| The composite box girder with corrugated web and bottom plate is a new type of steel-concrete composite structure developed in recent years.This type of composite box girder is famous for its novel structure form,light dead weight,long span,strong shear and fatigue resistance.Replacing the thick concrete slab of traditional corrugated composite box girder with good steel performance,giving full play to the material performance advantages of the new steel-concrete composite bridge,which is more convenient for site construction,improves construction efficiency,and saves time and economic cost.However,with the continuous popularization and application of composite box girder with corrugated web and steel bottom plate,a series of problems have appeared,among which corrosion and fatigue are the most intractable problems.The vast territory of our country,the eastern coast has a long coastline,rivers;The northwest has a large area of saline soil,salt lake and groundwater with high salt content,which all contain high concentration of chloride ions.For steel-concrete composite Bridges serving in this environment for a long time,under the repeated action of chlorine salt erosion and vehicle load at the same time,the material performance is gradually degraded,the bearing capacity is reduced,the fatigue performance and service life are reduced and other problems are not optimistic,which leads to the inevitable corrosion and fatigue failure problems of steel-concrete Bridges during the service period.Therefore,in this paper,based on the scientific research project of Gansu Provincial Department of Transportation "Research on the Whole Life Design and Application Technology of Highway Concrete Bridge in Gansu Province",taking a 30 m span steel composite box girder with corrugated web bottom plate in Gansu Province as the structural design prototype,the influence of chlorine salt corrosion on the fatigue performance of steel composite box girder with corrugated web bottom plate and model test study.At the same time,it can also provide certain reference value for the future development and application of this new type of composite bridge.The main research content and research achievements of this paper are as follows:(1)The development history,material properties,structural characteristics,chlorine salt corrosion mechanism and the research status of steel-concrete composite structure under corrosion conditions at home and abroad are expounded,and the influence of chlorine salt corrosion on the fatigue performance of steel composite box girder with corrugated web bottom plate is deeply analyzed.(2)Research on the theoretical design method of anti-fatigue of composite box girder with corrugated web and steel bottom Plate: By studying the principles and methods of anti-fatigue design of composite structure,and comparing the American AASHTO,British BS5400,European Eurocode,Japanese design codes and domestic anti-fatigue design codes,this paper explores the anti-fatigue theoretical design methods of new composite box girder,and summarizes the unified expression of anti-fatigue design.The life prediction calculation and S-N curve of this kind of composite box girder are carried out according to the domestic and foreign norms and test values.(3)Design test model box girder and fatigue load calculation: The process flow and theoretical design basis of making test model box girder are described in detail,including the formula derivation of the similarity theory of test model girder,the principle of scale,the basis of scheme design,the structural information of control section,the basic assumption of composite structure and the calculation of fatigue load and other key steps.(4)Numerical simulation analysis of composite box girder with corrugated web bottom plate under chloride corrosion: fatigue performance tests of test beams were conducted for100,000 times,250,000 times,500,000 times,750,000 times,1 million times,1.25 million times,1.5 million times,1.75 million times and 2 million times respectively.The deflection,stress and other test results of the test beam were analyzed and compared with the uncorroded test beam data,and the change law of the integrity and stiffness of the test beam was further analyzed.(5)Numerical simulation analysis of composite box girder with corrugated web bottom plate under chloride corrosion: finite element solid model is established by ANSYS finite element software,and numerical calculation of test beam is carried out.The variation law of stress and deflection at the critical control point of the test beam under load is analyzed,and the measured results of the test beam are compared to verify the accuracy of the fatigue test. |
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