Effects of unbonded steel layout on seismic behavior of post-tensioned precast concrete shear walls

Unbonded post-tensioned precast connections have been studied widely in various applications and shown to be promising seismic resisting systems with superior seismic performance including exceptional self-centering capability and minimized structural damage. In this paper, effects of unbonded post-tensioned steel layout of precast concrete shear walls on seismic performance of a typical five-story precast concrete parking garage structure with the walls being the only lateral load resisting system is studied. The seismic behavior of the walls is determined using static nonlinear push-over, cyclic, and nonlinear time-history dynamic analyses under both the design and survival level ground motions. Three prototype unbonded post-tensioned precast concrete shear walls are designed with different unbonded post-tensioning steel tendon layout. Roof drift, post-tensioning force, and base shear and normal forces at the wall-foundation horizontal joint are monitored, and the demand for the coefficient of shear friction along the horizontal joint is calculated. The results show that seismic behavior of unbonded post-tensioned precast shear walls, in particular, maximum building drift, permanent losses in post-tensioning steel force, and coefficient of shear friction, is significantly influenced by layout of unbonded post-tensioned steel. The results and findings presented are valuable to improve design guidelines and provide a useful reference for practical applications of unbonded post-tensioned precast concrete connections in seismic applications.