Coupled static and dynamic buckling of thin walled beam by spline finite element

For the coupled static and dynamic buckling of thin walled beam subjected to various forces, such as axial force, uniform bending moment, and bending moment due to concentrated and distributed lateral forces, the spline finite element method is employed to obtain the dynamic stiffness matrix. Second order effects of the axial force and moment are considered. A doubly symmetric cantilever beam with uniform cross-section is investigated. Extensive static and dynamic interaction diagrams are plotted. The effects of warping rigidity, torsional rigidity, axial tension and compression on moment buckling, moment on axial buckling compression, higher buckling modes are discussed in detail. The spline finite element method is proved to be very efficient for the present problem and many interaction diagrams can be plotted easily. Some new results are presented. The methodology is based on finite element formulation and therefore it can be easily extended to analyze structural frames.     

门式刚架节点刚度的再探讨

对轻型门式刚架几种不同型式的端板-螺栓连接节点的刚度进行分析,并提出相应的计算方法.节点型式包括设置在边柱顶部的端板连接,斜置的端板连接和设置在中柱顶部的连接.还提出个别节点达不到刚性节点要求时必须考虑其对框架稳定的不利影响.     

三角形空间管桁架平面外稳定有效算法

三角形空间管桁架的平面外整体稳定是工程设计中必须考虑的问题。根据实腹式简支梁的弹性稳定临界弯矩公式,导出三角形空间管桁架梁的临界荷载的简化计算公式,其中包括三角形立体桁架的侧向抗弯刚度、自由扭转刚度和翘曲刚度的等效简化公式推导。在满足工程设计计算精度要求下,提出了一种简便可行的稳定验算方法。     

框架-剪力墙刚接结构连梁的分析和设计

针对框架－剪力墙刚接结构的连梁设计，提出了一种连梁单元。它考虑了由于剪力墙刚度很大而框架刚度较小所引起的连梁两端转角不相等的实际受力变形情况，因而更接近于工程实际。推导出了连梁单元刚度矩阵，编制了计算机程序，方法简单实用     

Simplified analysis of asymmetric high‐rise structures with cores

A simplified elastic hand‐method of analysis for asymmetric multi‐bent structures with cores subjected to horizontal loading is presented. The structures may consist of combinations of framed structures such as coupled walls, rigid frames and braced frames with planar and non‐planar shear walls. Results for structures that are uniform with height compare closely with results from stiffness matrix analyses. The method is developed from coupled‐wall deflection theory which is expressed in non‐dimensional structural parameters. It accounts for bending deformations in all individual members, axial deformations in the vertical members as well as torsion and warping in nonplanar walls. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building from which all internal forces can be obtained. The proposed method of analysis offers a relatively simple and rapid means of comparing the deformations and internal forces of different stability systems for a proposed tall building in the preliminary stages of the design. The derivation of equations for analysis shown in this paper are for unisymmetric stability systems only, but the method is also applicable to general asymmetric structures with cores. Copyright © 2002 John Wiley & Sons, Ltd.     

Torsional analysis of multi‐storey building structures under horizontal load

New closed‐form formulae are presented for the torsional analysis of asymmetrical multi‐storey buildings braced by moment‐resisting (and/or braced) frames, (coupled) shear walls and cores. The analysis is based on an analogy between the bending and torsion of structural systems. A closed‐form solution is presented for the rotation of the building. The torsional behaviour is defined by three distinctive phenomena: warping torsion, Saint‐Venant torsion and the interaction between the two basic modes. Accordingly, the formula for the maximum rotation of the building consists of three parts: the warping rotation is characterized by the warping stiffness of the bracing system, St Venant rotation is associated with the St Venant stiffness of the building and the third part is responsible for the interaction. It is demonstrated that the interaction between the warping and St Venant modes is always beneficial, as it reduces the rotation of the structure. It is shown how the proposed formula for torsion can be used for the determination of the maximum deflection of multi‐storey asymmetrical building structures. The results of a comprehensive accuracy analysis demonstrate the validity of the method. A worked example is given to show the ease of use of the procedure. Copyright © 2010 John Wiley & Sons, Ltd.     

竖向荷载下足尺半刚性连接组合框架试验研究

为研究半刚性连接组合框架在静载作用下的力学性能,进行了竖向荷载下两榀足尺的两层两跨半刚性连接组合框架试验。组合框架由H型钢柱和压型钢板混凝土组合梁组成,钢节点由焊接到钢梁端部的平端板通过螺栓与钢柱翼缘连接。为了解半刚性连接组合框架的结构性能和破坏特征,考察不同荷载水平作用下半刚性连接和楼板的组合效应对钢框架结构整体性能的影响,重点分析框架整体性能、节点性能和梁性能。试验表明:平端板型组合节点为半刚性连接、部分强度节点,具有较高的强度和刚度,其极限转角可满足不小于30mrad的延性设计要求;半刚性连接和楼板的组合效应对钢框架的强度、刚度和延性有较大影响,设计时应加以考虑。试验结果可为今后半刚性连接组合框架理论研究和工程实际应用提供参考。     

Nonlinear free vibration analysis of asymmetric thin-walled circularly curved beams with open cross section

A finite element formulation is present for the nonlinear free vibration of thin-walled curved beams with non-symmetric open across section. The kinetic and potential energies are derived by the virtual principle. The energy functional includes the effect of flexural–torsional coupling, the torsion warping and the shear center location. For finite element analysis, cubic polynomials are utilized as the shape functions of the two nodal thin-walled curved elements. Each node possesses seven degrees freedom including the warping degree of freedom. The nonlinear eigenvalue problem has been solved by the direct iteration technique. The results are compared with those for straight beams as available in the literature. The results for nonlinear free vibration analysis of curved beams for various radii and subtended angle are presented.     

