Seismic response evaluation of unbonded post-tensioned precast walls

The seismic behavior of a set of unbonded, post-tensioned, precast concrete walls under design-level and survival-level ground motions is evaluated based on nonlinear dynamic time-history analyses. The important seismic response characteristics of the walls are discussed, together with a critical evaluation of the design approach used for the walls. The effects of site seismicity, site soil characteristics, initial stress and eccentricity of the post-tensioning steel, assumed level of viscous damping, and inelastic energy-dissipation capacity on the response of the walls is investigated. The method used in design to prevent shear slip along the horizontal joints of the walls is verified. The analysis results indicate that, compared with cast-in-place reinforced concrete walls, unbonded, post-tensioned, precast walls undergo larger displacements. The amount of post-tensioning force and the initial stress and eccentricity of the post-tensioning steel are among the most important, design parameters affecting the behavior of the walls. The dynamic analyses show that the method used for estimating the design wall drift demands needs to be improved.