Performance of Strengthened, Reinforced Concrete Shear Walls with Opening

Abstract

Shear walls are one of the primary lateral resisting structural elements. Due to architectural and technical needs, openings in the structural wall are almost inevitable. Discontinuity regions and a reduction in wall stiffness result from these openings. The use of fiber-reinforced-polymer (FRP) systems is a sustainable construction solution for strengthening these areas and is a viable method to restore their integrity and serviceability. This paper presents an experimental and analytical study on the behavior of reinforced concrete (RC) shear walls with openings of various sizes and positions strengthened using glass-fiber-reinforced-polymer (GFRP) sheets. Ten RC shear walls were cast and tested; initially without strengthening; and then retested with a layer of bi-directional GFRP sheet added around the opening. The finite-element (FE) program ANSYS was used for modeling since using FE contributes to sustainability. The results showed that for un-strengthened walls with a 6.25% opening and strengthened walls with an 11.11% opening, the rate of stiffness degradation was reasonably low. As the opening size was enlarged, the strength and stiffness values were drastically reduced; and the shear walls with an opening at the mid-height position also have smaller load capacities compared to the bottom and top opening positions. In addition, the ability of the GFRP sheets to control stress redistribution and crack propagation improved the overall performance of the walls. The FE and experimental results match well. Furthermore, the ACI and ECP calculations revealed a good prediction of lateral load capacity without considering the opening position, whereas the other proposed models were inaccurate. Finally, the author proposed a reduction factor (β) to the shear strength equation provided by ECP-203-2020 depending on openings sizes and locations; and suggests that FRP sheets be used around openings to assure the appropriate performance and avoid unexpected failure.