Optimal Design Of Prestressing Tendons In PC Continuous Beam Bridge

Large span continuous beam is generally used three to the box section of the beam, the design of the prestressed design is the key to the bridge superstructure design. Reasonable layout of prestressed beam and prestressed value can not only improve the performance of the bridge, reduce the bridge disease, but also reduce the amount of material used. However, in the optimization design of continuous beam bridge, the optimization problem of the reasonable prestress still hasn’t been solved. This paper is based on the 104 National Highway Long River Bridge as the project, the optimization design of prestressed beam, the following work is mainly carried out:(1) Prestressed concrete continuous beam bridge longitudinal prestressed tendons and the reasonable distribution of beam are studied. Analysis shows that the long-span prestressed concrete box section continuous beam should be set up under the web of bending beam to resist shear force and principal tensile stress of the bridge damage. According to the different web beam anchoring position established four groups of finite element model, through compared four groups of model girder internal force calculation, stress and deflection value of size, to examine the influence of the different web beam anchor position on the stress state of bridge structure. The results show that the web beam under bending and anchored in the 2H/3 more appropriate.(2) The quadratic programming and bending energy method of cantilever construction of continuous beam longitudinal prestress optimization design method based on, Yalmip toolbox optimization model is established based on and the main idea is to discrete unit of main girder structure of the bending strain energy minimum as the objective function, the construction and a bridge stage stress as constraint conditions, using mathematical programming method the tensioning pre-stressed reinforced number are optimized. By comparing and analyzing the performance index of the continuous beam, it is found that the optimization of the continuous beam is not only better, but also more economical. It shows that this method is feasible to optimize the longitudinal prestress of the continuous beam.(3) Analysis of the influence factors of Web principal tensile stress of the main factors, the adverse impact of vertical prestress eccentricity on the web stresses are calculated, and in calculating webs of live load effect based on the proposed active set inside the eccentric vertical ribs, can offset part of the live load internal force and to improve the web by force. By using the orthogonal test method, the optimization of the spacing of the vertical prestressing tendons at different thickness of the web plate can make the distribution of the main stress of each section more uniform.