| The Gobi and desert are widely distributed in the northwest of China,and sandstorms of different levels occur frequently.The wind and sand will cause erosion and wear to the coating material on the surface of steel structures such as bridges until the coating fails,and the steel substrate is exposed and corroded,which further leads to a decrease in structural safety and service life and other serious problems,causing major hidden dangers to traffic safety and greatly increasing maintenance costs.Coating erosion wear research is mainly focused on the newly prepared steel structure coating specimens for erosion characteristics,mechanism analysis,etc.,but for the engineering of existing steel-hybrid composite beam structure surface coating by sand erosion wear research results are less,lack of knowledge.In addition,little research has been reported on the wind and sand erosion life of structural coating,which is the key to solve the design process and later maintenance of steel-hybrid composite beam surface coating in the northwest wind and sand region.In this paper,we analyze the wind-sand erosion characteristics and wear mechanism of steel composite coating,the relationship between particle distribution,turbulent kinetic energy and coating erosion rate around steel-hybrid composite beam surface coating in wind-sand environment,and predict the erosion wear rate and the most serious location of the composite beam surface coating.The prediction equation of wind and sand erosion life of the coating is also proposed.The main findings of the study are as follows:(1)The specimens of composite coating on steel matrix were designed and prepared.The steel substrate composite coating specimens were designed and prepared,and the wind and sand erosion characteristics of the composite coating were studied by building a sand jet test system.The results showed that under the same erosion mechanics,the abrasion resistance of polyurethane topcoat and epoxy cloud iron intermediate paint were close to each other and had better resistance to sand erosion,while the epoxy zinc-rich primer was relatively poor.When the erosion angle α=60°,the composite coating is subjected to the most serious erosion damage,and the erosion wear of the coating is the largest,and its erosion wear characteristics are between typical plastic materials and brittle materials.The erosion wear of the composite coating increases with the increase of sand flow.The greater the erosion speed,the more serious the erosion damage of the coating,and the relationship between the two is approximately exponential.(2)A model for calculating the erosion damage of composite coating on steel substrate is proposed,and the reliability of the model is verified by comparing and analyzing with the test data.At the same time,the computational fluid dynamics(CFD)method was applied to re-validate the coating erosion damage calculation model,and the results showed that the CFD simulation software can be used to analyze the erosion rate distribution characteristics of the composite coating on the surface of steel-hybrid composite beam under wind and sand erosion more accurately.(3)Based on the CFD simulation software Fluent,the discrete phase model(DPM)and the composite coating erosion damage calculation model were used to analyze the erosion rate distribution characteristics of the coating on the surface of the steel-hybrid composite beam.Therefore,the design and maintenance of the bridge coating should consider the characteristics of the coating erosion by wind and sand in this area.(4)The prediction formula of the wind and sand erosion life of the composite coating on the surface of steel-hybrid composite girders was proposed,and the wind and sand erosion life of the composite coating on the surface of steel-hybrid composite girders was predicted and analyzed in the actual sandy weather environment in the Hexi Corridor of Gansu Province.The first location of coating failure on the entire waveform steel web surface will be located at the bottom side of the web near the bottom plate.It is recommended that the steel-hybrid composite beam in this area should be designed with a polyurethane topcoat thickness of not less than 80μm and an epoxy cloudy iron intermediate paint thickness of not less than 120μm to meet the requirements of durability as specified in the code. |
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