Study On Mechanical Behavior Of Partially Earth-anchored Elliptic Single Tower Cablestayed Bridge

The partially anchored cable-stayed bridge is a structural form between the selfanchored cable-stayed bridge and the ground anchored cable-stayed bridge.In this structural form,there are differences in the number of cables anchored on the main and secondary spans,resulting in considerable unbalanced longitudinal horizontal thrust on the girders.If it happens to be an oval tower,the connection between the girder and the anchor(abutment)may also affect the force of the entire structure(mainly the girder,bridge tower).The "elliptical bridge tower",as a visually strong "arch tower" model,under vertical load,the bridge tower has a tendency of outward expansion in the lateral direction(referred to as "lateral extension effect" in the article).The paper is based on a cable-stayed bridge with partially anchored oval-shaped towers.It mainly studies the following aspects:(1)A brief introduction of the overall balanced force pattern of the double-span cable-stayed bridges with inclined towers was conducted.In addition,the paper analyzed the characteristics of the lateral deformation of the bridge tower under the "vertical cable force component" and "lateral cable force component.",as well as the lateral deformation characteristics of bridge towers under the "bridge tower form of girder with support" and " bridge tower form of bridge tower with transverse beam"(2)Briefly introduces the necessity of the "girder-anchor ingot(abutment)connection form" in the discussion of the structural system of partially anchored cablestayed bridges.Based on the three " girder-anchor(abutment)connection" and the three " girder-tower connection types",nine new types of structural systems were formed,after excluding obviously unreasonable types of structures.The force characteristics of each combined structure system under dead load,live load,temperature and load combination effects are discussed in detail.Then the comprehensive comparison of the force modes of each combination system is performed,and the relative optimization of combined structural system types of the cable stayed bridge is analyzed and discussed.(3)Due to the considerable unbalanced longitudinal horizontal thrust of the main girder under this structural form,the research object is the main girder form of "oblique tower,large longitudinal slope",which causes the influence of the parameters of the inclination angle of the tower and the longitudinal slope of the girder on the structural force will be different from that of the conventional cable-stayed bridge.The degree of influence of the inclination angle of the tower and the longitudinal slope of the main girder on the structural forces is analyzed in this paper.The internal forces of the structure that cannot be ignored in the design are briefly summarized.(4)For cable-stayed bridges with transverse “elliptical” towers,when adjusting cables,regardless of displacement,internal force or energy as the objective function,the “longitudinal shape of the bridge tower” is often controlled.In this process,the cable tension is determined with the determination of the required “bridge tower longitudinal shape”,it can be seen that it is difficult for the conventional cable adjustment process to better control the lateral force of the tower.However,the effect of the elliptical tower on lateral effect is very obvious.In view of this situation,this paper proposes to improve its lateral effect from the structure.Based on the analysis of the transverse force of the elliptical tower under a variety of factors including “position of cable arrangement”,“change of elliptical length axis and short axis”,“truncated position of elliptical bridge tower root” and “lateral stiffness of elliptical bridge tower”,some suggestions for improvement of the lateral force control of the “elliptical” tower under the condition of tuning cable are proposed.