Lateral load behavior of unbonded post-tensioned precast concrete walls

Unbonded post-tensioned precast walls are constructed by post-tensioning precast panels across horizontal joints with the post-tensioning steel unbonded to the panels over a significant portion of its length. The lateral load behavior of these walls differs significantly from that of conventional cast-in-place reinforced concrete walls and precast concrete walls designed to emulate cast-in-place walls. An unbonded post-tensioned wall can be designed with strength and initial stiffness similar to those of a conventional cast-in-place reinforced concrete wall. In addition, however, the unbonded post-tensioned wall can be designed to undergo significant nonlinear lateral drift without significant damage. The nonlinear behavior results from the opening of gaps along the horizontal joints. Subsequent closing of these gaps, as a result of the post-tensioning, results in a self-centering behavior that eliminates residual lateral drift. The paper reports on the experimentally and analytically observed lateral load behavior of unbonded post-tensioned precast concrete walls. The limit states in the behavior are outlined. Results of monotonic and cyclic lateral load tests of large-scale wall specimens are presented and compared with analytical results. Conclusions regarding the suitability of the observed behavior are given.