STRENGTHENING AND REHABILITATION. IN: BRIDGE ENGINEERING: CONSTRUCTION AND MAINTENANCE

About half of the approximately 600,000 highway bridges in the United States were built before 1940, and many have not been adequately maintained. Most of these bridges were designed for lower traffic volumes, smaller vehicles, slower speeds, and lighter loads than are common today. In addition, deterioration caused by environmental factors is a growing problem. The purpose of this paper is to identify and evaluate the various methods of strengthening existing highway bridges and to a lesser extent railway bridges. Information is given on five strengthening procedures: lightweight deck replacement, composite action, strengthening of various bridge members, post-tensioning, and development of bridge continuity. In numerous situations, strengthening a given bridge, rather than replacing or posting it, is a viable economical alternative which should be given serious consideration.