Experimental Assessment of Seismic Behavior of short Shear Walls with Unplanned Off-center Opening (Case Study)

Document Type : Original Research

Authors
P. Kavehie 1
M. bayat 1
A. Kheyroddin 2
M. Gholhaki 3
1 Master of structural engineering, Semnan university
2 Professor of Semnan university, Faculty of Civil Engineering of Semnan University, Semnan, Iran
3 Assistant Professor of Semnan university, Faculty of Civil Engineering of Semnan University, Semnan, Iran
Abstract
Owing to their excellent stiffness, reinforced concrete shear walls, as lateral load-bearing elements, considerably reduce the structurechr('39')s seismic demand. Structural walls are designer-favorite components for their excellent stiffness and rigidity under lateral loading. Unlike steel chevron braces that buckle after a few loading cycles, shear walls retain stiffness and promote damping within the system by allowing cracks in the web plate. Meanwhile, openings placed in the wall for architectural reasons or to give access between different parts or to run facilities can considerably affect the behavior of these structural elements by forming new elements in the wall, besides reducing the wall stiffness. The seismic behavior of each of these elements can affect the wall system and its behavior. These less investigated structural elements include base walls, the seismic regulations of which were first outlined in ACI318-14. Unique seismic regulations apply to these structural elements based on their aspect ratio. Accordingly, certain seismic design considerations are required for these elements. The present study investigates the cyclic behavior of squat walls with eccentric non-predesigned openings at the top, under cyclic loading. Given the complex behavior of squat walls in stress transfer, a 155-cm-tall, 160-cm-wide, and 13-cm-thick experimental model integrating a 50 cm by 100 cm opening was used. The non-predesigned opening in the shear wall results in inconsistencies with the development length and rebar bending and cutting regulations aro9und openings, all of which are important in designing reinforced concrete elements. The opening introduces new elements, including the base wall and the coupling beam, which exhibit different behavior and failure mechanism under cyclic lateral loading. The present study discusses experimental parameters, such as the hysteresis loop, equivalent damping, and the dissipated energy curve of the wall. Further, cracking patterns in different parts of the wall are studied. Experimental results showed that a concrete-wall opening that stretches across 21.85% of the wall area changes the wall cracking pattern by introducing new elements and the shear wall does not exhibit a specific failure mode upon collapse. Asymmetry of the opening location also affects the maximum load-bearing capacity in compression and tension, as the peak load-bearing capacity was estimated at 189.645 kN under tension and 195.5 kN under compression. Violating bending and development length requirements around opening edges resulted in rebar slip and concrete separation after cracking.

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Modares Civil Engineering journal
Volume 21, Issue 5
November and December 2021
Pages 29-40