Safety Assessment Method For Fatigue Damage Of Orthotropic Deck Based On Crack Eigenvector

Due to the advantages of high strength,light weight and integrity,steel box girder orthotropic bridge deck is widely used in bridge engineering.The residual stress and various welding defects during the welding process are all adverse factors affecting its normal use,and the fatigue cracking of steel box girder caused by these factors has become one of the main reasons hindering its development.In this paper,the characteristic vector data of fatigue crack is constructed based on the inspection results of the fatigue crack in the orthotropic steel bridge deck.Combined with multi-scale finite element model to analyze the damage of various kinds of cracks to local components,the causes of various kinds of cracks were summarized according to the calculation results of coupled fatigue crack finite element model.Based on the fuzzy statistical method,the fuzzy relation between the characteristic vector of fatigue crack and the damage degree of typical members is studied.The research contents of this paper are as follows:(1)According to the inspection results of fatigue cracks in the steel box girder of a suspension bridge,a feature vector data set that containing crack initiation location,development trend,length and other information was constructed.The data association analysis algorithm is used to excavate the hidden relationship between the feature vectors of fatigue cracks and obtain the distribution law of fatigue cracks relative in the whole steel box girder.(2)In order to take into account the overall stress conditions of susp ension bridge and the calculation accuracy requirements of the detailed structure of fatigue crack initiation,a multi-scale finite element model including beam element,plate and shell element and solid element was established by using large finite elemen t software ABAQUS.The crack propagation process is simulated by the extended finite element method,and the damage degree of different types and lengths of cracks to local components is calculated.In order to make the equivalent stress of local components under wheel load more practical,the probability of lateral deviation when the wheel is traveling is considered with reference to relevant specifications.(3)The causes of various fatigue cracks are analyzed according to the results of multi-scale finite element model of coupled fatigue crack feature vector.The fuzzy mathematical theory is introduced and the fuzzy statistical method is used to study the evaluation criteria of the fuzzy relation between the characteristic vector of fatigue crack and the degree of fatigue damage in typical components.Based on the fuzzy linear transformation principle,a comprehensive evaluation method for safety rating of fatigue damage of orthotropic steel bridge deck based on fatigue crack vectors is studied.