) Marine Operations

J) Cleaner EnergyO) Subsea Systems


3/164DET NORSKE VERITAS

Offshore Standard DNV-OS-C501, October 2010

Changes Page 3

MOTIVES

No design code for Fibre Reinforced Plastic, often called com-posite structures, exists today except for some special applica-tions like FRP pipes, pressure vessels and ships.

The realization of even simple designs of FRP structures tendsto become a major undertaking due to the lack of applicabledesign standards. It is DNV's impression that the lack of a goodFRP guideline is one of the major obstacles to utilize FRPstructurally in a reliable and economical way.

For this reason DNV started a JIP to develop a general standardfor the design of load carrying structures and components fab-ricated from fibre-reinforced plastics and sandwich structures.

Upon termination of the JIP, the members participating i.e.Advanced Research Partnership, ABB Offshore Technology,Ahlstrm Glassfibre, AMOCO, Akzo Nobel Faser AG, Baltek,Devold AMT, FiReCo, MMS, Norsk Hydro, Reichold, SagaPetroleum, Tenax Fibers, Umoe Shat Harding agreed thatDNV shall transform the resulting project report into a DNV

Offshore Standard.The new DNV Offshore Standard is indexed: DNV-OS-C501Composite Components, and has a contents layout as shownoverleaf.

CHANGES

General

As of October 2010 all DNV service documents are primarily

published electronically.

In order to ensure a practical transition from the print schemeto the electronic scheme, all documents having incorporatedamendments and corrections more recent than the date of thelatest printed issue, have been given the date October 2010.

An overview of DNV service documents, their update statusand historical amendments and corrections may be foundthrough http://www.dnv.com/resources/rules_standards/.

Main changes

Since the previous edition (January 2003), this document hasbeen amended, most recently in April 2009. All changes havebeen incorporated and a new date (October 2010) has beengiven as explained under General.




Page 4 Changes




Contents Page 5

CONTENTS

Sec. 1 General................................................................. 11

A. Objectives .............................................................................11A 100 Objectives .......................................................................11

B. Application - Scope ............................................................11B 100 General............................................................................11

C. How to use the standard........................................................11C 100 Users of the standard.......................................................11C 200 Flow chart of the standard ..............................................12C 300 How to use the standard..................................................12

D. Normative References ..........................................................13D 100 Offshore Service Specifications......................................13D 200 Offshore Standards .........................................................13D 300 Recommended Practices.................................................13D 400 Rules ...............................................................................13D 500 Standards for Certification and Classification notes.......13D 600 Other references..............................................................13

Sec. 2 Design Philosophy and Design Principles......... 14

A. General..................................................................................14A 100 Objective......................................................................... 14

B. Safety philosophy .................................................................14B 100 General............................................................................14B 200 Risk assessment .............................................................. 14B 300 Quality Assurance...........................................................14

C. Design format .......................................................................14C 100 General principles...........................................................14C 200 Limit states......................................................................14C 300 Safety classes and Service classes..................................15C 400 Failure types....................................................................15C 500 Selection of partial safety factors ...................................15

C 600 Design by LRFD method................................................15C 700 Structural Reliability Analysis........................................ 17

D. Design approach ...................................................................17D 100 Approaches .....................................................................17D 200 Analytical approach ........................................................17D 300 Component testing ..........................................................17D 400 Analyses combined with updating..................................17

E. Requirements to documentation ...........................................18E 100 Design Drawings and Tolerances ...................................18E 200 Guidelines for the design report...................................... 18

Sec. 3 Design Input ........................................................ 19

A. Introduction ..........................................................................19

A 100 ........................................................................................19B. Product specifications...........................................................19B 100 General Function or main purpose of the product ..........19

C. Division of the product or structure into components,parts and details ....................................................................19

C 100 ........................................................................................19

D. Phases ................................................................................... 19D 100 Phases.............................................................................. 19

E. Safety and service classes.....................................................19E 100 Safety classes ..................................................................19E 200 Service classes ................................................................ 20

F. Functional requirements .......................................................20

F 100 ........................................................................................20

G. Failure modes .......................................................................20G 100 General............................................................................20G 200 Failure modes..................................................................20G 300 Identification of the type of limit states..........................20

H. Exposure from the surroundings...........................................20H 100 General............................................................................20H 200 Loads and environment...................................................21H 300 Obtaining loads from the exposure from

the surroundings............................................................. 21

I. Loads.....................................................................................21I 100 General............................................................................21I 200 Probabilistic representation of load effects..................... 22I 300 Simplified representation of load effects........................22I 400 Characteristic load effect ................................................22I 500 The sustained load effect................................................23I 600 The fatigue load effects ..................................................24

J. Environment .........................................................................25J 100 General............................................................................25J 200 Effects of the environment on the material properties ...26

K. Combination of load effects and environment .....................26K 100 General............................................................................26K 200 Load effect and environmental conditions for ultimate

limit state ....................................................................... 26K 300 Load effect and environmental conditions for time-

dependent material properties......................................... 27K 400 Load effect and environmental conditions for fatigue

analysis ........................................................................... 27K 500 Direct combination of loads............................................ 27

Sec. 4 Materials - Laminates ........................................ 28

A. General..................................................................................28A 100 Introduction.....................................................................28A 200 Laminate specification....................................................28A 300 Lay-up specification ....................................................... 28A 400 Orthotropic plies .............................................................28A 500 Mechanical properties.....................................................29A 600 Characteristic values of mechanical properties .............. 29

A 700 Properties of laminates with damage.............................. 29

B. Static properties ....................................................................29B 100 General............................................................................29B 200 Static properties .............................................................. 30B 300 Relationship between strength and strain to failure........31B 400 Characteristic values.......................................................31B 500 Experimental measurement of matrix

and fibre dominated strain to failure............................... 32B 600 Experimental measurement of ply shear properties........32

C. Properties under long term static and cyclic and highrate loads...............................................................................32

C 100 Introduction.....................................................................32C 200 Creep...............................................................................33C 300 Stress rupture .................................................................. 33C 400 Static strength reduction due to permanent static loads.. 34C 500 Stress relaxation.............................................................. 34C 600 Change of Modulus of elasticity under cyclic fatigue....34C 700 Cycles to failure under cyclic fatigue loads.................... 35C 800 Cycles to failure under fatigue loads for matrix

dominated strengths........................................................ 36C 900 Static strength reduction due to cyclic loads .................. 36C 1000 Effect of high loading rates - shock loads - impact ........37C 1100 Characteristic values.......................................................37

