Published by ICE Publishing, 40 Marsh Wall, London E14 9TP Distributors for ICE Publishing books are USA: Publishers Storage and Shipping Corp., 46 Development Road, Fitchburg, MA 01420 www.icevirtuallibrary.com A catalogue record for this book is available from the British Library ISBN: 978-0-7277-0108-4 © Thomas Telford Limited 2011 ICE Publishing is a division of Thomas Telford Ltd, a whollyowned subsidiary of the Institution of Civil Engineers (ICE) All rights, including translation, reserved Except as permitted by the Copyright, Designs and Patents Act 1988, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the prior written permission of the Publisher, ICE Publishing, 40 Marsh Wall, London E14 9TP This book is published on the understanding that the author is solely responsible for the statements made and opinions expressed in it and that its publication does not necessarily imply that such statements and/or opinions are or reflect the views or opinions of the publishers Whilst every effort has been made to ensure that the statements made and the opinions expressed in this publication provide a safe and accurate guide, no liability or responsibility can be accepted in this respect by the author or publishers FATIGUE IN OFFSHORE STRUCTURAL STEELS Implications of the D e p a r t m e n t of Energy's Research Programme FATIGUE I N O F F S H O R E S T R U C T U R A L STEELS Implications of the Department of Energy's Research Programme Proceedings of a C o n f e r e n c e o r g a n i z e d b y t h e Institution of Civil Engineers, h e l d in L o n d o n o n - F e b r u a r y 1981 THOMAS TELFORD LTD, LONDON, 1981 Contents Opening address H G CRISP 1 The design of the UKOSRP basic fatigue programme J G H I C K S Constant amplitude corrosion fatigue strength of welded joints G S B O O T H Discussion on Paper 15 Corrosion fatigue of welded joints under narrow band random loading G S B O O T H a n d R H O L M E S Discussion on Paper An introduction to crack growth testing in the U KOS RP and its relevance to the design of The effect of North Sea service conditions on fatigue crack growth in structural steel offshore structures H G M O R G A N and T W T H O R P E T W T H O R P E , A R A N C E , D R V S I L V E S T E R , P M S C O T T a n d H G M O R G A N 17 23 25 35 Discussion on Papers and 45 Review of stress analysis techniques used in UKOSRP N M I R V I N E 47 Stress concentration factors at K and KT tubular joints A G W O R D S W O R T H 59 Discussion on Papers and 67 71 The fatigue strength of tubular welded joints K J M A R S H Modes of fatigue crack development and stiffness measurements in welded tubular joints J G W Y L D E a n d A M c D O N A L D 79 10 Experimental results of fatigue tests on tubular welded joints A M c D O N A L D a n d J G W Y L D E Discussion on Papers and 89 101 1 Prediction of crack growth in tubular joints—an alternative design approach A M C L A Y T O N 105 Discussion on Paper 11 111 Summary of current design and fatigue correlation P J FISHER 113 Relationship of Guidance Notes and applicability to offshore design J R PETRIE 123 Discussion on Papers 12 and 127 H G CRISP, Manager, UK Offshore Steels Research Project Opening address T h e p u r p o s e o f t h i s a d d r e s s is to g i v e a b r i e f d e s c r i p t i o n o f t h e o r g a n i z a t i o n of the O f f s h o r e S t e e l s R e s e a r c h P r o j e c t and to show h o w p r o b l e m s are d e a l t w i t h W h e n s e t t i n g u p the p r o j e c t in - it w a s a p p r e c i a t e d that m o s t o f the a v a i l a b l e d a t a on f a t i g u e w e r e not d i r e c t l y a p p l i c a b l e to conditions offshore The initial requirements t h e r e f o r e w e