Vibration, buckling and parametric instability behaviour of plates with centrally located cutouts subjected to in-plane edge loading (Tension or compression)

The vibration, buckling and parameterc instability behaviour of a plate with internal opening subjected to in-plane compressive or tensile periodic edge loading are studied. Different shapes and sizes of the cutout are considered. Compression and tension buckling results are discussed. The vibration analysis for this problem shows that for certain parameters of tensile loading and the opening, the frequency of the plate initially rises' with the load, but then begins to decrease with increasing tension showing the onset of tension buckling. Dynamic instability behaviour of the plate under compressive and tensile loading shows that the instability regions are affected by the size, shape of the opening and the loading parameters. Instability behaviour due to all the parameters are discussed.     

Vibration, buckling and dynamic stability of cracked cylindrical shells

The presence of cracks in a structure can considerably affect its behaviour. This paper presents a finite element study on the vibration, buckling and dynamic stability behaviour of a cracked cylindrical shell with fixed supports and subject to an in plane compressive/tensile periodic edge load. The effects of crack length and orientation are analysed. Under tension load, the results show that the frequency of the shell initially increases with the load, but then decreases as the load further increases leading to buckling due to tension load. The size and the orientation of the crack and the loading parameter can all have a significant effect on the dynamic stability behaviour of the shell under both compressive and tensile loading. The effects of these parameters are discussed in detail.     

带有开口增强的复合板在剪切荷载作用下的应力集中和屈曲性能研究

数值和试验研究是了解碳／环氧复合板在面内剪力载荷作用下开口周边补强后应力集中和屈曲性能的两种重要方法。研究了采用四种不同开口型式及材料排列模式下的补强效果。采用有限元分析方法和基于平板理论的研究方法，分析了不同补强设计中的参变量。完成了4个试验板的制造和试验，并验证了分析结果。分析结果和试验结果吻合很好。基于有效分析模型，确定了最佳的开口补强方法。     

Buckling of laminated composite stiffened panels subjected to in-plane shear: A parametric study

The presence of in-plane loading may cause buckling of stiffened panels. An accurate knowledge of critical buckling load and mode shapes are essential for reliable and lightweight structural design. This paper presents some parametric studies on simply supported laminated composite blade-stiffened panels subjected to in-plane shear loading. A total of 450 models were analyzed using ANSYS 7.1 and a database is prepared for different plate and stiffener combinations. Studies are carried out by changing the panel orthotropy ratio, stiffener depth, pitch length (number of stiffeners), smeared extensional stiffness ratio of stiffener to that of the plate and extensional stiffness to shear stiffness ratio of the plate. Based on the studies, few important parameters influencing the buckling behaviour are identified and guidelines for better stiffener proportioning are developed, which will be helpful for the designer.     

Buckling and dynamic instability analysis of stiffened shell panels

The static and dynamic instability characteristics of stiffened shell panels subjected to uniform in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover, the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented through convergence and comparison with the published results from the literature. The effect of various parameters like shell geometry, stiffening scheme, static and dynamic load factors, stiffener size and position, and boundary conditions are considered in buckling and dynamic instability analysis of stiffened panels subjected to uniform in-plane harmonic loads along the boundaries.     

Experimental study of screw connections in CFS-calcium silicate board wall panels

Cold-formed steel (CFS) wall panels with different board materials are used extensively in residential and commercial buildings to resist lateral loads by in-plane shear, in addition to helping the studs resist gravity loads. Generally the screw connection between the board and CFS skeleton frame, which experience shear, dictates the behaviour and strength of such panels. In this paper, details of an experimental study on behaviour and strength of the screw connections between the cold-formed steel profiles and calcium silicate boards, under monotonic and cyclic shear loading, are presented. The objectives of the experimental study are: (a) to develop a new test procedure that realistically represents the behaviour and failure of screw connections in CFS wall panels; (b) to investigate the effect of edge distance of the screws and thickness of the boards on behaviour and strength; (c) to study behaviour under monotonic and cyclic loading; (d) to develop the values of the important parameters that determine the load–deformation behaviour of the screw connection in such wall panels under in-plane shear; and (e) to develop design equation to evaluate the ultimate shear strength and its resistance factor required in load resistance factor design (LRFD).     

边界裂纹导致的剪力墙板性能退化时的屈曲和后屈曲强度分析

目前有很多关于反复荷载作用下细长墙板所出现的疲劳裂纹的报告。裂纹可能最初是由焊接、腐蚀或错误使用造成的。板边裂纹一般会发展到靠近翼缘、加劲肋和其他边界构件。这些裂纹会导致薄壁墙板的承载能力下降。本文主要研究具有板边裂纹的剪力墙板的屈曲和后屈曲性能。假定裂纹与边界平行或者呈常态分布。通过有限元线性和非线性分析,确定裂纹和板的各种几何与力学特性的影响(如裂纹的长度和位置,边界条件,表面比和板材的长细比,材料的泊松比和弹性模量)。结果显示:当张力场区域内产生裂纹时,结构构件的性能会发生退化。     

Postbuckling behaviour of square compression loaded graphite epoxy panels with square and elliptical cut-outs

This paper investigates the influence of cutout shape, size and orientation upon the buckling stability of square CFRP panels. The study undertaken uses the ANSYS Finite Element Code for eigenvalue buckling and the postbuckling responses of the panels. Square panels with clamped edge conditions under displacement loading are considered. Results for square, circular and elliptical cutouts under uniaxial loading are presented. The results are shown for 300 mm square, 2.1 mm thick, 16-ply, quasi-isotropic (0/90/ ± 45)_2s panels with centrally and eccentrically located cutouts.     

