| The steel-concrete hybrid bridge, which is the third kind of bridge different from the steel bridge and the concrete bridge, is being attached importance by the world bridge engineering circles. In this kind of bridge, the advantages of steel and concrete material can be exerted respectively and thoroughly to fetch up each other's failings to make the bridge construction more economical and reasonable. So it has been being used more and more widely in railway and highway engineering in the new bridge construction, including the girder bridge, the rigid frame bridge, the arch bridge, the cable-stayed bridge and so on, and in the reinforcement construction of the existed bridge. Though great progress has been achieved on researches on the design theory, structural type, structure details and construction method of the composite bridge, there are still many problems, such as crack control of the concrete deck, influence of the connecting rigidity over the structural mechanical characteristics and mutual dependency between design and construction, need deeper researches for better solutions. Hence, on the basis of research achievements of other countries, the mechanical characteristics of the statically indeterminate composite bridge is analyzed in this thesis by utilizing the large universal finite element software, MSC/NASTRAN and MSC/PATRAN, to promote the application and development of the composite bridge in China. The emphases of the research works of this thesis are laid on the mechanical performance of the shear connector of the continuous composite bridge, the crack status and design method for crack control of the concrete deck in the negative moment zone of the continuous composite bridge, the influence of the connecting rigidity and the construction method over the structural mechanical characteristics of the continuous composite bridge, and the force transmission mechanism and the stress distribution of the rigid node connecting the girder and the pier in the mixed bridge and so on. The main research achievements are as the followings:(1) Establishment of the 3D-FEM models of the continuous composite bridge and the rigid node of the continuous hybrid bridgeRelatively exact 3D-FEM models of the continuous composite bridge and the rigid node of the continuous hybrid rigid frame bridge are established through MSC/NASTRAN and MSC/PATRAN. The author advances that the shear connector is simulated by two spring elements, which are vertical to each other and parallel to the interface between steel and concrete, and one multipoint constraint element, MPC element, which is vertical to the interface. The author also puts forward that the crack of the deck is simulated by the Gap element which can't support longitudinal tensile force but can support longitudinal compressive force. In the model, the bonding force between steel and concrete cause by friction and block is neglected. These models can be used to analyze the mechanical performance, stress and displacement, oi the composite bridge and hybrid bridge very well and have relatively high precision.(2) 3D-FEM analysis for the load-bearing capacity of the stud connectorAs the prevailing method to determine the shear rigidity and the limit load-bearing capacity of the shear connector is the push test, which is time consuming and laborious, in this thesis the push tesi specimen of the stud connector is simulated through the non-linear analysis module of the MSC/NASTRAN and the numerical analysis results are in good coherence with that of the practicality lev; As a result, the shear rigidity and the limit load-bearing capacity of the stud connector can be determined by the finite element method and only a few practicality verification tests. Consequently time and cost can be saved greatly.(3) Design method for controlling cracks in the negative moment zone of the continuous composite girderThe crack mechanism of the concrete deck in the negative moment zone of the coniinuous composite girder, the relationship between the crack and the int...
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