Seismic behavior of a steel truss bridge near a thrust fault

The three dimensional nonlinear earthquake response behavior of a steel truss bridge near a thrust fault is investigated. The input ground motions with permanent displacements due to the thrust fault with the Japan Meteorological Agency Magnitude M6.5, subjected to each supports of the bridge, are simulated using the stiffness matrix method where the kinematic source model and the horizontally layered half space are assumed. The steel truss bridge is modeled as the three dimensional nonlinear frames using the Fiber Element Method. The effects of the sedimentary layer and the depth of the upper edge of the fault upon the ground motions, and upon the behavior of inelastic response of the steel truss bridge are examined. It is found that the vertical ground motions are distinguished and they significantly affect on the inelastic response behavior of the steel truss bridge. It is also found that the thickness of sedimentary layer as well as the spatial position of the bridge strongly affect on the response behavior of the bridge.