OS C501 Composites

OFFSHORE STANDARDDNV-OS-C501

COMPOSITE COMPONENTSJANUARY 2003DET NORSKE VERITAS

FOREWORDDET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life, prop-erty and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification and consultancyservices relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out researchin relation to these functions.DNV Offshore Codes consist of a three level hierarchy of documents: Offshore Service Specifications. Provide principles and procedures of DNV classification, certification, verification and con-

sultancy services. Offshore Standards. Provide technical provisions and acceptance criteria for general use by the offshore industry as well as

the technical basis for DNV offshore services. Recommended Practices. Provide proven technology and sound engineering practice as well as guidance for the higher level

Offshore Service Specifications and Offshore Standards.DNV Offshore Codes are offered within the following areas:

A) Qualification, Quality and Safety MethodologyB) Materials TechnologyC) StructuresD) SystemsE) Special FacilitiesF) Pipelines and RisersG) Asset Operation

MotivesNo design code for Fibre Reinforced Plastic, often called composite structures, exists today except for some special applicationslike FRP pipes, pressure vessels and ships.The realization of even simple designs of FRP structures tends to become a major undertaking due to the lack of applicable designstandards. It is DNV's impression that the lack of a good FRP guideline is one of the major obstacles to utilize FRP structurallyin a reliable and economical way.For this reason DNV started a JIP to develop a general standard for 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, Ahl-strm Glassfibre, AMOCO, Akzo Nobel Faser AG, Baltek, Devold AMT, FiReCo, MMS, Norsk Hydro, Reichold, Saga Petroleum,Tenax Fibers, Umoe Shat Harding agreed that DNV shall transform the resulting project report into a DNV Offshore Standard.The new DNV Offshore Standard is indexed: DNV-OS-C501 Composite Components, and has a contents layout as shown over-leaf.Comments may be sent by e-mail to [email protected] subscription orders or information about subscription terms, please use [email protected] information about DNV services, research and publications can be found at http://www.dnv.com, or can be obtained from DNV, Veritasveien 1, N-1322 Hvik, Norway; Tel +47 67 57 99 00, Fax +47 67 57 99 11.

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Offshore Standard DNV-OS-C501, January 2003 Contents Page 3CONTENTS

Sec. 1 General................................................................... 9

A. Objectives ...............................................................................9A 100 Objectives ......................................................................... 9B. Application - Scope ..............................................................9B 100 General.............................................................................. 9

C. How to use the standard..........................................................9C 100 Users of the standard......................................................... 9C 200 Flow chart of the standard ..............................................10C 300 How to use the standard..................................................10

D. Normative References ..........................................................11D 100 Offshore Service Specifications......................................11D 200 Offshore Standards .........................................................11D 300 Recommended Practices .................................................11D 400 Rules ...............................................................................11D 500 Standards for Certification and Classification notes.......11D 600 Other references.............................................................. 11

Sec. 2 Design Philosophy and Design Principles......... 12

A. General..................................................................................12A 100 Objective......................................................................... 12B. Safety philosophy .................................................................12B 100 General............................................................................12B 200 Risk assessment .............................................................. 12B 300 Quality Assurance...........................................................12C. Design format .......................................................................12C 100 General principles ...........................................................12C 200 Limit states......................................................................12C 300 Safety classes and Service classes ..................................13C 400 Failure types....................................................................13C 500 Selection of partial safety factors ...................................13C 600 Design by LRFD method................................................13C 700 Structural Reliability Analysis........................................ 15

D. Design approach ................................................................... 15D 100 Approaches .....................................................................15D 200 Analytical approach ........................................................15D 300 Component testing ..........................................................15D 400 Analyses combined with updating..................................15

E. Requirements to documentation ...........................................16E 100 Design Drawings and Tolerances ...................................16E 200 Guidelines for the design report......................................16

Sec. 3 Design Input ........................................................ 17

A. Introduction ..........................................................................17A 100 ........................................................................................17

B. Product specifications...........................................................17B 100 General Function or main purpose of the product ..........17

C. Division of the product or structure into components, parts and details ....................................................................17

C 100 ........................................................................................17

D. Phases ...................................................................................17D 100 Phases..............................................................................17

E. Safety and service classes.....................................................17E 100 Safety classes ..................................................................17E 200 Service classes ................................................................18

F. Functional requirements .......................................................18F 100 ........................................................................................18

G. Failure modes .......................................................................18G 100 General............................................................................18G 200 Failure modes..................................................................18

H. Exposure from the surroundings...........................................18H 100 General............................................................................ 18H 200 Loads and environment................................................... 19H 300 Obtaining loads from the exposure from

the surroundings.............................................................. 19

I. Loads.....................................................................................19I 100 General............................................................................ 19I 200 Probabilistic representation of load effects..................... 20I 300 Simplified representation of load effects........................ 20I 400 Characteristic load effect ................................................ 20I 500 The sustained load effect ................................................ 21I 600 The fatigue load effects .................................................. 22

J. Environment .........................................................................23J 100 General............................................................................ 23J 200 Effects of the environment on the material properties ... 24

K. Combination of load effects and environment .....................24K 100 General............................................................................ 24K 200 Load effect and environmental conditions for ultimate

limit state ....................................................................... 24K 300 Load effect and environmental conditions for time-

dependent material properties......................................... 25K 400 Load effect and environmental conditions for fatigue

analysis ........................................................................... 25K 500 Direct combination of loads............................................ 25

