Study On Corrosion Resistance And Mechanical Properties Of Uncoated Weathering Steel

Weathering steel has been widely used in the field of bridge because of its good atmospheric corrosion resistance,low life cycle cost and good mechanical properties.In recent years,weathering steel has been gradually used in bridges in China.However,the research on the corrosion resistance of weathering steel,the connection characteristics of high-strength bolt connections,the design method of corrosion allowance and other aspects in China lags behind,which limits the promotion of weathering steel in bridges.In this paper,the bridge weathering steel Q345 q DNH is taken as the research object.Through experimental research and finite element numerical simulation,the corrosion mechanism of weathering bridge steel,the anti-sliding characteristics of high-strength bolt connections and the stress characteristics after corrosion of weathering steel bridges are studied.The main work and conclusions are as follows:(1)The corrosion characteristics of bridge weathering steel Q345 q DNH were analyzed by comparing the weight loss,macro-morphology,cross section of rust layer,XRD and electrochemical characteristics of weathering bridge steel q345 q DNH and low alloy steel Q345 q D.The results show that,compared with ordinary low alloy steel,the rust layer of weathering steel is divided into two layers under the action of atmospheric corrosion.The outer rust layer is relatively loose,mainly composed of γ-Fe OOH,while the inner rust layer is uniform and dense,mainly composed of α-Fe OOH.During the evolution of the rust layer,the alloy elements added in the weathering steel effectively promoted the process of transformation from γ-Fe OOH to α-Fe OOH in the rust layer,which forms a more stable and dense inner rust layer,effectively isolates the infiltration of corrosion medium,and improves the electrochemical corrosion resistance of the rust layer.Therefore,weathering steel has better corrosion resistance in the atmospheric corrosion environment.(2)The experiment of anti-sliding coefficient of high strength bolt connection has been carried out in laboratory and numerical simulation has been carried out in ABAQUS.Shot peening combined with wire brushing was used to treat the friction surface.The test results show that after 9 months of outdoor exposure,the anti-sliding coefficient of high-strength bolt connection can be ensured to be no less than 0.5 by shot peening and wire brushing.The anti-sliding coefficient decreases slightly in the early stage,but increases with the corrosion of the connection in the later stage.(3)In this paper,the design method of corrosion allowance in different countries is studied.Based on the research background of a two span duplex steel-concrete composite girder bridge,the change of mechanical properties of the bridge under uniform corrosion is studied.The results show that the deflection of the bridge,the Mises stress of the main girder and the concrete stress in the negative bending moment area change little under the uniform corrosion of the weathering steel bridge in the atmospheric environment,while the shear stress in the web with small thickness changes greatly.The final corrosion allowance should base on the changing degree of stress after corrosion.