Behavior of partially concrete-filled steel tube bridge piers under bi-directional seismic excitations

Abstract During the past decades, amounts of research efforts have been concentrated to investigate basic characteristics of the seismic response of steel bridge piers by cyclic bi-directional loading tests or finite element analysis. However, dynamic test results on partially concrete-filled steel tube (PCFST) bridge piers under coupled ground motions in two horizontal directions are insufficient. To investigate the behavior of PCFST bridge piers under bi-directional seismic excitations, a series of cyclic static loading tests and single- and bi-directional hybrid (pseudo-dynamic) loading tests for circular-section test specimens with three different concrete-filled ratios were performed in this study. The failure patterns were observed after the tests. The experimental results showed that the restoring force of PCFST bridge piers obtained in bi-directional loading tests was almost the same as that obtained in single-directional loading tests. However, deformation capacity deteriorated considerably when subjected to bi-directional dynamic loadings. This study also shows that the seismic behavior of PCFST bridge piers can be effectively improved if the concrete fill height is significantly increased.