Seismic Fragility Analysis of Simply Supported Beam Bridges with Precast Columns

摘要

The fragility analysis of simply supported beam bridges with precast columns was conducted using nonlinear time history analysis based on probability theory. The precast column featuring with flag shape hysteresis lateral force-displacement response was used here aiming to alleviate the substructure damage during earthquake. Peak ground acceleration (PGA) was selected as seismic intensity measure (IM). The finite element model used nonlinear beam-column element for substructures, and used elastic beam element for super beams. Rubber bearings were modeled with nonlinear bearing element. The interaction between adjacent beams, abutment and beam, and abutment and backfill soil were modeled with various appropriate nonlinear elements. Four bridge limit states are considered: slight, moderate, extensive and complete damage. The capacity limits were derived from empirical results suggested by literature with minor revisions. The uncertainty of the excitation ground motion and structural material strengths, such as steel bar and concrete, was considered. Twenty seismic waves were selected from PEER STRONG MOTION DATABASE. The probabilistic seismic demands of components, such as the piers curvature ductility, abutment active and passive displacement, and bearing displacement, were estimated. The component fragility were drawn using the probabilistic seismic demand model (PSDM). At last the fragility curves of the whole bridge was derived by the combination fragility of the components.