Seismic strengthening of RC beam-column joints using CFRP sheets I: Experimental study

The objective of this research is to develop effective strengthening schemes for reinforced concrete (RC) beam-column joints using carbon fiber reinforced polymer (CFRP) sheets. The existence of transverse beams brings a major obstacle to the practices of directly strengthening joint cores using CFRP sheets in two-way RC frames. Two seismic strengthening schemes using CFRP sheets around cores to upgrade shear capacity of the joints in two-way RC frames are designed and another strengthening scheme for the joints in one-way RC frames is also designed for the cases without transverse beams. Seven, full-scale interior RC beam-column joints which were designed with nonductile detailing characteristics of pre-seismic construction code were constructed; namely a control specimen and six strengthened specimens. These specimens were tested under quasi-static cyclic loading to examine the effectiveness of the schemes. Conclusions show that the tested strengthening schemes were successful in improving seismic behavior of the joints, which are drawn from the comparison of test results between the control joint and the strengthened ones in aspects of failure modes, load versus displacement curves, shear deformation of joint cores, strength and stiffness degradation, and cumulative energy dissipation capacity.