Inelastic buckling behavior of stocky plates under interactive shear and in-plane bending

Inelastic buckling and postbuckling behavior of stocky plates under combined shear and in-plane bending stresses are investigated and compared to slender plates. Aluminum and steel plates having various slenderness ratios are modeled and analyzed by means of (i) numerical nonlinear finite element method and (ii) theoretical p-Ritz energy method; and both results are compared to the classic interaction equation. It is observed that whereas in slender plates, elastic buckling occurs prior to the material's proportional limit load, stocky plates buckle in an inelastic way within the post-yield stage. In contrast to slender plates with considerable postbuckling reserves, the buckling of stocky plates is immediately followed by softening. In addition, it is shown that the classic interaction equation overestimates buckling loads; and therefore, a modified equation that can safely be applied to both stocky and slender plates is proposed.     

Plastic shear buckling of unstiffened stocky plates

A number of moderate to stocky steel and aluminum plates, with various slenderness ratios and boundary conditions are numerically analyzed under the action of pure in-plane shear and the results are validated against available analytical methods. Numerical non-linear finite element analyses are performed to assess different theoretical approaches and to picture buckling behaviors of moderate stocky plates. It is observed that while thick stocky plates possess some post-yield capacity during the hardening stage prior to plastic buckling, moderately thick plates yield and buckle concurrently followed by softening due to sudden loss of stiffness. It is also concluded that changes in the modulus of elasticity and shear modulus should be considered in the analysis and that the secondary bending stresses induced by initial out-of-plane curvature can cause significant reduction in the post-yield capacity and ultimate resistance of stocky plates.     

Buckling and postbuckling behavior of unstiffened slender curved plates under uniform shear

Buckling and postbuckling behavior of curved plates under in-plane shear are investigated. After revisiting classic elastic buckling results, the elastoplastic postbuckling behavior and the effects of curvature parameter and aspect ratio are simulated via geometrical and material nonlinear analyses. Imperfection sensitivity is studied for various imperfection shapes and magnitudes. An increase in curvature parameter raises the elastic buckling load, produces unstable buckling and reduces postbuckling reserves. The buckling load and shear capacity are higher in shorter plates. Small initial imperfections are found to have severe effects on the initial buckling load of plates with large curvature parameter, but little effect on ultimate postbuckling capacity.     

Ultimate capacity of battened columns composed of four equal slender angles

Cold-formed steel structural members play a great role in modern steel structures due to their high strength and light weight. The behavior and strength of battened column members composed of slender angle sections are mainly governed by local buckling of angle legs or torsional buckling of the angle between batten plates. Moreover, local buckling depends on the interaction between the width–thickness ratio of angle leg, overall slenderness ratio of angle between batten plates and overall slenderness of column. Theoretical study has been carried out by a nonlinear material and geometrical finite element model. Numerous cases of slender battened column sections having different width–thickness angle leg ratios, overall slenderness ratios between batten plates and overall slenderness ratios are chosen in this study. Complete ultimate strength curves are drawn and different failure modes are studied by taking different member lengths, which produce local or torsional buckling of single angles between batten plates or overall buckling of the member. Empirical equations for the effect of shear deformation factor and the ultimate axial load capacities of members formed of battened slender angle sections are proposed. Strengths of axially loaded battened members predicted using finite element as well as the proposed empirical equations is compared with the design strengths obtained using North American and European codes. It is concluded that the design strengths predicted by North American and European codes are generally conservative, and these design rules have been shown to be reliable using reliability analysis.     

加固钢柱的非线性屈曲性能研究

尽管加固设计方法很多,负荷焊接加固技术由于耐久可靠仍然被广泛地应用于既有钢结构的加固领域.以某电厂钢支架结构加固设计为例,应用一种负荷下钢柱翼缘外侧贴焊钢板的加固技术,采取在翼缘和钢板之间点焊加强二者的共同作用.为了验证该加固技术的可行性,并得到对工程结构设计有实际意义的非线性屈曲极限荷栽,运用通用有限元分析软件ANS...     

