Study On Corrosion Grading Standard And Evaluation Technology Of Main Cable Of Suspension Bridge

As the most important structural component of suspension bridge,the main cable has been exposed to natural environment for a long time,which inevitably contacts with corrosive medium in the environment,resulting in the corrosion of the main cable steel wire.At the same time,the main cable can not be replaced like the suspension cable.According to foreign experience,if the maintenance measures are not in place,after decades of operation,the internal steel wire of the main cable may be seriously corroded.Safety of sound suspension bridge structure.It has been 27 years since the first modern suspension bridge Shantou Bay Bridge was built and opened to traffic in 1992.The corrosion of main cables of suspension bridges will become the next research focus of bridge maintenance and evaluation.This paper firstly studies the corrosion test of the main cable wire by domestic and foreign scholars,and expounds the main cable structure of the suspension bridge.The related literatures were introduced to introduce the main diseases of the suspension bridges,and the two major causes of corrosion of the main cable wires were summarized,namely the temperature,humidity,corrosion of corrosive media under environmental factors,and the stress state and material sensitivity under their own characteristics.For the corrosion of steel wire,a suitable main cable protection system is proposed.Subsequently,the failure time of the main cable anticorrosion system similar to that used in the project was counted,and the failure time of the main cable anticorrosion system of the project was proposed.At the same time,the time required for the corrosion of the main cable galvanized layer was calculated.The smaller value is used as the time for the main cable steel substrate to start corrosion;the corrosion current density of the main cable wire is calculated according to the temperature of the environment in which the main cable is placed,the relative humidity,the stress value under the dead load of the main cable,etc.;Based on the analysis,the section loss rate and the loss of elastic modulus of the steel wire under uniform corrosion are analyzed,and the main cable corrosion grading standard is proposed based on this.Then the Midas/civil finite element model was established for the Guojiatuo Yangtze River Bridge,and the stress values and internal force values of the main cable,sling,upper and lower chord,oblique web and main tower were calculated under the combined conditions of constant load and live load.And compare with the corresponding specification design values to see if the structure meets the requirements of bearing capacity.The natural vibration frequency and vibration mode of the suspension bridge under dynamic characteristics are calculated and correlated.The effects of main cable corrosion on the mechanical properties of the key parts of the whole bridge under different corrosion years are studied.The suspension bridge structures under different corrosion years are used.The law of natural frequency variation under modality is studied.Finally,the strength evaluation method of the main cable of suspension bridge is studied.Combined with the relying project,the number of steel wires under different corrosion conditions,the tensile strength and the strength of the corroded steel wires in the effective recovery section are calculated.Finally,the strength of the main cable is evaluated by the corresponding strength model,which can provide a reference for the state evaluation of the main cable of suspension bridge.