Analysis And Research On Mechanical Behavior Of Single Tower Self Anchored Suspension Bridge

In recent years,the single tower self anchored suspension bridge with its novel structure,beautiful shape and flexible site selection has been favored by the engineering community,a large number of self anchored suspension bridges have emerged.Because the main cable is anchored on the stiffening beam,the huge anchorage ingot is omitted,which is suitable for construction in the area with poor geology,and it also has certain competitiveness in some urban bridge schemes with small and medium span.In order to ensure the safety of self anchored suspension bridge in the operation stage and make its structural design more economical and reasonable.In this paper,based on the engineering background of JiuQiao road single tower self anchored suspension bridge in Hangzhou,the mechanical behavior of its structural system is analyzed and discussed.The main contents are as follows:(1)This paper introduces the development and research status of self anchored suspension bridge at home and abroad,summarizes the structural and mechanical characteristics of self anchored suspension bridge.This paper expounds three basic analysis theories of self anchored suspension bridge,geometric non-linear influence factors and advantages or disadvantages and applicability of each calculation method of main cable shape.(2)Based on the theory of suspension bridge and the basic principle of finite element,the finite element modle of the whole bridge is established by Midas Civil,the whole mechanical behavior of self anchored suspension bridge is analyzed and commented.The calculation results of the stiffening beam,the crane system and the main tower are discussed respectively,and the mechanical characteristics are summarized,which paves the way for the later two chapters.The main cable saddle and upper crossbeam are the important parts of the bridge tower.Ansys is used to establish the finite element model of the main cable saddle and the upper crossbeam.Combined with the stress characteristics of the bridge,the local stress is analyzed,It is concluded that the stress at the junction of the bottom of the upper beam and the bridge tower is relatively weak,and the main cable saddle causes the stress concentration due to the size mutation.(3)After the completion of the bridge,the stress of structure under live load,temperature effect and different load combinations are analyzed.The influence of structural parameters on the static performance of self anchored suspension bridge is discussed.By using the single variable method,the influence law of structural internal force and displacement is discussed by changing the design parameters such as the rise span ratio of main cable,the suspender spacing,the tensile rigidity of main cable,the vertical bending rigidity of stiffening beam and the dead load set.It is concluded that the design parameters not only affect the structuralstiffness,but also affect the internal force distribution of the whole bridge.(4)The dynamic characteristics of the bridge are studied.The main vibration modes and natural frequencies of the structure are calculated by the subspace iteration method of eigenvalue analysis,and the results are analyzed.The sensitivity analysis of dynamic characteristics of structural parameters of the bridge is also discussed.The influence of the variation of the main cable rise span ratio,the suspender spacing,the main cable tensile stiffness,the vertical bending stiffness and the dead load set on the natural frequency of the structure are discussed respectively,It is found that the structural stiffness and cable sway are affected by the parameters.The above research provides a certain reference value for the future construction design.