开口薄壁杆的板件面内拉弯综合抗力体系

针对薄壁杆件力学分析较为复杂的问题，讨论了一种把开口薄壁杆的分析拆分为2个较简单部分的方法。针对薄壁中面内荷载效应的分析问题，首先在适当简化基本应力应变条件的基础上，按平面应力问题分析单肢板件面内荷载效应，然后对其进行向量综合，得到反映开口薄壁杆轴向伸缩、弯曲及翘曲性质的“板件面内拉弯综合抗力体系”及其变形方程；探讨了刚度方程的建立及其计算特点，并与经典理论进行对比。分析表明，在板件面内弯矩定义中引入板件间纵向相互作用力，可简化该体系分析过程和结论，使之具备与平面弯曲问题一致的形式。作为应用举例，推导了求解薄壁截面主轴方向、主轴惯性矩、弯心坐标、主扇性惯性矩的线性方程组，剖析了经典理论中这些截面几何特性对于计算的意义及其效率。     

考虑弯扭耦合的解析型薄壁梁单元

为提高分析薄壁梁杆件弯扭问题的精度和效率,以Vlasov薄壁杆件理论为基础,考虑大位移和截面翘曲的影响,建立弯扭杆件位移控制方程,构造了薄壁梁杆单元的解析位移形函数,采用势能原理建立了薄壁梁杆势能泛函。利用势能驻值变分原理构造了用于内力分析的解析型薄壁梁杆单元列式,给出了解析型单元刚度矩阵,将其与理论解、插值多项式弯扭杆单元进行对比分析。结果表明,采用构造的解析型单元计算的薄壁梁扭转角及翘曲率的精度远高于插值多项式单元,且不需划分单元,即可保证计算结果与理论解的相对误差在0. 065%之内,可用于开口薄壁杆件结构的弯扭耦合受力分析及稳定计算。     

高强冷弯薄壁型钢杆件变形的原因分析

结合某门式刚架厂房杆件发生弯曲变形的实例,通过现场调查、取样、检测,核查结构构造并验算承载力,以及对杆件发生弯曲变形的原因进行综合分析,提出高强冷弯薄壁型钢连接板的厚度偏小、板件的宽厚比过大,易引起平面外变形。     

关于弹性薄壁杆件翘曲变形的讨论 五 闭口薄壁杆件的翘曲变形

在弹性薄壁杆件中,计算翘曲变形的理论常以"刚性周边"假定为基础,不考虑周边形状的改变.本文认为,在开口薄壁杆件中,"周边形状改变"与"周边形状不变"的翘曲变形都是同等重要的翘曲变形,不计前者是不恰当的;在闭口薄壁杆件中,在此假定的基础所导出的结论与实际不符。本文在中直线假定的基础上,用转角向径表示截面上各板的转角,用弯矩矢量表示各板的内力,使翘曲变形的基本方程的力学涵义和几何意义更为直观,从而较方便地导出计算各种翘曲变形的方法和结论.本文认为,在薄壁杆件中,不仅一对等值反向弯矩应组成力因素--双力矩;一对等值反向的双力矩,也应组成新的力因素--四力矩.同理,在截面图形中,不仅存在描述截面是否发生刚性扭转的扭转中心,而且存在描述截面是否发生相对扭转的双扭中心.它们都是同等重要的几何点.本文在建立新概念时,力求形象具体,推理方法尽量和计算平面变形的方法相同,使翘曲变形的计算和平面变形的计算能和谐地衔接成一体.目前,在工程中,随着材料质量的提高,溥壁杆件的应用更广,进一步探讨薄壁杆件的计算问题在实用上是有意义的.     

关于弹性薄壁杆件翘曲变形的讨论 三 开口四板杆件的翘曲变形

在弹性薄壁杆件中,计算翘曲变形的理论常以"刚性周边"假定为基础,不考虑周边形状的改变.本文认为,在开口薄壁杆件中,"周边形状改变"与"周边形状不变"的翘曲变形都是同等重要的翘曲变形,不计前者是不恰当的;在闭口薄壁杆件中,在此假定的基础所导出的结论与实际不符。本文在中直线假定的基础上,用转角向径表示截面上各板的转角,用弯矩矢量表示各板的内力,使翘曲变形的基本方程的力学涵义和几何意义更为直观,从而较方便地导出计算各种翘曲变形的方法和结论.本文认为,在薄壁杆件中,不仅一对等值反向弯矩应组成力因素--双力矩;一对等值反向的双力矩,也应组成新的力因素--四力矩.同理,在截面图形中,不仅存在描述截面是否发生刚性扭转的扭转中心,而且存在描述截面是否发生相对扭转的双扭中心.它们都是同等重要的几何点.本文在建立新概念时,力求形象具体,推理方法尽量和计算平面变形的方法相同,使翘曲变形的计算和平面变形的计算能和谐地衔接成一体.目前,在工程中,随着材料质量的提高,溥壁杆件的应用更广,进一步探讨薄壁杆件的计算问题在实用上是有意义的.     

