Analyze The Structure Performance Of Steel Bridge Deck And Pavement Based On The Fatigue Load Model ?

In recent years,with the rapid development of large-span bridges,the utilization rate of steel box girders has become higher and higher.Therefore,the fatigue damage of steel bridge decks has received increasing attention from scholars at home and abroad.The fatigue design of China's railway steel bridges is relatively complete,however,before 2015,the fatigue design of highway steel bridges is based on the relevant foreign and railway fatigue load regulations.Due to the relatively large differences in the actual traffic conditions at home and abroad,and also aims at the actual traffic patterns in China,the Ministry of Transport of the People's Republic of China have been issued a Design Specification for Highway Steel Bridges(JTG D64-2015),It based on the British BS5400 specification,the Eurocode specification,and the relevant fatigue loads in the US AASHTO specification.Among them,there are three fatigue load models for steel bridges,and fatigue load model III is mainly designed for fatigue checking of orthotropic steel bridge decks.Based on the actual completed bridge project,this paper through ? fatigue load model and three kinds of foreign standard of fatigue load of steel bridge deck fatigue calculation and assessment,and analyzed the applicability of the model ? fatigue load in our specification.This thesis mainly carries on the following work:Firstly,this paper summarizes the typical fatigue failure phenomena of steel bridge decks and bridge deck pavements,and reviews the research and development history of domestic and international fatigue loads.This paper introduces the development of fatigue damage mechanism of steel bridge,mainly expounds the research method of linear cumulative damage theory on fatigue,determining the Theory of Linear Cumulative Damage as the Theoretical Basis of the Paper.Secondly,based on the in-service bridge project,Midas FEA finite element software was used to establish two finite element models of orthotropic steel bridge decks in the pavement condition.The results of the linear static calculation confirm that the steel bridge deck is at the most unfavorable loading position on the transverse bridge,and then the steel bridge deck is fatigue checked on the fatigue details of the fast and slow lanes according to the two paving conditions.The fatigue load models in each specification are loaded separately to determine the stress frequency spectrum of the four fatigue details.The actual traffic investigation and forecast data are used to determine the traffic volume during the design reference period,and the first principal stress amplitude calculation result is linear.The fatigue damage theory was converted to 2 million equivalent stress amplitudes,and the fatigue details of the fatigue details studied were determined by the verification method in the specification.The calculation results show that the fatigue details 4 should be used as the control details during fatigue checking.At the same time,under the fatigue load model III,the fatigue details 1,2 and 4 have been fatigued under the condition of the intact pavement layer,under the condition of the damaged pavement layer.Fatigue failures occurred in all four fatigue details,and all requirements were satisfied under the condition of damaged pavement layers using British BS5400 specifications.Finally,the structural properties of the steel deck pavement were analyzed.The fatigue load model III of the design code for highway steel bridges is used to determine the most unfavorable loading position of the vertical bridge to the single-lane loading to determine the stress and vertical deformation of the steel bridge deck pavement.The horizontal bridge was loaded into the two lanes to determine the position of the transverse bridge to the most unfavorable loading position,and then the maximum value of the longitudinal stress of the bridge under the condition of pavement layer damage was 0.914>0.229 MPa,then the crack resistance performance did not meet the reference control conditions;The maximum interface shear stress is 0.349<0.893 MPa,which satisfies the reference control conditions;the maximum vertical displacement is 3.229<4.375 mm,which is a normal vertical displacement range.Based on the above conclusions,the differences between the newly issued code and the calculated values of the verified orthotropic steel decks and pavements under fatigue loading are summarized,and the correlation coefficient values of the fatigue load model III in the fatigue checking process are further improved.Good understanding and recommendations for reinforcement of bridges that have been completed and are in service.