Stress Effect And Fatigue Life Prediction Of Detail Structure Of Orthotropic Plate Of Continuous Steel Box Girder Bridge

Orthotropic steel bridge deck is widely used in bridge construction at home and abroad because of its advantages of high material utilization,large carrying capacity,wide application range and convenient installation.However,its structural complexity,a large number of cross welds lead to the stress of fatigue.The stress on the connection between the deck,the longitudinal ribs and the diaphragms of the orthotropic steel deck is very complex,so it is easy to produce fatigue cracks.The form of diaphragm and the section form of longitudinal rib have a great influence on the stress distribution at the connection point of bridge roof,longitudinal rib and diaphragm.In this paper,a two span continuous steel box girder bridge is taken as the engineering background.The fatigue stress distribution of the orthotropic plate is studied and the fatigue life of the orthotropic plate is studied.The specific research contents of this paper are as follows:(1)Software ANSYS is used to establish orthotropic steel deck finite element models with different diaphragms and different longitudinal rib sections.Under the single wheel load,the influence of the form of the diaphragm and the section of the longitudinal rib on the stress of the bridge panel and the longitudinal rib,the bridge deck and the diaphragm,the diaphragm and the longitudinal rib of the orthotropic steel bridge deck is analyzed.So as to determine the best form of diaphragm and form of longitudinal rib section.(2)First of all,the whole bridge unit model is established by Midas-civil,and the whole bridge is subjected to the static load analysis to get the most disadvantageous steel box girder segment in the full bridge model.Then the submodel technique is used to generate the boundary condition of the ANSYS submodel based on the whole model.Through ANSYS,a 33 m long local shell element model is established.By comparing longitudinal and transverse loading conditions,the most unfavorable location of the concerns is determined.Based on the fatigue load model III in the code for design of highway steel structural design(JTG D64-2015),the load calculation for the finite element model of the bridge segment is carried out.The stress history of the load is converted into stress spectrum by the rain flow counting method,and the fatigue life of 5 fatigue concerns in the segment model is predicted according to the fatigue life prediction method of the European standard,which shows that the fatigue design life of the bridge satisfies the requirements and has a certain safety reserve.The maximum fatigue amplitude comparison of the 5 points of concern selected in the segment model under different specifications shows that the stress amplitude of the 5 concerns of the Chinese fatigue car is the largest,the second of the British fatigue car and the smallest fatigue car in the United States.