Seismic performance of strengthened reinforced concrete columns

Abstract

Post-earthquake reconnaissance studies have reported severe damage to reinforced concrete buildings. In a moment resistant framed building, columns are the critical members of the load path. Shear failure of a column is brittle, leading to quick degradation of the lateral strength and vertical load carrying capacity. The reported study focuses on seismic strengthening of a short shear-critical column by concrete jacketing technique. For a shear-critical jacketed column, the integrity of the new and old concrete depends on any slippage at their interface. The investigation on the effects of three different interfaces such as surface roughening, providing dowel bars or bent shear connector bars in addition to surface roughening, on the seismic performance of jacketed columns, is presented in this paper.Large-scale column specimens were tested to shear failure under lateral monotonic and cyclic loads, in presence of estimated service level axial loads. The details of the experiments and the comparison of their results in terms of shear strength, stiffness and behavior are included. The specimens with different interfaces were found to be similar in their lateral load resistance, showing negligible difference in strength. However, the specimens with bent bars showed higher stiffness compared to the specimens with other two types of interfaces. The strengths of the specimens were predicted using codal provisions and a strut-and-tie model. Their behavior was traced using a piecewise linear model. The predictions were compared with the test results. The proposed method of analysis for shear deformation can be used in developing non-linear shear hinge properties for short jacketed columns, in a pushover analysis of a building.