Tension buckling and parametric instability characteristics of doubly curved panels with circular cutout subjected to nonuniform tensile edge loading

This paper deals with the study of tensile buckling, vibration, and parametric instability behaviour of doubly curved panels with central circular cutout subjected to uniaxial in-plane partially distributed tensile edge loadings using finite element method. First order shear deformation theory is used to model the curved panels, to consider the effects of the transverse shear deformation and rotary inertia. The vibration analysis for this problem shows that for certain parameters of the tensile loading, the frequencies of the panel initially rise with the load, but begin to decrease with increasing tension, showing the onset of tension buckling. The parametric instability behaviour under tensile periodic edge loading with different load parameters shows that instability regions are influenced by the cutout size, load width and its location.     

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.     

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.     

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 strengthenings

This paper studies the buckling behaviour of simply supported square plates, which have weakening or strengthening bands. The weakening/strengthening bands are equally spaced and their thickness is either decreased or increased. The analysis assumes that the stress state in the plate before and during the buckling process remains in the elastic range. Two cases of plate loading are studied, one with compressive forces and one with tangential forces. The buckling coefficients are calculated for different numbers and thicknesses of strengthening/weakening bands. The thickness of strengthening/weakening bands and the thickness of the remaining plate is varied so that the volume/weight of the plate remains constant. In one case it is found that the buckling load at constant weight of the plate can be increased by 118% if an optimal ratio of the thickness of strengthening bands and the thickness of the remaining plate is used.     

装配式可退化支撑受力性能分析及试验研究

装配式可退化支撑主要由外筒、内筒、核心板及约束部件组成，通过对其承载力退化及受力性能进行分析，提出描述可退化支撑恢复力特性的力学模型。通过3组装配式可退化支撑的低周往复加载试验对其构造的可行性进行验证，研究不同核心板厚度对滞回特性、承载力退化及耗能能力的影响，并与提出的力学模型的分析结果进行对比。结果表明：无论在压力或拉力作用下，可退化支撑均可通过核心板的局部受压屈曲实现支撑整体承载力的退化；支撑受拉、受压承载力具有较好的对称性，刚度与耗能能力呈现不对称的特点；相同初始挠度下，可退化支撑的相对承载力随核心板厚度增加而提高；可退化支撑通过核心板屈曲耗能，耗能能力随核心板厚度的增加而提高；三折线恢复力模型能够有效地反映支撑构件的实际受力情况。     

Parametric instability of edge cracked plates

The presented paper deals with the parametric instability behavior of a simply supported rectangular plate with a crack emanating from one edge, subjected to in-plane compressive periodic edge loading. The problem is reduced to computing the free vibration frequencies and the corresponding mode shapes and substituting them into an integral equation based formula, which leads to a compact matrix form. Once the components of this matrix are found, the rest of the computation, i.e., establishing regions of instability, buckling loads and modified frequencies, is straightforward and fast. Several plates, each with a different dimension and crack length size are analyzed using this approach. The comparison of results with those of finite element models is found to be in close agreement.     

屈曲约束钢板剪力墙受力性能分析及盖板简化计算方法

内嵌钢板与混凝土盖板之间相互作用机理较为复杂,难以通过简单方法确定屈曲约束钢板墙连接螺栓拉力与混凝土盖板弯矩.为此,采用有限元软件ABAQUS建立屈曲约束钢板剪力墙计算模型,并通过与模型试验对比验证其可靠性.通过非线性有限元数值模拟,分析钢板高厚比、盖板与钢板厚度比以及盖板与钢板间隙等参数对应力分布、屈曲变形和滞回性能...     

Experimental study of low yield point steel gusset plate connections

Concentrically braced frames have been used widely in the seismic-resistant design of steel building structures. During earthquake excitation, the braces of the concentrically braced frame are subjected to recursive tensile and compressive forces. The compressive strength of the brace is usually less than its tensile strength because of the buckling of the brace, and this may degenerate the seismic resistance capacity of the braced frame. In this reported research, an alternative design concept that adopts the weak gusset plate-strong brace is examined. The gusset plate is designed to yield prior to the buckling of the brace. Low yield point (LYP) steel is selected for the gusset plate. The LYP steel possesses low yield strength and high elongation capacity. A series of experimental studies was carried out to examine the LYP steel gusset plates under cyclic loads. It is found that adding slot-type restrainers (STR) to the LYP steel gusset plate greatly enhances the seismic resistance of the gusset plate. The proposed LYP steel gusset plate with an STR is able to provide similar strengths under tensile and compressive loads. The energy dissipation capacity of the gusset plate is also increased substantially. Based on this study, suggestions are made for the design of LYP gusset plates.     

