【作者】 张弛；

【导师】 尹晓春；

【作者基本信息】 南京理工大学 ， 工程力学， 2021， 硕士

【摘要】 在大型炼钢厂,常采用多跨行车梁结构,连接加料跨、接受跨和冶炼跨,方便钢水包的运输和钢水的冶炼。吊装搬运钢水包的行车负荷大,工作频率高,对行车梁的强度和刚度提出了较高的要求。行车梁一旦出现结构性变形和损坏,比如大幅度晃动,啃轨、局部筋板开裂,甚至断裂等,势必会危及生产安全和生命安全,带来严重后果。因此,行车梁的稳定性和安全性至关重要。在设计行车梁结构时,目前普遍按照传统的钢结构设计规范进行设计,只做内力分析,不对关键部位进行应力分析。内力分析的结果虽然符合规范,但是,并不代表局部强度能够满足实际使用要求。局部强度的不足,可能引起结构失效,危及行车梁承载安全。某钢厂加料跨行车梁在生产中,发现局部结构开裂,行车梁下挠变形较大,立柱水平横向偏移较大等问题。本文针对上述问题,采用UG软件,建立了加料跨的全尺寸三维几何模型。采用Hypermesh软件,建立了全尺寸三维有限元模型。然后,采用Ansys软件,进行了危险工况下的变形场和应力计算。分析结果发现:(1)加料跨北侧西的行车梁下翼缘与梁端竖板交界处存在高应力区,应力值严重超出构件设计强度;(2)立柱抗压刚度和抗弯刚度不足;(3)行车梁下挠较严重,柱顶的水平横向位移较大。局部高应力区与现场开裂位置吻合,表明加料跨的有限元数值分析结果准确可靠。针对上述存在的问题,提出了结构优化改造方案。方案为:(1)对J列立柱采用全包柱加固方案,即在立柱四面焊接钢板,加固高度从底部基础承台上表面至柱肩下沿板;(2)在行车梁下翼缘与梁端竖板交界内侧,堆焊打磨出倒角;(3)在行车梁两端竖板侧焊接立筋板;(4)加宽立柱柱肩上沿,增加垫板面积。针对所提出的结构优化改造方案,建立了相应的三维有限元模型。对结构优化改造方案的有限元分析表明:优化后的行车梁顶部水平横向位移和下挠挠度分别降低了41.2%和36.7%;行车梁高应力区内的最大应力从295MPa降低为136.8MPa。通过本文的研究,找出了加料跨行车梁局部开裂的原因,提出了加料跨行车梁结构优化改造方案。可以消除空间应力集中,降低行车梁下挠和柱顶水平横向位移,提高了行车梁的强度和刚度。可避免行车梁局部应力过高和变形过大造成的结构失效,对炼钢的生产安全具有理论指导意义。更多还原

【Abstract】 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.更多还原