Retrofit of RC frames with captive-column defects

Abstract

A large number of Reinforced Concrete (RC) buildings are constructed with masonry infill for functional or aesthetic reasons. Sometimes window or ventilator openings have been left in the wall for architectural necessities. RC constructions with such partial masonry infill face serious earthquake shear damages in columns due to captive-column effect. The purpose of this research is to investigate the behavior of non-ductile RC frames with partial masonry infill under lateral loading and to reduce the potential for captive-column damage induced by partial infill. An experimental study is carried out with one-third scale, two-bay two-story laboratory models having partial infill in the bottom story. A local retrofitting strategy of strengthening RC structural elements with Glass-Fiber Reinforced Polymer (GFRP) composites is adopted. Two frames namely, a control specimen and a retrofitted specimen are tested under quasi-static cyclic load to failure. The control specimen showed a brittle shear failure in bottom story columns due to the induced captive-column effect while the retrofitted specimen exhibited an improved performance. Results demonstrated the behavior with respect to strength, stiffness and ductility characteristics. The aim is, therefore to contribute for developing a sustainable structure to overcome the seismic failure due to captive-column defects.