Study On Time-varying Effects And Mechanical Analysis Of Yutang Stiff Skeleton Reinforced Concrete Arch Bridge

The stiff skeleton concrete arch bridge has excellent mechanical performance and super span ability.It is a kind of arch bridge structure with great development prospect.The traditional stiff skeleton arch bridges are all built with stiff skeletons before pouring outsourcing concrete.It is precisely because of the shortcomings of the outer concrete that it takes a long time to cast and the difficulty of hanging the formwork in the air.The prefabricated floor concrete on the stiff skeleton will cause large differences in the age of the concrete of each component.At the same time,the concrete in the pipe has high strength and high relative humidity,which is also significantly different from that of the outer concrete.All of these characteristics have complex long-term time-varying effects on stiff skeleton arches.So far,research on the time-varying effect of stiff skeleton arch bridges with precast floor concrete has not been carried out at home and abroad.In this paper,the Guizhou Yutang Bridge with a span of 200 m is taken as the research object,and the finite element method is used to compare and analyze the differences and characteristics of the representative prediction models at home and abroad.JTG 3362-2018,CEB-FIP 2010,GL2000 Three kinds of shrinkage and creep prediction models are carried out to study the influence of shrinkage and creep on the stress and deformation of the main arch of Yutang Bridge.The main contents are as follows:(1)Using MIDAS/Civil finite element software,a new modeling method of "spatial beam element + joint section at construction stage" is proposed,and the shrinkage and creep calculation model in China’s code JTG 3362-2018 is used to evaluate The effects of stress and deformation due to shrinkage and creep effects were analyzed.According to the characteristics of the concrete with prefabricated bottom slab of Yutang Bridge,and compared with the time-varying effects of different prefabricated concrete bottom slabs and different construction methods of the main arch ring on the long-term mechanical behavior of the rigid skeleton arch.(2)Combining the CEB-FIP2010 model and GL2000 model,the shrinkage and creep response of the main arch ring of Yutang Bridge is analyzed.The prediction results of these two models are compared with the calculation results in JTG 3362-2018,and the deformation and stress redistribution of the three prediction models on the stiff skeleton arch of Yutang Bridge are compared and analyzed.(3)Based on the arch bridge pre-camber theory,five common pre-camber distribution methods in arch bridges are summarized,the cumulative deformation value of each segment of the stiff skeleton arch is analyzed by formal assembly,and the pre-arch of each segment is compared using the least square method The sum of the square deviation of the minimum deviation between the degree and the accumulated deformation value.The results show that the shrinkage and creep effect increases the stress of the steel tube and the concrete in the tube,and reduces the stress of the encased concrete.Comparison of methods,the concrete of each component of the bridge construction method is not uniformly stressed,and the tensile stress between the precast floor and the cast-in-place web is large;The completion of shrinkage and creep deformation after 10 years of bridge completion is CEB-FIP2010>JTG2018-3362>GL2000,stress redistribution: GL2000> CEB-FIP 2010> JTG 2018-3362;The precamber of the stiffness skeleton arch of the Yutang Super Bridge is the most reasonable distribution according to the arch foot thrust influence line.