D. Other properties ....................................................................37D 100 Thermal expansion coefficient .......................................37D 200 Swelling coefficient for water or other liquids ...............38D 300 Diffusion coefficient....................................................... 38D 400 Thermal conductivity......................................................38D 500 Friction coefficient.......................................................... 38D 600 Wear resistance............................................................... 38

E. Influence of the environment on properties..........................39E 100 Introduction.....................................................................39E 200 Effect of temperature...................................................... 39E 300 Effect of water ................................................................ 40E 400 Effect of chemicals ......................................................... 41




Page 6 Contents

E 500 Effect of UV radiation.....................................................41E 600 Electrolytic Corrosion .....................................................41E 700 Combination of environmental effects............................41

F. Influence of process parameters ...........................................41F 100 Introduction.....................................................................41F 200 Change of production method.........................................41F 300 Change of processing temperature and pressure.............41F 400 Change of post cure procedure........................................42

F 500 Change of void content ...................................................42F 600 Correction for change in fibre volume fraction ..............42F 700 Control of fibre orientation:............................................42F 800 Control of fibre tension:..................................................42

G. Properties under fire .............................................................42G 100 Introduction.....................................................................42G 200 Fire reaction ....................................................................43G 300 Fire resistance .................................................................43G 400 Insulation.........................................................................43G 500 Properties after the fire....................................................43

H. Qualification of material properties......................................43H 100 Introduction.....................................................................43H 200 General test requirements................................................43H 300 Selection of material qualification method .....................43

H 400 Direct measurement ........................................................43H 500 Representative data .........................................................43H 600 Qualification against representative data ........................44H 700 Confirmation testing for static data.................................46H 800 Confirmation testing for long term data -

high safety class ..............................................................46H 900 Confirmation testing for long term data -

normal safety class..........................................................47H 1000 Use of manufacturers data or data

from the literature as representative data ........................47H 1100 Confirming material data by component testing.............47H 1200 Comparing results from different processes

and lay-ups ......................................................................47

I. Properties with damaged or nonlinearly deformed matrix... 48I 100 Introduction.....................................................................48I 200 Default values .................................................................48

I 300 Experimental approach ...................................................48

Sec. 5 Materials Sandwich Structures...................... 50

A. General..................................................................................50A 100 Introduction.....................................................................50A 200 Sandwich specification ...................................................50A 300 Lay-up specification........................................................50A 400 Isotropic/orthotropic core layers .....................................50A 500 Mechanical and physical properties................................51A 600 Characteristic values of mechanical properties...............51

B. Static properties ....................................................................51B 100 General............................................................................51B 200 Static properties...............................................................51B 300 Relationship between strength and strain to failure ........54

B 400 Characteristic values .......................................................54B 500 Shear properties...............................................................54B 600 Core skin interface properties .........................................55

C. Properties under long term static and cyclic loads ...............56C 100 General............................................................................56C 200 Creep...............................................................................56C 300 Stress rupture under permanent static loads....................56C 400 Static strength reduction due to permanent static loads..56C 500 Stress relaxation..............................................................56C 600 Change of modulus of elasticity under cyclic fatigue.....57C 700 Cycles to failure under fatigue loads...............................57C 800 Static strength reduction due to cyclic loading...............57C 900 Effect of high loading rates - shock loads - impact.........58C 1000 Characteristic values .......................................................58

D. Other properties .................................................................... 58

D 100 Thermal expansion coefficient........................................58D 200 Swelling coefficient for water or other liquids ...............58D 300 Diffusion coefficient .......................................................58D 400 Thermal conductivity ......................................................58D 500 Friction coefficient..........................................................58D 600 Wear resistance ...............................................................58

E. Influence of the environment on properties..........................58E 100 Introduction.....................................................................58E 200 Effect of temperature ......................................................59E 300 Effect of water.................................................................59E 400 Effect of chemicals..........................................................60E 500 Effect of UV radiation.....................................................60E 600 Electrolytic corrosion......................................................60E 700 Combination of environmental effects............................60

F. Influence of process parameters and core density................60F 100 Core production...............................................................60F 200 Sandwich production.......................................................60F 300 Influence of core density.................................................60

G. Properties under fire .............................................................60G 100 Introduction.....................................................................60G 200 Fire reaction ....................................................................60G 300 Fire resistance .................................................................60G 400 Insulation.........................................................................60G 500 Properties after the fire....................................................61

H. Qualification of material properties......................................61H 100 Introduction.....................................................................61H 200 General test requirements................................................61H 300 Selection of material qualification method .....................61

H 400 Direct measurement ........................................................61H 500 Representative data .........................................................61H 600 Qualification against representative data ........................62H 700 Confirmation testing for static data.................................63H 800 Confirmation testing for long term data..........................63H 900 Use of manufacturers data or data from the literature

as representative data ......................................................63H 1000 Confirming material data by component testing.............63

Sec. 6 Failure Mechanisms & Design Criteria ........... 64

A. Mechanisms of failure ..........................................................64A 100 General............................................................................64A 200 FRP laminates - failure mechanisms and failure type.....66A 300 Sandwich structures - failure mechanisms and failure

type..................................................................................67A 400 Displacements and long term failure mechanisms and

failure type ......................................................................67A 500 Link between failure modes and failure mechanisms.....68

B. Design criteria - general approach........................................69B 100 General............................................................................69B 200 Design criteria for single loads ......................................69B 300 Design criteria for combined loads.................................69B 400 Time dependency and influence of the environment......70

C. Fibre failure ..........................................................................70C 100 General............................................................................70C 200 Fibre failure at the ply level ............................................70C 300 Fibre failure check using a modified Tsai-Wu criterion.71C 400 Special considerations for fibre failure under inplane

compressive loads ...........................................................72C 500 Fibre failure checked by component testing ...................72

C 600 Fracture mechanics approach..........................................72D. Matrix cracking.....................................................................73D 100 General............................................................................73D 200 Matrix failure based on simple stress criterion...............73D 300 Matrix failure based on Puck's criterion .........................74D 400 Obtaining orientation of the failure surface ....................75D 500 Matrix cracking caused only by shear.............................75D 600 Matrix failure checked by component testing.................75

E. Delamination.........................................................................76E 100 General............................................................................76E 200 Onset of delamination .....................................................76E 300 Delamination growth.......................................................76

F. Yielding ................................................................................76F 100 General............................................................................76

G. Ultimate failure of orthotropic homogenous materials.........76G 100 General............................................................................76

H. Buckling................................................................................77H 100 Concepts and definitions.................................................77




