The primary objective of this study is to predict post-peak behavior of high bridge piers with hollow section. If hollow piers are subjected to large flexural force, inside concrete is fractured by compression after spalling of concrete cover and buckling of longitudinal reinforcement, and collapse of the whole flange part in compression suddenly occurs. Therefore, in the seismic design of hollow piers, it is important to predict when spalling of concrete cover and buckling of reinforcement occur and to analyze the post-peak behavior of piers. In order to predict spalling and buckling, a new analysis model was proposed. In this model, axial compressive force, secant elastic modulus and curvature of reinforcement are used, and reduction of buckling length, which was induced by decrease of reinforcement stiffness after yielding, can be calculated. Then, this model was installed in the 3 dimensional nonlinear FEM analysis program using layered shell elements. As a result, comparing with past experiments, □we successfully predicted not only spalling and buckling but also the post-peak behavior of piers such as moment-curvature response. In addition, we succeeded to predict the post-peak behavior of piers which are subjected to torsional force caused by the horizontal deformation of the girder.
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