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。     

High strength thin-walled rectangular concrete-filled steel tubular slender beam-columns,Part II: Behavior

Experimental and numerical research on full-scale high strength thin-walled rectangular steel slender tubes filled with high strength concrete has not been reported in the literature. In a companion paper, a new numerical model was presented that simulates the nonlinear inelastic behavior of uniaxially loaded high strength thin-walled rectangular concrete-filled steel tubular (CFST) slender beam-columns with local buckling effects. The progressive local and post-local buckling of thin steel tube walls under stress gradients was incorporated in the numerical model. This paper presents the verification of the numerical model developed and its applications to the investigation into the fundamental behavior of high strength thin-walled CFST slender beam-columns. Experimental ultimate strengths and load-deflection responses of CFST slender beam-columns tested by independent researchers are used to verify the accuracy of the numerical model. The verified numerical model is then utilized to investigate the effects of local buckling, column slenderness ratio, depth-to-thickness ratio, loading eccentricity ratio, concrete compressive strengths and steel yield strengths on the behavior of high strength thin-walled CFST slender beam-columns. It is demonstrated that the numerical model is accurate and efficient for determining the behavior of high strength thin-walled CFST slender beam-columns with local buckling effects. Numerical results presented in this study are useful for the development of composite design codes for high strength thin-walled rectangular CFST slender beam-columns.     

钢-竹组合工字形柱轴压性能试验研究

为研究钢-竹组合工字形轴心受压构件性能,设计制作了18根工字形柱试件,以含钢率与长细比为基本参数,对其进行了轴压试验,观测了试件的破坏形态和变形特征,分析了各参数对试件轴压性能的影响规律,得到了组合柱在轴压荷载作用下的荷载-位移关系,基于钢材与竹材本构关系使用纤维模型法推演了荷载-位移全过程曲线.通过分析组合柱的屈服条...     

焊接结构屈曲后承载力分析

目前,GB50018-2002《冷弯薄壁型钢结构技术规范》对冷弯薄壁型钢中受压板件屈曲后强度的利用进行了相关规定,GB50017-2003《钢结构设计规范》仅对承受静力荷载和间接承受动力荷载焊接梁腹板的屈曲后强度进行了考虑。为此,对焊接结构中板件考虑屈曲后强度的极限承载力进行深入研究,提出焊接结构中均匀受压板件在考虑几何缺陷和残余应力时的计算公式。此公式计算结果与GB50018-2002的接近,且公式形式简捷实用,可供工程设计使用。     

均匀剪力作用下无加劲肋的细长曲面板的屈曲和后屈曲性能

研究平面内剪力作用下曲面板的屈曲和后屈曲性能。回顾经典的弹性屈曲分析,通过对几何和材料非线性的分析,模拟了弹塑性后屈曲性能、及曲率参数和长宽比的影响。通过各种不同大小和级别的缺陷的影响分析,研究缺陷敏感度。随着曲率的增大,弹性临界荷载增大,并且产生不稳定屈曲现象,以及使后屈曲承载力储备减少。微小的初始缺陷都会引起较大曲率的曲面板的初始屈曲,但是几乎不会影响板的极限承载力。     

不锈钢焊接工字形截面短柱轴压局部稳定性能试验研究

对奥氏体型S30408和双相型S22253两种牌号的15个不锈钢焊接工字形截面短柱开展轴压局部稳定试验研究,考察截面组成板件的局部稳定性能和截面承载力,得出了试件截面的应力-应变关系曲线。研究结果表明：厚实截面的试件承载力高于其截面屈服荷载,试件截面应力-应变关系曲线表现出典型的非线性特性和应变硬化特征;而宽肢薄壁截面的组成板件发生过早的局部屈曲,使得试件承载力不能达到截面的屈服荷载,需要对截面强度进行折减。基于得出的试验结果和现有的其他试验数据,对现有设计方法,包括欧洲规范EN 1993-1-4和美国规范SEI/ASCE 8-02中的有效宽度法以及直接强度法计算得出的截面承载力进行评估,表明根据欧洲规范EN 1993-1-4和直接强度法计算得到的截面承载力偏于保守,而美国规范SEI/ASCE 8-02对宽厚比较大的截面承载力计算偏于不安全,而且计算离散性较大。     

往复剪切荷载作用下双波形薄钢板的弹塑性 屈曲行为

为研究双波形薄钢板在达到或接近钢材屈服时的弹塑性屈曲行为,完成了4个不同螺栓间距的双波形薄钢板试件和1个单片波形薄钢板试件在往复剪切荷载作用下的拟静力试验。结果表明:设计合理的双波形薄钢板能够先达到全截面屈服抗剪承载力,然后在往复剪切荷载作用下交替发生弹塑性局部剪切屈曲,形成X形屈曲褶皱及撕裂裂缝而破坏; 双波形薄钢板的极限抗剪承载力大于单片波形薄钢板的2倍,最大提高约18%; 双波形薄钢板的滞回曲线表现出一定的“捏拢”现象,在其抗剪承载力达到峰值之后,随着滞回圈数的增加其抗剪承载力和卸载刚度退化明显,但其等效黏滞阻尼系数无显著下降; 双波形薄钢板在剪切荷载作用下可分为弹性、弹塑性局部屈曲以及承载力退化3个工作阶段,由于波形钢板的“手风琴”效应,双波形薄钢板基本不具备屈曲后抗剪承载力,其极限抗剪承载力状态即为弹塑性局部剪切屈曲状态。     

