SEISMIC PERFORMANCE AND RETROFIT EVALUATION OF HOLLOW-CORE COMPOSITE BRIDGE COLUMNS

This paper presents the seismic behavior of large-scale hollow- core fiber-reinforced polymer-concrete-steel (HC-FCS) bridge column. The HC-FCS column consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner thin-walled steel tube. The width-to-diameter ratio for the steel tube was 147. The column had an outer diameter of 24 inches and a height-to-diameter ratio of 4.0. The steel tube was embedded into reinforced concrete footing with an embedded length of 1.25 times the steel tube diameter, while the FRP tube only confined the concrete wall thickness and curtail at the top of the footing level. The column was first tested as a vertical cantilever by applying cyclic horizontal and constant axial loads to the top of the column. Then, the column was repaired using a rapid repair technique within 6 hours duration and retested under the same seismic loading condition. The retrofitting technique includes wrapping three glass FRP layers around the outer bottommost FRP tube that ruptured at the interface joint between the column and the footing during the first test. The results revealed that the HC-FCS column achieved the ductile behavior with good inelastic deformation capacity under seismic loads. While, repaired column performed relatively well under cyclic loading, recovering 34% flexural strength and 80% of the lateral displacement capacity compared to the virgin tested column.