Seismic Performance of Large-Scale RC Eccentric Corner Beam-Column-Slab Joints Strengthened with CFRP Systems

Abstract

Eccentric corner beam-column joints of existing reinforced concrete (RC) frames, in which the beam axes are eccentric to the column axis, can be highly vulnerable to brittle joint shear failure under earthquake loading. Externally bonded fiber-reinforced polymer (FRP) composites provide a strengthening option, although research on this method is limited. This paper addresses such a knowledge gap by considering the influence of key parameters of joint transverse reinforcement ratio, eccentricity, and carbon FRP (CFRP) strengthening on the seismic performance of large-scale eccentric corner beam-column-slab joints containing a transverse beam and slab. Seven specimens, including four control specimens and three strengthened specimens, were designed and tested. Three CFRP strengthening schemes, aimed at improving joint shear capacity and overall seismic behavior, were proposed. Upon the comparison and discussion of test results, the influence of joint transverse reinforcement ratio, eccentricity, and the proposed CFRP strengthening schemes on the seismic behavior of such eccentric joints was established. Irrespective of the joint region and with or without adequate transverse reinforcement, all control specimens experienced joint shear failure due to the adverse effects of eccentricity. The CFRP intervention changed the failure mode from brittle joint shear failure to ductile beam-hinge failure. The mechanism and effectiveness of the proposed CFRP strengthening schemes were finally validated and several suggestions on CFRP strengthening are provided for eccentric joints.