顶底角钢螺栓节点有限元分析

1.分析过程1.1.理论分析1.2.简化过程如果将Pro/E中的3D造型直接导入Abaqus中进展计算,如此会出现裂纹缝隙无法修补,给后期的有限元分析过程造成不必要的麻烦,因此,在Abaqs中进展计算之前,对原来的零件模型进展一些简化和修整.A.法兰局部不是分析研究的重点,因此将其简化掉；B.经计算,M24×3的螺纹的升角很小,在度,因此可以假设螺旋升角为0；C.忽略螺栓和螺母的圆角等细节；1.3.Abaqus中建模查阅机械设计手册,得到牙型如如下图所示,在Abaqus中按照如下图所示创建出3D模型,如图11所示.同样的方式,我们建立螺母的3D模型nut,如图12所示.图11图12建立材料属性并将其赋予模型.在Abaqus的Property模块中,选择Material->Manager->Create,创建一个名为Bolt&Nut的新材料,首先设置其弹性系数.在Mechanical->Elastic中设置其杨氏模量为193000Mpa,设置其泊松比为0.3,如图14所示.建立截面.点击Section->Manager->Creat,建立Solid,Homogeneous的各向同性的截面,选择材料为Bolt&Nut,如图15所示.将截面属性赋予模型.选择Assign->Section,选择Bolt模型,然后将刚刚建立的截面属性赋予它.如图13所示.同样,给螺母nut赋予截面属性.图13图14图15然后,我们对建立的3D模型进展装配,在Abaqus中的Assembly模块中,我们同时调入两个模型,然后使用Constraint->Coaxial命令和Translate和Instance命令对模型进展移动,最终的装配结果如图16所示.第四步,对模型进展网格划分.进入Abaqus中的Mesh模块,然后选择Bolt零件,使用按边布种的方式对其进展布种,布种结果如图17所示.在菜单Mesh->Control中进展如图18所示的设置使用自由网格划分,其余设置使用默认.在菜单Mesh->Element type中选用如图19所示的设置.按下Mesh图标,对工件进展网格划分,最终的结果如图110所示.同样的方式对螺母模型nut进展网格划分,最终结果见图111所示.图17图18图19图110图111第五步,创建分析步.在Step模块中,点击Step->Manager图标,创建新的分析步,类型为Static,General,名称为Step-Load,其余使用默认设置即可.第六步,添加约束条件和载荷.在Interaction模块中,选择Tools->Surface-Manager,创建如图112所示的外表为集合Load_shang和Load_xia,分别用作加载载荷和约束.选择Load模块,在BC->Manager->Creat中创建约束BC-ENCASTED,选择刚刚定义的Load_xia集合,将6个自由度全部约束,如图113所示.下面我们为模型添加约束,选择Load->Create,进入约束创建界面,选择约束施加的外表为我们之前设定的Load_shang,施加的载荷的类型为Pressure,大小为372.835Mpa,具体设置如图114所示.图112图113图114第六步,定义接触面.接触面是Abaqus分析中非常重要的一环.进入Abaqus中的Interaction模块,先在Tools->Surface菜单中设置我们要定义的两个相互接触的面.如图115所示,螺栓上的接触面主要是螺纹的下外表,按着Shift键依次将其选中.如图116所示,螺母上的接触面主要是螺纹的上外表,同样按着Shift键依次将其选中.设置接触面的属性.选择Interaction->Manager->Creat中创建接触面,类型选择面和面接触,选择Mechanical->Tangential Behavior,输入摩擦系数为0.14,选择Mechanical->Normal Behavior,承受默认设置,最终设置如图117所示.选择Interaction->Creat,创建螺栓和螺母之间的接触,接触,类型选择刚刚定义的接触类型,设置结果如图118所示.图115图116图118最后,创建任务,承受默认设置,并提交计算.1.4.仿真结果将任务提交计算之后,得到的3维应力云图如图119所示.为了观察更为方便,我们将云图剖开,如图120所示.从云图中我们可以看出,螺栓头部与螺杆相接触的地方的应力较大,螺栓的螺纹处,由于截面发生变化也聚集着较大的应力.由于在仿真过程中,将压力施加在螺母的下外表,因此螺母的下方的变形较大,螺母的下方的几条螺纹的受力较大,顶层的两层螺纹几乎不受力.使用Abaqus中的工具对题目要求的节点的应力进展测量,结果如表1所示.图119图120表1。