Sec. 4 Materials - Laminates ........................................ 26

A. General..................................................................................26A 100 Introduction..................................................................... 26A 200 Laminate specification.................................................... 26A 300 Lay-up specification ....................................................... 26A 400 Orthotropic plies ............................................................. 26A 500 Mechanical properties..................................................... 27A 600 Characteristic values of mechanical properties .............. 27A 700 Properties of laminates with damage.............................. 27

B. Static properties ....................................................................27B 100 General............................................................................ 27B 200 Static properties .............................................................. 28B 300 Relationship between strength and strain to failure........ 29B 400 Characteristic values ....................................................... 29B 500 Experimental measurement of matrix and

fibre dominated strain to failure ..................................... 30B 600 Experimental measurement of ply shear properties........ 30

C. Properties under long term static and cyclic and high rate loads.......................................................................30

C 100 Introduction..................................................................... 30C 200 Creep............................................................................... 31C 300 Stress rupture .................................................................. 31C 400 Static strength reduction due to permanent static loads.. 32C 500 Stress relaxation.............................................................. 32C 600 Change of Modulus of elasticity under cyclic fatigue .... 32C 700 Cycles to failure under cyclic fatigue loads.................... 33C 800 Cycles to failure under fatigue loads for

matrix dominated strengths............................................. 34C 900 Static strength reduction due to cyclic loads .................. 34C 1000 Effect of high loading rates - shock loads - impact ........ 35C 1100 Characteristic values ....................................................... 35

D. Other properties ....................................................................35D 100 Thermal expansion coefficient ....................................... 35D 200 Swelling coefficient for water or other liquids ............... 36D 300 Diffusion coefficient ....................................................... 36D 400 Thermal conductivity...................................................... 36D 500 Friction coefficient.......................................................... 36D 600 Wear resistance............................................................... 36

E. Influence of the environment on properties..........................37E 100 Introduction..................................................................... 37E 200 Effect of temperature ...................................................... 37E 300 Effect of water ................................................................ 38DET NORSKE VERITAS

G 300 Identification of the type of limit states .......................... 18 E 400 Effect of chemicals ......................................................... 39

Offshore Standard DNV-OS-C501, January 2003Page 4 ContentsE 500 Effect of UV radiation.....................................................39E 600 Electrolytic Corrosion .....................................................39E 700 Combination of environmental effects............................39

F. Influence of process parameters ........................................... 39F 100 Introduction.....................................................................39F 200 Change of production method.........................................39F 300 Change of processing temperature and pressure.............39F 400 Change of post cure procedure........................................40F 500 Change of void content ...................................................40F 600 Correction for change in fibre volume fraction ..............40F 700 Control of fibre orientation: ............................................40F 800 Control of fibre tension: ..................................................40

G. Properties under fire ............................................................. 40G 100 Introduction.....................................................................40G 200 Fire reaction ....................................................................41G 300 Fire resistance .................................................................41G 400 Insulation.........................................................................41G 500 Properties after the fire....................................................41

H. Qualification of material properties...................................... 41H 100 Introduction.....................................................................41H 200 General test requirements................................................41H 300 Selection of material qualification method .....................41H 400 Direct measurement ........................................................41H 500 Representative data .........................................................41H 600 Qualification against representative data ........................42H 700 Confirmation testing for static data.................................44H 800 Confirmation testing for long term data -

high safety class ..............................................................44H 900 Confirmation testing for long term data -

normal safety class ..........................................................45H 1000 Use of manufacturers data or data from

the literature as representative data .................................45H 1100 Confirming material data by component testing.............45H 1200 Comparing results from different processes and

lay-ups .............................................................................45

I. Properties with damaged or nonlinearly deformed matrix ... 46I 100 Introduction.....................................................................46I 200 Default values .................................................................46I 300 Experimental approach ...................................................46

Sec. 5 Materials Sandwich Structures...................... 48

A. General.................................................................................. 48A 100 Introduction.....................................................................48A 200 Sandwich specification ...................................................48A 300 Lay-up specification........................................................48A 400 Isotropic/orthotropic core layers .....................................48A 500 Mechanical and physical properties ................................49A 600 Characteristic values of mechanical properties...............49

B. Static properties .................................................................... 49B 100 General ............................................................................49B 200 Static properties...............................................................49B 300 Relationship between strength and strain to failure ........52B 400 Characteristic values .......................................................52B 500 Shear properties...............................................................52B 600 Core skin interface properties .........................................53

C. Properties under long term static and cyclic loads ............... 54C 100 General ............................................................................54C 200 Creep ...............................................................................54C 300 Stress rupture under permanent static loads....................54C 400 Static strength reduction due to permanent static loads ..54C 500 Stress relaxation ..............................................................54C 600 Change of modulus of elasticity under cyclic fatigue.....55C 700 Cycles to failure under fatigue loads...............................55C 800 Static strength reduction due to cyclic loading ...............55C 900 Effect of high loading rates - shock loads - impact.........56C 1000 Characteristic values .......................................................56

D. Other properties .................................................................... 56D 100 Thermal expansion coefficient........................................56D 200 Swelling coefficient for water or other liquids ...............56D 300 Diffusion coefficient .......................................................56D 400 Thermal conductivity ......................................................56D 500 Friction coefficient ..........................................................56

