A Performance-Based Assessment of a Case Study Bridge and Impact of Retrofitting Interventions

With the rapidly increasing technological advancements and the minimization of computational effort, large sets of nonlinear time history analyses (NTHA) – 2D or 3D - are gaining more and more ground in seismic assessment and design verification of new structures. In this study, a probabilistic framework has been used to analyse and assess an existing case study bridge utilizing the concepts of performance-based earthquake engineering (PBEE). In particular, two different methodologies were followed to calculate the structural losses: a rather simplified approach (HAZUS), and a more comprehensive one (FEMA P-58). The damageable components of the case study bridge that were examined, were principally the bridge piers in this study. The eventual, and one of the most important, parameters extracted from this procedure was the expected annual loss (EAL) ratio, which is widely used for decision making during the seismic assessment or design of structures. Furthermore, the case study bridge was retrofitted with several interventions which were also evaluated via the same framework and compared with the as-built bridge. The main findings of the study were the relatively low monetary direct losses of the bridge, compared to buildings, even though the underlying seismic hazard was relatively high. The retrofitting interventions had the effect of reducing the structural demands and thus the direct losses, which have been already low. Additionally, the loss estimation between the simplified and comprehensive approach was seen to match very well in this study for both the pre- and post-retrofit structure, highlighting the adequacy of more simplified and direct approaches in the loss assessment of bridge structures.