Influence Of Pre-stress Strength For Concrete Resists To Crack

Go along with the long-term economic rapid development in China,the construction of high-grade highway and urban roads have rapid development.The pre-stressed long-span concrete bridge has been widespread application in our country.Especially,the prestressed concrete continuous box girder is the first chosen in design of the long-span bridge.Because the box girder possess many advantages,such as large stiffness structure, effective resistance in positive and negative space moment,adapting modern construction. In the varial cross-section box beam, prestressed reinforcement is longitudinal curve along bottom slab. Prestressed reinforcement is plane-bending and shaft-bending, at this moment prestressing effect will generate tension in the bottom slab.for that,the bottom slab possible has appearance distance and crack. The middle span joint section endurances the largest radial direction force,it is the most hazardous location.On the basis of consulting a large data about design and construction of bridge and studying mechanics principle of the bridge structure, the text calculate the radial direction force,which caused for prestressed reinforcement of the bottom slab stretching,and discussing the effects of the curve equation in the middle span joint section on bottom slab of middle span crack.Combination of structural characteristics of a long-span prestressed concrete continuous bridge, using large finite element analysis software ANSYS for entity structure numerical simulation analysis, setting up complete and unitary prestressed concrete structure analysis system.in the analysis system, structure mathematical model of all load carrying structures,contain concrete model, prestressed reinforcement model, simulative analysis of stretching process and so on, accurate simulate space position,size, material characteristics,connection form and load action of the load carrying structures,establish the initial form of the structural simulation, carry on structure effect analysis and calculation.On the basis of model,we can analyze ultimate tension of concrete bottom slab in the different curing time. Compiling procedure or making use of graphic display software for visibility of simulation result data,contain bottom slab stress in every working condition,so we can get detailed,accurate and reliable analysis result.Theoretical calculation and practices demonstration, concrete strength is different at the age of concrete, it is important to select proper time on prestressed reinforcement tension.Else if the prestressed reinforcement tension was too great,it would form bottom slab failure and prestress loss. Combination of engineering example, we must monitor loading state and deformation in every stage of bridge construction, it could keep shape of dead load state and loading state compliance with rule, material use value will be further improved, to prolong the life of bridge.