OPTIMAL PROBABILISTIC SEISMIC DEMAND MODELSFOR TYPICAL HIGHWAY OVERPASS BRIDGES

摘要

Performance-based seismic design is founded on our ability to evaluate the performance of astructure in a given seismic hazard environment. The Pacific Earthquake EngineeringResearch Center (PEER) is developing such a probability-based performance framework, onecomponent of which is a seismic demand model. While probabilistic seismic hazard modelshave been developed before, rigorous probabilistic demand models do not exist. Theobjective of this paper is the development of an optimal probabilistic seismic demand modelfor typical highway overpass bridges. This demand model relates ground motion IntensityMeasures, such as spectral displacement, to bridge Demand Parameters, such as columncurvature ductility or drift ratio. An optimal model is defined herein as practical, sufficient,effective, and efficient. A parametric finite element model, representing an entire bridgeportfolio, was used to compute values of bridge-specific Demand Parameters. Probabilisticseismic demand models were formulated by statistical analysis of the data produced duringtime history analyses of each bridge in the bridge portfolio under all ground motions. Arepresentative relation between chosen Intensity and Demand Measure pairs forms the basisof the demand models presented.