Study On Key Technology Of Self-walking Inspection And Repair Vehicle Of Suspension Bridge Main Cable

Main cable of suspension bridge is the most important load-bearing components,it carries the gravity load of bridge girder and vehicles.As main cable can not be replaced in the bridge service period,its health is closely related to bridge safety.At present,inspection and repair of main cable of suspension bridge is mainly carried out by workers climbing.This inspection method exists inspection blind area,and can not overhaul the main cable.In addition,workers high-altitude operations are difficult,low efficiency,poor accuracy,and existing security problems.To solve the above problems,this paper takes Qingshui River suspension bridge as research object and study inspection and repair equipment of main cable.Overall design scheme of inspection and repair vehicle of main cable is brought forward according to the structure of main cable of suspension bridge and the requirement of inspection and repair.Secondly,walking mechanics calculation of vehicle,design of key mechanism and finite element analysis ensure the function and performance of inspection vehicle meet the application requirements.Then,basic characteristics of wind and simulation method are introduced.Based on Davenport wind speed spectrum and harmonic superposition method,fluctuating wind speed time series is simulated.The wind resistant stability model is established and dynamic characteristics are analyzed by using ANSYS.Dynamic response of inspection vehicle under fluctuating wind load is studied.Finally,the finite element model of suspension bridge is established by Midas,and dynamic response of main cable under fluctuating wind is studied.Based on the comfort evaluation method in the field of vehicle engineering,comfort of inspection vehicle is evaluated.Research conclusions include followings:1.Intelligent control technology is applied to inspection vehicle,which realizes the function of automatic through cable clip and sling.Mechanical calculation and friction coefficient test of inspection vehicle are completed to ensure the climbing angle of inspection vehicle is not less than 26°.Calculation of overturning resistance show that the anti overturning safety factor is 3.0 under force 6 wind and 500kg,so that rollover phenomenon will not occur.The contact stress between driving wheel,clamping wheel and main cable is within the allowable stress range of wrapped surface of main cable.2.Design scheme of main truss is brought forward.and full overhaul of main cable is achieved.Static finite element analysis of main truss under multi working conditions is carried out,the results show that strength and stiffness of main truss meet requirements.The driving mechanism and pinch roller mechanism of inspection vehicle are designed,and the functions of self-working and through cable clip and sling.are realized.3.Research of wind resistance performance of inspection vehicle shows:the number of pinch wheel plays a decisive role in the stability of the vehicle,while the open position has little effect on the wind resistance performance.The transverse stiffness of vehicle structure is poor,and it is sensitive to wind load.The wind load of inspection vehicle is regarded as static load.The calculation result is smaller than that of fluctuating wind time history analysis method.The composite stress under fluctuating wind load is 11.5%higher than that under static load,and the maximum transverse displacement is increased by 70.3%.4.Comfort evaluation conclusion of inspection car at different height of main cable shows:the comfort evaluation conclusion based on total weighted acceleration method is "no discomfort" within the full length of main cable;while K coefficient method is adopted,the comfort of inspection vehicle between height of 5 and 35m of main cable is evaluated as"short-term vibration can be endured",and the comfort between height of 35 and 113m is evaluated as "can tolerate any long time vibration".The comfort of inspection vehicle increases with the increase of height of main cable.Inspection vehicle has good comfort when walking on the main cable.