Experimental investigation of temperature gradients in a three-cell concrete box-girder

To study the temperature field of a three-cell concrete box girder, a box girder model was poured, and 258 temperature sensors were embedded in the model. Environmental parameters, including air temperature, air humidity, wind speed, wind direction and solar radiation, were recorded by a weather station nearby the model. Data receiving frequency was once every 30 mins, and a wireless acquisition module for data collection was used. After a year of temperature observation, the temperature field of a three-cell concrete girder was obtained. Temperature prediction equations for a three-cell box girder were established for the first time, which used air temperature, solar radiation, and wind speed at a moment, rather than temperature prediction equations of previous studies, which used the maximum single-day temperature difference, the total single-day solar radiation and the average wind speed. The lateral temperature difference of the sunny side web was more obvious in winter. The lateral temperature difference with a 98% exceeded probability was 19.49 °C, which was larger than the recommended value of the European standard (15 °C). The negative temperature gradient influenced by cold wave was considered. The maximum lateral temperature gradient of the top plate and bottom plate in winter was larger than that in summer. The vertical and lateral temperature difference calculated by the present equations agreed well with the experimental values recorded by a five-tower six-span cable-stayed bridge.