Analysis Of Residual Stress Of Diaphragm-to-Rib Joint In Steel Bridge Decks

In order to quickly repair traffic and bear as much load as possible,orthotropic steel bridge system was conceived.Over the years,light deck orthotropic bridge deck has been widely used in bridge engineering with many advantages,such as strength to weight ratio,convenient transportation and assembly,short construction time and so on.especially in some long-span bridges such as suspension bridges,cable-stayed bridges.This type of structure of orthotropic steel bridge deck has experienced long-term development and improvement since 1950,while in recent decades,the economy of our country is growing day by day,and the traffic strength and vehicle load have been greatly improved.The fatigue problem of modern steel bridges in service life is also becoming more serious under heavy traffic pressure,and the number of fatigue cracks detected by the Japan Steel Structure Commission accounts for 56.3%of the total crack.The fatigue cracking problem seriously affects the durability and service life of the steel bridge.At the same time,because of the complex staggered structure of the orthotropic bridge deck slab,it is difficult to repair the cracks,and the problem of high cost is becoming more and more serious.and recent studies have pointed out that the detailed design of welded joints and the execution of welding are not always carried out in an optimal way.these complex and defective welding processes cause local stress concentration and initial defects,which directly lead to the fatigue cracks that appear in the service life of modern steel bridges are often concentrated in the thermal action area.Hence,from the starting point of heat treatment process,this paper studies the distribution law of welding residual stress at the junction of U rib and transverse diaphragm by means of numerical simulation and test.The main tasks include:(1)Starting with the development trend,the importance of the development and application of orthotropic bridge deck slab is introduced.At the same time,the phenomenon of fatigue caused by wheel load stress of orthotropic deck slab is introduced,which indicates that residual stress is an important factor affecting fatigue.This paper expounds the structure form of orthotropic bridge deck slab and the research status of residual stress in continuous machining process,and summarizes the existing research situation of cutting and welding residual stress respectively.This paper summarizes the current situation and shortcomings of the research on residual stress of orthotropic deck slab at home and abroad,and then puts forward the research contents of this paper.(2)The basic equation of conduction heat in the solution of transient temperature field is introduced.By controlling the differential equation and starting with three boundary conditions,the finite element method is used to solve the temperature field.The application of ABAQUS large-scale finite element software in numerical simulation of welding based on thermoelastic plasticity is introduced,and the coupling nonlinear analysis process of thermal structure in ABAQUS is introduced.(3)A distribution model of the cutting heat source is presented.The cutting process of the transverse partition and the welding process of the transverse partition U rib are simulated by the classical welding heat source model.the characteristics of temperature field distribution during cutting and welding under the action of moving heat source are studied.The characteristics of the residual stress distribution at the cutting free edge of the arc cut and the distribution law of the residual stress at the weld are obtained by finite element calculation.(4)Using the finite element analysis software(ABAQUS code)to establish the truncated 3D finite element model of longitudinal rib orthotropic plate with foot-scale cross-section,the HyperMesh professional finite element mesh division software is used to mesh and optimize the geometric model.Through the accurate finite element calculation,the residual stress distribution form and numerical characteristics of the structure after continuous machining operation are obtained.From the aspects of machining technology of orthotropic bridge deck,the variation of residual stress at arc cut of orthotropic steel bridge deck is analyzed by numerical simulation,which provides reference for reasonable working technology and fatigue design and calculation.(5)With Q345qD as the material,the cut-off model of transverse partition with roof plate-U rib foot ruler is designed.A groove penetration welding technique is used to weld the U rib-top plate of the specimen,and the transverse rib partition is welded to it by double-sided submerged arc welding.The surface of the arc cut of the weld seam and the transverse partition plate of the specimen was tested,and the residual stress distribution of the transverse partition plate in the longitudinal and transverse direction was investigated.the feasibility of the numerical simulation is verified by comparing the experimental and numerical simulation values.This paper provides a new idea for the study of fatigue cracking mechanism at arc cut of orthotropic bridge deck,and provides a theoretical basis for the design and fatigue research of orthotropic bridge deck based on the characteristics of residual stress distribution.