IMPROVED SCREENING PROCEDURE FOR SEISMIC RETROFITTING OF HIGHWAY BRIDGES

Recent damaging earthquakes in California and elsewhere have demonstrated once again the seismic vulnerability of highway bridges in the United States. Retrofitting programs for correcting deficiencies in existing bridges have been proposed since the 1970s, but until very recently only California has been active in the field. In 1983 FHWA published a set of retrofitting guidelines for bridges; recently they were revised to reflect advances made in the state of the art during the past decade. The improved screening procedure, which has been recommended in the revised FHWA manual, is presented. Differences between the old and new procedures include a new priority-ranking process, revised seismic performance categories, expanded definitions for bridge importance, and new flow charts to illustrate and clarify the assignment of structure vulnerabilities.