A comprehensive study of the thermal response of a long-span cable-stayed bridge: From monitoring phenomena to underlying mechanisms

Abstract

Abstract Structural deformation and variation in internal force are important considerations with regard to bridge health monitoring. Field measurements demonstrate that thermal effects of cable-stayed bridges—which represent high-order statically indeterminate structures—are extremely complex and nearly impossible to explicate in terms of temperature-limit states assumed during the design stage. Based on monitoring data recorded for the Shanghai Yangtze River Bridge—a steel box girder, twin-tower cable-stayed bridge with a 730 m central span—simultaneous investigations were performed concerning effects of seasonal as well as diurnal temperature variations on thermally induced changes in the mid-span vertical displacement ( D T ) and horizontal projection length ( L T ) of the girder, distance between the two tower tops ( S T ), structural total or elastic strains ( e M / e E ) at the mid-span section and average cable tensions of the longest centre-span cables ( F T ). In terms of variation amplitudes, correlations between temperature and structural response of a cable-stayed bridge can be classified into two modes. In the first mode, annual variation amplitudes are observed to be significantly larger compared with diurnal amplitudes. This applies to parameters L T , S T and e M . In the second mode, annual variation amplitudes approximately equal diurnal amplitudes. This is true for parameters D T , e E and F T . Temperature variables upon which structural response of cable-stayed bridges primarily depends usually differ from one another in that L T , S T and e M are governed exclusively by the average girder temperature while D T and F T are simultaneously determined by the cable and average girder temperatures; parameter e E is dominated by the temperature difference between the top and bottom plates of the girder. This study establishes a sound understanding of behavioural patterns in cable-stayed bridges to facilitate the determination of feasible measurement-point locations, useful with regards to bridge-monitoring systems, as well as selection of appropriate temperature variables for thermal-response modelling.