Abstract

In the past few decades, there have been considerable advancements in the design of reinforced concrete (RC) shear walls for new construction, such as performance-based seismic design and capacity design principles. These advancements have resulted in a concurrent need for upgrading the seismic performance of existing RC shear walls so that they can meet the safety requirements of modern seismic design codes. As such, there is a need to retrofit existing RC structural shear walls to increase their capacity at locations of higher seismic demands. These upgrades could be at the plastic hinge zone at the base of a wall, or at higher stories due to the effects of higher modes of vibration.
This research aims to evaluate the effectiveness of using externally bonded carbon fibre-reinforced polymers (CFRP) in the seismic retrofit of RC shear walls. The research program comprises three phases. First, the testing of two 8-storey RC shear walls rehabilitated using CFRP composites under dynamic excitation. The walls were designed according to the NBCC 2005 and the CSA-A23.3-04. The walls were first tested under a simulated earthquake excitation using the shake table at the École Polytechnique de Montréal, where they experienced higher demands and nonlinearity at the sixth storey panel due to the effect of higher modes of vibrations. The tested walls were rehabilitated at the ground and at the sixth-storey level and retested on the shake table when subjected to several levels of ground motion excitation. In the second phase, three RC shear wall
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panels were tested under cyclic lateral excitation at the Structures Laboratory of Concordia University. The tested wall panels represent the control wall and two FRP-retrofitted panels using two different retrofit schemes. All three wall panels had reinforcement details similar to those of the sixth-storey panel of the code-designed 8-storey shear walls from the first phase. 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 main purpose of the FRP-retrofit schemes was to increase the flexural and shear capacities of the tested wall panels and to assess the effectiveness of the FRP-retrofit schemes up to failure. In the third phase, a numerical macro-model was proposed to simulate the behaviour of the control and the retrofitted wall panels tested under cyclic loading.
The experimental test results of the FRP-retrofit schemes used in the two 8-storey RC shear walls and the three RC wall panels showed a satisfactory performance with improved flexural strength; the testing showed that the main retrofit objectives were achieved. The nonlinear numerical macro-model was able to simulate the monotonic and cyclic behaviour of the wall panels tested under cyclic loading.