卷边槽形截面受弯构件畸变屈曲计算方法研究

采用能量法分析冷弯薄壁型钢卷边槽形开口截面受弯构件弹性畸变屈曲应力及其畸变屈曲稳定系数。通过与有限条法分析的畸变屈曲应力进行对比分析,表明建议的畸变屈曲应力计算公式具有较高的精度,通过简化计算得到畸变屈曲稳定系数计算公式及部分加劲板件的局部畸变屈曲统一计算公式;给出了卷边槽形截面受弯构件考虑畸变屈曲的稳定承载力计算方法。最后通过分析计算受弯构件试验的构件承载力并与试验结果进行对比,表明本文提出的计算方法是合理的,相对于现行GB 50018—2002《冷弯薄壁型钢结构技术规范》能更准确地计算受弯构件部分加劲板件屈曲稳定系数及卷边槽形截面构件的稳定承载力。     

基于哈密顿理论的槽形梁桥剪力滞后分析

基于薄壁杆件结构双向弯曲理论,计及其剪切变形与纵向翘曲,引入纵向位移的插值函数,建立了考虑剪力滞后影响的槽形截面梁桥受弯分析的哈密顿对偶求解体系,用半离散精细积分法求该体系的高精度数值解。计算结果表明,本方法具有较高的精度和适用性,可方便地用于槽形截面梁桥的计算。     

考虑剪力滞后的薄壁杆件振动

本文根据位移变分原理，用一个叫做有限杆元法的离散方法对任意截面形状的薄壁杆件进行动力分析。动力分析除了考虑薄壁杆件的翘曲变形和扭转变形外，还考虑了反映剪力滞后现象的杆壁中面上剪应变的影响，与有限单元软件包COSMOS／M的计算结果比较，本文的方法能够精确，灵活和有效地进行薄壁杆件的动力分析。     

冷弯薄壁型钢受弯构件整体弯曲变形直接计算方法研究

对于冷弯薄壁型钢构件来说,目前的国外设计规范大多采用有效截面法来考虑局部屈曲对构件变形的影响.由于冷弯薄壁型钢构件的板件宽厚比较大,在正常使用阶段除了发生局部屈曲之外还可能发生畸变屈曲,从而影响构件的变形性能.通过探索一种无需求解构件的有效截面特性,利用全截面直接求解受弯构件整体弯曲变形的计算方法(简称“直接变形法”)...     

多室箱形梁非线性有限元分析

本文将单箱多室箱梁离散为若干个空间梁段单元,梁段单元的弯曲、扭转及其横截面翘曲均采用三次插值函数描述,其拉压变形采用线性插值。为了计算箱梁顶、底板的面外弯曲,剪力滞后及横截面畸变,采取横向有限条的概念,从梁段单元截取单位厚度的空腹桁架;取桁架的每根杆件为一平面梁单元,用三次插值函数描述其位移,单元节点位移参数用三次多项式表示为箱梁梁段单元节点位移参数的函数。箱梁各横隔板取为有结点转角的四结点平面单元,用基于连续介质力学的Ｕ．Ｌ．列式虚功增量方程,考虑剪切变形影响建立各种单元的弹塑性平衡方程。按照上述思路编制了计算程序,计算结果与模型测试结果接近。     

Large deflection analysis of flexible plates by the meshless finite point method

The classical finite difference technique and methods based on series expansions can only be adopted for solving plates with simple geometry, loading and boundary conditions. In contrast, the finite element method has been widely used for general analysis of bending and flexible plates (coupled bending and in-plane effects). Lack of stress continuity and relatively expensive mesh generation and remeshing schemes have led to the emergence of meshless methods, such as the finite point method (FPM). FPM is a strong form solution which combines the moving least square interpolation technique on a domain of irregularly distributed points with a point collocation scheme to derive system governing equations. In this study, coupled nonlinear partial differential equations of fourth order are solved to analyse large deflection behaviour of plates subjected to lateral and in-plane loadings. Several plate problems are solved and compared with analytical solution and other available numerical results to assess the performance of the proposed approach.     

The influence of the in-plane warping on the behavior of thin-walled beams

The paper presents a theoretical study of the importance of the in-plane deformation on the structural behavior of thin-walled isotropic and composite beams which are subjected to bending and torsional moments. To separate the effects of the out-of-plane warping and the in-plane warping, the overall solution methodology is based on a generic combination of two complementary “inner” and “outer” solutions. The inner model is based on numerical optimization tools which are employed to determine the in-plane deformation that will ensure a stationary (minimum) state of the total potential energy. The outer model performs global solution for cross-sections that are rigid in their own plane but includes the out-of-plane warping. The overall solution is capable of determining the influence of the in-plane warping on any existing approximate numerical scheme that do not include this deformation component. The results correlate well with known analytic solutions for isotropic tubes under pure bending. A parametric study of the relative importance of the in-plane warping as a function of the geometry and the loading parameters in rectangular thin-walled isotropic and composite beams is also presented along with some buckling considerations.     