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.     

Buckling of frames braced by flexural bracing

This paper investigates the buckling of multistory frames braced by vertical beams. The sectional properties of the frames and the bracing beam are assumed to vary linearly along the height; the axial forces in the columns and the bracing beam are also assumed to linearly change along the height. A relationship between the buckling load and the bracing rigidity is established. The threshold rigidity for the vertical bracing beam which is just enough to make the frames buckle in a non-sway mode is obtained. The result may be used as a rational basis for classifying sway frames and non-sway frames after taking the influence of initial imperfections and lateral loads into account.     

D型偏心支撑钢框架耗能梁段性能研究

通过对具有不同耗能梁段长度的D型偏心支撑钢框架的滞回性能及耗能梁段耗能性能的非线性有限元分析,表明耗能梁段的长度对偏心支撑钢框架的侧向刚度、延性和耗能能力有较大影响。随着耗能梁段长度的增加,D型偏心支撑钢框架的强度、刚度、延性和耗能性能均产生了不同程度的退减现象;耗能梁段越短,其塑性变形越大,进而导致耗能梁段过早塑性破坏的可能性增大。根据有限元模拟结果提出了对耗能梁段长度的设计建议。     

翘曲对薄壁结构后屈曲性能的影响

薄壁结构力学性能分析的一维模型,用于分析一些框架结构的初始后屈曲性能。该模型以一种非常简单的方式考虑了翘曲的初始边界条件,而且被证明是分析薄壁框架结构的一种有效模型。基于多物理场耦合分析软件的有限元法,给出许多L型框架的数值分析结果。     

The effects of warping on the postbuckling behaviour of thin-walled structures

A direct 1D model able to describe the mechanical behaviour of thin-walled beams is used to analyse the initial postbuckling of some sample frames. The model allows to take into account the boundary conditions on warping in a very simple way and proves to be a very efficient tool for the analysis of thin-walled frames. Making use of the FEM based COMSOL multiphysics software, numerical results for a number of L frames are obtained and shown.     

焊接工字形钢曲梁的极限承载力试验

针对目前曲梁承载力方面的研究比较缺乏 ,进行了 18根焊接工字形水平钢曲梁的极限承载力试验。通过试验研究 ,了解水平钢曲梁在弹塑性阶段的工作特性 ,给出每个构件的荷载 -位移曲线和极限承载力 ,得到了曲梁承载力随跨长、曲率半径以及截面尺寸的变化规律。同时将试验结果与有限元分析的结果进行比较 ,在考虑端部翘曲约束的情况下 ,两者符合较好。     

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.     

Second-order plastic-hinge analysis of space semi-rigid steel frames

This paper presents a numerical procedure based on the beam–column method for nonlinear static analysis of space semi-rigid steel frames. The second-order effects are considered by the use of stability functions obtained from the exact solution of beam–columns under end forces and the inelastic behavior of material are presented by the lumped inelastic concept using yield surface. An independent zero-length element comprising of six translational and rotational springs, of which rotational spring stiffness uses the Kishi–Chen power model, is used to simulate the rigidity of the steel beam-to-column connection. The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental–iterative scheme. The nonlinear response results are compared with those of existing studies to verify the accuracy of the proposed numerical procedure.     

基于拉压与翘扭插值函数几何非线性刚度矩阵

提出了翘曲扭转稳定函数的概念和计算公式,首次推导了基于扭转翘曲稳定插值函数的双轴对称开口轻型薄壁梁柱单元的翘曲扭转切线刚度矩阵,同时提出了基于拉压与翘扭稳定插值函数的轻钢梁柱单元空间几何非线性切线刚度矩阵。     

有摇摆柱的钢框架结构整体稳定性能分析

首先简要介绍了钢框架稳定设计中采用的两种方法并进行对比,然后采用通用有限元软件ANSYS对某具体工程实例进行了完善结构和有缺陷结构的几何非线性和几何及材料双重非线性整体稳定性分析,总结出轻型钢框架结构整体稳定性的特点,为类似工程的稳定设计提供参考。     

框架分析的点元迭代法及矩阵级数法

本文是在克劳斯(Cross)的弯矩分配法、卡尼(Kani)的迭代法以及点元θ_1迭代法基础上,经过进一步的力学分析和数学论证而提出的。文中先介绍“点有限元”概念,再从θ_1迭代法公式中,引出克劳斯及卡尼的间接渐近的分配与传递系数,并由此建立了点元传递系数,点元总分传矩阵等数学力学参量,又从卡尼法及θ_1迭代法模型中,视总分传矩阵为一个矩阵级数,通过数学论证,可以发现它是一个收敛的矩阵级数(数列),于是,解算框架内力成为易事,文中并举例以阐明之。