BRIDGE ABUTMENT MODEL SENSITIVITY FOR PROBABILISTIC SEISMIC DEMAND EVALUATION

Modeling the contribution of bridge abutments to overall bridge seismic response has been the focus of a significant research effort in the past decade. Many recent studies have shown how that abutment response significantly influences the response of short- and medium-length bridges. Some of these studies are based on sensitivity analyses using deterministic bridge models with varying abutment characteristics and capacities, and a relatively small number of earthquake ground motions. In this paper, a comparison of Probabilistic Seismic Demand Models (PSDMs) obtained using Probabilistic Seismic Demand Analysis (PSDA) is used to conduct a sensitivity study on how bridge abutment models affect seismic demand for short- and medium-length bridges. The advantages of this method are in a large number of earthquake ground motions used in the sensitivity analysis, and in a probabilistic interpretation and comparison of bridge demand. Abutment capacity is not considered at this point because of a shortage of reliable abutment capacity data. PSDMs are a part of a performance-based seismic design framework developed by the Pacific Earthquake Engineering Research (PEER) Center. This design framework is based on the principle of de-aggregation of uncertainties that define probabilistic performance-based seismic design. Given a class of structures, such as typical highway overpass bridges, PSDMs define the relation between seismic hazard and structural demand. They are typically used to compute the probability of exceeding an Engineering Demand Parameter (EDP), such as drift, given the value of a seismic hazard Intensity Measure (IM), such as Arias intensity. Comparison of PSDMs for bridges with systematically varied abutment models gives a probabilistic characterization of the effect of abutments and their importance in the overall seismic demand for a bridge.