Contents Page 7

H 200 General requirements......................................................78H 300 Requirements when buckling resistance is determined

by testing......................................................................... 78H 400 Requirements when buckling is assessed by analysis ....78

I. Displacements.......................................................................79I 100 General............................................................................79

J. Long term static loads...........................................................79J 100 General............................................................................79J 200 Creep...............................................................................79J 300 Stress relaxation..............................................................80J 400 Stress rupture - stress corrosion...................................... 80

K. Long term cyclic loads .........................................................81K 100 General............................................................................81K 200 Change of elastic properties............................................ 81K 300 Initiation of fatigue damage............................................81K 400 Growth of fatigue damage ..............................................82

L. Impact ...................................................................................82L 100 General............................................................................82L 200 Impact testing..................................................................82L 300 Evaluation after impact testing ....................................... 82

M. Wear......................................................................................82M 100 General............................................................................82M 200 Calculation of the wear depth......................................... 83M 300 Component testing ..........................................................83

N. High / low temperature / fire ................................................83N 100 General............................................................................ 83

O. Resistance to explosive decompression................................83O 100 Materials .........................................................................83O 200 Interfaces......................................................................... 83

P. Special aspects related to sandwich structures .....................83P 100 General............................................................................83P 200 Failure of sandwich faces ...............................................83P 300 Failure of the sandwich core...........................................83

P 400 Failure of the sandwich skin-core interface....................83P 500 Buckling of sandwich structures.....................................84

Q. Chemical decomposition / galvanic corrosion......................84Q 100 General............................................................................84

R. Requirements for other design criteria .................................84R 100 General............................................................................84

Sec. 7 Joints and Interfaces........................................... 85

A. General..................................................................................85A 100 Introduction.....................................................................85A 200 Joints...............................................................................85A 300 Interfaces......................................................................... 85A 400 Thermal properties..........................................................85

A 500 Examples.........................................................................85

B. Joints .....................................................................................85B 100 Analysis and testing ........................................................85B 200 Qualification of analysis method for other load

conditions or joints ......................................................... 86B 300 Multiple failure modes....................................................86B 400 Evaluation of in-service experience................................86

C. Specific joints .......................................................................86C 100 Laminated joints ............................................................. 86C 200 Adhesive Joints...............................................................86C 300 Mechanical joints............................................................86C 400 Joints in sandwich structures .......................................... 86

D. Interfaces ..............................................................................86

D 100 General............................................................................86

Sec. 8 Safety-, Model- and System Factors.................. 88

A. Overview of the various factors used in the standard...........88A 100 General............................................................................88

B. Partial load effect and resistance factors ..............................88B 100 General............................................................................88B 200 How to select the partial safety factors...........................88B 300 Simplified set of partial safety factors (general)............. 88B 400 Simplified set of partial safety factors

(for known maximum load effect).................................. 89B 500 Full set of partial safety factors ......................................89B 600 Partial safety factors for functional and environmental

loads as typically defined for risers ................................ 89

B 700 Partial safety factors for functional and environmentalloads as typically defined for TLPs ................................ 89

C. Model factors ........................................................................90C 100 General............................................................................90C 200 Load model factors.........................................................90C 300 Resistance model factors ................................................ 90

D. System effect factor..............................................................90D 100 General............................................................................90

E. Factors for static and dynamic fatigueanalysis .................................................................................90

E 100 ........................................................................................ 90

Sec. 9 Structural Analysis............................................. 91

A. General..................................................................................91A 100 Objective......................................................................... 91A 200 Input data ........................................................................ 91A 300 Analysis types.................................................................91A 400 Transfer function ............................................................91A 500 Global and local analysis ................................................ 91A 600 Material levels ................................................................92A 700 Non-linear analysis ......................................................... 92

B. Linear and non-linear analysis of monolithic structures.......92B 100 General............................................................................92B 200 In-plane 2-D progressive failure analysis.......................93B 300 3-D progressive failure analysis .....................................93B 400 Linear failure analysis with non-degraded properties ....93B 500 Linear failure analysis with degraded properties............ 94B 600 Two-step non-linear failure analysis method .................94

B 700 Through thickness 2-D analysis......................................95

C. Connection between analysis methods and failure criteria...95C 100 General............................................................................95C 200 Modification of failure criteria ....................................... 95C 300 Creep, stress relaxation and stress

rupture-stress relaxation.................................................. 96C 400 Fatigue ............................................................................96

D. Analytical methods ...............................................................96D 100 General............................................................................96D 200 Assumptions and limitations........................................... 96D 300 Link to numerical methods .............................................96

E. Finite element analysis .........................................................96E 100 General............................................................................96

E 200 Modelling of structures general ................................... 96E 300 Software requirements....................................................97E 400 Execution of analysis...................................................... 97E 500 Evaluation of results.......................................................98E 600 Validation and verification ............................................. 98

F. Dynamic response analysis...................................................98F 100 General............................................................................98F 200 Dynamics and finite element analysis ............................98

G. Impact response ....................................................................98G 100 Testing ............................................................................ 98

H. Thermal stresses....................................................................98H 100 General............................................................................98

I. Swelling effects ....................................................................99

I 100 General............................................................................99

J. Analysis of sandwich structures ...........................................99J 100 General............................................................................99J 200 Elastic constants..............................................................99J 300 2-D non-linear failure analysis ....................................... 99




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J 400 3-D progressive failure analysis....................................100J 500 Long term damage considerations ................................100

K. Buckling..............................................................................100K 100 General..........................................................................100K 200 Buckling analysis of isolated components ....................100K 300 Buckling analysis of more complex elements

or entire structures.........................................................101K 400 Buckling analysis of stiffened plates and shells............101

K 500 Buckling analysis for sandwich structures....................101

L. Partial load-model factor ....................................................101L 100 General..........................................................................101L 200 Connection between partial load-model factor and

analytical analysis .........................................................101L 300 Connection between partial load-model factor

and finite element analysis............................................101L 400 Connection between partial load-model factor

and dynamic response analysis .....................................102L 500 Connection between partial load-model factor

and transfer function .....................................................102

Sec. 10 Component Testing .......................................... 103

A. General................................................................................103

A 100 Introduction...................................................................103A 200 Failure mode analysis....................................................103A 300 Representative samples.................................................103

B. Qualification based on tests on full scale components .......103B 100 General..........................................................................103B 200 Short term properties.....................................................103B 300 Long term properties.....................................................104

