Study On Limit Of Vertical Deviation Of Tower In Pedestrian Suspension Bridge

Pedestrian suspension bridge has become the first choice in foot bridges and landscape bridges in mountainous areas because of its definite force transmission route and strong ability to adapt to the environment.With the constant advance of rural vitalization strategy,an increasing number of pedestrian suspension bridges are constructed in mountainous areas.At present,there is no specific standard of design,construction and acceptance for pedestrian suspension bridges in China,and the relevant standards and specifications of highway suspension bridges are mainly referred in practical engineering.However,whether in design load or in structural form,there are many differences between pedestrian suspension bridges and highway suspension bridges,so it is necessary to conduct a research on the relevant standards and specifications of pedestrian suspension bridges in mountainous areas.Since the height of cable tower in pedestrian suspension bridges is relatively low,both cost and construction difficulty will be enhanced if the relevant specifications of highway bridges are adopted.The perpendicularity limit of cable tower in pedestrian suspension bridges is theoretically and numerically studied in this paper,and the specific contents are as follows:Firstly,on the basis of consulting the existing research status on the mechanical properties,cable tower perpendicularity and stability analysis of suspension bridges,the frame model of full bridge and cable tower,and the solid model of cable tower are established by taking the pedestrian glass suspension bridge in Yongxi,Quanzhou as engineering background and developing the command stream of form-finding on main cables based on APDL.Secondly,the stability of cable tower is studied by using the frame model of cable tower.Five perpendicularity deviation operating conditions with different directions are set,and linear and nonlinear stability analysis is performed to research the influence of different conditions on the ultimate bearing capacity of cable tower.The results show that,as for this form of cable tower,the stability in the transverse direction is superior to that in the longitudinal direction,the worst operating condition of perpendicularity deviation is longitudinal deviation,and the worst loading condition is longitudinal wind load with uniform distribution.Finally,the influence of perpendicularity deviation in the cable tower on the dynamic and static mechanical properties of full bridge is analyzed by using the frame model of full bridge.The results reveal that perpendicularity deviation in the cable tower has less influence on the dynamic mechanical property of full bridge,the geometric shape of main cable and the axial force of main cable,and under the redistribution of internal force,the internal force change of stiffening beam and suspender is concentrated near the cable tower;and perpendicularity deviation in the cable tower has less influence on its own axial force,but substantially increases the bending moment at the bottom of tower column.The analysis of the influence of perpendicularity deviation in the cable tower on the ultimate bearing capacity of full bridge indicates that the cable tower will break in advance of other components under the action of both wind load and crowd load,and the ultimate bearing capacity of full bridge will decrease gradually as perpendicularity deviation in the cable tower increases.Based on the above research,taking cracks appearing in the cable tower as control condition,solid model is used to increase perpendicularity deviation gradually to obtain the limit of perpendicularity deviation.The research results of this paper can offer reference for the design and acceptance of similar type of pedestrian suspension bridges in mountainous areas as well as their future specification formulation.