梁柱节点翘曲位移传递的分析

考虑柱子和两个正交方向梁的翘曲自由度,再加上传统的节点位移和节点转动等6个自由度,空间框架中刚性连接节点的自由度应该为9个。对常用的梁柱刚性连接节点中的3个翘曲自由度之间的关系进行分析,得到了3个方向的翘曲自由度之间的关系,这些关系能够用于消去梁的翘曲自由度,从而保证一个节点仍然是7个自由度。采用ANSYS板壳有限元分析结果进行的验证表明,提出的公式是正确的。研究表明,目前各种通用软件中采用一个节点7个未知量的方法隐含的梁柱翘曲自由度之间的关系是不符合实际的。     

国际期刊导读

1 钢框架节点翘曲传递模型 摘要：由于薄壁钢框架节点的作用,局部翘曲变形具有连续性,应用梁有限元分析,给出考虑局部翘曲连续性影响的简单方法。通过子结构分析方法,得到节点的压缩刚度矩阵,采用翘曲弹簧模拟交叉构件间的局部翘曲约束。通过数值算例对该模型进行了验证,所给节点模型的梁有限元分析结果与精确壳有限元分析结果相符。     

考虑圣维南翘曲变形的初始扭转薄壁梁单元刚度矩阵

基于传统薄壁直梁力学模型,对初始扭转薄壁梁有限元数值模型进行系统的分析与研究。首先基于初始扭转梁的几何变形微分关系,导出初始扭转薄壁梁圣维南翘曲应变。根据传统薄壁直梁有限元力学模型,考虑初始扭转梁圣维南翘曲变形,建立其有限元单元刚度矩阵。最后,通过椭圆截面初始扭转梁算例,并与ANSYS三维实体有限元分析结果进行对比分析,表明建立的考虑圣维南翘曲变形的初始扭转薄壁梁单元刚度矩阵具有良好的精度。     

楼板对高层建筑核芯筒受力性能的影响

本文根据Vlasov的薄壁杆件翘曲理论,采用有限元和解析相结合的分析方法,研究了四周与楼板连接的开口薄壁核芯筒的扭转刚度,考察了楼板出平面刚度对核芯筒受力性能的影响,提出楼板有效宽度的概念,推导出相应的计算公式。在实际工程设计计算中,可考虑楼板对核芯筒约束扭转的制约作用。     

基于多尺度计算异形节点钢框架结构抗震性能研究

本文利用多尺度计算的方法对使用外环板式不等高节点的钢框架抗震性能进行了研究,使用MARC有限元软件中的多点约束法连接宏观单元与微观单元,同时根据一系列杆件模型算例验证了有限元模型的可靠性。通过对同一个钢框架分别使用多尺度单元和梁单元进行模态分析和动力时程计算,验证了多尺度模型可以准确地模拟结构的地震响应。提出了一种改进型的不等高异形节点,并对5种不同节点参数下的钢框架进行了动力时程分析,结果表明,外环板能够显著改善节点区域的应力状态,新型异形节点可以使节点域的受力更加均匀。     

装配式可更换混凝土框架节点非线性分析

对可更换新型混凝土框架梁柱节点的抗震性能进行仿真研究,采用有限元软件ABAQUS对节点进行非线性有限元分析,介绍了混凝土和钢结构的本构模型、混凝土与混凝土界面特性、混凝土与钢结构之间的黏结特性.将有限元计算结果与试验数据进行对比,发现数值模拟结果与试验数据吻合良好.基于所建立的有限元模型对节点进行参数化分析,结果表明混...     

曲线箱梁桥的地震反应分析

根据薄壁箱梁的翘曲扭转理论,建立了可以考虑截面翘曲和偏心影响的3维空间曲线箱梁桥的位移模式和能量泛函,利用有限元列式建立了动力方程。并编制了相应的程序。最后通过算例说明了翘曲扭转对曲线箱梁桥影响较大,不可忽略。     

无粘结预应力装配式框架中节点抗震性能分析

利用ABAQUS软件对预应力装配式框架中节点开展了低周反复加载下的有限元模拟分析,结合无粘结预应力装配式框架中节点在低周往复荷载下的试验,利用ABAQUS通用有限元计算软件建立对应框架节点的有限元模型,进行了预制装配式框架节点有限元模拟分析,对比分析试验结果和有限元分析结果,表明有限元模拟结果与试验结果能较好的吻合,证明了有限元模拟手段具有较好的可靠性和有效性。     

