Improving cyclic response of heat-damaged non-ductile RC joints using CFRP hybrid systems

Abstract

The behavior of non-ductile, heat-damaged reinforced concrete (RC) beam column joints was investigated in this experimental research work. A hybrid system formed of carbon fiber-reinforced polymer (CFRP) sheets and strings was used to improve the cyclic response of these non-ductile, heat-damaged joints. To evaluate the cyclic performance of these joints, twelve RC beam-column joints were cast and classified into four categories: Three joints were kept without strengthening as control specimens. Three joints were strengthened with one layer of CFRP sheets and one NSM-CFRP string in the beam and in the column; three joints were strengthened with two layers of CFRP sheets and two NSM-CFRP strings in the beam and in the column; and three joints were strengthened with three layers of CFRP sheets and three NSM-CFRP strings in the beam and in the column. In addition, the joints were tested at three different temperatures, which are: ambient, 400 °C, and 600 °C. The experimental findings show a considerable improvement in the cyclic performance of non-ductile heat-damaged RC beam-column joints strengthened with a hybrid CFRP system (greater lateral displacement, higher load capacity, higher energy dissipation, higher displacement ductility, and slower secant stiffness degradation). Furthermore, the effectiveness of CFRP composites increases as the degree of heat damage increases.