基于广义塑性铰线法的压弯钢构件极限承载力计算

采用广义塑性铰线法对H形截面钢构件绕强轴压弯区段板件组的极限状态进行了分析,并选用合理假定求解受压翼缘屈曲后达到的极限承载力;分析了表征极限状态截面的应力分布,并研究了周边板件约束与受压翼缘板件厚实程度对屈曲翼缘发展塑性的影响;采用考虑板件屈曲相关的等效荷载法分析了构件截面极限状态应力分布,针对广义塑性铰线法相对于传统塑性铰线法的适用性拓展及其应用现状,分析其存在的问题并做出解答;将计算结果与试验结果及有限元结果进行了对比。结果表明:基于广义塑性铰线法可准确预判构件绕强轴压弯的极限承载力。     

Linear and non-linear behaviour of steel plates with circular and rectangular holes under shear loading

In this work, linear buckling and the non-linear behaviour of steel plates with one perforation subjected to shear loading was studied. The influence of the dimension, position with respect to the two main axes, shape (circular or rectangular) and orientation of a hole with respect to the panel slenderness and aspect ratio were all investigated.In both circular and rectangular holes, the strong influence of hole dimensions on the shear buckling coefficient was observed, and the values of the shear buckling coefficient fell with the plate aspect ratio. Small differences in buckling coefficients were noted in rectangular plates with various hole diameters, and buckling coefficients were practically not influenced by the orientation of the rectangular hole. In both rectangular and circular holes, the coefficient remained constant, regardless of hole position for a given distance from the edge.Linear buckling and non-linear behaviour were compared by observing different shear failure modes for slender and thick perforated plates. Elastic and plastic regions were found, on the basis of critical slenderness, for some common geometries.     

圆端形钢管混凝土柱偏压性能研究

圆端形钢管混凝土柱具有外观优美、截面布置灵活、承载力高和施工方便等优点,已被应用于实际工程中.为了研究圆端形钢管混凝土长柱的偏压性能,完成了 12根圆端形钢管混凝土柱的偏压试验,变化参数为偏心距和长细比.结果表明:该类柱的承载力随偏心距和长细比的提高而降低,而其延性随偏心距和长细比的提高而增加;达到峰值荷载前,圆端形钢...     

Non-linear analysis of perforated steel plates subjected to localised symmetrical load

Although the literature contains a number of studies which have been developed to describe the non-linear behaviour of ordinary plates, few works are available on perforated plates, and studies on non-linear behaviour of perforated plates under localised symmetrical load are not studied in depth. The aim of this paper is to provide some insights into the elasto-plastic behaviour of plate girder web panels with circular holes under localised symmetrical load.Numerical analyses of square and rectangular perforated plates with centred and eccentric holes were developed. Results provide new insights into post-critical mechanisms in perforated plates subjected to localised loads when the length of the symmetrical compressive load, hole diameter and steel yield limit vary. An increase in the critical slenderness of the plate (a value at which transition from elastic to plastic collapse occurs) and a corresponding reduction in the elastic critical load occur when the dimensions of the hole increase. A further increase in the critical slenderness occurs when the length of the localised load is reduced. High-performance steel may be subject to buckling with a lower possibility of post-critical mechanisms: a reduction in critical slenderness occurs when the steel grade increases. Lastly, numerical analyses of slender and thick perforated plates were developed and their results compared.     

