SEISMIC EVALUATION AND RETROFITTING OF RC BRIDGES

Abstract

Reinforced concrete (RC) bridges are potentially among the most seismically vulnerable structures as they do not have redundancy as in case of high-rise buildings and other structures due to which no alternate path is available for load transfer. Seismic assessment of Bridges is very important to know the structural deficiencies in the existing bridges. In the recent past earthquakes, structural deficiencies in many of the existing bridges have been observed, because most of them were constructed before the advancement of seismic code. These bridges have failed in flexure, shear and bond due to insufficient shear strength, insufficient flexure strength and inadequate bond length in past earthquakes. Since these structures are the lifeline structure whose collapse not only leads to loss of life but also hampers post earthquake activities for normalcy, seismic retrofit measures for already existing vulnerable RC bridges needs to be determined. This study deals with seismic evaluation of bridge substructure to know its seismic performance. The finite element model of bridge substructure has been developed in SAP2000. The bridge considered in this study is railway bridge present in northeast region falling in seismic Zone-V over Dhaleswari River. The response spectrum analysis, nonlinear static analysis, and capacity spectrum methods have been done by using the design response spectrum given in IS: 1893 (part 3)-2014. The seismic deficiency has been obtained under MCE condition as per IS: 1893 (part 3)-2014. The reinforced concrete (RC) jacketing and carbon fiber reinforced polymer (CFRP) jacketing have been employed for improving the seismic performance of the bridge pier. The retrofitted bridge piers have been modelled in SAP2000 for the evaluation of its performance by using the pushover analysis and capacity spectrum method. The performance has been improved by RC jacketing and CFRP jacketing.