C. Verification of analysis by testing and updating ................104C 100 Verification of design assumptions...............................104C 200 Short term tests..............................................................105C 300 Long term testing ..........................................................105C 400 Procedure for updating the predicted resistance

of a component..............................................................106C 500 Specimen geometry - scaled specimen .........................106

D. Testing components with multiple failure mechanisms .....107D 100 General..........................................................................107D 200 Static tests .....................................................................107D 300 Long term tests..............................................................107D 400 Example of multiple failure mechanisms......................107

E. Updating material parameters in the analysis based oncomponent testing...............................................................108

E 100 .......................................................................................108

Sec. 11 Fabrication........................................................ 109

A. Introduction ........................................................................109A 100 Objective .......................................................................109A 200 Quality system...............................................................109

B. Link of process parameters to production machineparameters........................................................................... 109B 100 Introduction...................................................................109B 200 Process parameters........................................................109B 300 Production machine parameters ....................................109

C. Processing steps..................................................................109C 100 General..........................................................................109C 200 Raw materials................................................................109C 300 Storage of materials ......................................................109C 400 Mould construction .......................................................109C 500 Resin..............................................................................110C 600 Producing laminates and sandwich panels....................110C 700 Producing joints ............................................................110C 800 Injection of resin and cure.............................................110C 900 Evaluation of the final product......................................111

D. Quality assurance and quality control ................................111D 100 .......................................................................................111

E. Component testing..............................................................111E 100 General..........................................................................111E 200 Factory acceptance test and system integrity test .........111

E 300 Pressure testing of vessels and pipes.............................111E 400 Other testing..................................................................111E 500 Dimensions....................................................................111

F. Installation ..........................................................................111F 100 .......................................................................................111

G. Safety, health and environment ..........................................112G 100 .......................................................................................112

Sec. 12 Operation, Maintenance, Reassessment,Repair................................................................ 113

A. General................................................................................113A 100 Objective.......................................................................113

B. Inspection............................................................................113B 100 General..........................................................................113B 200 Inspection methods .......................................................113

C. Reassessment......................................................................113C 100 General..........................................................................113

D. Repair..................................................................................113D 100 Repair procedure ...........................................................113

D 200 Requirements for a repair..............................................113D 300 Qualification of a repair ................................................113

E. Maintenance........................................................................114E 100 General..........................................................................114

F. Retirement...........................................................................114F 100 General..........................................................................114

Sec. 13 Definitions, Abbreviations & Figures............. 115

A. Definitions ..........................................................................115A 100 General..........................................................................115A 200 Terms ............................................................................115

B. Symbols and abbreviations.................................................117

C. Figures ................................................................................118C 100 Ply and laminate co-ordinate systems...........................118C 200 Sandwich co-ordinate system and symbols ..................118

Sec. 14 Calculation Example:Two Pressure Vessels ....................................... 119

A. Objective.............................................................................119A 100 General..........................................................................119

B. Design input........................................................................ 119B 100 Overview.......................................................................119B 200 General function (ref. section 3 B100)..........................119B 300 Product specifications (ref. section 3 B200) .................119B 400 Division of the product into components

(ref. section 3 C)............................................................119

B 500 Phases and safety class definitions(ref. section 3 D and E) .................................................119B 600 Functional requirements (ref. section 3 F) ....................120B 700 Failure modes (ref. section 3 G)....................................120B 800 Loads (ref. section 3 I)..................................................121B 900 Environment (ref. section 3 J).......................................121

C. Failure mechanisms ............................................................121C 100 Identification of failure mechanisms

(ref. section 6 A) ...........................................................121C 200 Classification of failure mechanisms by failure types

(ref. section 6 A) ...........................................................122C 300 Failure mechanisms and target reliabilities

(ref. section 2 C500)......................................................123

D. Material properties.............................................................. 123D 100 General (ref. section 4)..................................................123

D 200 Ply modulus in fibre direction E1..................................124D 300 Matrix dominated elastic properties..............................124D 400 Fibre dominated ply strength and strain to failure ........125D 500 Matrix dominated ply strength and strain to failure......125D 600 Time to failure for fibre dominated properties..............125D 700 Time to failure for matrix dominated properties...........125




Contents Page 9

D 800 Test requirements..........................................................126

E. Analysis of gas vessel with liner ........................................126E 100 General..........................................................................126E 200 Analysis procedure (ref. section 9)............................... 126E 300 Fibre failure - short-term (ref. section 6 C) ..................127E 400 Fibre dominated ply failure due to static *

long-term loads (ref. section 6 J) .................................. 127E 500 Fibre dominated ply failure due to cyclic fatigue loads

(ref. section 6 K) ........................................................... 128E 600 Matrix cracking (ref. section 6 D) ................................128E 700 Unacceptably large displacement (ref. section 6 I).......128E 800 Impact resistance (ref. section 6 L)...............................129E 900 Explosive decompression (ref. section 6 O).................129E 1000 Chemical decomposition (ref. section 6 Q) ..................129E 1100 Summary evaluation .....................................................129

F. Non-linear analysis of vessel for water without liner.........129F 100 General..........................................................................129F 200 Analysis procedure (ref. section 9 B) ...........................129F 300 Matrix cracking (short term) at 1.48 MPa pressure

(ref. section 6 D) ........................................................... 130F 400 Matrix cracking under long-term static loads

(ref. section 4 C400) ..................................................... 131F 500 Matrix cracking under long-term cyclic fatigue loads

(ref. section 4 C900) ..................................................... 131F 600 Fibre failure - short term (ref. section 6 C)...................131F 700 Fibre dominated ply failure due to static long term

loads (ref. section 6 J)...................................................131F 800 Fibre dominated ply failure due to cyclic fatigue loads

(ref. section 6 K) ........................................................... 131F 900 Unacceptably large displacement (ref. section 6 I).......131F 1000 Impact resistance (ref. section 6 L)............................... 131F 1100 Explosive decompression (ref. section 6 O) ................. 132F 1200 Chemical decomposition (ref. section 6 Q) ..................132F 1300 Component testing (ref. section 10)..............................132F 1400 Summary evaluation .....................................................132

G. Linear analysis of vessel for water without liner................132G 100 General..........................................................................132G 200 Analysis procedure (ref. section 9 B) ........................... 132G 300 Matrix cracking (short term) (ref. section 6 D) ............132

G 400 Matrix cracking under long-term static loads(ref. section 4 C400) ..................................................... 132G 500 Matrix cracking under long-term cyclic fatigue loads

(ref. section 4 C900) ..................................................... 132G 600 Fibre failure short-term (ref. section 6 C)..................132G 700 Fibre dominated ply failure due to static long-term loads