带约束拉杆双层钢板内填混凝土组合剪力墙抗震性能试验研究

提出一种带约束拉杆双层钢板内填混凝土组合剪力墙,通过对6个剪跨比为2.0、轴压比为0.6的此类剪力墙试件的低周往复加载试验,研究试件的破坏形态、滞回曲线、骨架曲线、承载力退化、刚度退化、位移延性系数和耗能等抗震性能。结果表明：带约束拉杆双层钢板内填混凝土组合剪力墙抗震性能良好,6个试件的屈服位移角平均值为1/147,极限位移角平均值为1/48,位移延性系数平均值为3.57;减小约束拉杆间距和采用梅花式布置约束拉杆的方式,能更好地对钢板和混凝土提供约束,延缓钢板局部屈曲,增大混凝土的极限变形能力,提高剪力墙承载力、延性和耗能能力,减缓承载力退化和刚度退化,改善剪力墙抗震性能。     

Analysis on shear capacity and energy dissipation of corrugated steel plate shear wall with openings

为明确波形钢板剪力墙不发生屈曲的界限条件并分析开洞对其承载力及耗能能力的影响，基于波形钢板剪切屈曲理论推导其屈曲应力计算式，并采用数值分析及变形等级划分方法得到约束刚度比取值范围，由此提出波形钢板剪力墙不发生屈曲的界限条件为屈曲应力大于剪切屈服应力且约束刚度比大于3。通过对比开洞模型的变形等级计算参数，验证界限条件对开洞波形钢板墙的适用性，建立有限元模型研究钢板墙高宽比、钢板厚度、开洞率、洞口高宽比及洞口位置对波形钢板墙承载力及耗能能力的影响。结果表明：钢板高宽比越小、板厚越大，开洞对其承载力及耗能能力的削弱程度越大，洞口高宽比在0.33~0.5之间时开洞波形钢板墙的承载力及耗能最大，中心开洞时的最小。基于波形钢板剪力墙全截面剪切屈服的受力机理对其受剪承载力和塑性耗能计算式进行推导，并通过拟合得到考虑洞口参数影响的开洞波形钢板剪力墙受剪承载力及耗能折减系数计算式；通过9组不开洞模型和30组不同洞口尺寸及位置的开洞模型对计算式的有效性进行验证。结果表明计算值与模拟值的误差均在15%以内，适用于满足无屈曲界限条件的开洞波形钢板剪力墙。     

开洞波形钢板剪力墙受剪承载力及耗能能力分析

为明确波形钢板剪力墙不发生屈曲的界限条件并分析开洞对其承载力及耗能能力的影响,基于波形钢板剪切屈曲理论推导其屈曲应力计算式,并采用数值分析及变形等级划分方法得到约束刚度比取值范围,由此提出波形钢板剪力墙不发生屈曲的界限条件为屈曲应力大于剪切屈服应力且约束刚度比大于3。通过对比开洞模型的变形等级计算参数,验证界限条件对开洞波形钢板墙的适用性,建立有限元模型研究钢板墙高宽比、钢板厚度、开洞率、洞口高宽比及洞口位置对波形钢板墙承载力及耗能能力的影响。结果表明：钢板高宽比越小、板厚越大,开洞对其承载力及耗能能力的削弱程度越大,洞口高宽比在0.33～0.5之间时开洞波形钢板墙的承载力及耗能最大,中心开洞时的最小。基于波形钢板剪力墙全截面剪切屈服的受力机理对其受剪承载力和塑性耗能计算式进行推导,并通过拟合得到考虑洞口参数影响的开洞波形钢板剪力墙受剪承载力及耗能折减系数计算式;通过9组不开洞模型和30组不同洞口尺寸及位置的开洞模型对计算式的有效性进行验证。结果表明计算值与模拟值的误差均在15%以内,适用于满足无屈曲界限条件的开洞波形钢板剪力墙。     

纯压圆弧形钢管桁架拱平面内稳定性能及设计方法

目前针对钢管桁架拱平面内稳定性能及承载力的研究较少,缺少相应的设计方法。提出了钢管桁架拱截面剪切刚度表达式,考虑剪切变形的影响推导了纯压两铰圆弧桁架拱屈曲荷载的简化计算公式以及换算长细比表达式。基于有限元方法,全面分析了截面高宽比、矢跨比、腹杆夹角及腹杆截面尺寸等不同参数对平面桁架拱和空间桁架拱弹性屈曲性能的影响,结果表明采用简化公式与有限元分析结果吻合良好。借鉴实腹拱和格构柱的稳定设计方法,采用大挠度弹塑性有限元法系统研究了平面及空间纯压桁架拱的相关稳定承载力,发现节间弦杆长细比与桁架拱整体长细比的比值是衡量局部稳定对整体稳定影响的关键参数,在此基础上提炼出纯压桁架拱的相关作用影响系数,并拟合得到了纯压桁架拱的稳定设计曲线,从而为一般荷载作用下压弯桁架拱的稳定承载力的设计奠定了基础。