Design criterion for the self-centering capacity of precast segmental UHPC bridge columns with unbonded post-tensioning tendons

摘要

This paper aims to provide a novel quantitative design criterion for the self-centering (SC) capacity of precast segmental ultra-high performance concrete (UHPC) bridge columns based on the concept of the SC factor, which is deemed capable of depicting the formation mechanism of residual drift. A refined numerical model was developed to simulate the seismic performance and was verified by the results of the cyclic loading test. Parametric analysis was conducted to research the influence of seven common design parameters on the SC factor based on the proposed numerical model. According to the results of the parametric analysis, a simplified formula was established to assess the residual drift when the SC factor and the maximum drift were known. Nonlinear dynamic analysis was conducted to validate the simplified formula for precast segmental UHPC bridge columns subjected to far-field, no-pulse near-field, and pulse near-field earthquake motions. A design criterion for the SC capacity was proposed based on the SC factor limits determined by the simplified formula. Research results show that the SC factor corresponding to the ultimate drift is generally conservative for assessing the SC capacity of precast segmental UHPC bridge columns. The residual drift is dependent on the SC factor and the maximum drift. The residual drift decreases with the increasing SC factor or decreasing maximum drift. The proposed formula is verified by the results of nonlinear dynamic analysis to be conservative to calculate the residual drift. According to the proposed design criterion, the SC factor limits are increased with the drift demand up at the same earthquake design level. The adverse effects of pulse near-field earthquake motions on the earthquake resilience of precast segmental UHPC bridge columns should be taken seriously.