单轴对称截面圆弧拱弹性弯扭屈曲临界荷载

为了研究均布径向压力作用下的单轴对称截面均匀受压圆弧拱的弹性弯扭屈曲临界荷载,为一般荷载作用下压弯钢拱的稳定承载力设计奠定基础,采用平衡法推导得到了均匀受压圆弧拱的面外屈曲临界荷载的理论解.在微元段受力平衡的基础上,建立了任意轴线形状、截面形式的曲线构件的平衡方程,代入截面变形条件、内力与变形条件推导出了单轴对称截面均...     

纯压抛物线拱平面内稳定性及设计方法研究

采用大挠度弹塑性有限单元法对全跨竖向均布荷载作用下纯压抛物线拱平面内稳定承载力进行研究,考虑材料非线性、焊接残余应力、初始几何缺陷、矢跨比和支承条件等因素的影响,得到了热轧圆管截面、焊接工字形截面和焊接箱形截面纯压三铰、两铰和无铰抛物线钢拱的平面内稳定性设计曲线,给出纯压抛物线钢拱的平面内稳定设计公式。以拱的正则化长细比为基本参数,统一了三铰、两铰和无铰纯压抛物线钢拱的平面内稳定设计曲线,可用于全跨竖向均布荷载作用下纯压抛物线钢拱的平面内稳定性设计,同时可供实际设计时使用和制定有关规程时参考。     

波形钢腹板变截面梁剪力滞的差分解

基于波形钢腹板变截面形式逐步出现,针对其剪力滞的求解,提出对波形钢腹板变截面简支梁桥的剪力滞的分析,利用差分法建立矩阵方程[G]{U}=[F'(x)],然后对F'(x)求解,得到U,进而求得各个截面的剪力滞,分析其分别在集中荷载,均布荷载的作用下其剪力滞纵向分布情况,并利用有限元建立模型进行对比分析,结果表明二者能很好的吻合。     

均布压力作用下变截面Timoshenko悬臂柱的稳定性

对变截面Timoshenko悬臂柱承受均布荷载和柱顶集中荷载的屈曲进行研究,推导适用于变截面构件分析的物理刚度矩阵和几何刚度矩阵,编写程序获得不同参数下悬臂柱弯曲屈曲和剪切屈曲的相关关系曲线,提出的近似计算公式,可在实际应用中作参考,例如用于计算高层结构的二阶效应系数。     

均布荷载下简支波浪腹板H形截面钢梁弹性整体稳定性研究

采用能量法研究简支波浪腹板H形截面钢梁的弹性整体稳定性,推导了满跨均布荷载作用下简支波浪腹板H形截面钢梁的弹性临界弯矩公式,通过引入波浪腹板H形截面钢梁的等效翘曲惯性矩和绕虚轴等效惯性矩,得到均布荷载作用下简支波浪腹板H形截面钢梁的弹性临界弯矩表达式与普通H形截面简支钢梁形式相同。采用有限元方法对均布荷载作用下简支波浪腹板H形钢梁进行模拟分析,与本文公式计算结果对比验证了所提公式准确有效。均布荷载作用下不同参数简支波浪腹板H形截面钢梁的有限元分析表明,简支波浪腹板H形截面钢梁的弹性临界弯矩大于平腹板H形截面钢梁;随着波浪腹板波幅的增大、翼缘宽度和翼缘厚度的增大,简支波浪腹板H形截面钢梁的整体稳定临界弯矩增大。     

钢筋混凝土双坡梁矩形截面纵筋截面的计算

<正> 钢筋混凝土矩形截面单跨等截面梁,纵向钢筋按最大弯矩计算就可以了。但对坡梁来说,最大弯矩截面不一定是危险截面,如在均布荷载作用下单跨双坡梁,危险截面不在弯矩最大的跨中。因此,对于坡梁的计算,应首先求出危险截面位置,纵向钢筋应按此截面计算。一、矩形载面单跨双坡梁在均布荷载作用下截面的精确计算法双坡梁在均布荷载作用下如图l所示,距支座A为x截面的弯矩可表示为:     