翼缘削弱型节点空间钢框架在低周反复荷载

为研究翼缘削弱型节点空间钢框架在低周反复荷载作用下的抗震性能,采用有限元分析软件ABAQUS对普通节点和翼缘削弱型节点的空间钢框架模型进行有限元模拟,对2种钢框架模型的破坏形式、承载力、滞回性能、耗能能力、强度及刚度退化性能等进行了对比分析。结果表明:翼缘削弱型节点可使梁端塑性铰外移至梁端翼缘削弱处,避免梁端焊缝处应力集中导致脆性破坏;翼缘削弱型节点等效粘滞阻尼系数与普通节点空间钢框架相比有明显的提高,进入屈服阶段后由于应力重分布,其刚度及承载力退化速度较普通节点空间钢框架慢,翼缘削弱型节点钢框架具有梁铰延性破坏机制,抗震性能较好。     

波形腹板工字形梁截面翘曲惯性矩的推导

梁截面的翘曲惯性矩是梁平面外弯扭失稳和扭转变形分析的重要几何参数。对于梯形和正弦形波形腹板工字形截面梁,已有文献对其截面的翘曲惯性矩进行了推导,但由于推导过程中的假定不同,其结果存在差异。从截面翘曲惯性矩的定义出发,结合梯形和正弦形波形腹板工字形截面梁的受力特点,推导得到了梯形和正弦形波形腹板工字形截面梁的翘曲惯性矩计算公式,并从平面外弯扭失稳和扭转变形两个角度,与有限元数值计算结果进行了对比验证,也与其他学者推导的计算公式进行了比较。结果表明,在常用的波形尺寸范围内(波长为150～200mm,波幅为20～30mm),腹板不承受轴向力的理想受力状态可以得到保证。推导结果从理论上符合实际,在精度上也能满足工程需求。     

Torsion warping transmission at thin-walled frame joints: Kinematics, modelling and structural response

This paper reports on the use of simple kinematic models to simulate the torsion warping restraint and transmission at thin-walled frame joints in the context of beam finite element structural analysis. After reviewing the main concepts involved in the torsional behaviour of thin-walled members, the paper addresses the development of kinematic models aimed at simulating the torsion warping transmission at frame joints connecting two or more non-aligned plain channel (U-section) or I-section members. Finally, numerical results are presented and discussed, in order to illustrate the application and show the capabilities of the above kinematic models, which make it possible to use beam finite element models accounting for the joint torsion warping behaviour. For validation purposes, the beam finite element results obtained are compared with values yielded by rigorous shell finite element analyses.     

Warping and bimoment transmission through diagonally stiffened beam-to-column joints

For beam-to-column rigid joints with a diagonal stiffener, the warping degrees of freedom at the beam-to-column joint have been taken to be continuous in some current literature. A new warping transmission model is presented for this type of joint in this paper, in which the bending deformation and twisting of the diagonal stiffener are considered and the restraining of the web in the joint panel zone to the twist of the diagonal stiffener is taken into account. Comparison with FEA using shell elements demonstrated the high accuracy of the proposed model, while the results with the continuous warping assumption have greater deviation with the finite element results. The suggested model can be implemented simply though modifying the traditional thin-walled beam element matrix at the joints. The proposed model is applicable for solving combined flexural and torsional problems of frames composed of thin-walled members.     

Global buckling analysis of plane and space thin-walled frames in the context of GBT

This paper reports research work concerning the use of Generalised Beam Theory (GBT) to analyse the global buckling behaviour of plane and space thin-walled frames. Following a brief overview of the main concepts and procedures involved in the performance of a GBT buckling analysis, one presents in detail the formulation and numerical implementation of a GBT-based beam finite element that includes only the first four (rigid-body) deformation modes — namely, one describes (i) the kinematical models developed to simulate the warping transmission at frame joints connecting two or more non-aligned U- and I-section members, (ii) the procedures adopted to handle the effects stemming from the non-coincidence of the member centroidal and shear centre axes (cross-sections without double symmetry), and (iii) the definition of joint elements, which involves providing a relation between the connected member GBT degrees of freedom and the joint generalised displacements. Finally, one presents and discusses numerical results that make it possible to illustrate the application and show the capabilities of the above GBT-based finite-element formulation and implementation. For validation purposes, the GBT-based results (critical buckling loads and mode shapes) are also compared with values yielded by shell (mostly) and beam finite element analyses carried out in the code ANSYS.     

