| Welding residual stress is a self-balancing internal stress that remains in the welded structure due to the constraint of deformation during the welding process.As welding technology becomes more and more advanced,more attention has been focused on welding residual stresses and the adverse effects of welding residual stresses on structures.This paper focused on the large scale welds of the world’s largest span steel pipe and concrete arch bridge.The weld residual stress distribution patterns of butt welds of main arch ribs and spatially coherent welds of different angles between webs and arch ribs were analyzed by a combination of experimental studies and numerical simulations,and the influence of the arch rib load-holding state on the residual stress and deformation of the weld was analyzed.Based on this,the effect of residual stresses in the main butt welds of the arch rib joints on the force performance and the overall bridge performance during construction was finally revealed.The main research work of this paper is as follows:(1)By carrying out experimental research on weld residual stress in large scale butt welds of steel pipe arch ribs under load-holding condition,combined with refined numerical simulation results,the weld residual stress distribution pattern and weld residual deformation values of the butt welds of the main arch ribs were obtained,and it was found that the rib plate had a great influence on the weld residual stress,and the maximum weld residual stress appeared in the middle region of the rib plates and the circumferential weld.(2)Based on the accurate numerical model of the joints,a nodal butt weld calculation model with and without the influence of load was established,and it was found that the state of holding the load has a small effect on the residual stress distribution of the weld,and the influence of the load can be disregarded when analyzing the residual stress distribution of the weld,but the load increases the overall residual welding deformation by 7.4%.(3)By carrying out experimental research on weld residual stress of the main-branch spatial coherent welds of different angles,combined with the results of numerical simulation calculations,the welding residual stress distribution pattern of the mainbranch coherent welds of different angles was obtained.And through a comparative analysis to investigate the impact of the angle of coherence on the main-branch spatial coherent weld residual stress distribution pattern,it was found that the average axial welding residual stress levels are comparable near the weld of different angles of the coherent,the stress were between 160 MPa ～ 200MPa;the circumferential weld residual stresses showed a smaller residual stress at the crown point location as the branch angle increases,but the overall stress distribution is more even.(4)Based on the distribution pattern of welding residual stress in the butt welds of the arch rib joints,the effect of welding residual stress on the force performance of the joints was obtained by nodal ultimate bearing capacity analysis,and it was found that the welding residual stress reduced the ultimate bearing capacity of the joints by 29.4%,while the structural axial stiffness was reduced,of which the initial axial stiffness was reduced by 4.32%.(5)Based on the weld residual stress distribution pattern of the butt welds at the arch rib joints,which is applied to the 1/4 overall bridge model as the initial stress,the effect of the weld residual stress on the overall bridge performance during construction was analyzed and obtained.It was found that the welding residual stress increased the vertical deformation of the bridge by 4.59% compared to that under self-weight;the maximum value of Von mises stress in the whole bridge appeared at the location of the arch where the influence of gravity was less;the axial stress in the beam units was dominated by tensile stress,and the welding residual initial stress reduced the maximum compressive stress by 2.5%. |
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