Temperature variation in steel box girders of cable-stayed bridges during construction

This study investigated the variation of the temperature distribution in the steel box girder of a cable-stayed bridge during construction. Measured data were used to study the basic thermal characteristics because the thermal behavior of these bridges during construction is particularly difficult to predict and not well-known. In addition, a simple numerical approach was carried out to predict approximately the variation of the temperature distribution in a steel box girder. The temperature variation of the top flange showed a steep change, while the temperature variation of the bottom flange exhibited a smooth curve throughout the day because of the relative low amount of solar energy and encased internal air. At night, the bottom flange showed a higher temperature than the top flange and ambient temperature. In the top flange, the temperature decreased as the distance from the center increased, while the temperature in the bottom flange increased with the distance from the center. The time to reach the peak temperature at each location varied without correlation to the time of peak solar radiation because of the effect of the encased air. When compared with the measured data, the analysis results closely matched the temperature variations for different seasons in the center of the top flange, where the largest peak temperature and variation were observed. Thus, the adopted simple numerical approach can approximate the temperature variation of a steel box girder during construction in the planning and design phases.