r e to b u i l d u p a d a t a p o o l o f v i a b l e i n f o r m a t i o n w h i c h m o r e n e a r l y r e p r e s e n t e d the o f f s h o r e c o n d i t i o n s , and from t h i s d a t a b a s e to m o v e f o r w a r d to p r o v i d e i n f o r m a t i o n and an u n d e r s t a n d i n g that w o u l d b e o f v a l u e to d e s i g n e r s and to p r o v i d e a sound b a s i s for future guidance n o t e s T h e m o r e i m p o r t a n t g a p s to b e filled in the i n f o r m a t i o n a v a i l a b l e t h e n w e r e the e f f e c t s d u e to g e o m e t r y M o s t o f the i n f o r m a t i o n w a s t a k e n from p l a t e s p e c i m e n s , but in fact the a r e a s o f c o n c e r n o f f s h o r e are t u b u l a r j o i n t s At the start o f t h e p r o j e c t l i t t l e t u b u l a r w o r k had b e e n c a r r i e d out and not all the r e s u l t s had been published T h e r e w a s an o b v i o u s n e e d to s t u d y t u b u l a r j o i n t s in as m a n y g e o m e t r i c a l and load c o n f i g u r a t i o n s as p o s s i b l e M u c h of the w o r k a v a i l a b l e in - w a s on base plate of unrepresentative thickness (6-10 m m ) , w h e r e a s the a r e a s of i n t e r e s t o f f s h o r e are in w e l d m e n t s in e x c e s s o f , say, 32 m m It w a s n e c e s s a r y t h e r e f o r e to get d a t a o n w e l d m e n t s in t h i c k e r p l a t e A l t h o u g h m u c h w o r k had b e e n d o n e o n c o r r o s i o n l i t t l e w o r k h a d b e e n done o n c o r r o s i o n f a t i g u e in sea w a t e r , or to show t h e e f f e c t s o f c a t h o d i c protection, temperature, intermittent wetting and d r y i n g and so o n Most fatigue work had b e e n d o n e in air and so t h e s t a n d a r d a i r f a t i g u e c u r v e s had to be m o d i f i e d to t a k e account of offshore environments M u c h e f f o r t is spent in t h e o f f s h o r e i n d u s t r y in i m p r o v i n g the w e l d m e n t s b y t o e g r i n d i n g and h e a t t r e a t m e n t , and p o s s i b l y b y u s e o f T I G d r e s s i n g and p e e n i n g , and so it w a s d e s i r a b l e to q u a n t i f y t h e s e i m p r o v e m e n t s in t e r m s o f t h e i r e f f e c t on c o r r o s i o n f a t i g u e l i v e s Some w o r k w a s t h e r e f o r e p r o g r a m m e d to s t u d y t h i s p r o b l e m - w i t h h i n d s i g h t , u n f o r t u n a t e l y n o t as m u c h as is d e s i r a b l e M a n y v a r i a b l e s w e r e to b e s t u d i e d , s o m e o f w h i c h w e r e i n d e p e n d e n t and s o m e i n t e r d e p e n d e n t of one a n o t h e r T h e aim w a s to m a k e t h e w o r k g i v e r e s u l t s w h i c h would b e i m m e d i a t e l y u s a b l e in d e s i g n and a s s e s s m e n t and to a v o i d b e i n g lured into the i n t e r e s t i n g t r a p of d e e p s c i e n c e which may take a considerable amount of u n r a v e l l i n g b e f o r e b e i n g of p r a c t i c a l u s e N e v e r t h e l e s s , it w a s a p p r e c i a t e d that b a s i c w o r k on c r a c k g r o w t h and c o r r o s i o n f a t i g u e PROJECT MANAGEMENT UKAEA/SRD STRESS ANALYSIS of Tubular Joints MATERIAL PEDIGREE TESTS Computer Analysis ATKINS R&D Strain Gauged Acrylic Models LLOYDS REGISTER OF SHIPPING Photoelastic Studies NOTTINGHAM UNIVERSITY Fig UK O f f s h o r e S t e e l s R e s e a r c h BASIC FATIGUE TESTS TUBULAR JOINT in air and sea water TESTS (including cathodic protection) in air with constant and variable amplitude loads Tests on T-Joints with constant and Tests on Weldments variable amplitude loads WELDING INSTITUTE Tests on Large H-Joints NATIONAL ENGINEERING