Research On Key Technology Of A Long-span Single-tower Cable-stayed Bridge With Hybrid Girder

In the past 30 years,with the rapid development of China's economy,a large number of large-span Bridges have been built,and cable-stayed Bridges have been widely used due to their superior force performance,good economic indicators and graceful landscape modeling.The cable-stayed bridge with single tower mixed beam adopts two different materials,the main span adopts steel beam,and the side span adopts concrete beam,which has good economic indexes.Meanwhile,the overall stiffness of the cable-stayed bridge is improved,which is conducive to reducing the bending moment and deformation of the middle span main girder,and effectively controls the negative reaction of the side fulcrum of the side span.There are some key problems in the cable-stayed bridge with single tower mixed girder,such as the reasonable proportion of the middle span of the non-symmetric cable-stayed bridge,the adjustment of the cable of the non-symmetric cable-stayed bridge,the influence of the auxiliary piers on the structural performance,the transverse seismic resistance of the side pier,and the connection mode of the steel mixed joint section.Taking nanzhuang bridge in foshan city as the engineering background and combining with the single tower mixed girder cable-stayed bridge that has been built or under construction in China,this paper conducts systematic numerical simulation with finite element method,and conducts systematic research on the key problems existing in the single tower mixed girder cable-stayed bridge.The main work and results of this study are as follows:(1)the characteristics of single-tower hybrid girder cable-stayed Bridges and relevant studies are reviewed,and the key parameters of single-tower hybrid girder cable-stayed Bridges built or under construction in China are analyzed and summarized in detail.(2)based on theoretical research and statistical analysis,the reasonable proportion of span in the side of single-tower mixed girder cable-stayed bridge and the setting of auxiliary pier are mainly studied.It is pointed out that the middle span scale of single tower hybrid girder cable-stayed bridge is 0.45 ~ 0.7.It reveals the influence law of the setting of auxiliary pier on the static force and dynamic characteristics of the cable-stayed bridge with single tower mixed girder: the setting of auxiliary pier can improve the overall stiffness and natural vibration frequency of the cable-stayed bridge with single tower mixed girder.(3)because of the asymmetry of cable-stayed bridge with single tower mixed girder,it is difficult to find the reasonable cable-stayed force by using the method of rigid support continuous girder and the method of minimum displacement.In this paper,the effect matrixmethod is used to adjust the cable force of cable-stayed bridge with single tower.It is found that using the influence matrix method to adjust the cable can make the cable force of single-tower cable-stayed bridge more uniform and the internal force and deformation of the main tower and girder more reasonable.(4)cable-stayed bridge of single tower mixed girder generally adopts the consolidation system of pier tower girder,and the vertical seismic force is mainly borne by the main pier.Under the action of transverse seismic force,the side pier will bear the larger seismic force.In order to improve the stress on the side pier foundation,the effect of the friction pendulum shock absorber is studied in this paper.The results show that the friction pendulum damper can significantly reduce the transverse seismic force of side pier and save the engineering cost.(5)there is a problem of complex structure and unclear force transfer in the steel mixing section of the single-tower mixed girder cable-stayed bridge.The steel mixing section of nanzhuang bridge adopts the connection mode of rear pressure-bearing plate with grillage chamber,and the longitudinal prestressed steel beam and transverse prestressed beam are installed to strengthen the connection.Meanwhile,PBL shear key and welding nail are set in the steel grillage room for joint force transmission.In this paper,the finite element method is used to analyze the steel mixing section of nanzhuang bridge.The results show that the local stress of the steel mixed segment is small,the structure is reasonable and the path of force transfer is clear.Based on the above work,the key technical problems in the design of single-tower hybrid girder cable-stayed bridge are studied deeply and systematically,which provides reference for similar bridge design.