Study On Mechanical Properties Of High Performance Concrete Continuous Girder Bridge

With the development of civil engineering, reinforced concrete structure was more and more widely used. At the same time, concrete and steel were more strictly required, especially at bridge engineering. Concrete used to build bridge was required to be high stress and high-durability because of its work environment and long-span development direction. Attentions of bridge designers and builders were paid to high performance concrete (HPC) for its high-durability and higher strength.A prestressed continuous box girder-bridge was taken as instance in this paper. Midas Civil and FEA, the two kinds of finite element simulation software, were used to simulate the performance of some 3-span railway-bridge (48+80+48) m made up of prestressed continuous box girder based on high performance concrete, at Tianjin city. The meaning of this pepper was to provide reference for the application of high performance concrete in the prestressed continuous girder-bridges. The main contents of this paper were as followings.(1) Literature documents and data were consulted to better understand the requirements of high performance concrete mixing proportion design and construction maintenance. More attentions were paid to the mechanical properties of high performance concrete.(2) Based on some 3-span railway-bridge (48+80+48) m made up of prestressed continuous box girder, at Tianjin city, finite element models of continuous box girder-bridge, respectively made up of C50 common concrete, C80 HPC and C100 HPC, were built. Static behaviors, such as shrinkage, creep, deflection and prestress loss were calculated, compared and analysed. The results showed that HPC continuous box girder-bridge performed better than common concrete coutinuous box girder-bridge.(3) The continuous box girder-bridge was re-designed separately by using C80 HPC and C100 HPC. The difference of material usage and camber was calculated and compared. Dynamic performances before and after re-design were checked. The results showed that the re-design projects could meet the code well.(4) Solid finite element models of zero blocks were built with Midas FEA. The temperature effects caused by heat of hydration were simulated and analysed before and after re-design. Zero block stress of key construction stages and deflection of the maximum double cantilever stage were also simulated and compared. The results indicated that less hydration heat and more reasonable stress state of zero blocks and less defection of the maximum cantilever state could be realized by using HPC.(5) Analysed bridge common defects, which led to bridge structure bad durability, and the inducing factors of them. From the aspects of frost resistance, permeability resistance, sulfate attack resistance and carbonation resistance, durability of high performance concrete was studied and some measures to advance the durability of bridge structure were proposed.In this paper, finite element models were built to calculate the properties of the continuous box girder bridges respectively using C50 common concrete, C80 HPC and C100 HPC and the difference was compared and analyzed. The results showed that:(1) bridges with HPC had better volume stability and fulfilled the code requirements of static and dynamic properties well. (2) Stress state of bridges with HPC was more reasonable during construction stage. (3) Durability of bridges with HPC was better. Reference was provided for the same type bridge design with HPC based on the study of this paper.