Drift-based methodology for seismic proportioning of coupled shear walls

Abstract

This paper presents a design tool for size proportioning of reinforced concrete coupled shear walls built in seismic regions. It is based on the maximum allowable drift that can be selected by the designer. Free vibration and modal analyses are performed on a variety of coupled shear walls of different heights and geometries. From these analyses, fundamental periods are first related to geometric properties of coupled shear walls and then to maximum interstorey drifts. These maximum drifts are obtained from both spectrum analysis and pseudo-static approach. Closed-form formulas for estimating the required fundamental periods of coupled wall systems as a function of maximum allowable drift are derived. The design of the wall system can be based on geometric dimensions to yield the stiffness to achieve the required period. These formulas not only are thought to be useful for preliminary size proportioning, but also can constitute an advantageous starting point for more sophisticated analyses. To demonstrate the applicability of these formulas and to clarify design issues, a design example is treated and results are compared with static and dynamic analyses. Key words: coupled shear wall, reinforced concrete, ductility, force modification factor, interstorey drift, fundamental period, seismic.