BRIDGE STRENGTHENING NEEDS IN THE UNITED STATES

Large numbers of bridges in the United States are structurally deficient or are nearing the ends of their useful lives. Replacing these bridges in the near future is not economically feasible; therefore, rehabilitation and strengthening techniques are needed to extend the useful lives of bridges. Records from the National Bridge Inventory, responses from questionnaires to bridge engineers and other bridge specialists, and site inspections of load-restricted bridges were used to determine bridge types for which strengthening methods are most urgently needed. Steel stringer, timber stringer, and steel through-truss bridges have a particularly critical need for strengthening, because large numbers of these bridge types, if left unstrengthened, will have to be taken from service or retired in the near future. Other bridge types needing strengthening because of anticipated retirements are concrete slab, concrete tee, concrete stringer, steel girder-floor beam, and concrete deck arch. If strengthening and rehabilitation methods are not developed or made available for these bridge types in the near future, large numbers of bridge replacements will be required.