Seismic mobile shaker testing of full-scale RC building frames with high-strength NSM-FRP hybrid retrofit system

Abstract

Past seismic events have led to the premature failure of many existing seismically-vulnerable reinforced concrete building frames due to their inadequate column details. To ensure the ductile behavior of the non-ductile building frames, a hybrid retrofit system combining high-strength near surface mounted bars (flexural retrofit) with carbon fiber reinforced polymer sheets (shear retrofit) can be installed to the seismically-vulnerable columns. This study presents the experimental dynamic assessment of the non-ductile building frames retrofitted with the hybrid system. To prevent the column shear failure due to the flexural strengthening, a two-stage design procedure for the hybrid retrofit system was proposed. The full-scale dynamic testing was performed on the retrofitted test frame to realistically measure dynamic responses and quantify the retrofit effects. The hybrid retrofit system reduced the peak inter-story drift of the first-story columns by about 25% and their hinge rotation by approximately 76%. Additionally, the retrofit system can uniformly distribute the damage or drift over the entire structure, i.e. mitigation of soft-story mechanism.