Research On Residual Life Of Crack Propagation Of Orthotropic Plate Under Combined Action Of Corrosion And Fatigue

In recent years,the orthotropic steel bridge deck has become a highly efficient bridge deck due to its special structure.At the same time,due to the complexity of the structure and the large number of welds at the joints between the longitudinal ribs,the panels and the transverse partitions,the cracking phenomenon is particularly prominent.However,in actual engineering,the coupling effect of cyclic load and corrosive medium is usually more significant than the corrosion or fatigue acting on the bridge alone.This article is based on the combination of global-local finite element analysis and fracture mechanics.The tip stress intensity factor is used as an indicator,the corrosion factor is introduced,and the engineering correction model is used to calculate the remaining life of the corrosion fatigue crack at the arc-shaped notch of the transverse diaphragm of the orthotropic plate.The main research contents and conclusions are as follows:(1)In order to take into account the overall stress conditions of the steel bridge and the calculation accuracy requirements of the fatigue crack initiation detailed structure,the finite element software ABAQUS was used to establish a finite element model including beam elements,plate and shell elements and solid elements.A total of22 finite element models with crack size ranging from 1 mm to 35 mm were established.Considering the lateral offset probability of the wheel,the lateral load distribution is divided into four conditions,and the condition with the largest stress intensity factor at the crack location is selected as the most unfavorable load condition.According to the relevant stress diagram of the finite element model,the causes of cracks in three typical positions are analyzed.Although the number of cracks in the arc region of the diaphragm is less than that in the upper and lower edge of the weld,the crack size is longer.(2)At the same time,the influence of diaphragm thickness,spacing and roof thickness on SIF is explored.Compared with diaphragm spacing and roof thickness,the change of diaphragm thickness has a greater impact on SIF.(3)According to the theory of fracture mechanics and the residual life assessment theory of corrosion fatigue crack propagation based on pairs formula,the residual life curves of arc notch corrosion fatigue crack of orthotropic plate diaphragms with four different initial lengths are obtained.It is found that the short crack growth stage accounts for the main part of the whole life.When the crack reaches a certain length,the crack will expand rapidly until it reaches the critical length.Compared with pure mechanical fatigue,the residual life of corrosion fatigue crack growth is 70.40% lower.The influencing factors of corrosion factor are discussed by theoretical model.The corrosion factor in hot and humid environment is obviously higher than that in other environments.It can be seen that humidity and temperature have great influence on the corrosion rate.