Temperature effects on cable stayed bridge using health monitoring system: a case study

The Zhanjiang Bay Bridge, located in an inner gulf of South China, is a cable stayed bridge with a main span of 480 m. An analysis on the thermal effects experienced by the bridge is presented according to a health monitoring system (HMS) that began operation in 2006. The parameters studied in the analysis include thermal time lags and gradients of the steel box girder, concrete tower, and stayed cables, as well as displacements at center span and tops of the towers. Among the findings, temperature gradient in the steel girder was larger than the design specification, concrete temperature lagged significantly behind ambient air, and stayed cable temperatures were between those of ambient air and concrete. Additional findings were obtained by comparing the measured data to values calculated using a finite element model. The comparison made it possible to approximate the unmeasured thermal gradient on the surface of the towers, and to determine that an expansion joint was likely jammed and contributing to the bridge's asymmetrical displacement. This article presents these findings in a thorough manner, and in doing so conveys the ability of a HMS to provide realistic examples of thermal behavior, to estimate conditions at locations free of measurement devices, and to suggest areas of concern for future manual inspections. Furthermore, it provides evidence that a HMS is not only helpful for bridge design and management, but also for the development of itself.