Buckling and post-buckling strength of shear panels degraded by near border cracks

There have been many reports on fatigue cracks induced on slender webs breathing under repeated loading. Cracks may also initiate due to welding, corrosion, or mishandling. Edge cracks are generally formed adjacent to the flange, stiffeners or any kind of boundary members. It is also generally accepted that cracks degrade the load bearing capacity of thin panels. The aim of this paper is to investigate the buckling and the post-buckling behaviour of shear panels that have edge cracks. Cracks are presumed to be either parallel or normal to the boundaries. The influence of various geometrical and mechanical characteristics of cracks and panels, (such as the length and the position of cracks, boundary conditions, the aspect ratio and slenderness of panels, and Poisson’s ratio and Young’s modulus of materials) is determined by means of linear and nonlinear finite element analysis. It is shown that a substantial degradation can be anticipated if a crack forms in the area at which tension field occurs.     

Ultimate load of cylindrically curved panels under in-plane compression and bending—Extension of rules from EN 1993-1-5

A numerical study on the post-buckling behaviour of simply supported short cylindrically curved panels, with longitudinal edges unconstrained and loaded edges constrained (internal element of a section), including the influence of curvature and loading type (pure compression and in-plane bending) is presented in this paper. Additional relevant parameters are identified and their influence on the ultimate strength of cylindrically curved panels is studied. Numerical results of the ultimate reduction factor from the parametric study are converted into geometry (width) reduction factors by an iterative routine. Subsequently, an extension of rules for internal plated members’ ultimate load calculation from EN 1993-1-5 is proposed based on the effective width concept. It is concluded that (except for stocky panels) the increase in the curvature parameter led to an increase on the cylindrically curved panel's resistance and that the upper limit proposed by EN 1993-1-5 to the value of the curvature parameter is reasonable. Finally, a statistical study is performed that concludes that the proposed approach provides an accurate estimate of the ultimate load.     

钢-聚氨酯夹层板稳定分析

分别建立了钢-聚氨酯夹层板和普通钢板的有限元模型,在边界条件、加载情况均相同的条件下进行有限元稳定分析,夹层板采用板-实体-板结构模拟,结果表明在相同条件下,夹层板比普通钢板的屈曲强度均有较大程度的提高。同时进行了保持一定条件不变,分别改变夹芯层厚度、面层钢板厚度模拟分析,结果表明在一定范围内,夹芯层厚度与钢面板厚度增大,夹层板的屈曲临界荷载值也随之增大。夹芯层的抗弯刚度和横向剪切变形对板的影响不可忽略。     

Buckling and strength characteristics of some CFRP stiffened curved panels

This paper describes the initial and post-buckling behaviour of CFRP stringer-stiffened curved panels. The panels are of 500-mm radius, 2-mm thickness and have either three or four blade stringers. Initial buckling loads were calculated using the finite strip code VIPASA within the design optimisation program PASCO. An unstiffened, externally supported panel is also considered.Stringer stiffening gave higher buckling loads than external supports. The initial buckling behaviour was influenced by geometric imperfections, and methods of modelling these with PASCO are discussed. The imperfections caused scatter in buckling load, but there was minimal scatter in failure load, despite the presence of impact damage in some cases. The failure loads were about 50% higher than the buckling loads.     

Shear buckling in foam-filled web core sandwich panels using a Pasternak foundation model

Web core panels, foam-filled sandwich panels with interior webs, are a structurally efficient option for transverse load bearing applications. In web core panels, the interaction between the webs and core material can have a substantial impact on web shear buckling strength and is a key element of lightweight structural design. The present work is an investigation of web buckling behavior in web core panels under a distributed load. To solve this problem, web shear buckling was analyzed for the case of pure shear loading with foam support, and this analytic model was extended to the case of panels with a transverse distributed load. The webs are modeled as simply supported plates resting on a Pasternak elastic foundation. To that end, a buckling model for plates on a Pasternak foundation is presented, along with closed-form approximations of the solution for square and infinitely long plates. An accurate model for the foundation constants is developed using energy methods. Applicability of the plate buckling model to web core panels with transverse loads is presented via a finite element study. In panels, the slenderness and spacing of the webs have a slight effect on the boundary conditions between the webs and face sheets. The effect is relatively small, however, and the model presented in this work underpredicts buckling strength by less than 25%. The model in this work is thus a reasonable approach to the practical design of web core panels.     

