Research On Cable Force Optimization Of Cable-stayed Bridge Without Backstays

The cable-stayed bridge without backstays is favored by bridge designers all over the world because of its unique shape.Because this type of bridge is an asymmetric structure system of cable,tower and beam,cable force optimization is very important.Rational cable force can not only improve the mechanical properties of the bridge but also guarantee the safety of the structure.The purpose of cable force optimization of the construction cable force of cable-stayed bridge without back backstays is not only to ensure that the state of the bridge reaches the expected state of the design,but also to ensure the safety of cable-stayed bridges without backstays in the construction process.In this paper,a typical cable-stayed bridge without backstays is taken as the engineering background to determine the reasonable finished dead state of the bridge and optimize the construction cable force.The main research contents of this paper are as follows:Based on the basic principle of cable force optimization,summarizes the common finished bridge optimization and construction cable force optimization method.In view of the structural asymmetry and significant aging influence of all-concrete cable-stayed bridges without backstays,analyzes the advantages and disadvantages of all kinds of cable force optimization and the suitable situation,research results of the cable-stayed bridge without backstays for cable force optimization method provides a theoretical basis.Determine to finished bridge,In view of the asymmetric structure of cable-stayed bridge without backstays,the minimum bending energy-moment feasible region algorithm is used to optimize the cable force.First of all,using the finite element software Midas/Civil build a carried out bridge structure model,initial minimum bending energy method is used to determine a finished bridge,and then calculate the reasonable value range of bending moment of main beam under the action of dead load,considering the stress of the main tower,through the dead load bending moment feasible region optimize the rational cable force,get into the reasonable finished dead state.On the basis of reasonable bridge state indicators meet the specification requirements,the validity of the method is verified by comparing the calculated reasonable bridge cable force with the construction final cable force.In the process of construction cable force optimization,a finite element analysis model with construction stage is established.In view of the obvious influence of aging on the all-concrete cable-stayed bridge without backstays,the initial construction cable force is calculated by the method of forward iteration method,the variation trend of each cable force with construction stage is analyzed,and the safety factor of the cable is calculated.A typical construction stage is selected to analyze the variation trend of stress on the upper and lower edges of the key sections of the main girder and main tower,at the same time,the displacement trend of the key sections of the main girder and the main tower is analyzed.In the process of construction,the safety factor and various control indexes of cable meet the requirements of the specification.The practicability and feasibility of the method are verified by comparing the calculation of construction cable force and the actual measurement of construction monitoring cable force.Sensitivity analysis of parameters of cable-stayed bridge without backstays was carried out.First,analyzed the impact of cable force change on the structure.Second,the main tower stiffness,the main tower angle,length of non-cable area and beam sited on the main tower is set to the design parameters,analyzes the influence degree and sensitivity of design parameters on cable force and other control parameters of the cable-stayed bridge without backstays,and to study the suitable design parameters,and provide reference for cable force optimization.