| With the rapid development of the bridge business,various new structural forms continue to emerge.Among them,the low-tower cable-stayed bridge is a typical combined system bridge between the cable-stayed bridge and the continuous beam bridge.It has a broad range prospects of large and medium-sized span bridges.Because the low-tower cable-stayed bridge has only 20 years of development history in China,so far there is no standard design specification.In the construction of the project,the cable-stayed bridge can only be used as a reference,and no standard control system has been formed.Therefore,it is of great practical significance to study the structural system and stress characteristics of low-tower cable-stayed bridges.This article first introduces the origin and development of low-tower cable-stayed bridges by referring to relevant domestic and foreign literature,summarizes the cable force calculation theory and method of the cable-stayed bridges,and lays the foundation for the optimization of the cable-stayed cable-stayed bridges.The low-tower cable-stayed bridge belongs to multiple statically indeterminate structures.In theory,there are countless kinds of internal force solutions.The reasonable bridge state refers to an optimal solution that makes the internal force indicators of the bridge reach scientific and reasonable.To this end,this article takes a99+180+99m low tower cable-stayed bridge as the engineering background,uses the finite element software Midas/Civil2019 to establish a full bridge model,simulates the construction steps of the bridge,and conducts the cable strength of the completed bridge and the initial tension during the construction phase.Five methods including rigid support continuous beam method,zero displacement method and influence matrix method are selected to calculate the cable force of the low tower cable-stayed bridge one by one,and the calculation methods that are not applicable to the bridge are excluded based on bending moment,stress and displacement to establish a reasonable cable force.Then according to the construction process of one-time tension,the initial iteration tension of the construction under one-time tension is determinedby the difference iteration method.After four iterations,the cable force can converge well without considering the effects of shrinkage,creep and geometric linearity.It makes the bridge-building cable force obtained under the action of initial tension closer to the ideal bridge-building cable force.At the same time,the simulation analysis results of the bridge-building state and the operation state are compared and demonstrated.It is found that the indicators of the control cross-section on the bridge meet the specifications.Thus,the correctness of the reasonable initial tension calculated by the difference iterative method is verified.On the basis of determining the reasonable state on the bridge and the reasonable construction cable force,the influencing factors of the cable force on the bridge are analyzed,and the changes of the cable force on the low-tower cable-stayed bridge by the state parameters,shrinkage and creep effects and the phenomenon of broken cable function are analyzed.The impact of cable force changes on the structure is concluded.It draws some conclusions,which has certain guiding significance for the actual project. |
