Degradation Of Flexural Bearing Capacity Of Locally Corroded High-Performance Steel Beams In Bending And Shearing Sections

Compared with ordinary steel,High-performance Steel,(HPS)has the advantages of high strength,good toughness and lower thickness effect,and is widely used in bridge structures and high-rise buildings.However,with the passage of time,due to the aging and peeling of anti-corrosion coating,strong rain erosion and other factors,the bridge is more likely to be partially corroded,threatening the structural safety.In this paper,randomly corroded HPS steel beams in bending-shear section are taken as the research object,and the surface morphology of corroded HPS and the bearing capacity of corroded HPS specimens under the influence of pitting corrosion are mainly explored.The research contents are as follows:(1)The surface morphology characteristics of corroded HPS specimens are defined.Twelve Q550E standard tensile specimens and four Q550E H-shaped high-performance steel beams with non-thick flanges were manufactured,and the corroded Q550E specimens were electrochemically accelerated to different degrees by using DC power supply.The data of the surface morphology indexes of the corroded Q550E specimens were collected by FARO 3D scanner,and the cross-sectional area and pit depth data of the corroded specimens were obtained.The distribution types of cross-sectional area and pit depth,and the relationship between average pit depth,standard deviation of pit depth,pit depth-width ratio and quality corrosion rate were obtained by fitting data,and the residual geometric characteristics of partially corroded steel beams were analyzed.(2)The degradation of tensile bearing capacity of HPS pitting structure is studied.Based on the measured pitting corrosion data,the finite element model of random pitting corrosion was established,and the load-displacement curve of Q550E random pitting corrosion steel sheet was simulated.The calculation accuracy of the finite element model was verified by the existing test results.On this basis,the effects of pitting position,depth and size on the ultimate strength and maximum deformation are analyzed,and the relationship between the ultimate load and the maximum cross-section loss rate is discussed.(3)The degradation of flexural capacity of high-performance steel beams under different local corrosion conditions was investigated.The bending bearing capacity test of partially corroded H-shaped high-performance steel beams in bending-shear section was carried out,and the influence law of corrosion degree and corrosion position on the bearing capacity degradation of partially corroded high-performance steel beams in bending-shear section was obtained.Various failure modes that would occur under bending-shear corrosion were summarized.Considering the influence of corrosion factors on mechanical properties and geometric characteristics of materials,the bearing capacity of corroded steel beams was predicted by nonlinear iterative method.(4)The influence of random pitting corrosion on the ultimate bearing capacity and failure mode of HPS steel beams corroded by bending and shearing is analyzed.Based on the thermal analysis theory and eigenvalue analysis,considering the influence of residual stress and initial defects,and considering uniform corrosion,a three-dimensional finite element model of pitted steel beams is constructed by random sampling.After comparing the simulation results with the experimental results,the bearing capacity and failure modes of HPS steel beams under different DOPV and DOP pitting strengths are studied.