Study On Bearing Capacity Of Twice-prestressed Composite Structure Continuous Beam

As a new style of structure, twice-prestressed composite structure is also prestressed concrete technique used in the field of bridge. The new-type structure has obvious advantages in crack resistance property and deformation controll of bridge. Previous study is based on simple beam. In this thesis, the new-type structure is used in continuous beam. Twice-prestressed composite structure continuous beam was cast and the characteristic in construction and creep phase has been researched . Its performance in serviceability limit state and bearing capacity limit state is researched in this paper as follows:(1) A twice-prestressed composite structure continuous beam with two spans has be designed and cast. The performance of deflection and internal force before crack.of this test beam is researched in the cracking behavior experiment of the section of maximum positive moment and negative moment. The test results prove that this new-type structure has perfect crack resistance property and good behavior of unity work between precast part and succeeding-poured part.(2)Based on the experiment of ultimate bearing capacity, the performance of deflection and internal force after crack has been tested. This thesis first advances the formulas of over-reinforcement limit in terms of the phenomena of breaking in over-reinforcement way. This thesis indicates the types of crack on the joint surface and proposed some tectonic measures.(3)The nonlinear finite element program for linkage structure is designed and simulates the nonlinear all stage of loading to the model continuous beam. The program analysis results and experiment results are in better agreement at most time. So the validity of the program is proved and a reliable calculating method for the design and evaluating of carrying capacity of the twice-prestressed composite structure continuous beam is put forward.This research is based on research project as"Research on High Strength Concrete in Ultra Thin Beam Bridge"funded by Communication Bureau of Guangdong province. The study that twice-prestressed composite structure is used in thin beam bridge have been done before. The new-type structure is proposed to be applied to high-speed railway bridge in this thesis. Comparing with the conventional PC rail-way bridge structure, the new-type structure is capable of remarkably reducing the creep camber and is worth popularizing.