E. Influence of the environment on properties..........................56E 100 Introduction.....................................................................56E 200 Effect of temperature ......................................................57E 300 Effect of water.................................................................57E 400 Effect of chemicals..........................................................57E 500 Effect of UV radiation.....................................................58E 600 Electrolytic corrosion......................................................58E 700 Combination of environmental effects............................58

F. Influence of process parameters and core density ................58F 100 Core production...............................................................58F 200 Sandwich production.......................................................58F 300 Influence of core density.................................................58

G. Properties under fire .............................................................58G 100 Introduction.....................................................................58G 200 Fire reaction ....................................................................58G 300 Fire resistance .................................................................58G 400 Insulation.........................................................................58G 500 Properties after the fire....................................................59

H. Qualification of material properties......................................59H 100 Introduction.....................................................................59H 200 General test requirements................................................59H 300 Selection of material qualification method .....................59H 400 Direct measurement ........................................................59H 500 Representative data .........................................................59H 600 Qualification against representative data ........................60H 700 Confirmation testing for static data.................................61H 800 Confirmation testing for long term data..........................61H 900 Use of manufacturers data or data from

the literature as representative data.................................61H 1000 Confirming material data by component testing.............61

Sec. 6 Failure Mechanisms & Design Criteria ........... 62

A. Mechanisms of failure ..........................................................62A 100 General ............................................................................62A 200 FRP laminates - failure mechanisms and failure type.....64A 300 Sandwich structures - failure mechanisms and

failure type ......................................................................65A 400 Displacements and long term failure mechanisms and

failure type ......................................................................65A 500 Link between failure modes and failure mechanisms.....66

B. Design criteria - general approach........................................67B 100 General ............................................................................67B 200 Design criteria for single loads ......................................67B 300 Design criteria for combined loads .................................67B 400 Time dependency and influence of the environment ......68

C. Fibre failure ..........................................................................68C 100 General ............................................................................68C 200 Fibre failure at the ply level ............................................68C 300 Fibre failure check using a modified Tsai-Wu criterion .69C 400 Special considerations for fibre failure under inplane

compressive loads ...........................................................70C 500 Fibre failure checked by component testing ...................70C 600 Fracture mechanics approach..........................................70

D. Matrix cracking.....................................................................71D 100 General ............................................................................71D 200 Matrix failure based on simple stress criterion ...............71D 300 Matrix failure based on Puck's criterion .........................72D 400 Obtaining orientation of the failure surface ....................73D 500 Matrix cracking caused only by shear.............................73D 600 Matrix failure checked by component testing.................73

E. Delamination.........................................................................74E 100 General ............................................................................74E 200 Onset of delamination .....................................................74E 300 Delamination growth.......................................................74

F. Yielding ................................................................................74F 100 General ............................................................................74

G. Ultimate failure of orthotropic homogenous materials.........74G 100 General ............................................................................74

H. Buckling................................................................................75DET NORSKE VERITAS

D 600 Wear resistance ...............................................................56 H 100 Concepts and definitions.................................................75

Offshore Standard DNV-OS-C501, January 2003 Contents Page 5H 200 General requirements......................................................76H 300 Requirements when buckling resistance is

determined by testing......................................................76H 400 Requirements when buckling is assessed by analysis .... 76

I. Displacements.......................................................................77I 100 General............................................................................77

J. Long term static loads...........................................................77J 100 General............................................................................77J 200 Creep...............................................................................77J 300 Stress relaxation.............................................................. 78J 400 Stress rupture - stress corrosion ......................................78

K. Long term cyclic loads .........................................................79K 100 General............................................................................79K 200 Change of elastic properties............................................ 79K 300 Initiation of fatigue damage............................................ 79K 400 Growth of fatigue damage ..............................................80

L. Impact ...................................................................................80L 100 General............................................................................80L 200 Impact testing..................................................................80L 300 Evaluation after impact testing .......................................80

M. Wear......................................................................................80M 100 General............................................................................80M 200 Calculation of the wear depth .........................................81M 300 Component testing ..........................................................81

N. High / low temperature / fire ................................................81N 100 General............................................................................81

O. Resistance to explosive decompression................................ 81O 100 Materials ......................................................................... 81O 200 Interfaces......................................................................... 81

P. Special aspects related to sandwich structures .....................81P 100 General............................................................................81P 200 Failure of sandwich faces ...............................................81P 300 Failure of the sandwich core...........................................81P 400 Failure of the sandwich skin-core interface....................81P 500 Buckling of sandwich structures.....................................82

Q. Chemical decomposition / galvanic corrosion......................82Q 100 General............................................................................82R. Requirements for other design criteria .................................82R 100 General............................................................................82

Sec. 7 Joints and Interfaces........................................... 83A. General..................................................................................83A 100 Introduction.....................................................................83A 200 Joints ...............................................................................83A 300 Interfaces......................................................................... 83A 400 Thermal properties..........................................................83A 500 Examples......................................................................... 83

B. Joints..................................................................................... 83B 100 Analysis and testing ........................................................83B 200 Qualification of analysis method for

other load conditions or joints ........................................ 84B 300 Multiple failure modes....................................................84B 400 Evaluation of in-service experience................................84

