Study On Ultimate Bearing Capacity Degradation And Preventive Maintenance Of Weathering Steel-Concrete Composite Suspension Bridge

With the rapid development of national economy and the progress of science and technology,transportation plays a vital role in the development of a country.With the continuous increase of bridge span,its structure becomes more and more complex,among which the long-span Bridges,mainly cable-stayed Bridges and suspension Bridges,play an important role in promoting the development of cities.The failure mode of steel-concrete composite beam suspension bridge in the limit state is not clear,the corrosion degradation law of suspension bridge using new materials such as weathering steel in atmospheric environment is not clear,China has not established a written maintenance specification of weathering steel bridge,and the preventive maintenance system of suspension bridge is not mature.In view of the above problems,this paper takes a weathering steel-concrete composite suspension bridge as the background to study the degradation law of ultimate bearing capacity and preventive maintenance method of suspension bridge in atmospheric environment.The main contents of this paper are:(1)Using the Grillage method,adopting Mises yield criterion,considering geometric nonlinearity and material nonlinearity,based on THE U.L.The finite element calculation program of suspension bridge member system is programmed in a column.Six most unfavorable loading conditions were determined by selecting the most unfavorable loading components,and the elastic-plastic ultimate bearing capacity of suspension Bridges and the failure sequence of each component were analyzed under each condition.Finally,the safety of the suspension Bridges under the six loading conditions was analyzed.The failure mode of the suspension bridge under the limit state is recognized effectively,which provides a basis for the design of the suspension bridge.(2)The uniform corrosion depth was calculated by using the corrosion kinetics curve of weathering steel,and the maximum corrosion pit depth was calculated by using the two-parameter Weibull distribution to obtain the corrosion depth of weathering steel.The degradation of the main cable and the sling is calculated according to the transfer law that the corrosion degree of galvanized steel wire decreases from outer layer to inner layer.Taking the sections and mechanical properties of weather-resistant steel beams,main cables and slings as parameters,the ultimate bearing capacity degradation law of suspension Bridges is studied by changing the sections and mechanical properties parameters.The prediction of the limit state of the suspension bridge under long-term corrosion provides a basis for the preparation of the preventive maintenance plan of the suspension bridge.(3)The suspension bridge is divided into main cable,sling,stiffening beam,support system and auxiliary structure.Firstly,the content of preventive maintenance inspection is developed according to the components,focusing on the inspection of weather-resistant steel beams.Secondly,the calculation method of suspension bridge technical condition evaluation is given.Then preventive maintenance measures are formulated according to the inspection contents,focusing on weather-resistant steel beams;Finally,some suggestions are given on the establishment of preventive maintenance management system,forming a preventive maintenance system of weathering steel-concrete composite girder suspension bridge integrating inspection,evaluation,maintenance and management.