耗能支撑危险截面的有限元分析

应用ANSYS分析软件对T型截面防屈曲支撑进行单调荷载作用下三维有限元模拟,在模型中钢芯和混凝土之间采用接触单元,混凝土与钢套筒之间完全粘结。通过有限元模拟分析可知:当T型截面防屈曲支撑一端施加的面荷载增加到一定值时,构件应力最大值位于防屈曲支撑钢芯反面截面削弱处,此处是该构件的薄弱位置;构件应力最小值位于防屈曲支撑钢芯连接段反面处,此处是构件最安全位置。模拟分析与试验结果表明:T型截面防屈曲支撑最危险截面出现在加载端过渡段与工作段的连接处,该处可作为设计防屈曲支撑的控制截面。     

按部分剪力连接计算压型钢板-混凝土组合板承载力的简化方法

提出多种荷载作用下,简支压型钢板-混凝土组合板承载力的部分剪力连接简化计算方法。分析组合板纵向剪切破坏的部分剪力连接理论模型,阐明组合板纵向剪切破坏的机理,以及控制截面位置和极限荷载的求解思路。通过公式推导,分别得到了组合板在两点对称荷载和均布荷载作用下的承载力计算公式。在此基础上,提出点荷载和均布荷载共同作用下的组合板承载力计算方法,通过参数分析,对该方法进行简化,得到多个荷载作用下组合板承载力的简化计算公式。结合12个简支组合板的静力试验结果,进行公式验证,计算结果与试验值吻合良好。通过小比例滑块试验得到压型钢板与混凝土的界面强度参数,即可用该方法计算组合板的承载力。     

冷弯薄壁卷边H型钢受弯构件局部屈曲分析

采用有限条软件CUFSM对200种不同截面几何参数的冷弯薄壁卷边H型钢在荷载作用下的局部屈曲应力进行计算,并利用构件的屈曲应力分析了不同的卷边宽厚比、截面宽高比、腹板高厚比、翼缘宽厚比对冷弯薄壁卷边H型钢局部屈曲性能的影响。在此基础上,提出了适用于求解冷弯薄壁卷边H型钢在荷载作用下局部屈曲应力的简化计算式,并将简化公式计算的结果与有限条法计算的结果进行对比,表明所提出的简化计算式具有很好的适用性和精确性。     

不同剪力连接程度钢-混凝土组合梁的有限元分析

介绍钢-混凝土组合梁的有限元分析原理,建立了剪力连接件的单元刚度矩阵表达式,提出了连接件的非线性有限元模型。采用大型有限元软件ANSYS对均布荷载作用下的钢-混凝土简支组合梁在不同剪力连接程度下的应力、变形和滑移进行了分析。分析结果可用于组合梁实践应用中的连接程度优化选择。     

Buckling analysis of thin-walled sections under general loading conditions

This paper presents an investigation of the buckling behaviour of thin-walled sections subjected to general loading conditions. The semi-analytical finite strip method is used. The existing results are only for sections subjected to a uniform loading, namely: uniform compression, uniform bending and uniform distributed loads, which are applied at the shear centre. For a general loading condition, we proposed the realizing linear analysis first to give longitudinal stresses. The stiffness matrix is provided in the standard manner. Each strip is divided into cells and longitudinal stresses are recorded in these cells. The integrations are performed on each cell domain and the sum of them provides the geometric matrix of the strip.     