C. Specific joints .......................................................................84C 100 Laminated joints .............................................................84C 200 Adhesive Joints ...............................................................84C 300 Mechanical joints............................................................84C 400 Joints in sandwich structures ..........................................84

D. Interfaces ..............................................................................84D 100 General............................................................................84

Sec. 8 Safety-, Model- and System Factors.................. 86

A. Overview of the various factors used in the standard...........86

B. Partial load effect and resistance factors ..............................86B 100 General............................................................................ 86B 200 How to select the partial safety factors........................... 86B 300 Simplified set of partial safety factors (general)............. 86B 400 Simplified set of partial safety factors (for known

maximum load effect)..................................................... 87B 500 Full set of partial safety factors ...................................... 87B 600 Partial safety factors for functional and

environmental loads as typically defined for risers ........ 87B 700 Partial safety factors for functional and

environmental loads as typically defined for TLPs ........ 87

C. Model factors ........................................................................88C 100 General............................................................................ 88C 200 Load model factors ......................................................... 88C 300 Resistance model factors ................................................ 88

D. System effect factor ..............................................................88D 100 General............................................................................ 88

E. Factors for static and dynamic fatigue analysis .................................................................................88

E 100 ........................................................................................ 88

Sec. 9 Structural Analysis............................................. 89

A. General..................................................................................89A 100 Objective......................................................................... 89A 200 Input data ........................................................................ 89A 300 Analysis types................................................................. 89A 400 Transfer function ............................................................ 89A 500 Global and local analysis ................................................ 89A 600 Material levels ................................................................ 89A 700 Non-linear analysis ......................................................... 90

B. Linear and non-linear analysis of monolithic structures.......90B 100 General............................................................................ 90B 200 In-plane 2-D progressive failure analysis ....................... 91B 300 3-D progressive failure analysis ..................................... 91B 400 Linear failure analysis with non-degraded properties .... 91B 500 Linear failure analysis with degraded properties............ 92B 600 Two-step non-linear failure analysis method ................. 92B 700 Through thickness 2-D analysis...................................... 93

C. Connection between analysis methods and failure criteria...93C 100 General............................................................................ 93C 200 Modification of failure criteria ....................................... 93C 300 Creep, stress relaxation and

stress rupture-stress relaxation........................................ 94C 400 Fatigue ............................................................................ 94

D. Analytical methods ...............................................................94D 100 General............................................................................ 94D 200 Assumptions and limitations........................................... 94D 300 Link to numerical methods ............................................. 94

E. Finite element analysis .........................................................94E 100 General............................................................................ 94E 200 Modelling of structures general ................................... 94E 300 Software requirements .................................................... 95E 400 Execution of analysis...................................................... 95E 500 Evaluation of results ....................................................... 96E 600 Validation and verification ............................................. 96

F. Dynamic response analysis...................................................96F 100 General............................................................................ 96F 200 Dynamics and finite element analysis ............................ 96

G. Impact response ....................................................................96G 100 Testing ............................................................................ 96

H. Thermal stresses....................................................................96H 100 General............................................................................ 96

I. Swelling effects ....................................................................97I 100 General............................................................................ 97

J. Analysis of sandwich structures ...........................................97J 100 General............................................................................ 97J 200 Elastic constants.............................................................. 97DET NORSKE VERITAS

A 100 General............................................................................86 J 300 2-D non-linear failure analysis ....................................... 97

Offshore Standard DNV-OS-C501, January 2003Page 6 ContentsJ 400 3-D progressive failure analysis......................................98J 500 Long term damage considerations ..................................98

K. Buckling................................................................................ 98K 100 General ............................................................................98K 200 Buckling analysis of isolated components ......................98K 300 Buckling analysis of more complex elements or entire

structures .........................................................................99K 400 Buckling analysis of stiffened plates and shells..............99K 500 Buckling analysis for sandwich structures......................99

L. Partial load-model factor ...................................................... 99L 100 General ............................................................................99L 200 Connection between partial load-model factor and

analytical analysis ...........................................................99L 300 Connection between partial load-model factor and

finite element analysis.....................................................99L 400 Connection between partial load-model factor and

dynamic response analysis ............................................100L 500 Connection between partial load-model factor and

transfer function ............................................................100

Sec. 10 Component Testing .......................................... 101A. General................................................................................ 101A 100 Introduction...................................................................101A 200 Failure mode analysis....................................................101A 300 Representative samples .................................................101

B. Qualification based on tests on full scale components ....... 101B 100 General ..........................................................................101B 200 Short term properties.....................................................101B 300 Long term properties .....................................................102

C. Verification of analysis by testing and updating .............................................................................. 102

C 100 Verification of design assumptions...............................102C 200 Short term tests..............................................................103C 300 Long term testing ..........................................................103C 400 Procedure for updating the predicted resistance of a

component .....................................................................104C 500 Specimen geometry - scaled specimen .........................104

D. Testing components with multiple failure mechanisms ..... 105D 100 General ..........................................................................105D 200 Static tests .....................................................................105D 300 Long term tests..............................................................105D 400 Example of multiple failure mechanisms......................105

E. Updating material parameters in the analysis based on component testing............................................................... 106

