THERMAL DEFORMATION OF A STEEL TRUSS BRIDGE BASED ON MONITORING DATA

The periodic change of temperature will cause significant structural deformation of long-span bridges. Based on the field monitoring data of a three-span continuous beam bridge, this study investigates the temperature dependencies of the longitudinal displacements of bearings and the mid-span deflection of the girder. The field measurements are compared against the finite element analysis results, and the discrepancies are further discussed and explored in a qualitative way. The key findings of this study are as follows: Compared with the ambient temperature, the structural temperature of the background bridge is high during the daytime and low at night, with a variation amplitude approximately twice that of the ambient temperature. The temperature distribution across the bridge is relatively uniform at night due to the lack of solar radiation. The structural temperature change has more influence on the longitudinal displacement of the bearings than on the mid-span deflection of the truss girder. The frictional resistance results in different thermal motion patterns of the bearings at the left & right side piers. On a time scale as short as one day, the bearing displacements exhibit a hysteresis relationship with the structural temperature. This nonlinear phenomenon may be attributed to the bearing friction and the time-varying non-uniform temperature changes.