Research On Inverted Fink Truss Footbridge Systems And Preliminary Design

Inverted Fink Truss can be regarded as a variant form of tensegrity structure in bridge engineering,which is a new flexible cable-supported bridge structure composed of a series of tension cables and compression members(also called mast).It has broad prospects in the application of pedestrian bridges in medium span bridges with the outstanding advantages of high efficiency and elegant appearance.Little attention has been paid to the structure,and its system composition,mechanical properties and static and dynamic performance are rarely studied at present.The structural systems of Inverted Fink Truss footbridge were analyzed and studied in this paper.Firstly,the origin,evolution and application status of such structure were systematically introduced,and the advantages and prospects of such structures applied to footbridges were illustrated.The composition,forcing path and stress characteristics of the Inverted Fink truss were analyzed deeply.The main girder is the main load-bearing member,the cable and the mast are the transfer members,and the load of the bridge deck is passed to the pylon by the cable and the mast.Under the action of live load,Redistribution of cable internal force happened,leading to the decreasing of cable force in the inner span and the increasing of anchoring cable force.So,a simple and practical method for finding the initial cable force based on the specified displacement and internal force is proposed,ensuring that the cable is unfailing without complete unloading during the operation.Secondly,the parametric analysis was carried out using of RM Bridge developed by TDV company.The influence of the main design parameters,such as the initial cable force,the cable area and the height of the abdominal rod,on the structural stiffness,the cable stress amplitude,the stability and the self vibration characteristics are discussed,and some useful conclusions were given in this paper.The increase of the cable area and the height of the mast can significantly increase the structural stiffness,but higher mast leads to the decrease of the structural stability.The structural design can not look down upon other performance to meet only one certain performance index.At last,a specific Inverted Fink truss footbridge with a main span of 120 m were designed and optimized,and the calculation results are analyzed according to JTG code.The results show that Stability of such structure is the crirical factor for footbridge design with a large span.Effect of the cable area and the mast height on the mechanical behavior of the structure should be systematically balanced in the design.