Dynamic monitoring of structural health in cable-supported bridges

A sophisticated instrumentation system, called Wind And Structural Health Monitoring System (WASHMS), is devised by the Hong Kong Highways Department to monitor the structural health and performance of three long-span cable-supported bridges in Hong Kong. This system consists of about 900 sensors including accelerometers, strain gauges, displacement transducers, level sensing stations, anemometers, temperature sensors and weigh-in-motion sensors. The Hong Kong Polytechnic University is commissioned to investigate the feasibility of using measured dynamic characteristics for structural damage detection in these bridges. Explored in this paper are some key issues related to developing a viable vibration-based damage assessment strategy for these bridges: (a) Evaluation of possible damage likely to occur in the three bridges-the detectability of damage to structural components (cables, towers, deck, anchorages, bearings, and connections) by using global or local dynamic characteristics is discussed; (b) Concept and rules of damage detection oriented modeling for large-scale structures-a super-element formulation for complicated two-tier bridge deck is developed within this framework; (c) System identification methodology for heavily redundant structures-a neural network based hierarchical identification strategy is proposed for successively detecting the occurrence, type, location and extent of the damage.