Equivalent static methods for seismic design of straight integral abutment bridges

Integral abutment bridges (IABs) are becoming the solution of choice in the low to mid-length ranges because of their low cost compared with traditional solutions and their good performance under seismic actions. The main drawback of these bridges is the need to consider soil-structure interaction to assess their performance, a problem that is more pronounced for actions implying horizontal deck movements, such as temperature or the specific focus of this paper, that is, seismic action. In IAB design, simplified models are often used, where soil-structure interaction is modeled by means of beams on non-linear Winkler springs for the evaluation of seismic behavior. This paper, starting from an existing non-linear dynamic model (NLDM) that describes IABs longitudinal seismic response, derives two equivalent static models: one non-linear and the other linear, for displacement- or force-based design respectively. A parametric study is carried out to assess the static models performance in terms of the main design internal actions versus the NLDM. Finally, the assessed model errors are discussed in the context of partial factors safety format.