螺栓角钢钢节点的三维非线性有限元分析
顾正维;孙炳楠;童根树;徐和财
【期刊名称】《钢结构》
【年(卷),期】2003(018)002
【摘要】对螺栓角钢钢节点半刚性连接采用非线性有限元分析方法,对连接中的主要构件的顶部、底部、腹板角钢、高强螺栓、梁翼缘、柱翼缘和柱翼缘加劲肋进行三维非线性有限元精细模拟,针对有无柱加劲肋、有无腹板角钢等几种连接的情况进行比较分析,探讨了螺栓角钢半刚性连接的受力性能.
【总页数】5页(P48-52)
【作者】顾正维;孙炳楠;童根树;徐和财
【作者单位】浙江大学,杭州,310027;浙江大学,杭州,310027;浙江大学,杭
州,310027;浙江省工业设计研究院,杭州,310000
【正文语种】中文
【中图分类】TU31
【相关文献】
1.高强螺栓T型钢连接节点三维非线性有限元分析 [J], 韩敏;熊军辉;郑玉莹;龙谋识
2.螺栓端板连接节点的三维非线性有限元分析 [J], 匡祯斌;孙炳楠;顾正维
3.考虑螺栓间隙的窄基角钢塔节点强度分析 [J], 盛金马; 朱晓峰; 张壮; 常江; 牛忠荣; 肖俊俊
4.输电铁塔大角钢节点螺栓排布方案优化分析 [J], 武韩青
5.输电铁塔大角钢节点螺栓排布方案优化分析 [J], 武韩青
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土木工程学报ＣＨＩＮＡＣＩＶＩＬＥＮＧＩＮＥＥＲＩＮＧＪＯＵＲＮＡＬ第４０卷第９期２００７年９月Ｖｏｌ．４０Ｎｏ．９Ｓｅｐ．２００７钢梁柱半刚性节点顶底角钢弱轴连接的有限元分析郝际平１李文岭１，２（１．西安建筑科技大学，陕西西安７１００５５；２．山东建筑大学，山东济南２５０１０１）摘要：空间钢框架结构的高等分析必须考虑梁柱弱轴连接的抗弯特性。

为研究钢梁柱节点弱轴连接的弯矩－转角性能，进行３个顶底角钢弱轴连接大尺寸试件的单调加载试验，并建立有限元分析模型，有限元分析考虑几何大变形、材料非线性和接触非线性。

为与试验结果对比，有限元分析采用的构件几何尺寸、材料特性、摩擦系数等参数和加载过程均与试验相同，对比显示有限元分析结果和试验结果吻合较好。

这进一步明确了顶底角钢弱轴连接的应力分布、塑性发展、变形特点、接触摩擦状态和破坏模式。

研究表明：顶底角钢弱轴连接具备一定的弯矩承载能力和良好的转动变形能力，顶角钢可以形成３个塑性铰机构；角钢弱轴连接与角钢强轴连接不同的是，柱腹板过于薄弱可以改变弱轴连接的变形模式；顶底角钢弱轴连接在使用荷载作用下接触状态稳定。