Numerical modelling for buckling analysis of cracked shear panels

Utilizing shear panels is a common practice in civil, naval and aerospace engineering structures and the performance of the one with thin steel plate shear walls is an interesting issue of ongoing related researches. It is a well-recognized phenomenon that the behaviour, and consequently the design procedure, of shear panels are mostly dominated by pre-yield buckling occurrence. However the existence of crack defects due to corrosion, fatigue, welding or mishandling may shed more complexities to such panels in terms of bearing capacity degradation.

In this paper, a procedure for modelling and analysis of shear panels containing central or edge cracks, using the finite element method, is presented. Results can be incorporated to recognize the required mesh refinements around the crack tips and edges. In addition, the effect of relative crack length on buckling capacity of shear panels is investigated.     

Nonlinear response of laminated cylindrical panels

The geometric nonlinear responses of laminated composite cylindrical panels subjected to (i) axial compression and (ii) central concentrated load are investigated in this work. The parameters considered are: number of layers, symmetric/antisymmetric laminate constructions, cross-ply/angle-ply fibre orientation, boundary conditions and central angle of panel. An eight-node degenerated layered shell element with an efficient explicit through-thickness integration scheme is employed. It has been observed that the cylindrical panels under axial compression exhibit stable post-buckling paths and the number of layers in the laminate for a given total thickness has considerable influence on the load–deflection behaviour. The strength of shallow panels with longitudinal edges hinged, curved edges free and subjected to a central concentrated load is controlled by the limit point load, whereas for deep panels with other parameters remaining the same, the strength is controlled by the bifurcation load. The boundary conditions have significant influence on the load-carrying capacity. The panels with longitudinal edges hinged and curved edges free should be avoided in construction, as they undergo either limit point or bifurcation failure at very low load levels compared with other edge conditions.     

Tension buckling of plate having a hole

Generally, it is believed that buckling of plates never arises under tensile load. However, when a plate has a hole, compression stresses appear locally near the hole under a tensile load, and the compression stress may cause local buckling—so-called tension buckling—of the plate. In this paper, some results of numerical analysis on the tension buckling are presented, and basic behaviour on the tension buckling is discussed.     

Buckling of plates with a hole under tension

An FEM analysis is made on the elastic buckling of plates, each of which has a hole and is subjected to tensile loading.In a general way, no attention is paid to the buckling of plates if they are subjected to a tensile load. However, when a plate has a hole, compressive stresses appear near the hole under a tensile load, and the stress may cause local buckling of the plate.In this paper, stress distributions and buckling behaviours of such plates under tension are studied. Aspect ratios, shapes of holes and so on, are adopted as parameters.Through the analysis, variations of buckling coefficients and buckling modes against aspect ratios are obtained. The effects of the hole shapes on the buckling strength are also discussed.     

十字加劲钢板剪力墙的抗剪极限承载力

我国《高层民用建筑钢结构技术规程》规定了钢板墙剪切弹性屈曲不先于剪切屈服,其明显的不足是没有利用板的屈曲后强度,同时弹性屈曲也不能作为结构在弹塑性阶段的设计指标。本文应用板的大挠度弹塑性有限元方法对十字加劲方形钢板剪力墙的屈曲后性能和极限承载力进行了系统的研究,并在大量数值分析的基础上,提出了以板的平均剪切应变相应的剪应力作为钢板剪力墙承载能力的极限状态,以达到利用薄板屈曲后强度的目的,进而提出了钢板剪力墙承载力的设计简化计算公式及钢板墙侧柱刚度阈值的计算公式,供设计参考。数值计算结果表明,影响钢板墙抗剪性能主要有三个参数:板高厚比、肋板刚度比和边柱刚度。     

薄钢板剪力墙结构水平反复荷载试验研究

给出了薄剪力墙板拉力带对周边框架梁、柱产生的作用力计算公式,以此设计了试件的原型结构。薄墙板采用建筑结构胶和高强度摩擦型螺栓固定在焊于框架梁柱的角钢连接板上。对三层薄钢板剪力墙结构进行水平反复荷载作用下的试验研究,结果表明:墙板先屈曲,后屈服,屈曲后能继续承受荷载,并形成多条非常明显的斜拉力带;二层墙板最先出现屈服,底层墙板屈服时间最晚;试件破坏时,钢框架柱脚及梁柱连接部位形成了塑性铰,柱脚翼缘严重扭曲,腹板向外鼓曲。墙板发生很大的平面外凹凸变形,并有多个裂口,且在靠近角部梁端处出现撕裂。     

Finite Element simulation of dynamic buckling of cylinders subjected to periodic shear

This paper deals with the buckling of cylindrical shells under a dynamic shear load. The aim of our study is to compare static buckling load and buckling load during a sweep frequency excitation. First, we describe the special experimental device and the two Finite Element codes used in this study. In a second part static tests and corresponding Finite Element calculations are presented in order to have a reference buckling load and to understand the effect of initial imperfections. Then, a vibration analysis is performed in order to investigate the effect of geometric imperfection and a preload. In the last part, we discuss dynamic results. When we reach the first eigen frequency, the buckling load drops and the buckling deformations increase due to a parametric resonance. There is a coupling between vibration and buckling modes.