Experimental and analytical lateral load response of unbonded post-tensioned precast concrete walls

This study experimentally and analytically evaluates the response of unbonded post-tensioned precast concrete walls with horizontal joints under combined gravity and quasi-statically applied monotonic and cyclic lateral loads. A set of generalized closed-form expressions are derived to estimate base shear and lateral drift response values that define a tri-linear idealized base shear-lateral drift response curve for these walls under monotonic lateral loads. The closed-form expressions are incorporated into a previously-proposed seismic design approach for designing seismic resistant buildings using unbonded post-tensioned precast walls.; The seismic design approach allows these walls to be designed to soften and satisfy nonlinear displacement demands under code-specified design level ground motions without yielding the post-tensioning (PT) steel. These walls can also be designed to satisfy nonlinear displacement demands under maximum considered ground motions without fracture of the PT steel, or compression failure of the wall.; The experimental program consists of five walls tested under combined gravity and lateral loads. Results show that the limit states that characterize the lateral load response of the walls occur as anticipated. Test results show that these walls can undergo significant nonlinear lateral drifts without significant damage, and can maintain their ability to self-center, eliminating residual lateral drift. The experimental results are used to verify the accuracy of the closed-form expressions and of a nonlinear fiber model previously proposed to analyze unbonded post-tensioned walls under combined gravity and lateral loads.; In general, excellent agreement exists between experimental results, results from the closed-form expressions, and fiber model analysis results for monotonic loading, except that the analytical models overestimate the experimentally-observed lateral drift capacity of the walls. The accuracy of the fiber model in predicting the cyclic lateral load response of the walls depends on the amount of initial prestress on the walls. The fiber model is very accurate for the walls with higher prestress, but overpredicts the base shear capacity of the walls with lower prestress. In general, the accuracy of the analytical models is good, but caution must be exercised when analyzing walls under cyclic or dynamic loading using the fiber model, because the base shear capacity may be overestimated.