低屈服点钢扣板连接的试验研究

同心支撑框架被广泛用于钢结构房屋的抗震设计中。在地震激励下,同心支撑框架的支撑会承受循环拉压荷载。由于支撑的屈曲,其抗压强度通常低于抗拉强度,这可能会降低支撑框架的抗震性能。该文对采用弱扣板强支撑的设计理念进行了验证。扣板选用低屈服点钢(LYP),从而使设计的扣板在支撑屈曲前发生屈服。低屈服点钢的屈服强度很低,但其延性很好。通过一系列试验验证循环荷载作用下低屈服点钢扣板的性能。研究发现,在低屈服点钢扣板上增加槽型约束(STR)可以大大提高其抗震性能。在拉压荷载作用下,有槽型约束的低屈服点钢扣板可以提供类似大小的强度。扣板的耗能能力同样得到提高。基于此研究成果,给出低屈服点钢扣板的一些设计建议。     

脱层材料与槽接式挫屈束制支撑的性能研究

挫屈束制支撑耐震性能优劣与否与脱层材料性能有密切关系,首先提出了一种估算脱层不完全因子的方法,利用4组分别使用不同脱层材料的挫屈束制支撑进行构件试验;研究结果表明以黏性橡胶作为脱层材料具有可靠性、经济性与优良的施工性。特别介绍了地震工程研究中心近期所研发的槽接式挫屈束制支撑,并通过3组实尺寸构件试验验证了其耐震性能;测试构件包含一组长度为12.5m,最大抗压强度超过16800kN,核心消能段应变量达3.5%的构件。试验结果表明,新研发的槽接式挫屈束制支撑经济效益极高,迟滞消能行为良好稳定,具有优良的耐震性能,各组试体于试验停止前所累积的总非线性变形量皆超过400倍斜撑屈曲位移量;研究亦显示,非线性结构分析软件PISA3D可准确预测其受力与变形反应。     

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.     

Stiffened steel plates under uniaxial compression

The stability of steel plates stiffened with tee-shape sections under uniaxial compression and combined uniaxial compression and bending was investigated using a finite element model. The emphasis of the work presented in this paper was to find the parameters that uniquely describe the strength and behaviour of stiffened steel plates. A finite element model, validated using the results of tests on full-size stiffened plate panels, was used to investigate the scale effect for five dimensionless parameters. The parameters investigated were: the transverse slenderness of the plate, the slenderness of the web and flange of the stiffener, the ratio of torsional slenderness of the stiffener to the transverse slenderness of the plate, and the stiffener-to-plate area ratio. Average magnitude residual stresses and initial imperfections were assumed for this study.A parametric study covering a wide range of dimensionless parameters indicated that stiffened steel plates do not fail by stiffener tripping unless a bending moment is applied to create flexural compressive stresses in the stiffener. Although plate buckling and overall buckling were found to lead to a very stable post-buckling behaviour, the interaction between these two buckling modes was found to give rise to a sudden loss of capacity following initial plate buckling. The plate transverse slenderness, the stiffener slenderness-to-plate slenderness ratio, and the stiffener-to-plate area ratio were found to have a significant effect on this behaviour.A comparison of the numerical analysis results with API and DnV design guidelines indicates that the guidelines predict stiffened steel plate capacity with various degrees of success, depending on the governing mode of failure. Neither guidelines address the potential interaction-buckling phenomenon.     

Buckling of cracked functionally graded plates under tension

Buckling of functionally graded cracked plates under tension has not been investigated so far. In this paper critical buckling load of functionally graded plates containing a crack has been obtained using classical plate theory through the finite element method. Displacement in vicinity of crack tips has been approximated using previous solutions related to bending of cracked plates. Effect on buckling of plate under uni-axial and bi-axial tension of different parameters, such as plate dimensions and material properties, are studied. Results show that the critical load decreases as material gradient index increases, while bi-axial loading leads to higher critical loads compared to uni-axial case.     

Interactive instabilities of thin‐walled laminated composite pultrusion box columns

The problem of interactive buckling and post‐buckling of intermediate length thin‐walled columns built of laminated plate elements subjected to compressive load has been proposed and solved analytically. Pultrusion columns have wide‐range applications in high‐rise building due to their low weight and high load carrying capacity. Classic stability theory and laminate theory were implemented to prove the existence of mixed‐mode buckling in thin‐walled pultrusion columns. Interactive stability modes can result in lower loading capacity of most compressive members and affects their post‐buckling behaviour in major proportions. Interactive buckling load analysis has been performed by means of a simplified theoretical model and verified by means of numerical analysis. The calculations were carried out for commonly used square section thin‐walled composite columns dimensions. The post‐buckling performance of selected sections has been investigated and an optimum layup configuration criterion for each section has been extracted according to pre‐ and post‐critical behaviour. Copyright © 2010 John Wiley & Sons, Ltd.     

Inelastic seismic response of steel bracing members

A survey of past experimental studies on the inelastic response of diagonal steel bracing members subjected to cyclic inelastic loading was carried out to collect data for the seismic design of concentrically braced steel frames for which a ductile response is required under earthquakes. The parameters that were examined are the buckling strength of the bracing members, the brace post-buckling compressive resistance at various ductility levels, the brace maximum tensile strength including strain hardening effects, and the lateral deformations of the braces upon buckling. Equations are proposed for each of these parameters. In addition, the maximum ductility that can be achieved by rectangular hollow bracing members is examined.     