E 100 .......................................................................................106

Sec. 11 Fabrication ........................................................ 107

A. Introduction ........................................................................ 107A 100 Objective .......................................................................107A 200 Quality system...............................................................107B. Link of process parameters to

production machine parameters.......................................... 107B 100 Introduction...................................................................107B 200 Process parameters ........................................................107B 300 Production machine parameters ....................................107

C. Processing steps.................................................................. 107C 100 General ..........................................................................107C 200 Raw materials................................................................107C 300 Storage of materials ......................................................107C 400 Mould construction .......................................................107C 500 Resin..............................................................................108C 600 Producing laminates and sandwich panels....................108C 700 Producing joints ............................................................108C 800 Injection of resin and cure.............................................108C 900 Evaluation of the final product......................................109

D. Quality assurance and quality control ................................ 109D 100 .......................................................................................109

E. Component testing.............................................................. 109

E 200 Factory acceptance test and system integrity test .........109E 300 Pressure testing of vessels and pipes.............................109E 400 Other testing..................................................................109E 500 Dimensions....................................................................109

F. Installation ..........................................................................110F 100 .......................................................................................110

G. Safety, health and environment ..........................................110G 100 .......................................................................................110

Sec. 12 Operation, Maintenance, Reassessment, Repair ................................................................ 111

A. General................................................................................111A 100 Objective .......................................................................111B. Inspection............................................................................111B 100 General ..........................................................................111B 200 Inspection methods .......................................................111

C. Reassessment ......................................................................111C 100 General ..........................................................................111

D. Repair..................................................................................111D 100 Repair procedure ...........................................................111D 200 Requirements for a repair..............................................111D 300 Qualification of a repair ................................................111E. Maintenance........................................................................112E 100 General ..........................................................................112

F. Retirement...........................................................................112F 100 General ..........................................................................112

Sec. 13 Definitions, Abbreviations & Figures............. 113

A. Definitions ..........................................................................113A 100 General ..........................................................................113A 200 Terms ............................................................................113

B. Symbols and abbreviations .................................................115

C. Figures ................................................................................116C 100 Ply and laminate co-ordinate systems...........................116C 200 Sandwich co-ordinate system and symbols ..................116

Sec. 14 Calculation Example: Two Pressure Vessels........................................ 117

A. Objective.............................................................................117A 100 General ..........................................................................117

B. Design input........................................................................117B 100 Overview.......................................................................117B 200 General function (ref. section 3 B100)..........................117B 300 Product specifications (ref. section 3 B200) .................117B 400 Division of the product into components

(ref. section 3 C)............................................................117B 500 Phases and safety class definitions

(ref. section 3 D and E) .................................................117B 600 Functional requirements (ref. section 3 F) ....................118B 700 Failure modes (ref. section 3 G)....................................118B 800 Loads (ref. section 3 I) ..................................................119B 900 Environment (ref. section 3 J).......................................119C. Failure mechanisms ............................................................119C 100 Identification of failure mechanisms

(ref. section 6 A) ...........................................................119C 200 Classification of failure mechanisms by failure types

(ref. section 6 A) ...........................................................120C 300 Failure mechanisms and target reliabilities

(ref. section 2 C500)......................................................121D. Material properties..............................................................121D 100 General (ref. section 4)..................................................121D 200 Ply modulus in fibre direction E1..................................122D 300 Matrix dominated elastic properties..............................122D 400 Fibre dominated ply strength and strain to failure ........123D 500 Matrix dominated ply strength and strain to failure......123DET NORSKE VERITAS

E 100 General ..........................................................................109 D 600 Time to failure for fibre dominated properties..............123

Offshore Standard DNV-OS-C501, January 2003 Contents Page 7D 700 Time to failure for matrix dominated properties .......... 123D 800 Test requirements.......................................................... 123

E. Analysis of gas vessel with liner ........................................124E 100 General.......................................................................... 124E 200 Analysis procedure (ref. section 9) ............................... 124E 300 Fibre failure - short-term (ref. section 6 C) .................. 125E 400 Fibre dominated ply failure due to

static long-term loads (ref. section 6 J)......................... 125E 500 Fibre dominated ply failure due to

cyclic fatigue loads (ref. section 6 K) ........................... 126E 600 Matrix cracking (ref. section 6 D) ................................ 126E 700 Unacceptably large displacement (ref. section 6 I)....... 126E 800 Impact resistance (ref. section 6 L)............................... 127E 900 Explosive decompression (ref. section 6 O) ................. 127E 1000 Chemical decomposition (ref. section 6 Q) .................. 127E 1100 Summary evaluation ..................................................... 127

F. Non-linear analysis of vessel for water without liner.........127F 100 General.......................................................................... 127F 200 Analysis procedure (ref. section 9 B) ........................... 127F 300 Matrix cracking (short term) at 1.48 MPa pressure

(ref. section 6 D) ........................................................... 128F 400 Matrix cracking under long-term static loads

(ref. section 4 C400) ..................................................... 128F 500 Matrix cracking under long-term cyclic fatigue loads

(ref. section 4 C900) ..................................................... 128F 600 Fibre failure - short term (ref. section 6 C)................... 128F 700 Fibre dominated ply failure due to

static long term loads (ref. section 6 J) ......................... 129F 800 Fibre dominated ply failure due to

cyclic fatigue loads (ref. section 6 K) ........................... 129F 900 Unacceptably large displacement (ref. section 6 I)....... 129F 1000 Impact resistance (ref. section 6 L)............................... 129F 1100 Explosive decompression (ref. section 6 O) ................. 129F 1200 Chemical decomposition (ref. section 6 Q) .................. 129F 1300 Component testing (ref. section 10).............................. 129F 1400 Summary evaluation ..................................................... 130

