TWI Industrial Member Report Summary 150/1981
By J D Harrison
This document will be presented as a rapporteur's report at a conference on steel in marine structures to be organised by the Commission of the European Communities in Paris on 5-8 October 1981. It outlines the many choices that face an offshore structural design team in the field of material selection. These may be listed as: steel strength level, production route, product form, welding process, pre- and postweld heat treatment and welding consumables. The objective is to achieve a structure which fulfils the required function both safely and economically. Different structure types perform different functions, e.g. fixed platforms, tethered buoyant platforms, mobile rigs, mooring dolphins, flare towers, etc., and the function of course has a significant bearing on the materials choices since it affects the needs for lightness and stiffness or flexibility. With regard to safety one must consider the interaction of the material with the various fabrication problems that can lead to defects and also the main failure modes of fracture, fatigue and stress corrosion cracking. The report deals quite extensively with the problem of fracture because fatigue will be covered elsewhere in the conference and because the achievement of good fracture toughness for welds for offshore structures is currently of considerable interest.