SEISMIC RETROFITTING FOR HIGHWAY BRIDGES

The San Fernando earthquake of February 9, 1971 has demonstrated that bridges located in high risk seismic zones and which were designed in accordance to the then prevailing AASHO design criteria may not possess adequate seismic resistance. This narrative describes an effort which was undertaken to develop a set of practical retrofit measures that can be employed on existing bridges so as to reduce damage and minimize the threat to life should an earthquake occur. The process leading to the identification of potential bridge weaknesses, selection of retrofit measure and verification of its adequacy is illustrated using two analysis procedures, i. e. , a detailed analysis method and a simplified one.