Research On Welding Residual Stress Of The Tensile Anchor Plate Cable-girder Anchorage Structure Of Long-span Railway Cable-stayed Bridges

The cable-girder anchorage structure of the cable-stayed bridge is the key connecting component between cables and main girders.The anchor plate is one of the commonly used cable-girder anchorage structures.This cable-girder anchorage system mainly relies on the welding seams of anchor-tension plates to transfer the cable force.Finally,the cable force is transmitted to the beam through the welding seam between the anchor-tension plate and steel girder.Welding residual stress is an important factor affecting the mechanical properties and service life of steel structures in a bridge.There are many weld seams in the anchor plate,which are the key part to transfer the cable force.Besides,there are still a lot of residual stresses in the welding area.Therefore,it is necessary to master the distribution and variation of the temperature and stress field in the welding process.Yuekou Hanjiang Bridge,located in a branch line of the Qianjiang Railway,is a rare long-span railway cable-stayed bridge with the anchor plate in China.Its side web in the steel box girder extends above the bridge deck and is directly butted and welded with the anchor plate.In this paper,the anchor plate cable-girder anchorage structure of M12 stay-cable is taken as the research object.The welding processes of the butt joint of a local flat plate and the butt joint between the anchor plate and side web of steel box girder are simulated by a finite element software named ANSYS.And then,the distribution and variation of the temperature field and stress field in the welding process are analyzed and calculated.The main work is as follows:1.Briefly introduce the forms of the cable-girder anchorage structure in cable-stayed bridges and the research status at home and abroad;explaine the welding residual from four aspects: definition,causes,effects on components and research status;systematically explaine the characteristics of the finite element analysis of the welding process and the basic theoretical knowledge of the finite element analysis of the temperature and stress field.2.Based on ANSYS,separately establish two three-dimensional finite element models of the butt joints of a local flat plate and the anchor plate structure;determine the thermal and mechanical parameters of materials in the welding process,especially in high temperature environment;select appropriate element type,heat source model,welding parameters,etc.3.The generation of the element in the weld area can be controlled by the life-and-death element technology.At the same time,the load and move of the welding heat source can be realized by cyclic instructions in APDL command stream.The calculated temperature field distribution in the whole welding process is consistent with the general law,which shows that the welding simulation of the temperature field is basically correct.The indirect coupling method goes for figuring out the stress field.Based on the simulation results of the welding temperature field,the thermal elements in the finite element model are transformed into structural elements,and then the calculation results of the temperature field are read in turn and applied to the stress analysis model in the form of nodal load,to solve the welding residual stress field of the structure.4.External force is applied to the two finite element models of the anchorage plate with or without residual stress.Compare the difference of stress distribution between the two cases,and explore the effect of residual stress on the static strength of anchorage plate structures.Under the action of residual stress or not,the stress distribution at the weld seams varies dramatically,which indicates that the welding residual stress has a great influence on the static strength of anchor plates,and should be taken into account while analyzing the static strength at the weld seams of anchor plate structures.The welding residual stress field simulated in this paper paves the way for further explorations about the influence of welding residual stress on the fatigue strength or other characteristics of anchor plates in the future,and provides the theoretical basis and reference for the design of anchor plates in long-span railway cable-stayed bridges.