Study On Mechanical Properties Of Single Cable Plane Curved Beam Suspension Bridge

The single cable plane curved beam suspension bridge with its beautiful and smooth type of line,adequate space feeling,strong sense of transparency and other advantages has successfully been another new solution of the pedestrian bridges.The structure of the single cable plane curved beam suspension bridge has a unique structure which is combined with the structural advantages of the suspension bridge and the curved girder bridge,so it is very difficult to conduct a simple theoretical analysis.What's more,it is very important to study the static and dynamic performance of the bridge with the theoretical analysis and numerical simulation.The paper first summarizes the development status of the curved beam suspension bridge which has been built domestic and overseas and with the advantage of structural characteristics of different types.Based on this,in order to overcome the key problem of the unbalanced torque of the main beam of single cable plane curved beam suspension bridge,three methods are summarized,namely,the method of setting the rigid arm,adjusting the center of gravity method and the joint method,and the mechanical foundation of the design of unilateral suspension bridge laid.On the other hand,the paper analyzes the uniqueness and complexity of the shape finding of space cable for the single cable plane curved beam suspension bridge by combining the characteristics of this kind of bridge and explaining the difference between the shape analysis of the traditional suspension bridge and the single cable plane curved beam suspension bridge.Aiming at solving the problem that the existing spatial cable calculation theory is not suitable for finding the shape of the main cable of the single cable plane curved beam suspension bridge,the paper proposes an iterative calculation method which combined geometric nonlinear finite element and numerical analysis,with the help of the software Midas/Civil.This method is divided into three parts:(1)The single cable plane curved beam bridge is simplified as the equivalent straight beam suspension bridge based on the principle of gravity equivalent,and the shape of the main cable in this state is calculated,then the "straight line of cable plane in vertical" model is obtained;(2)The " straight line of cable plane in vertical" model is rotated around the main cable to make the anchoring point coincide with the anchor point of the main cable of the original bridge,then establishing the "three fold line of single cable plane in vertical" model;(3)Calculate the suspender's angle,internal force and tension force of the main cable iteratively,making the main cable gradually inward tilt,and ultimately becoming the shape of finished bridge state.The calculation results show that the main cable shape which determined by this method is smooth without mutation,and the distribution of the internal force of the bridge is reasonable under the living loads.They are all in accordance with to the requirements of the specification.On the basis of this model,the main cable shape of the empty cable state is obtained by the method named "the backward-calculation".Although the method used in the paper can effectively solve the problem of the main cable shape finding of the single cable plane curved beam suspension bridge,but there are many problems in the process of finding a finished bridge state,establishing a finite element model too many times,data processing capacity and the calculation process cumbersome.In order to solve this problem,the paper compute the program,based on finite element theory to calculate the main cable shape finding of the single cable plane curved beam suspension bridge.The calculation shows that the result is accurate and the calculation efficiency is high.Based on an example of the single cable plane curved beam suspension bridge,the paper researches the displacement and internal force of the bridge under different load conditions and sums up the characteristics of the single cable plane curved beam suspension bridge.The static characteristic analysis shows that the main beam deflection and the main components of the internal force meeting the requirements under its most unfavorable loads condition.The dynamic characteristic analysis shows that the fundamental frequency of the bridge is lower and the top ten step mode is dominated by vertical vibration.The calculation of the human vibration shows that under the crowd in a dense state,the bridge calculated does not meet the requirements of pedestrian comfort index,needing to install TMD or other shock absorbers.