关键词：角钢弱轴连接；弯矩－转角性能；有限元分析；试验研究中图分类号：ＴＵ３９１ＴＵ３１７＋．１文献标识码：Ａ文章编号：１０００－１３１Ｘ（２００７）０９－００３６－０７Ｆｉｎｉｔｅｅｌｅｍｅｎｔａｎａｌｙｓｉｓｆｏｒｔｈｅｔｏｐ－ａｎｄ－ｓｅａｔａｎｇｌｅｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎｏｆｓｅｍｉ－ｒｉｇｉｄｓｔｅｅｌｂｅａｍ－ｃｏｌｕｍｎｊｏｉｎｔｓＨａｏＪｉｐｉｎｇ１ＬｉＷｅｎｌｉｎｇ１，２（１．Ｘｉ’ａｎＵｎｉｖｅｒｓｉｔｙｏｆＡｒｃｈｉｔｅｃｔｕｒｅ＆Ｔｅｃｈｎｏｌｏｇｙ，Ｘｉ’ａｎ７１００５５，Ｃｈｉｎａ；２．ＳｈａｎｄｏｎｇＪｉａｎｚｈｕＵｎｉｖｅｒｓｉｔｙ，Ｊｉｎａｎ２５０１０１，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｔｈｅｍｏｍｅｎｔｂｅｈａｖｉｏｒｏｆｂｅａｍ－ｃｏｌｕｍｎｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎｓｓｈｏｕｌｄｂｅｉｎｃｏｒｐｏｒａｔｅｄｉｎａｄｖａｎｃｅｄｓｐａｃｅｆｒａｍｅａｎａｌｙｓｉｓ．Ｔｈｒｅｅｌａｒｇｅｓｃａｌｅｓｐｅｃｉｍｅｎｓｗｉｔｈｔｏｐ－ａｎｄ－ｓｅａｔａｎｇｌｅｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎｓｗｅｒｅｔｅｓｔｅｄｕｎｄｅｒｍｏｎｏｔｏｎｉｃｌｏａｄｉｎｇ，ａｎｄｔｈｒｅｅ－ｄｉｍｅｎｓｉｏｎａｌｎｏｎｌｉｎｅａｒＦＥＭａｎａｌｙｓｉｓｗａｓｐｅｒｆｏｒｍｅｄｗｉｔｈｃｏｎｓｉｄｅｒａｔｉｏｎｏｆｇｅｏｍｅｔｒｉｃｌａｒｇｅｄｅｆｏｒｍａｔｉｏｎ，ｃｏｎｔａｃｔ－ｆｒｉｃｔｉｏｎｂｅｈａｖｉｏｒａｎｄｍａｔｅｒｉａｌｎｏｎｌｉｎｅａｒｉｔｙ．Ｔｈｅｒｅｓｕｌｔｓｏｆｆｉｎｉｔｅｅｌｅｍｅｎｔａｎａｌｙｓｉｓｗｅｒｅｖｅｒｉｆｉｅｄｗｉｔｈｅｘｐｅｒｉｍｅｎｔａｌｒｅｓｕｌｔｓ．Ｔｈｅｓｔｕｄｙｉｎｄｉｃａｔｅｓｔｈａｔｔｏｐ－ａｎｄ－ｓｅａｔａｎｇｌｅｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎｓｐｏｓｓｅｓｓｃｅｒｔａｉｎｍｏｍｅｎｔｃａｐａｃｉｔｙａｎｄｇｏｏｄｒｏｔａｔｉｏｎｃａｐａｃｉｔｙ．Ｔｈｒｅｅ－ｐｌａｓｔｉｃ－ｈｉｎｇｅｍｅｃｈａｎｉｓｍｃａｎｂｅｆｏｒｍｅｄｉｎｔｏｐａｎｇｌｅｕｎｄｅｒｍｏｎｏｔｏｎｉｃｌｏａｄｉｎｇ．Ｄｅｆｏｒｍａｔｉｏｎｍｏｄｅｍａｙｃｈａｎｇｅｆｏｒｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎｓｗｉｔｈｔｈｉｎｃｏｌｕｍｎｗｅｂ，ｗｈｉｃｈｉｓｓｉｇｎｉｆｉｃａｎｔｌｙｄｉｆｆｅｒｅｎｔｆｒｏｍｓｔｒｏｎｇａｘｉｓｃｏｎｎｅｃｔｉｏｎｓ．Ｋｅｙｗｏｒｄｓ：ｂｅａｍ－ｃｏｌｕｍｎｍｉｎｏｒａｘｉｓｃｏｎｎｅｃｔｉｏｎ；ｔｏｐ－ａｎｄ－ｓｅａｔａｎｇｌｅｃｏｎｎｅｃｔｉｏｎ；ｍｏｍｅｎｔ－ｒｏｔａｔｉｏｎｂｅｈａｖｉｏｒ；ｆｉｎｉｔｅｅｌｅｍｅｎｔａｎａｌｙｓｉｓ；ｅｘｐｅｒｉｍｅｎｔａｌｓｔｕｄｙＥ－ｍａｉｌ：ｈａｏｊｉｐｉｎｇ＠ｘａｕａｔ．ｅｄｕ．ｃｎ引言半刚性连接具有良好的变形能力，可以调整弯矩在结构中的分配，从而使结构更经济合理［１］。

