Posttensioned Hybrid Coupled Walls under Lateral Loads

Abstract

This paper describes an analytical investigation of a new type of hybrid coupled wall system for seismic regions. Coupling of concrete walls is achieved by posttensioning steel beams to the walls using unbonded posttensioning tendons. Different from conventional hybrid coupled walls, the coupling beams of the new system are not embedded into the walls. The effect of structural design parameters such as the amount of posttensioning, beam properties, and wall properties on the behavior of multistory coupled walls under lateral loads, including the amount of coupling, energy dissipation, and displacement capacity is investigated. Systems with precast concrete walls as well as monolithic cast-in-place reinforced concrete walls are considered. The behavior of posttensioned coupled wall systems is compared with the behavior of systems with embedded steel coupling beams and systems without coupling. Design tools to estimate the nonlinear lateral load-displacement behavior of the walls are developed by quantifying selected limit states for the walls. The results indicate that posttensioned hybrid coupled walls with initial stiffness similar to walls with embedded steel coupling beams can be designed to provide stable levels of resistance under lateral loads over large nonlinear cyclic deformations. The degree of coupling between the walls can be controlled by changing the amount of posttensioning in the beams, as well as other beam and wall properties.