(ref. section 6 J) ............................................................ 134G 800 Fibre dominated ply failure due to cyclic fatigue loads

(ref. section 6 K) ........................................................... 134G 900 Unacceptably large displacement ................................. 134G 1000 Impact resistance...........................................................134G 1100 Explosive decompression .............................................134G 1200 Chemical decomposition...............................................134G 1300 Summary evaluation .....................................................134

App. A Check-lists for Design Input ........................... 135

A. Phases .................................................................................135

B. Functional requirements and failure modes........................135B 100 Functional requirements that shall be checked as a

minimum.......................................................................135B 200 Failure modes that shall be checked as a minimum......135B 300 Link between functional requirements and failure

modes............................................................................136

C. LOADS...............................................................................136C 100 Functional loads............................................................136C 200 Environmental loads ..................................................... 136C 300 Accidental loads............................................................137

D. Environments......................................................................137

E. Distribution types of basic variables ..................................137

App. B Lay-up and laminate specification .................. 138

A. Unique definition of a laminate ..........................................138A 100 ......................................................................................138

App. C Test methods for laminates.............................. 139

A. General................................................................................139A 100 Introduction...................................................................139A 200 General testing information .......................................... 139

B. Static tests for laminates .....................................................139B 100 Inplane tensile tests.......................................................139

B 200 Inplane compression tests .............................................139B 300 Inplane shear tests......................................................... 139B 400 Through thickness tensile tests ..................................... 139B 500 Through thickness compressive tests............................ 140B 600 Interlaminar shear tests (through thickness) ................. 140B 700 Inplane fracture toughness tests.................................... 140B 800 Interlaminar fracture toughness tests............................140

C. Tests to obtain properties under long term staticand cyclic loads...................................................................140

C 100 ......................................................................................140

D. Tests to obtain the fibre fraction.........................................140D 100 ......................................................................................140

E. Tests on tubular specimens.................................................140E 100 ......................................................................................140

F. Evaluation of stress versus strain curves ............................140F 100 Brittle characteristics ....................................................140F 200 Plastic characteristics....................................................141F 300 Ductile Characteristics .................................................141

App. D Test methods for sandwich materials ............. 142

A. General................................................................................142A 100 Introduction...................................................................142A 200 General testing information .......................................... 142

B. Core materials - static tests .................................................142B 100 Tensile tests ..................................................................142B 200 Compressive tests ......................................................... 142B 300 Shear tests ..................................................................... 142B 400 Shear test for balsa and high density cores...................143B 500 Fracture toughness Strain energy release rate ...........143B 600 Tests to obtain properties under long term static

and cyclic loads............................................................. 143

C. Adhesive materials - static tests..........................................143C 100 General..........................................................................143C 200 Tensile tests ..................................................................143C 300 Flatwise tensile tests ..................................................... 143C 400 Shear tests ..................................................................... 143C 500 Tests to obtain properties under long term static

and cyclic loads............................................................. 143

D. Core skin interface properties .............................................143D 100 Tensile tests ..................................................................143D 200 Fracture toughness of the interface............................... 143

D 300 Other tests ..................................................................... 143

E. Tests for other properties....................................................144E 100 Coefficient of thermal expansion..................................144E 200 Water absorption tests................................................... 144E 300 Diffusion and vapour transmission............................... 144E 400 Tests for thermal conductivity measurements ..............144E 500 Overall volume shrinkage for gap filling fillers ...........144E 600 Density tests.................................................................. 144

App. E Tables of Safety Factors................................... 145

A. Partial safety factors ...........................................................145A 100 General..........................................................................145

App. F Example for representative data

Stitch-bonded unidirectional (UD) plies -

E glass polyester............................................................... 149

A. General................................................................................149A 100 ...................................................................................... 149




Page 10 Contents

B. Definition of material .........................................................149

C. Quasi static properties in air (QSA) ...................................149C 100 Test environment...........................................................149C 200 Fibre dominated ply properties .....................................150C 300 Matrix dominated ply properties...................................150C 400 Through thickness ply properties..................................151

D. Long term properties in air .................................................151

D 100 Test environment...........................................................151D 200 Fibre dominated tensile properties................................151D 300 Fibre dominated compressive properties ......................154D 400 Matrix dominated inplane tensile properties.................156D 500 Matrix dominated inplane compressive properties .......156D 600 Matrix dominated inplane shear properties...................156D 700 Matrix dominated through thickness tensile properties 156D 800 Matrix dominated through thickness compressive

properties.......................................................................156D 900 Matrix dominated through thickness shear properties ..156

E. Long term properties in water ............................................156E 100 Test environment...........................................................156E 200 Fibre dominated tensile properties................................156E 300 Fibre dominated compressive properties ......................156E 400 Matrix dominated inplane tensile properties.................157

E 500 Matrix dominated inplane compressive properties .......157E 600 Matrix dominated inplane shear properties...................157E 700 Matrix dominated through thickness tensile properties 157E 800 Matrix dominated through thickness compressive

properties.......................................................................157E 900 Matrix dominated through thickness shear properties ..157

App. G Example for representative data

Unidirectional carbon tape AS4 12k.............................. 158

A. General................................................................................158A 100 .......................................................................................158


C. Quasi static properties in air (QSA) ...................................158C 100 Test environment...........................................................158

C 200 Fibre dominated ply properties .....................................159C 300 Matrix dominated ply properties...................................159C 400 Through thickness ply properties..................................159

D. Long term properties ..........................................................159D 100 .......................................................................................159

App. H Example for Representative Data:

Unidirectional Carbon Tapes made of

TPW tape with 5631 fibres ......................................... 160

A. General................................................................................160A 100 .......................................................................................160


C. Quasi Static Properties in Air (QSA)..................................161C 100 Test environment...........................................................161C 200 Fibre dominated ply Properties .....................................161C 300 Matrix dominated ply Properties...................................161C 400 Through thickness ply Properties..................................161

D. Long Term Properties ........................................................161D 100 General..........................................................................161

App. I Example for representative data

Unidirectional carbon tape TPW 0434 Prepreg........... 162

A. General................................................................................162A 100 .......................................................................................162


C. Quasi static properties in air (QSA)....................................162C 100 Test environment...........................................................162C 200 Fibre dominated ply properties .....................................163C 300 Matrix dominated ply properties...................................163C 400 Through thickness ply properties..................................163

D. Long term properties...........................................................163D 100 .......................................................................................163




Sec.1 Page 11

SECTION 1GENERAL

A. Objectives

A 100 Objectives101 The main objectives of this standard is to:

serve as a basic philosophy and standard provide an internationally acceptable standard for safe

design with respect to strength and performance by defin-ing minimum requirements for design, materials, fabrica-tion and installation of load-carrying Fibre ReinforcedPlastic (FRP) laminates and sandwich structures and com-ponents

serve as a technical reference document in contractualmatters between client and contractor and or supplier

provide cost-effective solutions based on complete limitstate design with reliability based calibration of safety fac-tors

reflect the state-of-the-art and consensus on acceptedindustry practice

to provide guidance and requirements for efficient globalanalyses and introduce a consistent link between designchecks (failure modes), load conditions and load effectassessment in the course of the global analyses.