Finite Element Analysis of Structural Steelwork Beam to Column Bolted ConnectionsJim ButterworthConstructional Research Unit,School of Science & Technology,University of Teesside, UK.AbstractA combination of simple fabrication techniques and speedy site erection have made bolted endplates one of the most popular methods of connecting members in structural steelwork frames. Although simple in their use bolted endplates are extremely complex in their analysis and behaviour. In 1995 the Steel Construction Institute (SCI) and the British Constructional Steelwork Association (BCSA) jointly published a design guide for moment resisting connections [1]. The Green Book design method offers increased connection capacity using a combination of theoretical overstress in the beam compression zone and plastic bolt force distribution. This paper reports on a PhD research program at the University of Teesside which uses a combination of full scale testing and materially non-linear three dimensional finite element analyses (FEA) in order to investigate extended end plate beam-to-column connections. The FEA analyses, incorporating MYSTRO and LUSAS software [2], use enhanced strain solid and contact gap elements to model the connection behaviour. IntroductionAn extended end plate connection consists of a plate welded in the fabrication shop to the end of the steel beam as shown in Figure 1. The end plate is pre-drilled and then bolted at site through corresponding holes in the column flange. The plate extends above the tension flange in order to increase the lever arm of the bolt group and subsequently the load carrying capacity. The connection is usually loaded by a combination of vertical shear force, axialforce in the beam member and a moment as shown in the diagram of an elevation on a beam-to-column joint in Figure 2.Figure 1 - Extended End Plate Connection Figure 2 - Connection Loading Accurate analysis of the connection is difficult due to the number of connection components and their inherit non-linear behaviour. The bolts, welds, beam and column sections, connection geometry and the end plate itself can all have a significant effect on connection performance. Any one of these can cause connection failure and some interact. The most accurate method of analysis is of course to fabricate full scale connections and test these to destruction. Unfortunately this is time consuming, expensive to undertake and has the disadvantage of only recording strain readings at pre-defined gauge locations on the test connection. A three dimensional materially non-linear finite element analysis approach has therefore been developed as an alternative method of connection appraisal.Connection Design TheoryDespite numerous years of extensive research [3], particular in the 1970’s, no fully agreed design method exists. Many areas of connection behaviour still require investigation. More recently Bose, Sarkar and Bahrami [4] used FEA to produce moment rotation curves, Bose, Youngson and Wang [5] reported on 18 full scale tests to compare moment resistance, rotational stiffness and capacity. The latest design method utilises plastic bolt force distribution to create an increased moment connection capacity and reduced column stiffening. In 1995 when the SCI and the BCSA produced the Green Book guide, based on the EC3 [6] design model, the editorial committee felt a number of areas, particularly bolt force distribution and compression flange overstress required further investigation. The authors PhD research program is currently nearing completion at the University of Teesside and is part of this investigation. The research has been undertaken with the financial assistance of the SCI.Full Scale TestsA series of five full scale tests were completed using the self straining frame in the Heavy Structures Laboratory at the University of Teesside. The basic arrangement of the testing rig and a test connection can be seen in situ in Figure 3.Figure 3 - Elevation on the Testing FrameThe beam to column joint was bolted into the frame and tested in an inverted position. Loading on the connection was provided with a 20 tonne jack situated on the top of the straining frame and activated by hand from a pull ram positioned on the laboratory floor. The jack was connected to the beam with a 25mm dia. high tensile steel bar and shackle arrangement. The shackle arrangement allowed adequate rotation to be obtained to ensure a truly vertical pull was always applied. To measure the force a load cell is placed between the jack and a steel block positioned on the top of the straining frame. The load cell is then connected to the statimeter. All connections used M20 grade 8.8 bolts which were torqued up to 110 Nm. 110 Nm is considered to represent a typical tightening force obtained using a steelwork erectors podger spanner. Test E1 used a lever arm of 1000mm, unfortunately this was found to be too small to produce failure with the loading equipment available. Therefore in subsequent tests the lever arm was increased to 1900mm. Connection details and dimensions were taken from ref. [1] with the exception of Test E2 which used an end plate thickness of 15mm. The Green Book recommended an end plate thickness of 20mm.All tests used the same arrangement for the location of the strain and dial gauges. Three strain gauges were applied to both beam compression and tension flanges. Six gauges were applied to the beam web, local to the tension and compression areas. Dial gauges were situated under the tension flange to measure rotation. The bolt strains were measured by bonding Kyowa type KFG-3-120-C20-11 gauges into the bolts. The 11 mm long circular strain gauges were inserted into a 2 mm dia. hole drilled into the centre of each bolt head. The bolts were previously all individually calibrated in a specially fabricated bolt testing assembly to obtain a bolt force to strain calibration factor. Strain readings were taken by connection of the gauges to two Vishay portable strain indicators and readings at each load increment noted.The arrangement of test strain/dial gauges are shown in Figure 4. Details of a bolt strain gauge are shown in Figure 5.Details of the five section sizes tested are given in the following table:Test Ref Beam Size(GR355)Column Size(GR355)ColumnStiffenedEnd PlateWxThkxLNo. of M20Gr 8.8BoltsBeam WeldsTop-Web-BtmE1356 x 127 x 33UB254UC73Yes200 x 20 x 460612-6-6 E2356 x 127 x 33UB254UC73Yes200 x 15 x 46088-6-6 E3356 x 171 x 51UB254UC73Yes200 x 20 x 4601010-6-6 E4254 x 146 x 37UB203UC60No200 x 20 x 37068-6-6 E5457 x 191 x 67UB203UC60No200 x 20 x 570810-6-6Table 1 - Full Scale Test DetailsFull Scale Test ResultsTest E1 had to be unfortunately halted at 215 kNm due to the capacity of the jack. Test E2 failed at 220 kNm when the compression flange buckled. Test E2 at its ultimate load of 220 kNm had a flange stress of 607 N/mm2 when the compression flange buckled. At this time the flange was overstressed by 70%. The Green Book design allows a compression flange to be overstressed by 40% with 20% of this apportioned to material strain hardening and the remaining 20% to dispersal into the beam web. Test E3 failed at a connection moment of 290 kNm due to thread stripping of both the bolts and nuts local to the tension area. At the time of failure considerable bending of