Numerical simulation of cyclic/seismic lateral response of square RC columns confined with fibre-reinforced polymer jackets

摘要

It is well known that strengthening/seismic retrofit with fiber-reinforced polymer (FRP) confinement is highly effective for circular reinforced concrete (RC) columns but much less effective for rectangular columns (including square columns as a special case). As a result, FRP-confined concrete in rectangular columns often exhibits a softening stress-strain response (i.e., a stress-strain response with a descending branch), leading to a softening sectional moment-curvature response. For such cases, localization of inelastic deformation occurs at the column ends, which presents a significant challenge for numerical simulations to obtain objective results. Existing studies on the numerical simulation of FRP-confined rectangular RC columns under cyclic/seismic lateral loading have however overlooked this issue. In the present paper, an objective numerical approach for FRP-confined square RC columns under cyclic/seismic lateral loading is presented, in which the force-based beam-column element with the modified Scott and Fenves integration scheme in OpenSEES (Open System for Earthquake Engineering Simulation) is employed. To use this element properly, the development and use of an equivalent plastic hinge length model for such columns is carefully examined. The objectivity and accuracy of predictions from the proposed numerical approach are demonstrated using numerical examples.