Performance based design of coupled wall structures

Coupled wall structures are outstanding lateral load resisting systems that not only reduce the deformation demands on the building, but also distribute the inelastic deformation both vertically and in plan, between the coupling beams and the wall piers. Coupled core walls (CCW's) result from the need to provide openings in elevator or stairwell shafts and often take C, L or H shapes. They provide inherent strength and stiffness, and in many cases they result in a compact plan, which results in more available rentable space on a floor plate. In addition, coupled core walls result in a relatively force-hardened and fire resistant structural system.;The research in this work considered a prototype 12-storey reinforced concrete coupled core wall (CCW) building located in Seattle, Washington. Five CCW prototype structures, having varying degrees of coupling and the same wall piers were designed allowing the study of the effects of decayed coupling action to be carried out. Elastic analyses using the equivalent lateral force (ELF) procedure and the continuous medium method (CMM) were utilized to establish initial proportions for the CCW system, and to determine the design forces and moments. Nonlinear static and dynamic analyses were conducted to investigate the CCW structural behavior, adequacy of the design, and the evolution of the structural form from CCW system to a collection of linked wall piers (LWP). An additional unique aspect of this work was that the wall piers in the CCW were significantly different in terms of their dynamic and geometric properties: the moments of inertia of the two wall piers differed by almost an order of magnitude.;The results of this study indicate that the dual systems, consisting of reinforced concrete wall piers and steel coupling beams, performed very well and as what would be expected. The dual system provided superior lateral stiffness as a CCW in the elastic range, and maintained a good stiffness during the evolution toward a collection of linked wall piers (LWP). When the CCW structure (dual system) was subjected to lateral demand, the system first resisted the lateral loads by a combination of actions: frame action generated by shear in the coupling beams and flexural behavior of the individual wall piers. During the evolution process, the frame action degraded as the steel coupling beams yielded and formed hinges at their ends and the moment resistance was redistributed to the walls piers.