Reduced formulation for post-elastic seismic response of dual load path bridges

The paper analyzes the transverse seismic behaviour of multi-span bridges with dissipative piers and a continuous deck transversally restrained at the abutments. These structural systems have a dual load path behaviour and their failure may occur in the piers or in the deck, depending mainly on geometry and stiffness distribution. A simplified analytical model and formulation are defined in order to derive the properties of an elasto-plastic single-degree-of-freedom system equivalent to the bridges, which can be used for design purposes or for preliminary analyses. Analytical expressions are proposed for describing the post-elastic system behaviour, the global dissipative capacity, and the failure modalities. These expressions can be written in terms of non-dimensional characteristic parameters to shed light on the relationship between the seismic capacity and the bridge properties. The proposed analytical formulation is applied to the analysis of a set of continuous multi-span steel-concrete composite bridges with different static schemes and stiffness distributions. The accuracy of the simplified model is tested by comparison with the results of incremental dynamic analysis performed on three-dimensional nonlinear finite element models. (C) 2013 Elsevier Ltd. All rights reserved.