The effect of projected air temperatures on concrete box girders thermal gradients and effective temperatures in Canada

Abstract

This study examines the impact of environmental thermal loads on the temperature behavior of bridges, focusing specifically on concrete box girders. Currently, the Canadian Highway Bridge Design Code (CHBDC) employs a single thermal gradient model for the entire country, which fails to account for the differences in the geographical conditions in the Canadian climate regions. Accordingly, in some cases, the temperature distributions along the girder depth and their thermally induced responses might not be determined accurately. To address this issue, a transient FE thermal analysis was conducted to develop positive and negative thermal gradients and the maximum effective temperatures (METs) for concrete box girders under extreme thermal load conditions of the projected air temperature for the years 2050–2100 and the historical solar radiation. Different parametric studies were conducted to determine how the geometric parameters of box girders affect the temperature distribution and found that the girder depth is a critical factor. Based on the analysis, a formula is proposed to predict the MET for concrete box girders. In addition, different adjustments were recommended to consider the effect of girder depth on the thermal gradients and METs of the box girders.