Seismic Performance Evaluation of Coupled Walls Using Innovative Highly Deformable Coupling Beams

Abstract eng:
Reinforced concrete (RC) coupled shear walls are commonly used in the design and construction of high rise buildings located in seismic zones to control drifts at upper storeys. When appropriate degree of coupling is provided, the overall seismic overturning moment is resisted by two mechanisms: i) bending at the base of each wall, and ii) moment of the couple of axial compression/tension forces at the base of each wall, the magnitude of which depends on the shear forces generated at the coupling beams. This shear wall system has proven very effective at controlling damage in structures where coupling beams are detailed to provide high energy dissipation. However, such coupling beams need to transfer high shear forces while undergoing large deformations, which in turn impose strain demands on the concrete well beyond its ultimate strain in compression (usually ε cu =0.35-0.40%). As a result, the potential benefit of very ductile coupling beams able to dissipate large amounts of energy is limited by concrete (crushing) failure. This paper presents results of an experimental and numerical study on a novel structural system that combines the use of conventional, ductile RC shear walls and coupling beams made of a new, confined Highly Deformable Concrete (HDC). HDC incorporates recycled rubber granules from waste tyres as partial replacement of the mineral aggregates. The inclusion of rubber in HDC increases its deformability in compression (up to ε cu =4-5%), which in turn enhances the ductility and energy dissipation capacity of the coupling beams. Pushover analyses are carried out in OpenSees to compare the seismic performance of building structures fitted with conventional coupled walls and walls using confined HDC coupling beams. The results of the study indicate that, for the same risk scenario, buildings with HDC coupling beams exhibit a better performance, in terms of ductility, displacement and energy dissipation capacity than the conventional RC counterparts.

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