NATIONAL ENGINEERING LABORATORY LABORATORY Tests on Steel Plate UKAEA/Harwell UKAEA/RFL FRACTURE TESTS Selection of Fracture Resistant Materials WELDING INSTITUTE Tests on T, K and TK Joints with constant amplitude loads WELDING INSTITUTE Project Fatigue in offshore structural steels T h o m a s Telford Ltd, London, 1981 OPENING ADDRESS b e h a v i o u r w o u l d b e n e c e s s a r y to a c o m p l e t e u n d e r s t a n d i n g o f t h e p r o b l e m s o f f s h o r e and t h i s has also been studied T h e requirement that the results should be i m m e d i a t e l y u s a b l e p u t c o n s t r a i n t s on t h e p r o j e c t to r e p r e s e n t w h e r e p o s s i b l e t h e c o n d i t i o n s f o u n d o f f s h o r e (in p a r t i c u l a r in t h e N o r t h S e a ) , b o t h in t h e s e l e c t i o n of r e p r e s e n t a t i v e s p e c i m e n s and o f r e p r e s e n t a t i v e test conditions T h i s led i n e v i t a b l y to s o m e compromises A c o n s i d e r a b l e a m o u n t o f w o r k w a s n e c e s s a r y to m o u n t a p r o j e c t o f t h i s m a g n i t u d e , b o t h in a d v i c e a n d in t h e p h y s i c a l p r o d u c t i o n o f s p e c i m e n s (from lb to 20 t o n s ) and t h e c o s t was £4.25 m i l l i o n (1980 p r i c e s ) Twelve c o n t r a c t o r s w e r e e m p l o y e d and a d v i c e and h e l p w e r e t a k e n f r o m m o s t o f t h e oil c o m p a n i e s , c o n t r a c t o r s and a s s e s s o r s a c t i v e o f f s h o r e in t h e North Sea I w o u l d l i k e to a c k n o w l e d g e t h e i r support w i t h advice, the use of their s p e c i f i c a t i o n s and f r e e a c c e s s to t h e i r construction yards O r g a n i z a t i o n a l l y t h e p r o j e c t w a s set out as s h o w n in F i g S t r e s s a n a l y s i s w a s r e q u i r e d to g i v e an u n d e r s t a n d i n g o f t h e d e t a i l e d b e h a v i o u r o f the t u b u l a r j o i n t s M a t e r i a l p e d i g r e e is r e a l l y a f i l i n g c a b i n e t w i t h all t h e d e t a i l s of materials, specimen manufacture, weld p r o c e d u r e s and so on for f u t u r e u s e and reference T h e b a s i c f a t i g u e t e s t s a r e d e s i g n e d to show the effects of the various testing p a r a m e t e r s T h e f o u r t h c o l u m n in F i g is c o n c e r n e d w i t h the tubular joint tests w h e r e the basic i n f o r m a t i o n from c o l u m n s 1-3 is b r o u g h t t o g e t h e r , and the f a i l u r e m o d e s o f t u b u l a r j o i n t s are studied T h e work done on fracture toughness of w e l d m e n t s u s e d o f f s h o r e is not y e t c o m p l e t e it c o u l d b e the s u b j e c t for a c o m p l e t e and c o n t r o v e r s i a l c o n f e r e n c e in i t s e l f I should like to a c k n o w l e d g e t h e f i n a n c i a l aid r e c e i v e d from the D e p a r t m e n t o f E n e r g y and t h e E u r o p e a n C o a l and S t e e l C o m m u n i t y , and a l s o t h e v a l u a b l e c o - o p e r a t i o n w i t h c o l l e a g u e s in the European Offshore Programme ... and also to facilitate comparison with existing data Although the main aim of the programme was to acquire stress/life data for constant amplitude and variable amplitude loadings a number of tests... cell as shown diagrammatically in figure The volume of each cell was approximately 10 litres and the sea water flow rate was approximately litre/ The sea water was prepared according to a standard... FATIGUE IN OFFSHORE STRUCTURAL STEELS Implications of the D e p a r t m e n t of Energy's Research Programme FATIGUE I N O F F S H O R E S T R U C T U R A L STEELS Implications of the Department