Seismic performance evaluation of retrofitted RC beam-column joints reinforced by plain and deformed bars

Abstract

The seismic retrofit of existing reinforced concrete (RC) beam-column joints in the case of the interior reinforcement of deformed bars and plain bars, as well as the decision regarding convenient retrofit strategies in the joints panel, are of major interest throughout the seismically active areas of the world. The efficiency of the proposed retrofit method called ‘joint enlargement’ in RC exterior and interior beam-column joints reinforced with deformed and plain bars, which have been performed under two different experimental setups in same university laboratories, is investigated. Seven half-scale beam-column joint reinforced by plain bars and four half-scale beam-column joint reinforced by deformed bars were tested. All specimens were subjected to a cyclic quasi-static loading to observe different levels of structural damage. The tested specimens comprised of five control specimens and six retrofitted specimens with various reinforcement detailing and varying dimensions of joint enlargement. The test results show significant improvement of the retrofitted specimens of both deformed and plain bars in terms of protecting the joint region, showing more ductile response and higher hysteresis energy capacity. The ultimate lateral load capacity was increased for all retrofitted specimens. The tests also show that the retrofit strategy for specimens reinforced with plain bars was performed well. Accordingly, the proposed retrofit strategy may be recommended for similar cases in existing old buildings reinforced with plain or deformed bars.