Retrofitting of Bridges

The extensive damage to bridges world over in earthquakes has generated considerable interest amongst the engineers and researchers on the seismic design of new bridges and retrofitting of existing ones. Prior to the development of modern codes, the bridges were designed for nominal seismic forces without provisions of ductility. Seismic codes began to incorporate ductility provisions only in 1970. Thus the bridges designed earlier may be deficient to withstand effect of future earthquakes. These structures may require seismic evaluation and retrofitting. The protection of bridges from damage in earthquakes has direct relevance in prevention of aggravation of disaster, as disruption of transportation routes hampers relief and rescue operations immediately following the earthquake. Several retrofitting techniques have been developed for bridges in recent years. Many of the existing bridges can be retrofitted by these techniques. Some seismic countries have undertaken the programmes of seismic assessment and retrofitting of bridges on a bigger scale. Such actions are proving to be effective as evidenced by performance of retrofitted bridges in recent earthquakes. There is need in India to investigate the likely behavior of existing bridge stock in future earthquakes and initiate seismic retrofitting. This paper highlights the important issues: structural deficiencies; retrofit philosophy, retrofit techniques, recent developments and effectiveness of retrofit techniques