Evaluating the Seismic Behavior of Segmental Unbounded Posttensioned Concrete Bridge Piers Using Factorial Analysis

摘要

Segmental unbounded posttensioned concrete bridge piers can resist large lateral drifts and eliminate residual deformation during an earthquake. The seismic behavior of posttensioned bridge piers depends on several factors, including concrete strength, posttensioning (PT) force, aspect ratio, and axial-load ratio. This study investigated the effects of these factors and their interactions on the seismic behavior of such piers, which are not adequately addressed in the existing literature. Here, finite-element models of unbounded posttensioned concrete piers were generated to perform a parametric study. These models were first validated with experimental results and then used to predict the seismic behavior of unbounded posttensioned concrete piers. At the initial stage, full factorial analysis was performed by considering the following three factors: PT level, PT ratio, and concrete strength. The results indicate that none of them in combination resulted negatively on pier yielding capacity and postelastic stiffness, as long as the axial-load ratio was within 20%. After this preliminary study, a more comprehensive fractional factorial study, including seven factors, was performed. In the fractional factorial analysis, each of the factors was considered at two levels. The piers were analyzed under reverse cyclic loading. Based on the lateral load-displacement responses of the piers, regression analysis was performed to propose equations for calculating global yielding and stiffness of piers.