| The corrosion problem of the web and bottom plate of the steel-concrete composite bridge is a major problem that plagues the life of the bridge in the industry,and the anticorrosion coating is an important means to ensure the durability of the bridge.When the steelconcrete composite beam is subjected to alternating stress,the anti-corrosion coating material closely combines with the bonding performance between the steel-concrete composite beam,and the repeated synergistic deformation effect occurs with the force of the steel-concrete composite beam,but the anti-corrosion coating does not It has the good physical ductility and plasticity of the steel base material,so when the coating material is subjected to fatigue load cycles,according to the Miner linear accumulation theory,local permanent damage will occur at the coating of the steel-concrete composite beam,which will lead to the coating.The layer is cracked or peeled.In addition,due to the large temperature difference environment in the northwest,due to the large difference in thermal expansion coefficients between steel and coating materials,different strains will be generated under alternating temperature and cold,and serious displacement will occur at the interface between the substrate and the coating,causing interface stress damage..In this paper,according to the structural stress characteristics of steel-concrete composite beams,finite element mechanical behavior analysis is carried out,and the anti-corrosion coating on steel-composite beams is taken as an example,and the fatigue cycle effects are studied by means of finite element refined simulation.Application adhesion and damage mechanism of organic coating,and evaluate the application life of the coating;use the method of test simulation to study the coating of the steel-concrete composite beam coating layer under the combined effect of static load and temperature change load within 20 years of life The deterioration process of the layer,and further analysis of its deterioration mechanism,and then the life prediction of the coating layer of the steel-concrete composite beam.The main research results of this paper are as follows:(1)Based on a steel box-concrete composite bridge with a span of 50 m in a scientific research project.Midas was used to establish a finite element model,and the internal force analysis under the ultimate bearing capacity and the normal service limit state was carried out,and the bending bearing capacity and webs were resisted.The shear resistance,deflection and crack resistance of the steel were checked and analyzed,and the results obtained meet the design and engineering requirements.(2)Based on the principle of stress equivalence,ANSYS software was used to establish a local nonlinear analysis model of the steel box-concrete composite bridge at the highest stress position,and the fatigue stress and coating of the coating and steel structure substrate under vehicle fatigue load were analyzed.Pattern of crack development.The study found that before the coating reaches its ultimate strength,as the number of fatigue cycles continues to increase,the thicker the coating within a certain range,the smaller the interface tensile stress,the greater the interface shear stress,the better the interface fusion,and the better the fatigue resistance.The stronger the sex.The coating at the most stressed part in the middle of the span will suffer from tensile cracking due to excessive interfacial tensile stress.For the coating of this project,considering the fatigue effect of the most stressed part of the steel structure,the fatigue life of the 150μm coating topcoat is about 17.8 years,and the life of the300μm coating topcoat can reach 22.8 years,so when designing The influence of fatigue stress on the failure efficiency of the coating should be fully considered.(3)Through the experimental research on the coating layer of steel-concrete composite beam under the coupling effect of static stress and temperature-dependent load,the effect of the coating topcoat,intermediate paint and primer under the action of static stress and temperature-dependent load is analyzed.Changes in focus and damage rate.The test results show that the adhesion of topcoat,intermediate paint and primer coatings under different working conditions shows a decreasing trend with the increase of the number of temperature cycles;static stress and temperature-varying load degrade the topcoat coating of steelconcrete composite beams The impact is greater.The adhesion of the topcoat under no static load is reduced by nearly 30% only under temperature cycles,and the adhesion of the intermediate paint under 0.7 times the yield load is reduced by about half compared with that under no static load.Fitting the adhesion curve of each paint layer of the test piece,according to the fitting result and combining the low cycle fatigue equation caused by thermal stress,it can be deduced that the coating on the steel-concrete composite beam is subjected to thermal fatigue and static load coupling.Life prediction formula. |
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