ASSESSING DAMAGE AND RELIABILITY OF STEEL BRIDGES

Fatigue and fracture as well as loss of section due to corrosion are time-dependent performance characteristics that have the potential to jeopardize the integrity of bridge structures. This paper reviews the experience with such time-dependent damage since 1970. It examines the experience with crack and corrosion detection and damage assessment. Changes in structural behavior as a result of corrosion, deterioration of deck and other adverse characteristics can result in unanticipated fatigue cracking as the analysis model and assumptions used in design are no longer valid. Often these changes in behavior are the cause of damage and crack development. Damage assessment requires a knowledge of the live load stresses while the structure is in service so that reasonable estimates of safe service life can be made for critical structural details, and inspection techniques and NDE tools can be rationally focused to insure reliability. Hence, methods of monitoring structural response and evaluating its live load stress range history are as important as crack detection and crack growth.