G. Linear analysis of vessel for water without liner................130G 100 General.......................................................................... 130G 200 Analysis procedure (ref. section 9 B) ........................... 130G 300 Matrix cracking (short term) (ref. section 6 D) ............ 130G 400 Matrix cracking under long-term static loads

(ref. section 4 C400) ..................................................... 130G 500 Matrix cracking under long-term cyclic fatigue loads

(ref. section 4 C900) ..................................................... 130G 600 Fibre failure short-term (ref. section 6 C).................. 130G 700 Fibre dominated ply failure due to

static long-term loads (ref. section 6 J)......................... 131G 800 Fibre dominated ply failure due to

cyclic fatigue loads (ref. section 6 K) ........................... 131G 900 Unacceptably large displacement ................................. 131G 1000 Impact resistance........................................................... 131G 1100 Explosive decompression ............................................. 131G 1200 Chemical decomposition............................................... 132G 1300 Summary evaluation ..................................................... 132

App. A Check-lists for Design Input ........................... 133

A. Phases .................................................................................133

B. Functional requirements and failure modes........................133B 100 Functional requirements that shall be checked as a

minimum....................................................................... 133B 200 Failure modes that shall be checked as a minimum...... 133B 300 Link between functional requirements and

failure modes................................................................. 134

C. LOADS...............................................................................134C 100 Functional loads............................................................ 134C 200 Environmental loads ..................................................... 134C 300 Accidental loads............................................................ 135

D. Environments...................................................................... 135

App. B Lay-up and laminate specification.................. 136

A. Unique definition of a laminate ..........................................136A 100 ...................................................................................... 136

App. C Test methods for laminates.............................. 137

A. General................................................................................137A 100 Introduction................................................................... 137A 200 General testing information .......................................... 137

B. Static tests for laminates .....................................................137B 100 Inplane tensile tests....................................................... 137B 200 Inplane compression tests ............................................. 137B 300 Inplane shear tests......................................................... 137B 400 Through thickness tensile tests ..................................... 137B 500 Through thickness compressive tests............................ 138B 600 Interlaminar shear tests (through thickness) ................. 138B 700 Inplane fracture toughness tests.................................... 138B 800 Interlaminar fracture toughness tests ............................ 138

C. Tests to obtain properties under long term static and cyclic loads .........................................................................138

C 100 ...................................................................................... 138

D. Tests to obtain the fibre fraction.........................................138D 100 ...................................................................................... 138

E. Tests on tubular specimens.................................................138E 100 ...................................................................................... 138

F. Evaluation of stress versus strain curves ............................138F 100 Brittle characteristics .................................................... 138F 200 Plastic characteristics.................................................... 139F 300 Ductile Characteristics ................................................. 139

App. D Test methods for sandwich materials ............. 140

A. General................................................................................140A 100 Introduction................................................................... 140A 200 General testing information .......................................... 140

B. Core materials - static tests .................................................140B 100 Tensile tests .................................................................. 140B 200 Compressive tests ......................................................... 140B 300 Shear tests ..................................................................... 140B 400 Shear test for balsa and high density cores................... 141B 500 Fracture toughness Strain energy release rate ........... 141B 600 Tests to obtain properties under long term static and

cyclic loads ................................................................... 141

C. Adhesive materials - static tests..........................................141C 100 General.......................................................................... 141C 200 Tensile tests .................................................................. 141C 300 Flatwise tensile tests ..................................................... 141C 400 Shear tests ..................................................................... 141C 500 Tests to obtain properties under long term static and

cyclic loads ................................................................... 141

D. Core skin interface properties.............................................141D 100 Tensile tests .................................................................. 141D 200 Fracture toughness of the interface............................... 141D 300 Other tests ..................................................................... 141

E. Tests for other properties ....................................................142E 100 Coefficient of thermal expansion.................................. 142E 200 Water absorption tests................................................... 142E 300 Diffusion and vapour transmission............................... 142E 400 Tests for thermal conductivity measurements .............. 142E 500 Overall volume shrinkage for gap filling fillers ........... 142E 600 Density tests.................................................................. 142

App. E Tables of Safety Factors................................... 143

A. Partial safety factors ...........................................................143DET NORSKE VERITAS

E. Distribution types of basic variables .................................. 135 A 100 General.......................................................................... 143

Offshore Standard DNV-OS-C501, January 2003Page 8 ContentsApp. F Example for representative data Stitch-bonded unidirectional (UD) plies - E glass polyester............................................................... 147

A. General................................................................................ 147A 100 .......................................................................................147

B. Definition of material ......................................................... 147

C. Quasi static properties in air (QSA) ................................... 147C 100 Test environment...........................................................147C 200 Fibre dominated ply properties .....................................148C 300 Matrix dominated ply properties...................................148C 400 Through thickness ply properties ..................................149

