Study On Static And Dynamic Behavior Of Multi-hybrid Arch Bridge

For long-span arch bridge, the objective of the structure schemes and construction techniques should meet its function, and reduce cost, shorten the duration, be convenient for construction, be safe and reliable, beautify the figuration. According to this, multi-hybrid arch bridge spreads rapidly and is widely used.Taking Dongping Bridge at Foshan City in Guangdong province as a researching case, this dissertation analyzes static and dynamic charateristics of the new structure system by classical mechanics and finite element method, and studies the differences between this new structure system and traditional arch bridge on the aspect of mechanic performence. Based on these analysis and study, Genetic Algorithm is adopted to optimize the designing parameter of this bridge. Beam coupling shell finite element model is used to analyze the local Stress of connection joint between main arch and sub arch, and identify its link stiffness. Due to the lifting cable force is determinted by the fuel tank during the swivel erected process, the structure calculation method during the swivel erected process is optimized and the calculation effect is improved. Meanwhile, the stress of key components which influences the safety of structure in the construction process is also studied. The main specific tasks of this paper are listed below:(1) Using force method and taking the design parameters of Dongping bridge as reference, in accordance with its mechanical features, simplify the static calculation model of multi-hybrid bridge composed by the main arch, sub arch, and tie beam, derived the static calculation formula of multi-hybrid bridge, qualitatively analysis the distinction of mechanical properties between the multi-hybrid bridge and flexible tied arch bridge. Finite element model of multi-hybrid bridge is established, the influence of sub arch and continuous beam on the overall structure is quantitatively is studied.(2) The combination finite element model of multi-hybrid arch bridge is established, the damp is used to amend the response spectrum, and the effective modal participation mass is used to determine the minimum number of modes for mode combination of response spectrum analysis. The reference of sub arch and continuous beam to the vibration characteristics and the results of spectrum analysis of the multi-hybrid bridge were studied.(3) Basing on genetic algorithm and the finite element method, the ratio of rise to span of main arch, the arch-axis coefficient, and the height and the thickness of steel box of the key section are selected as design parameters. Taking the material usage and the greatest stress of structure as restrictive conditions and minimizing the mean square stress of the control section, program GA-FEM is made and the structural optimization design of Dongping Bridge is carried out.(4) Basing on the plane cross-section assumption of slender beam, adopting constraint equations to build a total, partial coupled finite element model, and combining the local shell FEM model of connection joint with the space bar FEM model of entire structure to carry out the numerical analysis, the stress distribution of connection joint between main arch and sub arch of a multiple hybrid arch bridge is studied, the deformation of entire structure by the influence of local deformation of connection joint is identified, and the influence of stiffening ribs of connection joint to the calculate results of entire structure is analyzed.(5) The first-order optimization theory is introduced; the Optimization Model of swivel erected arch bridge is built. This model take the magnitude of lifting-cable forces at each suspension centre as design variables, the spatial coordinate of designated point on the structure constituting the objective function, and the control demands of hydraulic sync elevation technology constituting the constraint conditions. By minimizing the objective function, Artificial calculation is replaced by computer automatically calculation, the computational work is reduced significantly.(6) After the validation of the contact parameters of finite element model, the contact stress in pinned connection was computed systematically by using analytical method, simplifying design methods and refined nonlinear finite element method. Compared to the stress values measured in the field, the calculation results meet basically. Based on these results and comparison, some parameters such as lifting-force value, material constitutive relation, have been studied also by investigating their effects on the contact stress of pinned connections.