Abstract
To study the negative temperature gradient models of a rail transit U-shaped girder during the winter season, a U-shaped rail transit girder was researched in Qingdao. The temperature field of the midspan section was observed for a 48-h period during the winter. The maximum vertical and horizontal temperature difference distributions were obtained, and the negative temperature gradient models for the winter were established. The results show that the vertical temperature gradient models of the web and bottom slab should be considered. The vertical temperature gradient model of the web is a piecewise function composed of exponential and linear functions. The vertical temperature gradient model of the bottom slab is an exponential function. The transverse temperature gradient of the web is obvious, whereas the transverse temperature gradient of the bottom slab is slight.
Highlights
A pre-stressed concrete structure is significantly affected by environmental temperature changes and material heat conduction, which generate a non-uniform temperature field and temperature stress, the latter of which is considered an important reason for the cracks in a structure [1,2]
Study results have indicated that a structure has positive temperature gradients caused by a temperature increase in the environment, resulting from the surface temperature of the structure being higher than the internal temperature, and that the effects of a negative temperature gradient caused by a decrease in temperature should not be ignored [3,4]
Positive and negative temperature gradient models have been proposed for many different bridge design codes in various countries, they are all based on a box girder structure, and the temperature gradient models of a U-shaped girder have not been specified
Summary
A pre-stressed concrete structure is significantly affected by environmental temperature changes and material heat conduction, which generate a non-uniform temperature field and temperature stress, the latter of which is considered an important reason for the cracks in a structure [1,2]. Song et al established a thermodynamics model and proposed a sunshine temperature distribution curve of a trough-shaped section based on a cable-stayed bridge, respectively [5,6]. Quan investigated the temperature distributions of a U-shaped girder based on bridge monitoring, and obtained the vertical temperature gradient parameter measurements of the railway bridge design code [7]. Positive and negative temperature gradient models have been proposed for many different bridge design codes in various countries, they are all based on a box girder structure, and the temperature gradient models of a U-shaped girder have not been specified. Relevant researches on simple and accurate temperature gradient models of a U-shaped girder that can be used in an engineering design should be conducted. The maximum vertical and horizontal temperature difference distributions were obtained, and negative temperature gradient models for winter were established. All results were shown to be significant for use in an engineering design
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