Parameters affecting seismic behavior of self-centering concrete Bridge piers using factorial analysis

Abstract

Prevention of the collapse is the main philosophy of the seismic design. Conventional seismicresistant structures are capable of avoiding collapse to different degrees. Sometimes the damageis so large that the structure cannot be reused or repaired. Retrofitting of repairable damages istime consuming too. To avoid the tedious repair work, self-centering systems have beenintroduced. Self-centering systems help preventing collapse as well as minimize the seismicforce induced damages. In this study, performance of self-centering bridge pier is evaluatedusing 3D finite element modelling. The finite element models are developed and validated basedon the experimental program developed by Hewes and Priestley (2002) for piers of high aspectratio and low aspect ratio. A parametric study has been conducted for material and prestressparameters to understand their effects on the strength loss of the pier due to lateral loading.Factorial analysis method has been used for the parametric study. Using this analysis, theinteraction between different parameters like aspect ratio of the pier, concrete strength, steelratio, prestress force level and their contribution in the degradation of the pier strength has beendetermined. A set of regression equation has been suggested for the calculation of the strengthreduction of the self-centering pier. It is found that the strength loss of the pier depends mostlyon the initial prestress force level for the low aspect ratio piers and on the confining jacket thickness for the high aspect ratio piers. The other important factors include the properties and strengthof materials used in the pier. It is also found that longitudinal reinforcement in the pier blocksdoes not have significant contribution in the lateral strength and strength loss of the pier. Finally,optimum parameters have been suggested for the piers with high and low aspect ratio that causeminimum strength degradation for a prescribed loading protocol.It is found that for the suggested optimum parameters, the minimum strength reduction at 4% drift levelin the high aspect ratio pieris 3.68% and no strength loss in the low aspect ratio piers.