the end plate local to the tension flange was clearly visible. Tests E4 and E5 both failed as expected due to column flange bending. Table 2 shows details of the test results compared with the Green Book theoretical capacities and from these the relevant safety factors.Test RefGreenBookCapacityTestFailureLoadSafety Factor /Green BookMode of Test FailureE1160 kN215 kN 1.34Test halted at 215 kNm due to jackcapacity E2159 kN220 kN 1.38Beam compression flange buckled E3222 kN290 kN 1.31Upper rows bolt failure (thread stripping) E4101 kN135 kN 1.34Column flange bendingE5147 kN253 kN 1.72Column flange bendingTable 2 - Full Scale Test ResultsFinite Element ModelMYSTRO and LUSAS FEA software was used for the finite element analysis. The FEA models were created using command files rather than the CAD interface tools even though this method was longer and initially tedious. The command file could simply be copied and edited. The command file also was more logical in order than command files produced by the software after a model has been created. The command file was also well described bycomments within the file to provide a complete history of the model creation. FEA models can often be a black box that provides answers without the user being fully aware of what the model exactly entails. The extra work in creating the command files has been well worth the effort and allowed the subsequent models to be created quickly.The technique of FEA lies in the development of a suitable mesh arrangement. The mesh discretisation must balance the need for a fine mesh to give an accurate stress distribution and reasonable analysis time. The optimal solution is to use a fine mesh in areas of high stress and a coarser mesh in the remaining areas. To further reduce the size of the model file and the subsequent processing time symmetry was employed. The connection arrangement was symmetrical about a vertical centre line and therefore viewed from 1,1,1 only the rightFigure 6 - FEA ElementsElement TypesAt the beginning of the research a number of trial models were created. Models with fewer elements as well as models with only shell elements were tried and also a number of different methods of modelling the bolts were created before the final arrangement of mesh and elements used was decided upon. The final FEA models use the five element types as shown in Figure 6. HX8M elements are three dimensional solid hexahedral elements comprising 8 nodes each with 3 degrees of freedom. Although the HX8M elements are linear with respect to geometry, they employ an assumed internal strain field which gives them the ability to perform as well as 20 noded quadratic iso-parametric elements. These elements are used to model the beam flanges, end plate and connecting column flange. QTS4 and TTS3 elements are three dimensional flat facet thick shell elements comprising either 3 or 4 nodes each with 5 degrees of freedom and are used to model the beam and column webs, beam closing plate, column back flange and stiffeners. JNT4 elements are non-linear contact gap joint elements and are used to model the interface between the end plate and the column flange. The bolts were modelled using BRS2 elements for the bolt shank and HX8M elements for the head and nut as shown in Figure 10. BRS2 are three dimensional bar elements comprising 2 nodes each with 3 degrees of freedom. Each BRS2 element was equivalenced with the appropriate HX8M bolt head and nut to comprise the complete bolt assembly. All bolts used are M20 grade 8.8 and were assigned an area of 245mm2 which is equal to the tensile stress area [7]. The bolts in the full scale test were torqued to produce an consistent starting bolt force. This was included in the model as an initial prestress in the BRS2 elements. The bolt holes were modelled as square cut-outs in the end plate and column flange. Figure 7 shows a FEA model with the final arrangement of mesh discretisation. Figure 8 shows the FEA supports and loading.Figure 9 - Extended End Plate and Bolts Figure 10 - Enlarged FEA Bolt Arrangement In order to further reduce the models size and analysis time, tied slidelines were used to model the interface between the two sections of beam flange. The 1000mm long flange is split into two sections 300mm and 700mm long. The 300mm sections of the beam flanges adjacent to the end plate have two elements through the flange thickness to allow for greateraccuracy of analysis results. Similarly two elements are also used throughout the whole of the end plate thickness.Non-Linear AnalysisMaterial non-linearity occurs when the stress-strain relationship ceases to be linear and the steel yields and becomes plastic. The three sets of material data were as follows: For the elastic dataset all elements were defined as elastic isotropic with a Young’s Modulus of Elasticity of 2.05 x 105 N/mm2 and Poisson’s lateral to longitudinal strain ratio of 0.3. The actual materials test certificates were obtained for all steel and enabled stress/strain curves to be based on actual values rather than theoretical. Tensile tests were completed on a selection of bolts to enable material properties to be as accurate as possible. Von Mises yield criteria was used for all material.Boundary ConditionsDisplacements in the X,Y and Z directions were restrained at the top and bottom of the half column. Displacements in the X direction were restrained along all surfaces on the centre line of the model. The FEA model had problems converging when the beam end plate had no supports restraining movement in the Y direction due to the lack of bending resistance in the bolt BRS2 elements. Therefore supports had to be added to the underside of the end plate. This removed the shear force from the bolts but not of course from the remaining connection elements. Shear in moment connections is usually of minor importance but it is felt that the supports are a compromise. The column to end plate interface was modelled using JNT4 joint elements with a contact spring stiffness K of 1E9 N/mm2. Loading was via a 10 kN point load on the cantilever end. The load was then factored in the control file to achieve the required range of connection bending moments.FEA and Test ResultsThe Green Book capacity for Test E1 was limited to 160 kNm due to the capacity of the bolts. At this loading the compression flange was expected to have stresses in the order of 370 N/mm2. This agreed with the FEA model which also indicated considerable stresses, up to 500 N/mm2, in the bottom corner of the beam web. As the load on Test E1 increased the stresses in the compression flange reached up to 500 N/mm2. The area of beam web which had stresses above 400 N/mm2 increased to approximately a quarter of the beam depth. Test E2’s theoretical capacity was limited by its compression flange and at its failure load of 220 kNm had a compression flange stress of 607 N/mm2. At this point the flange was theoretically overstressed by 71% and finally caused buckling and ultimately failure. Figure 11 indicates the Von Mises stress contours at a load close to the test failure bending moment.Figure 11 - Von Mises Stress Contours E2As in Test E1, Test E3’s Green Book capacity was limited by the bolt strength and this was confirmed when at a moment of 290 kNm the bolts failed. At this load the compression