A model for warping transmission through joints of steel frames

A simple approach is developed in this paper which considers the effect of partial warping continuity through the joints of thin-walled steel frames when using beam finite element analysis. Using a condensed stiffness matrix for the joint generated by the substructuring technique, warping springs are introduced to represent the condition of partial warping restraint at intersections between members. The performance of the proposed model is demonstrated through a number of numerical examples. Excellent agreement is achieved between the results of beam finite element analysis using the suggested joint model and accurate shell finite element analysis.     

Modeling distortional shear in thin-walled elastic beams

In this paper, the theoretical background and the numerical analyses of an advanced beam finite element that relaxes the hypothesis of the cross-section non-deformability are presented. The corresponding new modes, called distortional modes, are added to the modes describing the behavior of a classical thin-walled beam: tension/compression, bending and torsion. For instance, a load acting in a cross-sectional plane of a beam is considered to induce not only bending and torsion but also distortion. The distortion produces non-uniform shear and axial stresses together with a non-uniform warping of the cross-section. These resulting effects, significant for very thin-walled open profiles (and thin-walled closed profiles with high distortional loadings), are shown in this paper to be important when compared to bending and torsion stresses even in simple loading cases.     

Influence of joint detail on the flexural/torsional interaction of thin-walled structures

For a structure formed from two thin-walled open members connected at 90°, torsion applied to one member can result in torsion as well as flexure in the second member, with the magnitude and direction of this torsion as well as flexure in the second member being determined by the type of joint used. Conventional structural analysis would normally assume the presence of only flexure in the second member. The results from a finite element study of structures formed from thin-walled channel sections connected by box, mitre and stiffened mitre joints is presented and an explanation for the behaviour of the different joint types is given. It is shown that for the box joint the warping deformation of the loaded member is the dominant factor in determining the magnitude and direction of the twisting of the second member, whilst this is determined for the stiffened mitre joint primarily by the St Venant rotation deformation of the loaded member. For the unstiffened joint it is shown that the warping and St Venant rotation deformation effects tend to cancel each other out.     

Frame mode method for thin-walled structures

The Rayleigh-Ritz method is extended to thin-walled structures on continuous supports by means of the combinations of frame modes transversely and continuous beam modes longitudinally. Effects of warping, distortion and shear-lag are considered simultaneously. The thin-walled structure problem is reduced to simpler plane frame and continuous beam problems. Numerical results are compared to the finite element and finite strip methods. The present method is advantageous over both the finite element and finite strip methods in the reduced number of generalised coordinates and its ability to use the existing frame programmes to analyse thin-walled structures. No new elements are required to be generated.     

Behaviour and strength of hollow flange channel sections under torsion and bending

Hollow flange channel section is a cold-formed high-strength and thin-walled steel section with a unique shape including two rectangular hollow flanges and a slender web. Due to its mono-symmetric characteristics, it will also be subjected to torsion when subjected to transverse loads in practical applications. Past research on steel beams subject to torsion has concentrated on open sections while very few steel design standards give suitable design rules for torsion design. Since the hollow flange channel section is different from conventional open sections, its torsional behaviour remains unknown to researchers. Therefore the elastic behaviour of hollow flange channel sections subject to uniform and non-uniform torsion, and combined torsion and bending was investigated using the solutions of appropriate differential equilibrium equations. The section torsion shear flow, warping normal stress distribution, and section constants including torsion constant and warping constant were obtained. The results were compared with those from finite element analyses that verified the accuracy of analytical solutions. Parametric studies were undertaken for simply supported beams subject to a uniformly distributed torque and a uniformly distributed transverse load applied away from the shear centre. This paper presents the details of this research into the elastic behaviour and strength of hollow flange channel sections subject to torsion and bending and the results.