Elastic post-buckling analysis of compressed plates using a two-strip model

This paper shows that a simple two-strip model can be used to describe the post-buckling behaviour of simply supported rectangular plates subjected to uni- and biaxial compression, provided the ratio of the post-buckling to pre-buckling stiffness of the perfectly flat plate is known. The formulas for this two-strip model are derived in two ways: by using a force method, and by using an energy method. The two-strip model is compared to other available solutions in literature and it is shown that the model can be regarded as a modification of the lower bound plate analysis method.     

运用双条板模型分析受压板弹性的后屈曲性能

在已知无缺陷板的后屈曲与前屈曲刚度比值的情况下,双条板模型可以被用于分析单轴及双轴压力作用下的简支矩形板后屈曲性能。通过力法和能量法推导出相关公式。与其他文献中的解决方案的对比发现,该模型可被视为板下限分析法的改进。     

Transverse-stiffener requirements for the post-buckling behaviour of a plate in shear

The optimum stiffener rigidity in a transversely-stiffened web under pure shear is sought in the post-critical range. An energy-based large-deflection scheme is employed to study the post-critical strength of the system up to the initiation of material yielding for the usual range of plate geometries and varying stiffener rigidities. Several criteria for “optimum” rib stiffness are assessed including stiffener deflection, the effective halving of the plate length and, finally, the strength of the plate itself. Tentative conclusions are reached on the basis of comparing optimal rib rigidities for the two instances of elastic and post-buckling regimes.     

Numerical and experimental investigations on the compression behaviour of stiffened plates

The main objective of this paper is to present the results of the finite element method for non-linear analysis of stiffened plates subjected to axial compression load considering post-buckling behaviour up to collapse. For this purpose two series of well executed experimental data on longitudinally stiffened steel plates with and without transversal stiffeners subjected to uniform axial in-plane load carried out to study the buckling and post-buckling up to final failure have been chosen. The first series are those of Ghavami where the influences of stiffener cross-section of the type rectangular (R), L and T, their spacing and the presence of rigid transversal stiffeners have been studied. The second series of Tanaka & Endo, where the behaviour of stiffened plates having three and two flat bars for longitudinal and transversal stiffeners respectively were analysed. For the purpose a well-established commercially available Finite Element program ANSYS has been chosen. The selected element was SHELL43, which can trace the full-range, elastic-plastic behaviour of the stiffened plates. It is seen that the simulated results of FEM are in good consistency with the test results.     

国内外钢结构设计规范的几点比较

以我国新修订的钢结构设计规范GB5 0 0 17 2 0 0 3为基础 ,结合美国钢结构设计规范LRFD 2 0 0 1及欧洲钢结构设计规范EC3,对 3本规范中拉、压杆的屈曲限值以及梁腹板受剪屈曲后强度的计算方法进行了计算分析和比较 ,有关分析结论可供工程技术人员了解国内外钢结构设计规范的技术水平和发展动态时参考     

Finite element based coupled mode initial post-buckling analysis of a composite cylindrical shell

This paper presents a finite element formulation of Koiter's initial post-buckling theory using a multi-mode approach. Initial post-buckling theory provides direct information about the imperfection sensitivity of a structure under compressive loading, and is also the basis of a nonlinear reduced order model. The objective of the present work is to illustrate the capability of the implementation for buckling analysis of shell structures including modal interaction. A coupled mode initial post-buckling analysis for a composite cylindrical shell under axial compression, including the effect of a nonlinear pre-buckling state, has been carried out using a small number of representative modes. For small imperfection amplitudes the limit-point buckling loads obtained with the reduced order model compare reasonably well with full model nonlinear analysis, illustrating that a fast prediction of the coupled mode response of imperfect shells is possible using the approach proposed.     

基于耦合模式下初始后屈曲分析的复合柱形壳的有限元分析

运用多模式预测方法,基于Koiter初始后屈曲理论提出了一个有限元公式。初始后屈曲理论提供了压力作用下结构缺陷敏感性的直接信息,同时也是非线性降阶模型的理论基础。研究的目的在于说明包含了模态作用在内的壳结构的屈曲承载力分析。利用一部分有代表性的模态模型,对包含非线性前屈曲效应的轴压作用的复合柱形壳进行了耦合模式下的初始后屈曲分析。当结构缺陷较小时,从降阶模型中得到的极限屈曲荷载与从全模型非线性分析中得到的结果具有良好的一致性,这说明可以运用本文提议的方法对带有缺陷的壳结构的耦合模态响应进行快速的预测。     

Simplified lower bound limit analysis of transversely loaded thin plates using generalised yield criteria

In this paper a simple method of deriving lower bound limit loads for thin plates is presented. This method is based on the method of elastic compensation, an iterative elastic technique, which has recently been extended to allow the analysis of structures using thin shell finite element analysis using generalised yield criteria. Here the method is modified to allow analysis of plates, including the effects of transverse shear. The elastic compensation method, combined with generalised yield criteria, is implemented using the finite element numerical analysis technique. Convergence studies are carried out and limit loads are obtained for a range of geometries, boundary conditions and loading. The calculated limit loads are compared with results available in the literature and with new elasto-plastic results and show that the method can be used to quickly obtain practical results.     

Evaluation of composite shear wall behavior under cyclic loadings

Composite steel shear walls (CSSW) are widely used in civil projects due to its high stiffness and deformability. It can be utilized by either laying a concrete layer connected to the steel plate by shear studs or bonding a Fiber Reinforced Polymer sheet. The present experimental and numerical investigations were focused on the effects of shear studs spacing variation, middle beam rigidity and the method of beam to column connection on the CSSW behavior. Results indicate that increasing the shear studs spacing reduces the slope of load-displacement curve and improves ductility up to a specific studs’ spacing. In addition, the effects of middle beam rigidity and beam to column connections are insignificant on the composite steel shear walls behavior.     