D. Long term properties in air ................................................. 149D 100 Test environment...........................................................149D 200 Fibre dominated tensile properties ................................149D 300 Fibre dominated compressive properties ......................152D 400 Matrix dominated inplane tensile properties.................154D 500 Matrix dominated inplane compressive properties .......154D 600 Matrix dominated inplane shear properties...................154D 700 Matrix dominated through thickness

tensile properties ...........................................................154D 800 Matrix dominated through thickness compressive

properties.......................................................................154D 900 Matrix dominated through thickness shear properties ..154

E. Long term properties in water ............................................ 154E 100 Test environment...........................................................154E 200 Fibre dominated tensile properties ................................154E 300 Fibre dominated compressive properties ......................155E 400 Matrix dominated inplane tensile properties.................155E 500 Matrix dominated inplane compressive properties .......155E 600 Matrix dominated inplane shear properties...................155E 700 Matrix dominated through thickness

tensile properties ...........................................................155E 800 Matrix dominated through thickness compressive

properties.......................................................................155E 900 Matrix dominated through thickness shear properties ..155

App. G Example for representative data Unidirectional carbon tape AS4 12k .............................. 156

A. General................................................................................ 156A 100 .......................................................................................156

B. Definition of material .........................................................156

C. Quasi static properties in air (QSA)....................................156C 100 Test environment...........................................................156C 200 Fibre dominated ply properties .....................................157C 300 Matrix dominated ply properties...................................157C 400 Through thickness ply properties..................................157

D. Long term properties ..........................................................157D 100 .......................................................................................157

App. H Example for Representative Data:Unidirectional Carbon Tapes made of TPW tape with 5631 fibres ......................................... 158

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


C. Quasi Static Properties in Air (QSA)..................................159C 100 Test environment...........................................................159C 200 Fibre dominated ply Properties .....................................159C 300 Matrix dominated ply Properties...................................159C 400 Through thickness ply Properties..................................159

D. Long Term Properties ........................................................159D 100 General ..........................................................................159

App. I Example for representative data Unidirectional carbon tape TPW 0434 Prepreg ........... 160

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


C. Quasi static properties in air (QSA)....................................160C 100 Test environment...........................................................160C 200 Fibre dominated ply properties .....................................161C 300 Matrix dominated ply properties...................................161C 400 Through thickness ply properties..................................161

D. Long term properties...........................................................161D 100 .......................................................................................161DET NORSKE VERITAS

Offshore Standard DNV-OS-C501, January 2003 Sec.1 Page 9SECTION 1GENERAL

A. ObjectivesA 100 Objectives101 The main objectives of this standard is to: serve as a basic philosophy and standard provide an internationally acceptable standard for safe de-

sign with respect to strength and performance by definingminimum requirements for design, materials, fabricationand installation of load-carrying Fibre Reinforced Plastic(FRP) laminates and sandwich structures and components

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 accepted in-dustry practice

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

B. Application - ScopeB 100 General101 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. Aspects re-lated 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 standardC 100 Users of the standard101 The client is understood to be the party ultimately re-sponsible for the system as installed and its intended use in ac-cordance with the prevailing laws, statutory rules andregulations.102 The authorities are the national or international regula-tory bodies.103 The contractor is understood to be the party contractedby the client to perform all or part of the necessary work need-ed to bring the system to an installed and operable condition.104 The designer is 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 contract-ed by the contractor to manufacture all or part of the system.Two types of manufacturers can be distinguished: the materialmanufacturers, which supply the composite material or its con-stituents (i.e. resin, fibres) and the product manufacturers,which fabricate all or part of the system.106 The third party verifier is an independent neutral partythat verifies the design of a structure or component.DET NORSKE VERITAS

Offshore Standard DNV-OS-C501, January 2003Page 10 Sec.1C 200 Flow chart of the standard

Figure 1 Flow chart of the standard

C 300 How to use the standard301 All users should go through section 1 and section 2 de-scribing the scope of the standard and the design principles.302 The client and contractor(s) should specify the DesignPremises according to section 3.303 The design analysis should be performed by the design-er according to section 6, section 7, section 8, section 9 and

section 10. The main input for the Design Report should comeout of these sections.304 The contractor(s) and manufacturer(s) should specifythe fabrication according to section 11.305 The client and 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.

FABRICATIONINSPECTION &

REPAIR

SECTION 1GENERAL

SECTION 2DESIGN

PHILOSOPHY

SECTION 3DESIGN INPUT

STARTDESIGN GENERAL

DESIGNPREMISES

DESIGNANALYSIS

GENERAL

SECTION 6Failure

mechanisms

SECTION 7JOINTS &

INTERFACES

SECTION 8SAFETY

FACTORS

SECTION 9STRUCTURAL

ANALYSIS

SECTION 10COMPONENT

TESTING

SECTION 11FABRICATION

SECTION 12INSPECTION

SECTION 14EXAMPLES

SECTION 13DEFINITIONS

SECTION 4MATERIALS -LAMINATES

SECTION 5MATERIALS -

SANDWICHDET NORSKE VERITAS

Offshore Standard DNV-OS-C501, January 2003 Sec.1 Page 11D. Normative ReferencesThe latest revision of the following documents applies:

D 100 Offshore Service Specifications

DNV-OSS-301 Certification and Verification of PipelinesD 200 Offshore Standards

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

MethodDNV-OS-C106 Structural Design of Deep Draught Floating

Units DNV-OS-C501 Composite Components

D 300 Recommended Practices

DNV RP B401 Cathodic Protection Design DNV RP-C203 Fatigue Strength DNV RP-F101 Corroded PipelinesDNV RP-F104 Mechanical Pipeline CouplingsDNV RP-F105 Free Spanning Pipelines DNV 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

DNV Rules for Certification of Flexible Risers and PipesDNV Rules for Planning and Execution of Marine operationsDNV Rules for Classification of Fixed Offshore Installations

D 500 Standards for Certification and Classification notes

DNV CN 1.2 Conformity Certification Services, Type Ap-proval

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

shore UnitsDNV CN 30.4 FoundationsDNV CN 30.5 Environmental Conditions and Environmen-

tal LoadsDNV 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 - De-sign and operation of subsea production sys-tems - 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.

