Temperature effects on strains of a continuous box-girder bridge with a long-term monitoring system

Daily and seasonal temperature-induced strains of a prestressed concrete (PSC) continuous box-girder bridge were presented. Strain measurement, using fiber Bragg grating sensors, constitutes a crucial component of the system in the monitoring of the bridge's key sections response in order to evaluate its structural behavior under environmental and traffic loads. This study was carried out to determine the effects of daily and seasonal temperature variations on the bridge deformation. Moreover, the insolation generates vertical temperature gradients in the box-girder cross sections, which are responsible for the strain differences in the plates and for its variation in the webs along their heights. In addition, in order to identify the qualitative and quantitative relation between the temperature and the strains on the cross sections, the monitoring temperature measurements of the bridge during the construction were applied. The results show that: (1) the seasonal temperature variation can significantly influence the strain of concrete bridges in cold regions; (2) in the high temperature periods the strain of the box-girder top plates experiences the largest variation, whereas for the bottom plates deformation the low temperature periods have a higher impact; (3) the daily and seasonal strain variations induced by uniform temperature reveal an inconsistent tendency for mid-span cross sections.