Effectiveness evaluation of seismic protection devices for bridges in the PBEE framework

Seismic protection measures for bridges can be used both for obtaining acceptable performances from new structures and for retrofitting existing ones. With the modern design philosophy based onthe probabilistic Performance-Based Earthquake Engineering (PBEE) approach, the engineers are allowed to investigate different design solutions in terms of vulnerability assessment. However, if probabilistic PBEE approaches are nowadays well established and widely studied also for bridges, the topic of using the PBEE frameworks for the evaluation of the effectiveness of seismic protection devices for bridges is not extensively treated in literature. The first objective of this work is to deal with the problem of assessing the earthquake performance of a highway bridge equipped with different bearing devices - the elastomeric bearings (ERB) and the friction pendulum systems (FPS). The second purpose is to evaluate the efficiency of a structure-dependent IM in case of an isolated system. The examined structure is a highway bridge with concrete piers and steel truss deck. A FE model of the bridge is developed by using nonlinear beam-column elements with fiber section and the devices are modeled by specific elements implementing their nonlinear behavior. The effectiveness of the different retrofitting strategies has been carried out in terms of damage probability. Choosing the example of slight damage, and referring to the curvature ductility as EDP, the probability of damage during a period of 50 years is: 23% for the structure without isolation, 7% for the structure equipped with ERB, and 3% for the structure equipped with FPS isolation.