B. Application - Scope

B 100 General

101 This standard provides requirements and recommenda-tions for structural design and structural analysis proceduresfor composite components. Emphasis with respect to loads andenvironmental conditions is put on applications in the offshoreand processing industry. The materials description and calcu-lation methods can be applied to any applications. Aspectsrelated to documentation, verification, inspection, materials,fabrication, testing and quality control are also addressed.

102 The standard is applicable to all products and parts madeof composite material and may be applied to modifications,operation and upgrading made to existing ones. It is intended

to serve as a common reference for designers, manufacturersand end-users, thereby reducing the need for company specifi-

cations.103 This standard assumes that material properties such asstrength and stiffness are normally distributed. If the propertiesof a material deviate significantly from the assumption of anormal distribution, a different set of safety factors than spec-ified herein has to be used.

104 All properties shall be estimated with 95% confidence.

C. How to use the standard

C 100 Users of the standard

101 The client is understood to be the party ultimatelyresponsible for the system as installed and its intended use inaccordance with the prevailing laws, statutory rules and regu-lations.

102 The authorities are the national or international regula-tory bodies.

103 The contractoris understood to be the party contractedby the client to perform all or part of the necessary workneeded to bring the system to an installed and operable condi-tion.

104 The designeris understood to be the party contracted bythe contractor to fulfil all or part of the activities associatedwith the design.

105 The manufacturer is understood to be the party con-tracted by the contractor to manufacture all or part of the sys-tem. Two types of manufacturers can be distinguished: thematerial manufacturers, which supply the composite materialor its constituents (i.e. resin, fibres) and the product manufac-turers, which fabricate all or part of the system.

106 The third party verifieris an independent neutral partythat verifies the design of a structure or component.




Page 12 Sec.1

C 200 Flow chart of the standard

Figure 1Flow chart of the standard

C 300 How to use the standard

301 All users should go through section 1 and section 2describing the scope of the standard and the design principles.

302 The clientand contractor(s) should specify the DesignPremises according to section 3.

303 The design analysis should be performed by thedesigneraccording to section 6, section 7, section 8, section 9and section 10. The main input for the Design Report should

come out of these sections.

304 The contractor(s) and manufacturer(s) should specifythe fabrication according to section 11.

305 The clientand contractor(s) should specify the installa-

tion and repair procedures according to section 12.306 The third party verifier should verify that the designdocumentation is according to the requirements of section 2E.

FABRICATION

INSPECTION &

REPAIR

SECTION 1

GENERAL

SECTION 2

DESIGN

PHILOSOPHY

SECTION 3

DESIGN INPUT

START

DESIGNGENERAL

DESIGN

PREMISES

DESIGN

ANALYSIS

GENERAL

SECTION 6

Failure

mechanisms

SECTION 7

JOINTS &

INTERFACES

SECTION 8

SAFETY

FACTORS

SECTION 9

STRUCTURALANALYSIS

SECTION 10

COMPONENTTESTING

SECTION 11

FABRICATION

SECTION 12

INSPECTION

SECTION 14

EXAMPLES

SECTION 13

DEFINITIONS

SECTION 4

MATERIALS -

LAMINATES

SECTION 5

MATERIALS -

SANDWICH




Sec.1 Page 13

D. Normative References

The latest revision of the following documents applies:

D 100 Offshore Service Specifications

DNV-OSS-301 Certification and Verification of Pipelines

D 200 Offshore Standards

DNV-OS-F101 Submarine Pipeline SystemsDNV-OS-F201 Dynamic RisersDNV-OS-C105 Structural Design of TLPs by the LRFD

Method

DNV-OS-C106 Structural Design of Deep Draught FloatingUnits

DNV-OS-C501 Composite Components

D 300 Recommended Practices

DNV-RP-B401 Cathodic Protection DesignDNV-RP-C203 Fatigue Strength

DNV-RP-C205 Environmental Conditions andEnvironmental Loads

DNV-RP-F101 Corroded PipelinesDNV-RP-F104 Mechanical Pipeline CouplingsDNV-RP-F105 Free Spanning PipelinesDNV-RP-F106 Factory applied Pipeline Coatings for Cor-

rosion Control(under development)DNV-RP-F108 Fracture Control for Reeling of Pipelines

(under development)DNV-RP-F201 Titanium RisersDNV-RP-F202 Composite RisersDNV-RP-O501 Erosive Wear in Piping Systems

D 400 Rules

DNVRules for Certification of Flexible Risers and PipesDNVRules for Planning and Execution of Marine operationsDNVRules for Classification of Fixed Offshore Installations

D 500 Standards for Certification and Classificationnotes

DNV CN 1.2 Conformity Certification Services, TypeApproval

DNV CN 7 Ultrasonic Inspection of Weld ConnectionsDNV CN 30.2 Fatigue Strength Analysis for Mobile Off-

shore UnitsDNV CN 30.4 FoundationsDNV CN 30.6 Structural Reliability Analysis of Marine

Structures

D 600 Other references

API RP1111 Design, Construction, Operation, and Main-tenance of Offshore Hydrocarbon Pipelines(Limit State Design)

API RP2RD Design of Risers for Floating ProductionSystems (FPSs) and Tension-Leg Platforms(TLPs)

ISO/FDIS 2394 General Principles on Reliability for Struc-tures

IS0/CD 13628-7 Petroleum and natural gas industries -Design and operation of subsea productionsystems - Part 7: Completion/workover risersystems

Guidance note:

The latest revision of the DNV documents may be found in thepublication list at the DNV website www.dnv.com.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---




Page 14 Sec.2

SECTION 2DESIGN PHILOSOPHY AND DESIGN PRINCIPLES

A. General

A 100 Objective101 The purpose of this section is to identify and address keyissues which need to be considered for the design, fabrication,and operation of FRP components and structures. Further-more, the purpose is to present the safety philosophy and cor-responding design format applied throughout this Standard.

