Thermal response of concrete box-girder bridges

Abstract

The first part of this research is concerned with the development of a method to predict the temperature distribution in the cross-section of concrete bridges. A computer program is developed; a listing and instructions to use the program are presented. The input data for the program are latitude, altitude of the structure and its orientation, the cross-section geometry, thermal properties of the material and parameters pertaining to the climatological conditions. The method of analysis involves the use of two-dimensional finite elements for the idealization of the cross-section area. The variation in temperature with time is treated using time-stepping technique based on Galerkin's weighted residual method. A parametric study is conducted to assess the most prominent factors influencing the temperature development in a bridge cross-section. The influences of various parameters, including time-dependent solar radiation, ambient temperature extremes, wind speed, surface cover, and section shape and dimensions are investigated. The developed method is used in the second part of this thesis to predict critical temperature distribution in the cross-section of a bridge recently built in Calgary, Alberta. The temperature distribution thus obtained is used as input to a nonlinear finite element analysis of a bridge of the same cross-section continuous over two equal spans. The effects of concrete cracking and yielding of the steel are taken into account. The temperature fields used in this analysis are those representing actual conditions in Calgary; also the thermal effect is accentuated by increasing the temperature values by a varying factor. These studies allowed the determination of the significance of thermal stresses on the serviceability of the structure.