Study On Early Vertical Crack Crack Mechanism Of Precast Concrete T-beam End

Precast concrete T beam is widely used in bridge superstructure because of its rigidity,simple structure and convenient construction.However,due to the unreasonable choices in the early design,construction and later maintenance process,as well as the lack of consideration of the environment and other factors,cracks of different forms appear in some Bridges during the construction prefabrication or operation stage,which has a great impact on the safety operation and durability of the overall structure of the bridge.Based on the ningxia hui autonomous region within the territory of a preeast eoncrete T beam bridge as the backing,which occurred in the stage of preeast beam end early vertical crack as the basic starting point,field research,using the finite element simulation combined with field experiment,the method of analyzing the reasons of the cracks and reasonably and research,and puts forward some prevention measures accordingly.The specific research contents of this paper are as follows:(1)through the ningxia autonomous region a precast concrete T beam bridge under construction in the research,found in the process of precast beam body part of the vertical cracks appeared on the beam end,access to many professional literature and books about concrete hydration heat,from the Angle of the theory of the cause of the cracks are analyzed,think beam end place belongs to web change section,the concrete usage of here more than any other site and size is larger,the resulting hydration thermal dissipation could be the root cause of the cracks.(2)Midas FEA finite element software is used to establish the corresponding three-dimensional simulation analysis model,and the simulation results show that the beam end is the position with the maximum temperature of the whole structure.Combined with theoretical analysis and finite element simulation results,hydration heat is identified as the root cause of this fracture.(3)based on finite element simulation analysis,the use of Midas FEA separately carried on the different working conditions,environment temperature and wind speed effect on the temperature field in precast eoncrete T beam structure analysis,studies the various parameters on T the influence law of temperature field distribution of concrete structure,and puts forward the need to focus on the disadvantages of construction.(4)in the same concrete preeast site relying on the project,the field experiment of temperature field test of precast concrete T beam was designed and carried out.By comparing the finite element results with the field test results,it was foimd that the field test results were in good agreement with the theoretical analysis and finite element simulation.Finally,combined with the above analysis and research results,the design and construction of precast concrete T beam put forward the preventive measures.