B. Safety philosophy

B 100 General

101 An overall safety objective is to be established, plannedand implemented covering all phases from conceptual devel-

opment until abandonment of the structure.102 This Standard gives the possibility to design structuresor structural components with different structural safetyrequirements, depending on the Safety Class to which thestructure or part of the structure belongs. Safety classes arebased on the consequence of failures related to the UltimateLimit State (ULS).

103 Structural reliability of the structure is ensured by theuse of partial safety factors that are specified in this Standard.Partial safety factors are calibrated to meet given target struc-tural reliability levels. Note that gross errors are not accountedfor. Gross errors have to be prevented by a quality system. Thequality system shall set requirements to the organisation of thework, and require minimum standards of competence for per-

sonnel performing the work. Quality assurance shall be appli-cable in all phases of the project, like design, designverification, operation, etc.

B 200 Risk assessment

201 To the extent it is practically feasible, all work associ-ated with the design, construction and operation shall ensurethat no single failure is to lead to life-threatening situations forany persons, or to unacceptable damage to material or to envi-ronment.

202 A systematic review or analysis shall be carried out at allphases to identify and evaluate the consequences of single fail-ures and series of failure in the structure such that necessaryremedial measures may be taken. The extent of such a review

is to reflect the criticality of the structure, the criticality ofplanned operations, and previous experience with similarstructures or operations.

Guidance note:

A methodology for such a systematic review is the QuantitativeRisk Analysis (QRA) which may provide an estimation of theoverall risk to human health and safety, environment and assetsand comprises (i) hazard identification, (ii) assessment of proba-bility of failure events, (iii) accident development and (iv) conse-quence and risk assessment. It should be noted that legislation insome countries requires risk analysis to be performed, at least atan overall level to identify critical scenarios, which may jeopard-ise the safety and reliability of the structure. Other methodolo-gies for identification of potential hazards are Failure ModeEffect Analysis (FMEA) and Hazardous Operations studies(HAZOP).


B 300 Quality Assurance

301 The safety format of this Standard requires that gross

errors (human errors) shall be controlled by requirements tothe organisation of the work, competence of persons perform-

ing the work, verification of the design and Quality Assuranceduring all relevant phases.

C. Design format

C 100 General principles

101 The basic approach of the Limit State Design methodconsists in recognising the different failure modes related toeachfunctional requirementand associating to each mode offailure a specific limit state beyond which the structure nolonger satisfies the functional requirement. Different limitstates are defined, each limit state being related to the kind offailure mode and its anticipated consequences.

102 The design analysis consists in associating each failuremode to all the possible failure mechanisms (i.e. the mecha-nisms at the material level). A design equation or a failure cri-terion is defined for each failure mechanism, and failurebecomes interpreted as synonymous to the design equation nolonger being satisfied.

103 The design equations are formulated in the so-calledLoad and Resistance Factor Design (LRFD) format, where

partial safety factors (load factors and resistance factors) areapplied to the load effects (characteristic load values) and tothe resistance variables (characteristic resistance values) thatenter the design equations.

104 The partial safety factors, which are recommended in

this Standard, have been established such that acceptable andconsistent reliability levels are achieved over a wide range ofstructure configurations and applications.

105 This section discusses the limit states that have beenconsidered relevant for the design of structures made of FRPmaterials, presents the underlying safety considerations for therecommended safety factors and finally introduces the adoptedLRFD format.

106 As an alternative to the LRFD format a recognisedStructural Reliability Analysis (SRA) may be applied. Theconditions for application of an SRA are discussed at the endof this section.

C 200 Limit states

201 The following two limit state categories shall be consid-ered in the design of the structure:

Ultimate Limit State (ULS) Serviceability Limit State (SLS).

202 The Ultimate Limit State shall be related to modes offailure for which safety is an issue. The ULS generally corre-sponds to the maximum load carrying capacity and is related tostructural failure modes. Safety Classes are defined in accord-ance with the consequences of these failure modes on safety,environment and economy. The ULS is not reversible.

203 The Serviceability Limit State should be related to fail-ure modes for which human risks or environmental risks are

not an issue. The SLS is usually related to failure modes lead-ing to service interruptions or restrictions. Service Classes aredefined in accordance with the frequency of service interrup-tions due these modes of failure. The SLS is usually reversible,i.e. after repair or after modification of the operating condi-tions (e.g. interruption of operation, reduction of pressure or




Sec.2 Page 15

speed) the structure will again be able to meet its functionalrequirements in all specified design conditions.

Guidance note:

Ultimate Limit States correspond to, for example:

- loss of static equilibrium of the structure, or part of the struc-ture, considered as a rigid body

- rupture of critical sections of the structure caused by exceed-

ing the ultimate strength or the ultimate deformation of thematerial- transformation of the structure into a mechanism (collapse).- loss of stability (buckling, etc)

Serviceability Limit States corresponds to, for example:

- deformations which affect the efficient use or appearance ofstructural or non-structural elements

- excessive vibrations producing discomfort or affecting non-structural elements or equipment

- local damage (including cracking) which reduces the durabil-ity of the structure or affects the efficiency or appearance ofstructural or non-structural elements.


C 300 Safety classes and Service classes301 Safety classes are based on the consequences of failurewhen the mode of failure is related to the Ultimate Limit State.The operator shall specify the safety class according to whichthe structure shall be designed. Suggestions are given below.

302 Safety classes are defined as follows:

Low Safety Class, where failure of the structure impliessmall risk of human injury and minor environmental, eco-nomic and political consequences.

Normal Safety Class, where failure of the structure impliesrisk of human injury, significant environmental pollutionor significant economic or political consequences.

High Safety Class, where failure of the structure implies

risk of human injury, significant environmental pollutionor very high economic or political consequences.

303 Service classes are based on the frequency of serviceinterruptions or restrictions caused by modes of failure relatedto the Serviceability Limit State. These modes of failure implyno risk of human injury and minor environmental conse-quences. The operator shall specify the service class accordingto which the structure shall be designed. Suggestions are givenbelow.

304 Service classes are defined according to the annualnumber of service failures. The Normal and High ServiceClasses are defined by the target reliability levels indicated inTable C1.

