Mechanical Properties Of Half-through Suspension Footbridge And Comparative Analysis With Through Suspension Footbridge

In order to optimize the force of cable-structured bridges and adapt to the surrounding environment,some unconventional suspension footbridges are applied in engineering practice,but the related theoretical research is not yet perfect.Compared with the conventional through suspension footbridge,the half-through suspension footbridge has the advantages of reducing the height of the tower,reducing visual obstacles and improving the overall stiffness of the structure on the premise that the clearance under the bridge meets the requirements.This thesis takes a certain halfthrough suspension footbridge as the main research subject,takes a conventional through suspension footbridge under the same design conditions as the comparison object,and uses finite element software to conduct numerical simulation to compare and analyze the static and dynamic characteristics and stability of the two bridge types,and parametric analysis of the above three characteristics of the half-through suspension footbridge was carried out.The main research work and results are as follows:(1)The comparison analysis of the reasonable finished bridge state and static characteristics of the two bridge types were carried out,the comparison results show that the line of the two bridge types is similar,except for the position where the main cable changes,the internal force of each member are relatively close;impact of different load on the two types is the same;two types of bridge along the span direction of the internal force and displacement distribution differences,the displacement of lower cable of half-through suspension footbridge is smaller,indicating that the overall stiffness is relatively larger;(2)The comparison analysis of the self-vibration characteristics and comfort of the two bridge types were carried out,the bending-torsion coupling coefficients was defined to analyze the modal coupling characteristics of the two bridge types.The comparison results show that the torsional fundamental frequency of the half-through suspension footbridge is larger,and the vertical and transverse bending frequencies are similar to that of the through suspension footbridge;the overall vibration modes of the two bridge types with similar self-vibration frequencies are the same,and there are differences in the modes of the main cable vibration alone;Both bridge types have modal coupling of transverse bending and torsion,but the coupling degree of halfthrough suspension footbridge is larger;the comfort level of half-through suspension footbridge is relatively good;(3)The comparative analysis of the first and second stability problems of the two bridge types was carried out.The comparison results showed that the overall stability of the two bridge types meet the specification requirements,but the stability of the half-through suspension footbridge is worse than that of the through suspension footbridge,and the instability modes of the two bridge types are different;the stability of the half-through suspension footbridge can be improved by setting windresistant cable,reducing the height of the struts and increasing the stiffness of the main beam;(4)The effects of different heights of strut,rise-span ratio and inclination angle of wind-resistant cable on the static and dynamic characteristics and stability of halfthrough suspension bridge were determined.