RETROFITTING OF REINFORCED CONCRETE BRIDGE COLUMNS FOR EARTHQUAKE FORCES

Abstract

Reinforced concrete bridge piers constructed before mid 1970s are vulnerable to earthquake forces because of lack of ductile detailing provisions. The vulnerability of these piers has been emphasized in San Fernando, Northridge, Kobe, Whitter and some other earthquakes all over the world. These columns have failed in flexure, shear and bond. In order to safeguard these structures in future earthquakes, it is necessary to retrofit columns. 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. Many experimental studies have been done to determine the behavior of the retrofitted columns. In this study an attempt has been made to determine the behavior of the columns by analytical approach and comparative study for base shear capacity and ductility of columns before and after retrofitting. Pushover analysis is done by using SAP software to evaluate the capacity of the columns. Steel and concrete jackets have been used as retrofitting materials and parametric study has been carried out by varying the length and thickness of the jacket. Results of the analysis are presented and comparison has been made for the behavior of column before and after retrofitting, and also for the effectiveness of steel and concrete jackets. Results of this study indicate that significant improvement in capacity and ductility can be achieved after retrofitting. The method demonstrated in this thesis can be used for design and analysis of retrofitting of pier or column.