16.04: High strength steel (HSS) S690 in highway bridges: Comparative design

Abstract

The use of High Strength Steel (HSS) S690 in highway bridges decks is not yet widespread. A research program investigated the optimal use of HSS S690 within bridges was conducted. A comparative design is presented for a 21.5 m wide highway bridge, with a typical 80 m long span and a composite steel‐concrete twin plate girder deck. Two designs are compared, using the Eurocodes: Design (A) adopted standard S355 NL steel grade whereas Design (B) uses HSS S690 QL or QL1 on the main girders. Comparison between the two designs shows that using S690 enables reductions of 25% on the steel weight and about 65% on full penetration welding volume, compared to design with S355. The deck can be slender using HSS and have thinner plates, but it is more susceptible to local buckling phenomena. Brittle fracture is slightly less dimensioning using HSS, but girders are likely to be much more prone to fatigue, which proves to be the main issue of the design together with the local buckling phenomena. The critical fatigue welded joints are analysed according to EN 1993–1‐9. For plate girders with transverse stiffeners, fatigue presents a major design constraint, namely on span sections, due to allowable plate stresses range near the welded joints. Standard fatigue load model FLM3 with the damage equivalent factor concept is used for fatigue design of several plate girder details. Fatigue resistance of the welded joint between the transverse stiffeners and the bottom tension flange proved to be the most relevant aspect of the design of the composite steel‐concrete twin plate girder deck designed for HSS S690.

Experimental and numerical fatigue assessment of duplex welded transversal stiffeners

“…The selection of the presently studied specimen was done in two previously published papers of the same authors [66,78], in which extensive numerical investigations were performed on a variety of fatigue prone welded bridge details pointing out that the chosen detail is one of the most critical one regarding fatigue. Similar findings were underlined in [79].…”

Lifecycle cost assessment of high strength carbon and stainless steel girder bridges

“…The beneficial effect of higher strength steel grade was combined with low maintenance costs, and the duplex option turns out to have a lower lifecycle cost (LCC). Very similar observations were made in (Habraken et al, 2019;Lemma et al, 2020;Pedro et al, 2018Pedro et al, , 2017 where the possible weight reduction when S690 is used instead of S355 in a steel girder bridge is calculated. The weight reduction of structures via the use of higher strength materials is reported in many other studies (Budano et al, 2007;Günther, 2005;Lagerqvist et al, 2007;Sedlacek et al, 2002;Shi et al, 2014) but, to the authors' best knowledge, most of these studies did not consider fabrication/maintenance costs.…”

Web Buckling of High Strength Steel Plate Girders Induced by Bending Curvature

“…Several comments can be made to the assumptions from the Basler model: 1) The curvature 1/ is based on the strain in the flange and the neutral axis placed at middle height of a symmetric girder; steel plate girders can be symmetrical, but steel-concrete composite plate sections are unlikely to be; still, for a simply supported girder with a class 4 symmetric cross-section, the effective cross-section is asymmetric, and so the position of the neutral axis shifts downwards to the bottom tension flange; the curvature based on the compressive flange and the ensuing web compressive stress σz will therefore decrease, and the web slenderness limit may slightly increase; 2) When using HSS, the stability and fatigue issues often govern the design [2]; in such case ULS combinations create stresses lower than the high steel strength; So, the compressive deviation force applied to the web can be reduced from the maximum assumed value | 162 f = f yf , and the slender limit imposed by flange-induced buckling on the web will therefore be increased; 3) Basler model assumed that the web is simply supported by the flanges and so the column buckling length of the web is equal to the web depth ℎw; however, the web edges are welded to the flanges, and a top slab may exist, and so some rotational stiffness caused by the flanges may exist. In that case, the buckling length is smaller than the web depth, increasing the web slenderness limit; 4) Basler model neglects the longitudinal web stresses x due to bending, much higher than the vertical stresses z .…”

“…The use of high strength steel (HSS) S690 is being proposed in bridge deck applications to reduce steel quantity of plate girder, designed for bending and shear. According to recent investigations, for highway plate girders decks, the use of HSS S690 QL enables a reduction of 25-30% of the steel weight compared to designs using standard in S355 NL [1,2].…”