C 400 Failure types401 Failure types are based on the degree of pre-warningintrinsic to a given failure mechanism. A distinction shall bemade between catastrophic and progressive failures, andbetween failures with or without reserve capacity during fail-ure. Thefailure types for each failure mechanism described inthis Standard are specified according to the following defini-tions:

ductile, corresponds to ductile failure mechanisms withreserve strength capacity. In a wider sense, it correspondsto progressive non-linear failure mechanisms with reservecapacity during failure.

plastic, corresponds to ductile failure mechanisms withoutreserve strength capacity. In a wider sense, it correspondsto progressive non-linear failure mechanisms but withoutreserve capacity during failure.

brittle, corresponds to brittle failure mechanisms. In awider sense, it corresponds to non-stable failure mecha-nisms.

402 The different failure types should be used under the fol-lowing conditions for materials that show a yield point:

failure type ductile may be used if:ult > 1.3 yield and ult > 2 yield

failure typeplastic may be used if:ult 1.0 yield and ult > 2 yield

in all other cases failure type brittle shall be used.Where ult is the ultimate strength at a strain ult andyield is the yield strength at a strain yield.

C 500 Selection of partial safety factors

501 Partial safety factors depend on the safety class and thefailure type. The partial factors are available for five differentlevels and are listed in Section 8.

502 The selection of the levels is given in the table C1 for theultimate limit state.

503 The recommended selection of the levels for the service-ability limit state is given in the table C2.

C 600 Design by LRFD method

601 The Partial Safety Factor format (or Load and Resist-ance Factor Design, LRFD) separates the influence of uncer-tainties and variability originating from different causes.Partial safety factors are assigned to variables such as loadeffect and resistance variables. They are applied as factors onspecified characteristic values of these load and resistance var-iables, thereby defining design values of these variables for usein design calculations, and thereby accounting for possibleunfavourable deviations of the basic variables from their char-acteristic values. The characteristic values of the variables areselected representative values of the variables, usually speci-fied as specific quantiles in their respective probability distri-butions, e.g. an upper-tail quantile for load and a lower-tailquantile for resistance. The values of the partial safety factorsare calibrated, e.g. by means of a probabilistic analysis, such

that the specified target reliability is achieved whenever thepartial safety factors are used for design. Note that characteris-tic values and their associated partial safety factors are closelylinked. If the characteristic values are changed, relative to theones determined according to procedures described elsewherein this document, then the requirements to the partial safetyfactors will also change in order to maintain the intended targetreliability level.

Guidance note:

The following uncertainties are usually considered:

- Uncertainties in the loads, caused by natural variability,which is usually a temporal variability

- Uncertainties in the material properties, caused by naturalvariability, which is usually a spatial variability

- Uncertainties in the geometrical parameters, caused by- deviations of the geometrical parameters from their char-

acteristic (normal) value- tolerance limits- cumulative effects of a simultaneous occurrence of sev-

eral geometrical variation

Table C1 Target reliability levels for ULS

SAFETY CLASS FAILURE TYPE

Ductile/Plastic BrittleLow A B

Normal B C

High C D

Table C2 Target reliability levels for SLS

SERVICE CLASS SERVICE FAILURES

Normal A

High B




Page 16 Sec.2

- Uncertainties in the applied engineering models

- uncertainties in the models for representation of the realstructure or structural elements

- uncertainties in the models for prediction of loads, owingto simplifications and idealisations made

- uncertainties in the models for prediction of resistance,owing to simplifications and idealisations made

- effect of the sensitivity of the structural system (under- or

over-proportional behaviour)---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

602 Partial safety factors are applied in design inequalitiesfor deterministic design as shown by examples in 606. The par-tial safety factors are usually or preferably calibrated to a spec-ified target reliability by means of a probabilistic analysis.Sometimes the design inequalities include model factors orbias correction factors as well. Such model or bias correctionfactors appear in the inequalities in the same manner as the par-tial safety factors, but they are not necessarily to be interpretedas partial safety factors as they are used to correct for system-atic errors rather than accounting for any variability or uncer-tainty. Model factors and bias correction factors are usually

calibrated experimentally.603 The following two types of partial safety factors are usedin this standard:

Partial load effect factors, designated in this standard byF .

Partial resistance factors, designated in this standard byM .

604 In some cases it is useful to work with only one overallsafety factor. The uncertainties in loads and resistance are thenaccounted for by one common safety factor denoted gFM. Thefollowing simple relationship between this common safety fac-tor on the one hand and the partial load and resistance factorson the other are assumed here corresponding to the general

design inequality quoted in 606:FM= F x M

605 The following two types of model factors are used in thisStandard:

Load model factors, designated in this Standard by Sd . Resistance model factors, designated in this Standard by

Rd .

Guidance note:

- Partial load effect factors F are applicable to the characteris-tic values of the local response of the structure. They accountfor uncertainties associated with the variability of the localresponses of the structure (local stresses or strains). Theuncertainties in the local response are linked to the uncertain-ties on the loads applied to the structure through the transferfunction.

- Partial resistance factors M account for uncertainties associ-ated with the variability of the strength.

- Load model factors Sd account for inaccuracies, idealisa-tions, and biases in the engineering model used for represen-tation of the real response of the structure, e.g. simplificationsin the transfer function (see section 9). For example, windcharacterised by a defined wind speed will induce wind loadson the structure, and those loads will induce local stresses andstrains in the structure. The load model factor account for theinaccuracies all the way from wind speed to local response inthe material.

- Resistance model factors Rd account for differences betweentrue and predicted resistance values, e.g. differences between

test and in-situ materials properties (size effects), differencesassociated with the capability of the manufacturing processes(e.g. deviations of the geometrical parameters from the char-acteristic value, tolerance limits on the geometrical parame-ters), and differences owing to temporal degradationprocesses.

- Uncertainties or biases in a failure criterion are accounted forby the resistance model factor.

- Geometrical uncertainties and tolerances should be includedin the load model factor.


606 A factored design load effect is obtained by multiplyinga characteristic load effect by a load effect factor. A factored

design resistance is obtained by dividing the characteristicresistance by a resistance factor.The structural reliability is considered to be satisfactory if thefollowing design inequalities are satisfied:

General design inequality for the Load Effect and ResistanceFactor Design format:

where,

F partial load effect factorSd load model factor

Sk characteristic load effectRk characteristic resistanceM partial resistance factorRd resistance model factor.

Design rule expressed in terms of forces and moments:

where,

code check function (e.g. buckling equation)F partial load or load effect factorSd load model factor

Sk characteristic load or load effectRk characteristic resistanceM partial resistance factorRd resistance model factor.

Design rule expressed in terms of a local response such as localstrains:

where,

code check functionF partial load effect factorSd load model factork characteristic value of the

ABS Standards OS-501

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