The effects of local buckling and material yielding on the axial stiffness and failure of uniformly compressed I-section and box-section struts

The behaviour of thin-walled compression members is known to be significantly influenced by the effects of local buckling. Thin-walled sections lose axial compressive stiffness and the compressive carrying capability of the members can be considerably reduced as a result of the effects of local buckling. Finite element simulation is employed in this paper to examine the post-buckled response of thin-walled I-section and box-section struts, giving due consideration to the influence of geometric imperfections and to elasto-plastic material behaviour. A detailed account of the growth and redistribution of stresses after local buckling as well as the initiation of yielding and yield propagation throughout loading is given in the paper. The influence of different in-plane displacement boundary conditions imposed in the simulations at the section plate junctions is also detailed in the paper as well as the effect of yielding on the post-buckled stiffness and failure of the sections. It is shown that the effects of geometrical imperfections are most prominent for strut designs with near simultaneous buckling and yielding and that the ultimate failure and unloading of strut designs, in general, is synonymous with the development of yielding at the section junctions along the full length of the struts and through to the middle surface of the section walls.     

Reliability of pressurised pipelines subjected to longitudinal ground movement

A methodology was developed to calculate the probabilities of tensile rupture and compressive local buckling for pressurised pipelines that are buried in unstable slopes and subjected to longitudinal loading imposed by the slopes. The limit state functions were established by comparing the tensile and compressive strain demand with the corresponding strain capacities. The strain demand is calculated using an analytical model reported in the literature, which is capable of accounting for the elastic–plastic behaviour of the pipeline and the elastic–perfectly plastic behaviour of the pipe–soil friction. The strain capacities are characterised based on the information available in the literature. The spatial variability of the soil and pipe properties is incorporated in a simplified manner. A numerical example was used to illustrate the proposed methodology and impact of the spatiality variability of the soil and pipe properties on the failure probability. The analysis results suggest that the spatial variability of pipe wall thickness and yield strength tends to increase the failure probability, whereas the spatial variability of the soil ultimate resistance tends to decrease the failure probability.     

Time-dependent in-plane behaviour and buckling of concrete-filled steel tubular arches

This paper presents a theoretical analysis for the time-dependent behaviour and buckling of concrete-filled steel tubular (CFST) circular arches due to shrinkage and creep of the concrete core under a sustained uniform radial load. The algebraically tractable age-adjusted effective modulus method is used to model the time-dependent behaviour of the concrete core, based on which the differential equations of equilibrium for the time-dependent analysis of CFST arches are derived and analytical solutions for the long-term displacements, stresses and internal forces of CFST arches under the sustained load are obtained. It is shown that the visco-elastic effects of creep and shrinkage of the concrete core have significant long-term effects on the in-plane structural behaviour of CFST arches. The long-term radial and axial displacements, as well as the bending moment, increase substantially with time. For a CFST arch with a low area ratio of the steel tube to the concrete core, the long-term deformations may be excessive and affect the serviceability of the CFST arch. The increases of the long-term stresses in the steel tube with time are significant, while the long-term stresses in the concrete core decrease with time and may change from compressive to tensile if the time is sufficiently long. It is demonstrated that the time-dependent change of the equilibrium configuration of the CFST arch can lead to a buckling configuration being attained in the time domain under a sustained load, which is lower than the buckling loads of the CFST arch under short-term loading. The solution for the possible prebuckling structural life for time-dependent creep buckling of deep CFST arches is derived and can be used to determine the effects of various parameters on the creep buckling of a CFST arch.     

Compressive behavior of central gusset plate connections for a buckling-restrained braced frame

Buckling-restrained braced frames (BRBFs) are used as lateral-load resisting systems in seismic design. The braces in BRBFs are connected to beams and columns by gusset plate connections, and can yield in both tension and compression instead of buckling. Although tests of buckling-restrained braces (BRBs) have demonstrated their ability to withstand significant inelastic axial deformation, large-scale BRBF tests have exhibited central gusset plate buckling before BRBs develop the ultimate compressive strength. To extend and better understand the experimental work, this paper presents an analytical study of the compressive behavior for BRBF central gusset plate connections using the finite element computer program ABAQUS. A model of a previously tested BRBF is conducted to predict experimental buckling load of the central gusset plate and verify the accuracy of a simple model of a central gusset plate connection including a beam and part of the BRB. The out-of-plane deformation of the central gusset plate resembles the buckled shape of a gusset plate with low bending rigidity provided by the BRB end. The experimental buckling load of the central gusset plate cannot be predicted based on the AISC-LRFD approach with an effective column length factor of 1.2. Therefore, a parametric study on the compressive strength of BRBF central gusset plate connections is conducted with various gusset plate dimensions and free-edge stiffeners. An inelastic plate buckling equation together with coefficient charts is proposed to predict ultimate load. For gusset plates with sufficient free-edge stiffener rigidity, the yield load can be developed and increased to the post-yield strength level. A required free-edge stiffener size is also recommended for BRBF central gusset plates to develop compressive yield load.