Elastic flexural buckling of non-uniform members: Closed-form expression and equivalent load approach

Experienced structural engineers have an intuitive understanding of the buckling behavior of uniform members subjected to compressive loads. The Euler critical load and the concept of buckling length are extensively used in this context. Unfortunately, the extension of this intuitive approach to cases with non-uniform load or non-uniform members is not straightforward. Based on an extensive numerical parametric study, the paper first presents a closed-form expression for the buckling load of constant cross-section members with non-uniform axial loading. Consequently, an equivalent load approach for non-uniform members subjected to non-uniform axial load distribution is proposed and validated. The combination of both procedures has the power of transforming the general complex case of a non-uniform member under non-uniform load into an equivalent simple case of a uniform member subjected to uniform load. The new methodology is simple and direct, and produces more than acceptable approximate results.     

A finite strip analysis of locally buckled plate structures subject to nonuniform compression

The post-local-buckling behaviour of thin plate structures is governed by the mode of loading which can be either one of prescribed load eccentricity or displacement pattern of end sections. A finite strip approach to the analysis of post-local-buckling behaviour under either mode of loading is presented. A particularly simple initial postbuckling analysis based on the perturbation technique is discussed in detail. Examples are presented to illustrate the convergence of the solution and contrast the behaviour of the structure under the two modes of loading. In particular it is demonstrated that a channel-section strut is stiffer and attains a higher collapse load under uniform end shortening that when loaded through the centroid of the cross-section.     

The computational post-buckling analysis of fuselage stiffened panels loaded in shear

Fuselage panels are commonly fabricated as skin-stringer constructions, which are permitted to locally buckle under normal flight loads. The current analysis methodologies used to determine the post-buckling response behaviour of stiffened panels relies on applying simplifying assumptions with semi-empirical/empirical data. Using the Finite Element method and employing non-linear material and geometric analysis procedures it is possible to model the post-buckling behaviour of stiffened panels without having to place the same emphases on simplifying assumptions or empirical data. Previous work has demonstrated that using a commercial implicit code, the Finite Element method can be used successfully to model the post-buckling behaviour of flat riveted panels subjected to uniform axial compression. This paper expands the compression modelling procedures to flat riveted panels subjected to uniform shear loading, investigating element, mesh, idealisation and material modelling selection, with results validated against mechanical tests. The work has generated a series of guidelines for the non-linear computational analysis of flat riveted panels subjected to uniform shear loading, highlighting subtle but important differences between shear and compression modelling requirements.     

Calculating the global buckling resistance of thin-walled steel members with uniform and non-uniform elevated temperatures under axial compression

This paper develops a method, based on the Direct Strength Method (DSM) global buckling curve, to calculate the global buckling ultimate strength of cold-formed thin-walled (CF-TW) steel members under uniform and non-uniform elevated temperatures. The assessment is carried out by checking the DSM curve-based results with numerical simulation results using the general finite element software ABAQUS. The numerical model has been validated against a series of ambient temperature and fire tests on panels made of two different lipped channel sections tested to their ultimate load carrying capacities at ambient temperature or to their fire resistance at different load levels. The validated numerical model has been used to generate a database of numerical results of load carry capacity of CF-TW members with different uniform and non-uniform temperature distributions in the cross-sections under different boundary and loading conditions and with different dimensions. It is concluded that the DSM global buckling column curve is directly applicable for uniform temperature but a simple modification is required for non-uniform temperature distributions.     

复合荷载作用下钢梁弯扭屈曲的临界弯矩:(Ⅱ)系数计算及数值算例

基于平面外4种边界约束条件简支钢梁在满跨均布荷载、跨中对称集中荷载和端弯矩作用下,以及平面外4种边界约束条件固支钢梁在满跨均布荷载、跨中对称集中荷载作用下的M_cr三系数(C_1,i、C_2,i、C_3,i)计算式,计算了典型单一荷载工况的M_cr三系数数值,给出了横向荷载与端弯矩共同作用简支钢梁以及横向荷载两两共同作用固支钢梁的复合弯矩系数C_b计算式,通过数值算例验证了本文M_cr三系数和复合弯矩系数计算式的精度。最后对比了本文的M_cr三系数数值与EN 1999-1-1:2007和ENV 1993-1-1:1992中单一荷载的M_cr三系数数值,校验了"4M"等效弯矩系数计算式对简支钢梁、固支钢梁的适用性。结果表明:对于除平面外边界约束条件为R-R(平面外两端简支且约束转动)外的单轴或双轴对称截面简支钢梁以及双轴对称截面固支钢梁,单一荷载的M_cr三系数的数值或计算式以及复合弯矩系数...     

