Local failure mechanisms of existing steel-concrete composite decks

The design of Steel-Concrete Composite (SCC) bridges is usually oriented to the solution of global problems, governed by strength and ductility issues of the whole structure, while minor attention is generally given to local effects, associated with the transfer mechanisms of inertia forces from decks to substructures. However, local failure mechanisms of the deck may be of importance since they may compromise the overall response of the bridge, especially for existing bridges, designed ac-cording to lower seismic actions compared to those defined by modern codes. In this paper, the seismic response of an existing SCC bridge is investigated, focusing on the role of local failure mechanisms of the deck on the overall response of the bridge. Two local paths for the seismic action are analyzed: the first involves the shear connection through which inertia forces act-ing at the level of the concrete slab are firstly transferred to steel members; the second is represented by truss cross-beams at supports, one of the most widespread typologies for existing SCC decks, through which the shear forces are transferred to bearings and substructures. Results of seismic analyses on the selected case study are shown and discussed, highlighting the vulnerabilities of the investigated local components.