The Study On Temperature Distribution And Thermal Stress Of Concrete Box-girder Bridge Under Solar Radiation

Nonlinear temperature gradients exist in concrete box girder bridge structures incomplex climatic conditions such as solar radiation and ambient temperature variationetc. That results in thermal stress and deformation which can be comparable toexternal action in magnitude. Temperature effects become one of the most importantreasons of the cracking of concrete box girders. However, due to the complexity ofthe problem, a simplified theory and model to computing the temperature effects arewidely used in the present bridge design. This simplistic method will lead toconsiderable error sometimes. This paper presents depth study on solarradiation-induced temperature effects on concrete box-girder bridge. This papermakes the following aspects of research on these issues:1. Based on astronomy and heat transfer theory, analysis model for concretebox girder bridge temperature field is established. In this modal a practical solarradiation intensity computing method is applied. And the boundary conditions of heattransfer between box-girder and its surroundings are studies. Finite element programbased on the above is compiled for the analysis of temperature effects on box-girderbridges. The computing results illustrate the characteristics of temperature distributionin concrete box girder.2. In order to study various kinds of environmental factors on the girdertemperature field and identify the key factors，we use parametric program to make adetailed analysis of all the factors which impact temperature distribution of box-girderbridge under solar radiation. The study illustrates that the solar radiation intensity isthe most critical influence factors.3. Thermal stress of box-girder bridges consists of thermal self-stress andsecondary stress. For the analysis of thermal self-stress, we used a computing methodconsidered Poisson Effect which is deduced on the basis of an integral property. Thiscomputing method not only has a higher accuracy than the widely used method butalso is simple and convenient to apply. The results not only prove the necessity of theconsideration of Poisson Effect but also illustrate that the traditional thermal stresscomputing method is sometimes impartial security. In this paper, finite element method to analyze the girder temperature effects isachieved. The key influence factors of nonlinear temperature gradients are analyzedby the program. A simple and relatively high accuracy thermal stress computingmethod is applied. The content and conclusions of this paper can provide a referenceto the computing of temperature effects in bridge design.