Buckling analysis of thin-walled cold-formed steel structural members using complex finite strip method

In this paper, a generalised complex finite strip method is proposed for buckling analysis of thin-walled cold-formed steel structures. The main advantage of this method over the ordinary finite strip method is that it can handle the shear effects due to the use of complex functions. In addition, distortional buckling as well as all other buckling modes of cold-formed steel sections like local and global modes can be investigated by the suggested complex finite strip method. A combination of general loading including bending, compression, shear and transverse compression forces is considered in the analytical model. For validation purposes, the results are compared with those obtained by the Generalized Beam Theory analysis. In order to illustrate the capabilities of complex finite strip method in modelling the buckling behavior of cold-formed steel structures, a number of case studies with different applications are presented. The studies are on both stiffened and unstiffened cold-formed steel members.     

在应力梯度下边缘加劲板的试验和设计

薄钢板结构有3种典型类型:非加劲(无边缘加劲板),加劲(有充足边缘的加劲板)和部分加劲(有部分边缘加劲板)。当被用于冷弯薄壁型钢时,在承受均匀压力和应力梯度下,钢板可能发生弹性屈曲,有6种可能的荷载组合条件。除了应力梯度作用下的部分加劲构件,对所有类型的钢板都进行了试验研究并提出了设计公式。阐述了当部分加劲板的加劲单元尺寸从零到足够产生加劲作用时,在应力梯度作用下部分加劲板的试验情况。研究了单一加劲和复合加劲的边缘加劲类型。利用有效宽度概念,提出了部分加劲构件在应力梯度作用下的设计公式。在此基础上提出了适用于所有构件在任意荷载条件下的有效宽度公式。     

钢异形柱弯扭相关屈曲研究

用弹性薄壁柱理论,推导了开口任意截面柱弯扭屈曲相关方程,并由此简化到单轴对称截面、双轴对称截面经典方程。进而研究了L形柱轴向受压的承载力即φ-λ曲线,以便工程设计应用。     

强冰雪灾害下大型薄壁圆柱钢壳结构稳定性研究

2008年我国南方地区发生强冰雪灾害,造成不少钢结构破坏。在化工、电力等工程中有很多作为整个系统关键设备的大型薄壁圆柱钢壳结构,柱壳内通常需设置一些横梁支承工艺设备,壳体既受到由上部壳体、顶盖和设备自重等荷载形成的沿环向均匀分布的整体轴向压力,又受到横梁支座传递来的局部轴向压力。在这些荷载作用下结构已经积累了一定的内力和变形,一旦再遭受强冰雪灾害,面积较大的顶盖和相连的其他管道上会快速积聚较大的雪荷载,导致结构发生失稳破坏。根据结构施工和使用过程,考虑加载路径的影响,先施加整体均布轴向压力,再施加局部轴向压力,然后施加模拟强积雪荷载的均布轴向压力,对112个带焊缝初始缺陷的薄壁圆柱壳结构进行了非线性稳定性数值分析。研究表明:随着初始整体荷载水平提高,柱壳承受积雪荷载的能力下降;随着缺陷幅值的增大,柱壳承受积雪荷载的稳定承载力与整体均布轴压下的稳定设计承载力的比值增大,其后屈曲承载能力也提高。柱壳下部储有浆液时;壳体承受积雪荷载的能力有小幅提高。根据大量计算结果,提出了考虑加载历史的遭受强冰雪荷载的圆柱壳稳定性设计建议。