Seismic Behavior of RC Shear Walls Strengthened with Fiber-Reinforced Polymer

Abstract

This paper investigates the seismic behavior of RC shear walls strengthened by using carbon fiber-reinforced polymer (CFRP) composites. Three RC shear walls were tested: one control wall and two walls strengthened by fiber-reinforced polymer (FRP), using two different strengthening schemes. The walls were tested when subjected to a constant axial load along with synchronized cyclic moment and shear force at the top of the tested panel. The primary purpose of the FRP retrofit schemes was to increase the flexural and shear capacities of wall panels that experienced higher seismic demands than the design ones. The walls represent the sixth story panel of an eight-story RC, moderately ductile, shear wall designed according to the 2005 National Building Code of Canada. Reported shake table tests on two eight-story walls demonstrated the increase in the demand in higher story levels as a result of the effect of higher modes of vibration, which calls for increasing the capacity of the walls at a high floor level. In this study, the first wall was strengthened by using two layers of unidirectional CFRP sheet that were applied vertically and anchored to the top and bottom slabs, above which unidirectional horizontal C-shaped CFRP sheets were applied. The second wall was strengthened by applying cross-FRP bracings on the two sides of the wall. The three walls were tested under constant axial load and with increasing cycles of synchronized top moment and lateral load with a top moment-to-shear ratio of 2.75 up to failure. The strengthened walls showed satisfactory performance with improved flexural and shear strengths compared to the control wall. The two retrofitted walls showed different load and deformability capacities because of the nature of crack propagation and the orientation of the applied CFRP sheets.