| With the continuous development of China’s economy and transportation,steel consumption policy has changed from early overall planning to the current guidance and encouragement,resulting in the construction of steel bridges showing an increasing trend year by year.Steel bridge in the service process is faced with a very severe service environment.After the corrosion protection layer is failure,steel bridge is easy to appear corrosion phenomenon.According to the actual service situation of steel bridges at home and abroad,many steel bridges built in the last century are corroded in different degrees,which causes great harm to the normal service of steel bridges.After being corroded,the performance of steel bridge deteriorates to a certain extent,which leads to the failure of steel bridge to reach its designed service life.Therefore,in view of the corrosion phenomenon of steel bridges,the numerical simulation method was used to reduce the corrosion morphology,and the tensile properties and residual fatigue life degradation law of steel bridge components after corrosion are studied.On this basis,the residual fatigue life of the existing steel bridge longitudinal beams after corrosion was evaluated.The main research work includes:(1)Based on the research of domestic and foreign scholars on corrosion morphology,the pitting distribution model was established according to the existing statistical data of pitting depth.The random distribution of corrosion depth,size and location of different pits was realized.The random pitting entity model was established through Python scripting language programming and ABAQUS secondary development,which laid the foundation and provided support for the performance deterioration analysis of components after corrosion.(2)By means of numerical simulation,the influence trend of erosion pits with different shapes on stress concentration was studied.It was found that the semi-ellipsoidal erosion pits had the most obvious influence on stress concentration.Therefore,the semi-ellipsoidal erosion pits were selected as the research object of subsequent erosion pits.At the same time,based on the pitting erosion distribution model,the deterioration trend of uniaxial tensile mechanical properties of specimens under different corrosion degrees was analyzed,and it was found that the ultimate tensile strength of specimens was affected by the surface corrosion rate and the average corrosion depth.(3)A pitch-crack model was established,and the influence of pitting on the stress intensity factor of crack tip was studied by numerical simulation.The surface roughness of specimens with different corrosion degree was extracted and the variation law of surface roughness and fatigue resistance degradation coefficient was calculated and discussed.FRANC3D software was used to calculate the residual fatigue life of specimens with different unevenness,and the influence of uniform corrosion and pitting corrosion on the residual fatigue life of specimens after corrosion was studied and analyzed.(4)According to the actual corrosion of the existing aged steel bridge,a beam-solid hybrid model of the dangerous section with serious corrosion was established to analyze the stress of the severely corroded area,and then the residual fatigue life of the dangerous section after corrosion was analyzed.At the same time,the residual fatigue life of components under different stress amplitude and corrosion degree was calculated,and the deterioration law of the residual life of full-cycle fatigue was obtained.The relevant research results can provide reference for the optimization design and durability evaluation of the actual bridge steel structure. |
