Influence of model parameter uncertainty on seismic transverse response and vulnerability of steel-concrete composite bridges with dual load path

This paper uses a fully probabilistic approach to investigate the seismic response of multispan continuous bridges with dissipative piers and a steel-concrete composite (SCC) deck, the motion of which is transversally restrained at the abutments. This bridge typology is characterized by complex dual load path behavior in the transverse direction, with multiple failure modes involving both the deck and the piers. Proper assessment of the seismic vulnerability of these structural systems must rigorously take into account all pertinent sources of uncertainty, including uncertainties in both the seismic input (record-to-record variability) and the properties defining the structural model (model parameters). Model parameter uncertainty affects not only the structural capacity, but also the seismic response of a structural system. However, most of the procedures for seismic vulnerability assessment focus on the variability of the response resulting solely from seismic input uncertainty. These procedures either neglect model parameter uncertainty effects or incorporate these effects only in a simplified way. A computationally expensive but rigorous procedure is introduced in this work to include the effects of model parameter uncertainty on the seismic response and vulnerability assessment of SCC bridges with dual load path. Monte Carlo simulation with Latin hypercube sampling, in conjunction with probabilistic moment-curvature analysis, is used to build probabilistic finite-element models of the bridges under study. Extended incremental dynamic analysis is used to propagate all pertinent sources of uncertainty to the seismic demand. The proposed pro-cedure is then applied to the assessment of three benchmark bridges exhibiting different seismic behavior and dominant failure modes. Comparison of the response variability induced by seismic input uncertainty and the response variability induced by model parameter un-certainty highlights the importance of accounting for the latter when evaluating the safety of the typology of bridges considered in this study.