SEISMIC EVALUATION AND RETROFITTING TECHNIQUES OF BRIDGE COLUMNS

Abstract

Reinforced concrete bridge columns constructed before mid 1970's are vulnerable to earthquake forces because of lack of ductile detailing provisions. The vulnerability of these columns has been emphasized in San Fernando, Northridge, Kobe, Whittier and some other earthquakes all over the world. These columns have failed in flexural, shear and bond. In order to decide the strategy to retrofit these bridge columns, it is necessary to carry out seismic evaluation for determining seismic capacity, weaker sections and failure modes. In this study an attempt has been made to compare the load carrying capacity and ductility of columns before and after retrofitting. Two columns are constructed and tested in quasi-static test facility under cyclic loading. Two columns are designed as per IS: 456-2000 with special confining reinforcement and its lateral load carrying performance has been studied under cyclic loading. One of these columns has been retrofitted using steel jacketing and other by glass fiber reinforced polymer (GFRP) to increase their lateral confinement. These retrofitted columns have been tested again using similar loading condition. Test data are presented and comparison has been made for their behavior before and after retrofitting. Results of this study indicate that significant improvement in ductility and energy absorption capacity can be achieved after retrofitting.