flange indicated stresses up to 500 N/mm2 with again beam web stresses up to a quarter of the beam depth reaching 500 N/mm2. Approximately half of the beam web at the end plate interface had stresses over 400 N/mm2. In all cases it was found that the higher the connection force the greater the distribution of stresses into the beam web. Test E4 & E5 Green Book capacities were both governed by shear on the column web panel. For Test E4 at 135 kNm the column section failed due to column flange bending rather than web failure. Similarly Test E5 failed by flange deformation but at a considerably higher connection moment than the theoretical capacity.Connection Bolt ForcesStrain gauged bolts from the tests are compared in Table 3 with the forces obtained from the FEA and the Green Book theory. FEA and test results for the bolt forces indicated good correlation. In comparison with the Green Book theory it was found that in nearly all casesthe forces obtained from the top rows of bolts were higher in the FEA and test results than in the predicted theory. It was also found that the Green Book design guide assumed larger forces in the lower bolt rows than in both the FEA and test models. The plastic bolt force distribution theory assumes some deformation of the end plate or column flange takes place in order that the connection forces can be distributed down the connection into the lower bolts. This was found not to happen to the extent expected in the theory. From tensile tests on the connection bolts it was found that the bolts had considerable reserve capacity. In all the tests the steel rolling mill certificates were also obtained and it was found that all cases the steels yield strength was considerably larger than required by the British Standard. In some cases almost a grade higher. It is considered that the increased strength in the material prevented the connection force transmitting itself down the connection into the lower rows. This would explain the larger forces in the higher rows and the reduced forces in the lower rows. In spite of these observations the Green Book theory was found to have approximately a 30% safety margin over the test failure load.Green Book Bolt forces kNFEABolt forces kNFull Scale TestBolt forcesTest E1Top row2nd rowBtm row 230252246258826026012Test E2Top row2nd row3rd rowBtm row184239107(186)25225812042662548216Test E3Top row2nd row3rd row4th rowBtm row 2332522171293083081856083103121302412Test E4Top row2nd rowBtm row222193(231)2442203024023034Test E5Top row2nd row3rd rowBtm row226189(227)0(221)17716692141761649026Figures in brackets () indicate the potential bolt forces if the connection was not limited by some other failure criteria e.g. beam compression flange, column web panel, etc.Table 3 - Bolt ForcesFigures 12 and 13 indicates a comparison between test and FEA bolt forces for models E1 and E5.RotationsInitially the FEA models had the top and bottom of the columns restrained fully in all directions. In comparison with the full scale tests it was found that the rotations on the test connections were considerable larger than on the FEA models. Although connection rotations are not considered an important aspect of this particular research program it was felt that the models should reflect the tests as close as possible. Upon investigation it was found that the steel column in the full scale test had only a 10mm thick end plate welded onto the column ends for fixing the column to the frame. During the test it was found that the end plate started to bend and lift at the centre causing the greater rotations. The FEA models were therefore modified with springs added to the top and bottom of the columns. Figure 14 shows a comparison of the FEA and test rotations for E3 after correlation.ConclusionsIn both the FEA and the laboratory tests it was consistently found that the Green Book design theory underestimated the bolt forces in the top rows of the connection andoverestimated the forces in the lower rows. Overall plastic bolt distribution was not seen to happen in the manner assumed by the new theory. Tested bolts had a substantial reserve ofcapacity. The lowest bolt failure load found in tensile tests was 206 kN. The Green Book theory allows 137 kN in tension.In Test E3 connection failure was caused by thread stripping of both the bolt and the nut. This could be resolved if bolts used were specified to European Standards rather than BS 3692.The new rule of thumb allowing the compression flange to be theoretically overstressed by 40% did not appear to be unreasonable. The 40% rule is derived from a 20% dispersal of stress into the beam web and the remaining 20% apportioned to material strain hardening. It was found the higher the loading on the connection the greater the distribution of stress into the beam web.It was also discovered that the steel beams and columns rolled in the mill have a substantially greater yield stress than required, in some cases almost a grade higher. Whilst in elastic design this reserve of capacity is of benefit to the Engineer. In plastic design when members and connections are designed to yield this reserve of capacity has the effect of not allowing the connection to behave in the manner assumed. In connections using plastic bolt force distribution the end plate and/or column flange are assumed to deform in order that the force in the bolts can be dispersed down the connection into the lower rows.In spite of this the new Green Book theory with the increased connection capacities still had a reserve of approximately 30%.Overall the finite element analysis of extended end plate connections can be seen to provide advantages in terms of time and expense over full scale testing and can produce a more complete picture of stress, strain and force distributions.AcknowledgementsThe steelwork used in the tests was kindly donated and fabricated by Cleveland Bridge & Engineering in Darlington and Kvaerner Oil and Gas in Middlesbrough. Use of the MYSTRO and LUSAS software and technical support is also acknowledged as is the financial and technical assistance of the Steel Construction Institute.References1. Joints in Steel Construction - Moment Connections, BCSA/SCI Pub. No. 207/95.2. MYSTRO/LUSAS is produced by FEA Ltd, Kingston-upon-Thames, KT1 1HN.3. Nethercott D.A., Steel beam to column connections - A review of test data,Construction Industry Research & Information Association, 1985.4. Bose B, Sarkar S, and Bahrami M, Finite Element Analysis of unstiffened extended endplate connections, Structural Engineering Review, 3, 211-224, 1991.5. Bose B, Youngson G K, and Wang Z M, An appraisal of the design rules in Eurocode 3for bolted end plate joints by comparison with experimental results, Proceedings from the Institute of Civil Engineers Structures and Buildings, 1996.6. DD ENV 1993 - 1.1:1992 Eurocode 3: Design of steel structures Part 1.1 General rulesfor buildings.7. British Standards Institute, Specification for ISO metric precision hexagonal bolts,screws and nuts BSI London, 1967, BS 3692.Contact InformationJim Butterworth,Constructional Research Unit,School of Science & Technology, University of TeessideEmail: jimbutterworth@ FEA LtdForge House66 High StreetKingston upon Thames Surrey, KT1 1HN, UK. Tel: +44 (0)20 8541 1999 Fax: +44 (0)20 8549 9399 Email: info@ 。

