Application of duplex stainless steel for welded bridge construction in an aggressive environment

Steel bridges are increasingly using complex welded steelwork solutions. Recently, the most widespread construction type has been the orthotropic deck, used to build bridges ranging from a medium-span length (100 m) up to the longest-span suspension bridges (Akashi Kaikyo, Storebaelt East). Recently, many research projects and experimental activities have studied the in-service behaviour of these complex steelworks, all of them concentrating on traditional construction steel grades, i.e. S355. Although the basic duplex mechanical properties are well known, however, it is not enough just to promote this material for huge welded bridge construction — because of the importance of such structures, more specific investigations on structural components typical of bridge structure are needed. In order to learn more, the most critical bridge components have been selected for testing and 29 tonnes of duplex grade EN 1.4462 (UR45NMo) have been produced by Industeel. During fabrication of duplex components, welding procedure specifications have been developed and differences/difficulties arising in fabrication highlighted. The testing activity concerned material characterisation by mechanical and corrosion testing, fatigue tests on several different components also involving full-scale tests, corrosion fatigue on selected critical detail, and static tests on typical elements of steel bridges, i.e. the main longitudinal beams, also produced on a large scale. Finally, an existing bridge (the Verrand viaduct) was used for both final design and life-cycle costs analysis comparing two alternative materials: high strength low alloy S460 and duplex EN1.4462 stainless steel. Experimental and numerical activities performed during the project confirmed that duplex stainless steel satisfies the bridge-design requirements: structural safety and integrity, reliability and durability. Life-cycle costs analysis demonstrated that duplex stainless steel can also be economically attractive when considering whole service-life costs: ini- tial capital expense is recovered after 50 years of service life.