Study On The Temperature Field And Thermal Stress In The Special-shaped Concrete Box Girder Bridges

Concrete bridge structures are usually exposed to the natural environment. Because ofsunshine, wind, precipitation, etc natural environment influence, the concrete structure ischanging temperature. With the poor thermal conductive performance of concrete, the upperstructure temperature gradient appears while the temperature is changing. The existence ofthe nonlinear temperature field will lead to thermal stress in concrete bridge structure. Theoverall deformation temperature produced by lifting, in the longitudinal bridge can be solvedwith the method of setting expansion joint. Because of the unconstrained in the crossbridge, it will not produce temperature stress. While the thermal stress of gradient temperatureshould be dissipated in the longitudinal direction of the bridge by directly setting expansionjoint, there is no way to release the thermal stress in the cross bridge. For stable sectionbridge, the thermal stress of gradient temperature is uniform in the longitudinal bridge andin the cross bridge, its value is easily calculated in practice. It is necessary for specializedresearch that the bridge with variable cross section, because each cross section deformation,will produce deformation constraint each other and result in the thermal stress which can notbe ignored.In this paper, a highway interchange viaduct project is researched as an example and thefollowing several aspects of the research is conducted on the specific work:(1) The temperature of the variable cross-section box girder section has been observedfor three months. Based on the actual observations, simplifying the system necessarily andreasonably and choosing the corresponding boundary conditions according to the projectneeds, the selected variable cross-section box girder section on temperature field is analyzedand calculated by using the finite element software ABAQUS. And the calculated resultscompare to the current "general code for design of highway bridges and culverts".(2) Based on the distribution of temperature field,the thermal stress on variablecross-section box girder structure is calculated. After calculating results, analysis summed upthe main law of variable cross-section box girder temperature stress distribution. And on thisbasis, the box girder section thermal stress load spectrum is obtained.(3) Using the rain flow calculation method and MATLAB software, the computer program is edited to deal with the thermal stress spectrum, and the average temperature stressload spectrum and amplitude distribution, and summarizes the basic rule of temperature stressload spectrum.