Spatial Deformation And Stress Analyses For Feeding Straddle Crane Girder In Large Steelmaking Plant

The multi-span crane girder structure which connects the charging across,accepting across and smelting across is convenient for transportation of steel ladle and molten steel smelting in large steelworks.High requirements are required for the strength and stiffness of the crane girders because of the heavy load and high operating frequency of the hoisting and handling ladle.Once the girder appears large structural deformation and structural damage,such as large shaking,gnawing on the rail,local reinforcement plate cracking or even fracture,it is bound to endanger the safety of production and life safety,and brings serious consequences.Therefore,the stability of the crane girders and the security are very important.In the design of crane girders,the design is current widely carried out according to the traditional steel structure design specifications.Only the internal forces are calculated,and not stresses of key parts are analyzed.Although the internal force analytical results satisfy the design specifications,it does not mean that the local strength can meet the actual requirements in the operation.The inadequacy of local strength may endanger the bearing capacity of crane girders and cause structural failure.In the operation of the feed span crane girder,the local structural cracking,large downward deflection of the crane girder and large horizontal lateral deviation of the column have been found.Aiming at the above problems,the UG software is used to establish a whole-size of 3D geometric model of feeding span.A whole-size 3D finite element model is established by using Hypermesh software.The Ansys commercial software is applied to simulate the deformation and stress fields under dangerous working condition.The analysis results are showed as the followings:(1)There is a high stress zone exist at the junction between the bottom flange and the vertical plate of the girder in the west of the north side of the feeding cross.The stress exceeds largely the material strength.(2)The bending stiffness of the girder and the compressive stiffness of the column are insufficient.(3)The down flexural deformation of the crane girder is large,and the horizontal displacement at the top of the column is also large.(4)The local high stress zone is found and coincident with the cracking position found in the operations.It is shown that the results of the finite element analysis for the crane girder of feeding across are accurate and reliable.According to the abovementioned analyses,we present the scheme of structure optimization:(1)The columns in Column J are reinforced with full envelop columns.The steel plates are welded on all sides of the columns.The reinforcement height is from the surface of the base platform at the bottom to the bottom edge of the column shoulder.(2)The wedge-shaped blocks are welded at the junctions between the lower flange of the crane girder and the vertical plate of two ends of the girder.They should be polished to form inner chamfers.(3)The vertical plate is welded with the vertical plates of the ends of the crane girder.(4)The plate of the column shoulder is widen along the backing plate.For the proposed optimization scheme,the corresponding three-dimensional finite element model is established.The finite element analysis of the optimized scheme shows that the horizontal displacement of the top of the column and the down flexural deformation of the girder are reduced 41.2% and 36.7%,respectively.The maximum stress in the originally high stress zone of the crane girder decreases from 295 MPa to 136.8MPa.Through the present research,the reason of the partial cracking of the feeding cross girder are found out.The structural optimization scheme of the feeding across girder is put forward.The scheme can eliminate the spatial stress concentration,reduce horizontal displacement of the top of the column and the down flexural deformation of the girder,and improve the strength and stiffness of the crane girder.The structural optimization scheme can avoid the structural failure and large deformation of crane girder,and provide theoretical guiding for steelmaking safety production.