1 概述螺栓是机载设备设计中常用的联接件之一。

其具有结构简单,拆装方便,调整容易等优点,被广泛应用于航空、航天、汽车以及各种工程结构之中。

在航空机载环境下，由于振动冲击的影响，设备往往产生较大的过载，对作为紧固件的螺栓带来强度高要求。

螺栓是否满足强度要求，关系到机载设备的稳定性和安全性。

传统力学的解析方法对螺栓进行强度校核，主要是运用力的分解和平移原理，解力学平衡方程，借助理论和经验公式，理想化和公式化。

没有考虑到连接部件整体性、力的传递途径、部件的局部细节(如应力集中、应力分布)等等。

通过有限元法，整体建模，局部细化，可以弥补传统力学解析的缺陷。

用有限元分析软件MSC.Patran/MSC.Nastran提供的特殊单元来模拟螺栓连接，过程更方便，计算更精确，结果更可靠。

因此，有限元在螺栓强度校核中的应用越来越广泛。

2 有限元模型的建立对于螺栓的模拟，有多种模拟方法，如多点约束单元法和梁元法等。

多点约束单元法(MPC)即采用特殊单元RBE2来模拟螺栓连接。

在螺栓连接处，设置其中一节点为从节点(Dependent)，另外一个节点为主节点(Independent)。

主从节点之间位移约束关系使得从节点跟随主节点位移变化。

比例因子选为1,使从节点和主节点位移变化协调一致，从而模拟实际工作状态下，螺栓对法兰的连接紧固作用。

梁元法模拟即采用两节点梁单元Beam，其能承受拉伸、剪切、扭转。

通过参数设置，使梁元与螺栓几何属性一致。

本文分别用算例来说明这两种方法的可行性。

2.1 几何模型如图1所示组合装配体，底部约束。

两圆筒连接法兰通过8颗螺栓固定。

端面受联合载荷作用。

图1 三维几何模型2.2 单元及网格抽取圆筒壁中性面建模，采用四节点壳元(shell)，设置壳元厚度等于实际壁厚。

法兰处的过渡圆弧处网格节点设置密一些，其它可以相对稀疏。

在法兰上下两节点之间建立多点约束单元(RBE2，算例1,图3)或梁元(Beam, 算例2,图4)来模拟该位置处的螺栓连接。

(5)施工第一批锚索时,应首先选择3孔锚索进行检测试验,以确定锚索锚固力与设计锚固力是否相等,每孔8束锚索试验荷载为1400kN ,试验采用的锚具均为工具锚,试验合格后,应按设计初始预应力重新张拉锁定。

(6)锚索施工完成后,应随机抽选3孔锚索进行张拉试验,每孔8束锚索张拉力不小于1200kN 。

(7)锚索张拉完成前,严禁下一分层桩前岩土体开挖。

5　体会(1)压力注浆对锚索的抗拔力起很大的作用,注浆时在锚索孔口安装止浆塞,注浆压力将增大很多,使水泥砂浆渗入到周围岩土层中,增加了锚固段锚固体与岩土层的摩擦力,从而增加了锚索的抗拔力。

(2)锚索的抗拔力又取决于水泥砂浆对锚索的握裹力,这就要求有高强度等级水泥砂浆及确保钢绞线的清洁度。

(3)锚索自由段水泥砂浆也参加了抗拔工作,在进行3号桩1号锚索张拉试验,第一次张拉到1400kN 时(自由段没补注浆)的伸长量比第二次张拉到1400kN 时(自由段已补注浆)大,这说明自由段水泥砂浆与孔壁岩土层摩擦力阻止了锚固体的位移。

(4)锚固段处土层中从锚索测力计上反映出预应力损失比处于岩层中的大得多,从施工实践中证明处于土层中的锚索加大压力注浆,能大大提高锚索的抗拔力,必要时应进行二次压力注浆。

(5)锚索结构轻便美观,造价低。

收稿日期:20030929基金项目:天津市自然科学基金资助项目(编号:023650511)第一作者简介:薛　强(1962—),男,副教授,1993年毕业于天津大学。

