| Failure or even collapse of bridge structures in past earthquakes were largely. In particular, shear failure of short bridge pier columns is the most dangerous failure pattern due to the brittle nature. Consequently,it is quite meaningful to study the seismic resistance performance and retrofitting for reducing bridge damages and losses. As FRP composite material has a series of advantages such as lightweight, high strength, easy construction and good resistance to corrosion and fatigue, the retrofitting method utilizing FRP is widely used in civil engineering. This thesis presents a test program on seismic behavior of short bridge columns.(1) A total of three reinforced concrete large scale circular short columns were designed, whose shear-span ratios are 1.5. One column was tested under"as-built"condition and the others were retrofitted with GFRP.(2) The failure mode, strength, stiffness, energy capacity and ductility of the columns with glass fiber reinforced polymer were described in details to investigate the seismic behavior and mechanism of columns under cyclic load.(3) On the basis of experimental and theoretical analyses, parameters including axial compression ratio, steel strength, ratio of reinforcement, concrete strength and slenderness ratio that affect hysteretic behavior are studied. Simplified models for the moment-curvature response and load-restoring force are suggested. Results from the suggested models show good agreement with the experimental results, and the models can be applied to elastoplastic dynamic analysis of structure.(4) In the end, this thesis summarizes the novel ideas and raises some problems for future studies.
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