塔-线耦联对输电塔抗地表变形的影响研究

以典型的110kV双回路自立式耐张塔为例,通过ANSYS有限元软件建立单塔和塔-线耦联体系两种有限元模型,研究了两种模型在采动区地表变形下的内力响应差异。有限元分析结果表明:塔-线耦联的影响使得整塔杆件在地表变形下最大轴向力比单塔模型增加了一倍多,各杆件的轴向力都增加显著;塔-线耦联作用使得整塔杆件在地表变形下的平面内弯矩也有所增加,但与轴向力的变化相比较为平缓;单塔和塔-线耦联体系杆件的最大截面应力都发生在塔腿根部主材上,应力值差别不大,但塔-线耦联体系整个结构其它杆件的截面应力都增加明显,塔-线耦联作用对输电塔抗地表变形性能的影响不容忽视。     

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.     

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。     

Dynamic buckling of thin-walled viscoplastic columns

The purpose of this paper is the analysis of strain-rate effect in dynamic stability of thin-walled orthotropic column of closed rectangular cross-section, subjected to in-plane pulse loading of finite duration. For the solution the first-order shear deformation theory displacement field is employed with the Green–Lagrange strain tensor application. The effect of strain rate sensitivity is included in the framework of the viscoplasticity constitutive Perzyna model for material behaviour under high strain rate loading. The numerical results are obtained with the finite element method application. In the performed analysis the strain-rate effect influence on the dynamic buckling load is examined as well as the initial imperfections of walls, pulse shape and the orthotropy ratio are considered. The results of dynamic criteria application are compared furthermore.     

Flexural-torsional buckling of shallow arches with open thin-walled section under uniform radial loads

An arch with an open thin-walled section that is subjected to a radial load uniformly distributed around the arch axis may suddenly buckle out of its plane of loading and fail in a flexural-torsional buckling mode. The classical flexural-torsional buckling load for an arch with an open thin-walled section under a uniform radial load has been obtained by a number of researchers, based on the consideration that the uniform radial load produces a uniform axial compressive force without in-plane bending prior to the occurrence of flexural-torsional buckling. This assumption is correct for deep arches. However, the uniform radial load may produce substantial bending actions in shallow arches prior to flexural-torsional buckling, and so the classical buckling analysis based on the assumption of uniform axial compression may produce incorrect flexural-torsional buckling loads for shallow arches. This paper investigates the flexural-torsional buckling of shallow arches with an open thin-walled section that are subjected to a radial load uniformly distributed around the arch axis. It is found that shallow arches under a uniform radial load are subjected to combined in-plane compressive and bending actions prior to flexural-torsional buckling, and that using the classical buckling solution for circular arches under uniform compression produces incorrect buckling loads for shallow arches. A rational finite element model is developed for the flexural-torsional buckling and postbuckling analysis of shallow arches with an open thin-walled section, which allows the buckling loads to be obtained correctly.     

用无网格有限点方法对柔性板的大挠度分析

基于级数展开的经典差分法只适用于分析具有简单几何特性、加载和边界条件的板。相反,有限元法却可以广泛应用于分析柔性板(弯曲和平面内作用)。应力不连续以及网格划分复杂导致了无网格分析法的出现,如有限点法(FPM)。有限点法是结合了带插值的最小二乘法和不规则点分布的一种方法,可以采用其推导出系统的控制方程。研究中,采用耦合的4阶非线性偏微分方程,分析板在侧向和平面内加载作用下的大挠度性能。研究中同时也解决了板的其他一些问题,并且利用其他的数值分析结果对文中提出的方法进行了评估。     

预制蝶形腹板混凝土箱梁抗弯性能研究

为了解预制蝶形腹板混凝土箱梁在荷载作用下的受力特点、破坏形态、变形能力以及腹板中钢筋内力分布等情况,设计制作了预制蝶形腹板混凝土箱梁试件,并对其受弯性能进行了试验研究,采用对称加载,得到了完整的荷载-挠度曲线,沿高度纵向应变曲线、钢筋屈服曲线、沿纵向跨径方向挠度曲线。研究表明,在对称荷载作用下,预制蝶形腹板混凝土箱梁表现为弯曲破坏,同时,伴随着弯剪断腹板接缝处出现断裂,结构失效。针对挠度,对比分析了费氏空腹理论变形公式计算值、有限元分析值和试验值,三者吻合性良好,研究结果可为预制蝶形腹板混凝土箱梁的进一步研究和工程应用提供参考。     

Calculation of pure distortional elastic buckling loads of members subjected to compression via the finite element method

An analysis procedure is presented which allows to calculate pure distortional elastic buckling loads by means of the finite element method (FEM). The calculation is carried out using finite element models constrained according to uncoupled buckling deformation modes. The procedure consists of two steps: the first one is a generalised beam theory (GBT) analysis of the member cross-section, from which the constraints to apply to the finite element model are deduced; in the second step, a linear buckling analysis of the constrained FEM model is performed to determine the pure distortional loads. The proposed procedure is applied to thin-walled members with open cross-section, similar to those produced by cold-forming. The distortional loads obtained are rather accurate. They are in agreement with the loads given by GBT and the constrained finite strip method (cFSM).