钢轨接头螺栓的有限元应力集中分析薛　强,苗德华(天津科技大学机械工程学院　天津　300222) 摘　要:应用有限元接触分析方法,研究钢轨螺栓螺纹根部的应力集中。

通过优化螺栓螺纹根部圆角半径和螺母结构、改变螺纹根部直径的方法,缓解螺纹根部的应力集中,改善应力分布,实现提高螺栓疲劳强度的目的。

关键词:钢轨螺栓;有限元分析;应力集中 中图分类号:TH1313 文献标识码:B 文章编号:10042954(2004)04007003 铁路机车能否安全行驶取决于钢轨的强度和可靠性。

经验公式与有限元分析相结合的螺栓强度校核方法1. 概述螺栓是应用广泛的可拆卸紧固件，实际工程中经常需要进行螺栓强度校核和选型。

机械设计手册中给出了螺栓选型的经验公式，这些公式是合理有效的，但需要明确输入螺栓的轴向和横向载荷，这些载荷通常很难用理论计算或经验估计方法确定。

有限元分析能够处理螺栓连接的结构，但有限元分析中的螺栓连接通常是做了大量简化，导致螺栓应力结果不准确，无法作为螺栓校核选型的依据。

因此，本文考虑将经验公式与有限元分析相结合来进行螺栓校核选型。

通过有限元分析来确定螺栓所受的轴向和横向载荷，以此作为经验公式的输入，完成螺栓校核选型计算。

关于螺栓选型，需要明确最小拉力载荷和保证载荷这两个概念。

当试验拉力达到最小拉力载荷时，要求螺栓不得发生断裂。

在试件上施加保证载荷后，其永久伸长量(包括测量误差)，不应大于12.5微米。

最小拉力载荷和保证载荷的具体数值参见GB/T 3098.1-2000~ GB/T 3098.17-2000。

跟螺栓选型相关的几个标准规范如下：· GB/T 3098-2000 紧固件机械性能· GB/T 16823.1-1997 螺纹紧固件应力截面积和承载面积· QC/T 518-2007 汽车用螺纹紧固件紧固扭矩· GB/T 5277-1985 紧固件螺栓和螺钉通孔2. 螺栓强度校核经验公式2.1 受横向载荷普通紧螺栓在预紧力作用下，压紧被连接件，被连接件间产生摩擦力，抵抗横向载荷。

螺栓杆受拉伸扭转综合作用。

如果连接件之间的摩擦力不足以抵消横向载荷，则被连接件发生横向错动，螺杆可能被剪断。

图1受横向载荷普通紧螺栓其强度校核计算公式如下： 螺栓所受横向外载荷为F A 。

为产生足够的摩擦力抵抗F A ，所需最小预紧力F p 为：上式中，K f 为可靠性系数，一般取1.1-1.3；m 为结合面数目；f为结合面摩擦系数。

按照最小预紧力F p 计算螺栓应力σ，进而确定所需的螺栓屈服强度σs ，最终可选定螺栓公称直径和强度等级。

高强度摩擦型螺栓节点板有限元分析高强度摩擦型螺栓节点板有限元分析摘要随着我国国民经济的不断发展和科学技术的进步，钢结构在我国的应用范围也在不断扩大。

整个结构是由构件和节点构成的，单个构件必须通过节点相连接，协同工作才能形成结构整体。

即使每个构件都能满足安全使用的要求，但如果节点设计处理不恰当，连接节点的破坏也常会引起整个结构的破坏。

可见，正确的节点设计十分重要。

本文就是利用ANSYS对钢结构节点(两段工字钢用高强度摩擦型螺栓通过连接板件连接构成的节点)进行研究，为钢结构节点的研究出一份力，同时提高我们对钢结构节点的认识。

关键词构件节点高强度摩擦型螺栓工字钢钢结构1、模型尺寸如上图所示，工字钢翼缘宽299mm，高23mm。

工字钢腹板宽15mm，高844mm。

两段工字钢用高强度摩擦型螺栓连接，每段工字钢长200mm，连接间隙为5mm。

连接板件长365mm，宽10mm，高740mm。

高强度螺栓的公称直径为M24，螺栓孔的直径应该比螺栓直径略大，所以螺栓孔直径取为26mm，螺栓头部直径为40mm。

螺栓在构件上的排列应同时满足连接的受力，构造和施工等要求。

受力要求：端距不能太小，要求端距不小于2d，d为螺栓孔直径。

螺栓距也要适当。

构造要求：当螺栓距过大时，被连接板件的接触就不紧密，潮气就会侵入板件间的缝隙内，造成钢材锈蚀。

所以螺栓距和线距，特别是处于边缘的端距和边距均不能太大。

施工要求：布置螺栓时必须考虑到采用扳手拧紧螺母的可能性，这都要求有一定的施工净空，否则就无法施工。

综合上述三个方面的要求，螺栓的排列如上图所示。

2、剪力和弯距共同作用下的分析图2-1是剪力和弯矩共同作用下的钢结构螺栓节点的有限元模型。