Analysis And Research On Static And Dynamic Characteristics Of Long-span And Multi-tower Cable-stayed Bridge

For some wide rivers or mountain valleys,such as the middle and lower reaches of the Yangtze River in China and some sea-crossing channels,the use of a multi-tower cable-stayed bridge system can reduce the number of bridge piers and provide multiple continuous large spans,which can reduce the obstruction of water flow.Function,reduce the impact of bridges on river flooding,and provide greater freedom for ships to pass,and have more economic and technical advantages in mountain valleys.Therefore,the system has been widely used.But on the one hand,due to the lack of back cable constraints,the middle tower of the multi-tower cable-stayed bridge has reduced the overall rigidity of the structure.Under live load,the horizontal deformation of the top of the middle tower and the vertical deflection of the main beam of the mid-span are relatively large.The internal force at the bottom of the tower and the fatigue stress amplitude of the stay cables also increase accordingly,which may affect the normal function of the structure.On the other hand,with the rapid development of transportation and the continuous improvement of construction technology,the spans of highway bridges are increasing day by day,the weight is becoming lighter,and the driving vehicles are constantly developing toward high speed and heavy load.The multi-tower cable-stayed bridge has a large span and small structural rigidity.Therefore,when the operating vehicle is stimulated by the inherent unevenness of the bridge and other factors,it will have an impact on the bridge,causing a large displacement of the long-span cable-stayed bridge,causing it to the dynamic response of the vehicle increases.Therefore,systematically developing the static and dynamic performance of multi-tower cable-stayed bridges has important engineering application value and theoretical significance.For the static performance,the cable force optimization method of a typical multi-tower cable-stayed bridge—three-tower cable-stayed bridge is studied.The cable force optimization method in the bridge-building state is proposed,and the internal force of the tower beam and the cable force distribution in the bridge-building state obtained by each method are compared.State,a cable force optimization method suitable for a reasonable construction state of a multi-tower cable-stayed bridge system is obtained.It provides a reference for the engineering optimization of cable force of multi-tower cable-stayed bridge.In terms of dynamics,the influence of commonly used methods to improve the rigidity of the bridge on the dynamic characteristics of the structure was studied.The characteristics of the low-order vibration frequency of the multi-tower cable-stayed bridge were summarized.Based on the actual engineering,the multi-tower cable-stayed bridge was completed and constructed.The stability analysis of the multi-tower cable-stayed bridge is the most prone to instability and the corresponding safety factor.Relying on actual engineering,Midas is used to establish the bridge analysis model and seismic calculation model,the modal synthesis method is used,Matlab is used to compile the vehicle-bridge coupling calculation program,and the Newmark-β method is used to solve the equations.,Vehicle speed,and displacement,speed and acceleration response under different influencing factors provide reference for the study of dynamic performance of multi-tower cable-stayed bridge.Using the time-history analysis method,the bending moment time history of each calculated section of the multi-tower cable-stayed bridge is obtained,and the precautions in the seismic analysis of the multi-tower cable-stayed bridge are proposed.