Analysis Of Cable Breaking Response Of Long-span Prestressed Concrete Cable-stayed Bridge With Central Cable Plane

Central cable plane cable-stayed bridge has become one of the most popular long-span bridge structures because of its strong traffic capacity,beautiful appearance and reasonable stress.As the main force transmission component of cable-stayed bridge,stay cable plays the main role of "connecting the preceding and the following" to the whole structure,and it is an important lifeline to ensure the safety and normal traffic of the whole structure.The cable will break suddenly due to fire,explosion,impact,cable corrosion fatigue and so on,which will cause the dynamic response of the structure,lead to the change of the structure form and affect the structure stress.And for the whole structure,the location of the broken cable has a wide range of randomness.Therefore,this paper takes the location of broken cable as the starting point,calculates the reliability index of each cable by introducing svm-ga-pso algorithm to determine the location of broken cable,and on this basis,analyzes the broken cable response of long-span prestressed concrete cable-stayed bridge with central cable plane.The specific research contents are as follows:1.Determine the dynamic analysis method and related parameters of the broken cable.Taking the cable-stayed bridge with symmetrical distribution of central cable plane of double towers as an example,the theoretical analysis of dynamic response of the structure after cable breaking is carried out.The basic principles of dynamic equation establishment,dynamic eigenvalue solution and dynamic equation solution in the finite element software are analyzed in detail.The comparison of two commonly used finite element simulation methods for dynamic analysis of cable breaking is made.Finally,"semi-dynamic" simulation method is selected to realize cable breakage response analysis of cable-stayed bridge,and the concrete process of "semi-dynamic" simulation for cable breakage dynamic analysis is given.2.Elaborate the structure of "SVM" and the working principle of "SVM-GA-PSO" algorithm,verify the SVM-GA-PSO algorithm with a classic example,and give the process of locating broken cable based on "SVM-GA-PSO" algorithm.The classical example shows that this method is accurate and reliable,and it combines the advantages of SVM response surface method,such as small sample learning ability,high fitting precision,strong searching ability and fast convergence of PSO algorithm,and can solve the problem that the reliability index of implicit function solution does not converge,and can be used for the analysis of practical engineering reliability.3.Location of broken cable based on SVM-GA-PSO algorithm.The finite element model is established for a practical project,and the reliability analysis of the cable of a longspan cable-stayed bridge based on stress control is carried out by using the "SVM-GA-PSO" algorithm proposed in this paper,and the broken cable position is located according to the reliability index.The results show that the reliability index value of the cables near the bridge tower is relatively large,while the cables far away from the bridge tower are relatively small;The reliability index of cables numbered 56#,57# and 58# near the mid-span is low,so it is easier for cables numbered 56#,57# and 58# to break compared with other cables under extreme conditions such as fire,explosion,impact and cable corrosion fatigue.4.According to the actual project,a finite element model is established to analyze the cable-stayed bridge with a long-span prestressed concrete semi-floating system in the central cable plane.The results show that the broken cable has the greatest influence on the cable force of the adjacent first cable,and the maximum dynamic amplification factor is greater than 2.0 recommended for cable-stayed bridges in American PTI,and the dynamic response can not be ignored When the cable is broken near the mid-span,the cross-section internal force of the main girder changes the most,and the dynamic response of the cross-section internal force at the broken cable is the largest.The dynamic response of the cross-section internal force tends to decrease with the increase of the distance from the broken cable,and the dynamic impact of the broken cable has a great influence on the shear force of the main girder section.When the cable is broken near the mid-span,it has a great influence on the bending moment along the bridge at the bottom of the cable tower,and the bending moment along the bridge at the bottom of the cable tower on the side where the broken cable is anchored will have a great dynamic response after the cable is broken,and the bending moment vibration along the bridge at the bottom of the cable tower on the side where the non-broken cable is anchored is basically unaffected by the dynamic action of the broken cable.When the impact effect of broken cable and the stress of the structure under dead load need to be considered,the amplification factor can be multiplied by the static calculation result of the damaged structure under dead load to simplify the calculation.