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Offshore Standard DNV-OS-C501, January 2003Page 12 Sec.2SECTION 2DESIGN PHILOSOPHY AND DESIGN PRINCIPLES

A. GeneralA 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 philosophyB 100 General101 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 safety re-quirements, depending on the Safety Class to which the struc-ture or part of the structure belongs. Safety classes are based onthe consequence of failures related to the Ultimate Limit 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 assessment201 To the extent it is practically feasible, all work associat-ed with the design, construction and operation shall ensure thatno single failure is to lead to life-threatening situations for anypersons, or to unacceptable damage to material or to environ-ment.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 necessary re-medial measures may be taken. The extent of such a review isto 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).

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B 300 Quality Assurance

rors (human errors) shall be controlled by requirements to theorganisation of the work, competence of persons performingthe work, verification of the design and Quality Assurance dur-ing all relevant phases.

C. Design formatC 100 General principles101 The basic approach of the Limit State Design methodconsists in recognising the different failure modes related toeach functional requirement and 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, wherepartial 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 inthis 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 states201 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 arenot 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-DET NORSKE VERITAS

301 The safety format of this Standard requires that gross er- tions (e.g. interruption of operation, reduction of pressure or

Offshore Standard DNV-OS-C501, January 2003 Sec.2 Page 13speed) the structure will again be able to meet its functional re-quirements 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 of

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

303 Service classes are based on the frequency of service in-terruptions or restrictions caused by modes of failure relatedto the Serviceability Limit State. These modes of failure implyno risk of human injury and minor environmental consequenc-es. The operator shall specify the service class according towhich 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-warning in-trinsic to a given failure mechanism. A distinction shall bemade between catastrophic and progressive failures, and be-tween failures with or without reserve capacity during failure.The failure types for each failure mechanism described in thisStandard are specified according to the following definitions:

ductile, corresponds to ductile failure mechanisms with re-serve strength capacity. In a wider sense, it corresponds toprogressive 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 a wid-er sense, it corresponds to non-stable failure mechanisms.

402 The different failure types should be used under the fol-

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

failure type plastic 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 and yield 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 method601 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 load ef-fect 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 possible un-favourable deviations of the basic variables from their charac-teristic 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, suchthat 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 natural

variability, 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 ULSSAFETY CLASS FAILURE TYPE

Ductile/Plastic BrittleLow A B

Normal B CHigh C D

Table C2 Target reliability levels for SLSSERVICE CLASS SERVICE FAILURES

Normal AHigh BDET NORSKE VERITAS

lowing conditions for materials that show a yield point: - Uncertainties in the applied engineering models

Offshore Standard DNV-OS-C501, January 2003Page 14 Sec.2- 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- orover-proportional behaviour)


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 usuallycalibrated 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 de-sign inequality quoted in 606:

FM= F x M605 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 local re-sponses of the structure (local stresses or strains). The uncer-tainties in the local response are linked to the uncertainties onthe loads applied to the structure through the transfer func-tion.

- 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 betweentest 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 for

- 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 factoreddesign resistance is obtained by dividing the characteristic re-sistance 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 factorSk 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 factorSk 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 factor k characteristic value of the local response of the structure(strain) to applied load Sk

k characteristic value of strain to failureRk characteristic resistanceM partial resistance factorRd resistance model factor.607 The load model factor shall be applied on the character-istic local stresses or strains. The resistance model factors ap-ply on the characteristic resistance of the material used at thelocation on the structure where the design rule is to be applied.608 The characteristic values for load effects and resistancevariables are specified as quantiles of their respective probabil-ity distributions.609 The characteristic load effect, Sk, is a value that shouldrarely be exceeded. For time dependent processes, it is gener-ally given in terms of return values for occurrence, e.g., oncein a given reference time period (return period). See section 3

RdM

kkSdF

RS

.

..

1.

,..

RdM

kkSdF

RS

1.

,..

RdM

kkSdF

DET NORSKE VERITAS

by the resistance model factor. I400 for characteristic loads.

Offshore Standard DNV-OS-C501, January 2003 Sec.2 Page 15610 The characteristic resistance, Rk, is a value correspond-ing to a high probability of exceedance, also accounting for itsvariation with time when relevant. See section 4 A600 and sec-tion 5 A600 for characteristic resistance.611 The partial safety factors are calibrated against the targetreliabilities indicated in Tables C1 and C2. See also Section 8.612 The partial safety factors defined in this Standard applyto all failure mechanisms and all safety- and service classes.They depend on the target reliability, the load distribution type(or the local response distribution type when applicable) andits associated coefficient of variation, and

OS C501 Composites

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