| Due to the large volume of steel box girder bridge,usually the construction method is to prefabricate the segments in the factory and then assemble the segments at the scene,and steel structure welding is the most critical construction process.Based on the establishment and improvement of numerical simulation methods for steel structure welding,in this paper,aiming at the two welding construction conditions of T-rib welding on top and bottom plate of steel box girder and longitudinal seam welding between transverse block sections,the influence laws of welding sequence and welding spacing on mechanical behavior of stress and deformation field of steel box girder are discussed in depth,and some engineering guiding suggestions such as welding sequence and block width of steel box girder are put forward.The main work and achievements are as follows:(1)Aiming at the trivial operation and difficult modification in the fine simulation of the welding process,a rapid simulation analysis method of welding layer by layer based on python secondary development is proposed:Through script development,birth-death element can be activated layer by layer,and the analysis step and increment step of temperature field can be imported and modified quickly.(2)Carrying out numerical simulation of steel plate welding test,the influence of parameters(af、ar、b、c)of double ellipsoid heat source model and thermal efficiencyη on molten pool shape parameters after welding is completed is analyzed.The analysis shows that η has the most significant effect on the shape parameters of molten pool,b has the greatest influence on the melting width,c has the greatest influence on the melting depth,and the influence of front half-shaft length parameter af on melt length is greater than that of rear half-shaft length parameter ar.(3)Based on the thermo-elastic-plastic finite element method,the numerical simulation analysis model of steel plate welding is established for welding sequence of single T-rib,different spacing of multiple T-ribs and welding sequence of multiple T-ribs,and the mechanical behavior of welding stress and deformation field of steel plate T-rib is studied.It is proposed that when welding a single rib,the best welding scheme is to weld both sides in the same direction at the same time,the second is to weld both sides in the same direction in sequence and the worst is to weld both sides in the opposite direction in sequence;Critical influence spacing of deformation and stress for multi-rib welding is 500 mm and 450 mm,respectively;Synchronized welding is the best in multi-rib welding,followed by symmetrical synchronous welding of double welds from inside to outside,the single weld is the best in jump welding from inside to outside,and the worst in sequence.(4)The simulation analysis of transverse multi-section steel box girder welding based on the inherent strain method is carried out and the influence of different welding sequences of section weld and different section blocking schemes on welding deformation of longitudinal weld of steel box girder is put forward.When welding the longitudinal seam of the steel box girder,the scheme of first descending and then going up has less deformation.Deformation of steel box girder is in the form of downward deflection of the welded zone and upper arch of middle section;When the total width remains unchanged,the vertical deformation increases from 8.779mm to 36.448mm,which increases by 315.2%when the width of the middle segment increases from 0.29 to 0.58 times of the beam width.Thus,the width of the middle segment has a significant effect on the deformation of the upper arch,which should be paid attention to when the segment is divided into blocks. |
