Static Performance Parameters Analysis And Seismic Response Of Three-tower Suspension Bridge With Various Support Systems

With the development of the transportation industry,the requirements for bridge spanning capabilities are getting higher and higher.While the traditional two-tower suspension bridge is difficult to meet the demand,the large-span three-tower suspension bridge is gradually being valued.Many large-span suspension bridges with three towers have been built one after another in the river basins of our country.Compared with the traditional two-tower structure with simple structure,the structural characteristics of the three-tower suspension bridge have been changed due to the multi-tower and main span.For the three-tower suspension bridge to be widely used and promoted,its mechanical properties must be studied and analyzed in detail.Suspension bridge is characterized by its strong geometric nonlinearity,which requires accurate shape finding of its main cable.The professional analysis software Bnlas for the geometric nonlinearity of suspension bridges based on the segmented catenary theory is used in this paper.The finite element static and dynamic models of three-tower suspension bridge with four types of stiffening beam supporting systems:simply supported,floating,articulated and consolidated,are established in this paper.The difference in static performance and seismic performance of three-tower suspension bridges with four stiffening beam support systems has been studied.Main span,vertical span ratio,side main span ratio,height difference between middle tower and side tower,middle tower stiffness,side tower stiffness,stiffening beam stiffness and dead load concentration,the influence of these parameters on the main cable axial force,middle tower cable safety performance,internal force of stiffening beam,displacement of stiffening beam and lateral structure performance have been analyzed.Finally,the law was summarized.The effect of the load,the internal force of the stiffening beam and the anti-sliding safety performance of the main cable are affected by the supporting form of the stiffening beam.The stiffening beam support form will interact with some structural parameters,and the mechanical properties of the structure will be affected by it.The increase in the span of the main span will lead to a significant increase in the axial force of the main cable,the live load axial force of the main cable,and the horizontal and vertical deflection of the stiffening beam.The reduction of the vertical span ratio will significantly increase the bridge axial force of the main cable,the live load axial force of the main cable,the vertical deflection of the stiffening beam and the anti-sliding safety factor of the main cable of the middle tower.The stronger the stiffening beam is restrained,the greater the increase in the anti-sliding safety performance of the main cable of the centering tower.The side-span performance of the three-tower suspension bridge is affected by the side-to-main-span ratio,but the impact is small.As the height difference between the middle tower and the side tower increases,the torsion-span ratio of the stiffening beam increases,but the safety performance of the main cable of the middle tower increases more.The increase in the stiffness of the middle tower will greatly reduce the stiffening beam torsion-span ratio and the safety performance of the main cable of the middle tower.The greater the rigidity of the center tower,the smaller the influence of the stiffening beam support form on the anti-sliding safety performance of the center tower main cable.The mechanical properties of the three-tower suspension bridge are affected little by the stiffness of the side towers,so it can be ignored.The stiffness of the stiffening beam has a huge influence on the lateral and vertical deflection and bending moment of the stiffening beam.The greater the vertical stiffness of the stiffening beam,the more obvious the contribution of the supporting system to the anti-sliding safety performance of the main cable of the center tower.Increasing the constant load concentration of the stiffening beam will cause the axial force of the main cable to increase significantly,but it will also significantly reduce the live load internal force of the main cable and the stiffening beam,and significantly reduce the transverse and vertical deformation of the stiffening beam.The stronger the stiffening beam is restrained,the shorter the basic period of the three-tower suspension bridge structure.The floating system three-tower suspension bridge has the best longitudinal seismic performance,and the simply-supported system has the worst longitudinal seismic performance,but the floating system pylons and stiffening beams have the largest seismic response displacement.The continuous system has the best lateral seismic performance,and the seismic response internal force of the bottom of the middle tower is smaller than that of the simply supported system.The combination of vertical earthquake and horizontal earthquake has minimal influence on the internal force of the earthquake response.