Fine Analysis On Hydration Heat Effect Of Arch Foot Of Railway Long-span Tied-arch Bridge

The arch foot of concrete-filled steel tube tied arch bridge is very complex,and it is very important for structural safety.Cracks are often found on the surface of arch feet of tied arch bridges after the pouring process.Moreover,cracks have a great influence on the structure,which will affect the appearance of the structure when slightly and threaten the safety of the structure when seriously.Therefore,it is very important to study the temperature field and stress field of the arch foot of tied arch bridge under the temperature effect of concrete hydration.Previous studies have focused on the stress and safety performance of the arch foot in the operation process,or on the hydration heat temperature effect of the concrete-filled steel tube.In the rare research on the hydration heat of arch foot pouring,the analysis focuses on the influence of layered pouring and pipe cooling measures on the temperature field and stress field of arch foot.In this paper,the temperature effect of hydration heat on the arch foot of tied arch bridge during pouring is studied.Firstly,this paper introduces the theory of finite element calculation and using Midas civil model to establish the whole tied arch bridge model based on the theory.After finding the deficiency of the whole model for the part of arch foot,Midas FEA is used to establish the refined finite element model of arch foot.Then,based on the clue of heat generation,heat conduction and heat loss of cement hydration heat,the corresponding theory and its application in this study are introduced.Finally,the correct finite element model of hydration heat is established.According to the actual situation of the bridge pouring,the important parameters of the hydration heat calculation are selected according to the specifications and relevant literature,and the hydration heat model is established.The correctness of the model is verified by comparing with the measured temperature.Secondly,by changing the different pouring environment factors,the changes of the hydration heat temperature field and stress field of the arch foot and the difference of the crack rate calculated by the software are compared when the concrete temperature,wind speed,cement content,environment temperature and removal time are different.It can be found that different influence factors lead to the difference of temperature field and stress field of the model arch foot,which provides feasible suggestions for the similar type of arch foot modeling and construction in the future.