Main Girder Deflection Variations in Cable-Stayed Bridge with Temperature over Various Time Scales

The cable-stay bridge is a complex hyperstatic structure with large span and slender proportions, making it highly sensitive to temperature, especially in terms of deformation. A cable-stayed bridge with a steel tower and steel box girder was taken as an example in this study to explore the temperature effects on the deflection of the main girder under different time scales. The temperature gradient characteristics of the girder and tower were observed; then, the daily and annual variations of girder deflection were investigated. Finally, the main influencing factors of deflection variations with temperature were verified by finite element simulation. The results show that the girder/pylon temperature gradient under current Chinese code is not applicable to cable-stayed bridges, and the measured values are usually underestimated. In terms of diurnal variations, the deflection is greatly affected by the temperature difference between the cable and beam and the temperature gradient of the girder. The annual variation law of deflection data and temperature at 1 : 00am shows obvious linear characteristics. The daily deflection at 1 : 00am., after removing the temperature effect, can thus be used as an index to evaluate the long-term degradation of bridges. This is a workable approach for efficient and rapid mining of large sets of monitoring data.