Openings in walls greatly influence the stiffness and strength of reinforced concrete (RC) shear walls. Several parameters influence the reduction in strength and stiffness, such as size, shape, and location of the opening, reinforcement around the opening, and failure mode of walls (flexural or shear critical). The influences of each opening parameter on the structural performance of RC walls are still poorly understood. The objective of this study is to experimentally investigate the effect of two parameters—opening size and additional reinforcement around the opening using six reinforced concrete wall specimens. They were tested under a novel test setup capable of applying pure shear cyclic loading. In addition, a simplified analytical model is proposed to calculate the initial stiffness of RC wall with a single opening. Results showed that the reduction in strength follows a linear pattern with the increase in opening size. However, the initial stiffness follows a nonlinear pattern associated with a large drop in stiffness for the big opening size. In addition, the additional reinforcement around the opening had improved maximum strength but had an insignificant influence on the initial stiffness of RC walls. Finally, the proposed analytical model for initial stiffness was verified with the test results and was depicted close agreement with the test.
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