Response of substandard reinforcing details T connections upgraded with concrete covers and CFRP

This paper introduces the responses of two substandard reinforcing details exterior beam-column T connections, which were upgraded by a new retrofitting method using concrete covers and carbon fiber reinforced polymer (CFRP). Two reinforced concrete (RC) exterior beam-column connections without transverse reinforcement at the joints were cast and tested. A mix of epoxy resin and 20% thickener was used to glue the first connection (the Strengthened specimen, TS) with the concrete covers around the column at the joint area to modify it from a square to a circular section and then it was wrapped with CFRP to strengthen. A load was first applied on the second connection (the Repaired specimen, TR) to cause a serious failure then it was repaired. The repair scheme of the second connection was identical to the first connection. Results of testing the two connections have shown that the shear strength and ductility of both the strengthened and the repaired connections were improved significantly. The glued concrete covers not only increased the volume of the joint so that increase its shear strength but also helped in increasing the CFRP effectiveness by increasing the confinement effect on the concrete and reduce the possibility of CFRP debonding at the joint regions.