组合剪力墙的滞回性能研究

组合型钢剪力墙刚度大、延性好,在土木工程中应用广泛。组合型钢剪力墙一般通过铺设与钢板连接的混凝土层或纤维增强复合板形成。本试验和数值研究主要分析剪力钉间距、中间梁刚度、梁柱连接方法对组合型钢剪力墙性能的影响。结果表明:增大剪力钉间距可减小荷载-位移曲线的斜率,并提高结构韧性。中间梁刚度和梁柱连接对组合型钢剪力墙性能的影响是非常微小的,可以忽略。     

循环荷载下组合剪力墙的性能评估

组合钢板剪力墙(CSSW)由于其具有极高的刚度及可变性,在土木工程领域内应用广泛。它可以用于混凝土覆层,与钢板采用剪切螺钉连接,或者与FRP板黏结。现有的试验和数值研究集中在剪切螺钉间距变化时,梁跨中刚度和梁柱连接方法对组合钢板剪力墙的影响上。结果显示:剪切螺钉间距的增加使荷载-位移曲线斜率减小,改善了由特定螺钉间距影响的延性。此外,梁跨中刚度和梁柱节点对组合钢板剪力墙也有很显著的影响。     

组合剪力墙的滞回性能评价

组合型钢剪力墙刚度大、延性好,在土木工程中应用广泛。组合型钢剪力墙一般通过铺设与钢板连接的混凝土层或纤维增强复合板形成。本试验和数值研究主要分析剪力钉间距、中梁刚度、梁柱连接方法对组合型钢剪力墙性能的影响。结果表明:增大剪力钉间距可减小荷载-位移曲线的斜率,并提高结构韧性。中梁刚度和梁柱连接对组合型钢剪力墙性能的影响非常小,可以忽略。     

Computational modelling of flange crushing in cold-formed steel sections

The computational modelling of the flange crushing phenomenon in cold-formed steel profiles is described in this paper, with particular emphasis to the development of shell finite element (SFE) models and performance of quasi-static analyses with an explicit integration scheme. Web crippling failure is widely recognised as the most relevant collapse mode of cold-formed steel members subjected to transverse concentrated loads. However, it has been experimentally and numerically observed that a somewhat different collapse mode may occur, due to the heavy stress concentrations stemming from the adoption of narrow bearing plates. This phenomenon, termed flange crushing, should not be confused with web crippling. Usually, the web crippling phenomenon is numerically investigated by means of non-linear static SFE models with an implicit integration scheme. In this study, SFE models are developed in ABAQUS code to study the flange crushing failure of a plain channel beam subjected to Internal Two Flange (ITF) loading conditions. These models are described in detail, as well as additional modelling concerns regarding quasi-static analyses and the explicit integration method. Different parameters are discussed in this article and the numerical results obtained are commented throughout. Such parameters include the (i) SFE type and mesh, (ii) load rate, mass scaling, adoption of smoothed displacement amplitude curves and control of inertial effects, (iii) contact and friction definitions, (iv) effects of forming cold-work and manufacturing process and (v) geometrical imperfections. Finally, the load–displacement response obtained with the quasi-static model and an equivalent non-linear static analysis are compared with the experimental test curves. It is concluded that very good results are achieved with the quasi-static approach, not only in terms of the ultimate load prediction, but also regarding the post-collapse load–deflection curve and the failure mechanism.     

高强钢轴心受压构件的稳定性研究

高强钢轴心压杆的稳定性是目前高强铜应用和研究的重点。在分析了目前高强钢轴心受压构件稳定性研究现状和高强钢稳定性设计方法存在的不足的基础上,结合大型有限元分析软件ANSYS的稳定分析功能及模型试验方法,对高强钢轴压心受构件的整体稳定性进行了研究,提出了以材料屈服强度和构件长细比为参数计算高强铜轴心受压构件稳定系数的计算公...     

使用预拱钢板对矩形预应力混凝土柱进行轴向加固

钢套常用于钢筋混凝土(RC)柱加固。之前的试验研究评估了钢套柱的延性和抗剪性能。然而,实践中常使用预压轴向荷载对RC柱进行加固。尚未对预应力引起的传统柱和新型套管之间的应力滞后效应进行研究。使用一种简单的新型卸载方法,利用预拱钢板提高预应力RC柱的轴向承载力,试验证明该方法能够有效提高RC柱的轴向承载力。提出相应理论模型来计算钢板加固柱的轴向承载力,将模型的预测结果与试验结果相比较,验证了该模型的准确性。     

欧特克发布基于BIM的概念设计软件--Autodesk Infrastructure Modeler 2012

欧特克有限公司宣布,欧特克建筑信息模型（BIM）基础设施产品组合新增面向概念设计的Autodesk Infrastructure Modeler 2012软件。基于BIM的基础设施产品组合主要用于规划、设计、建设和管理更具可持续性的基础设施。新产品将与2012版欧特克基础设施设计套件配套,可帮助业内专业人士提高效率,并...     

Comparison of measured distributions of concentrations of trace elements in air particulates with normal and lognormal probability functions

Concentrations of Cd, Cr, Cu, Fe, Mg, Mn, Pb, V and Zn in air particulates were measured at several sites in Québec. A computer program was written to perform a statistical analysis of this data. We found that the distributions of these concentrations are generally better described by a log normal rather than a normal probability function. Also the position of the median and the value of the coefficient of skewness are useful indicators of normality or lognormality of the measured distribution.