各国规范轴心受压构件相关稳定设计方法对比分析

钢结构轴心受压构件在板件宽厚比超过一定范围时会发生整体局部相关失稳。介绍美国、欧洲、中国和英国4种钢结构设计规范中关于轴心受压构件相关稳定的设计方法,并以焊接工字型截面轴心受压构件为例对各种规范的设计方法进行对比分析。美国钢结构设计规范通过引入屈曲折减系数Q对强度进行折减的方法考虑板件局部屈曲的影响,欧洲和英国钢结构设计规范均采用有效截面面积考虑板件的局部屈曲,并对构件长细比进行一定程度的折减。我国钢结构设计规范对于轴心受压构件相关稳定的设计方法仍需进一步研究和完善。     

高强度等边单角钢轴压构件稳定设计研究回顾与问题探讨

高强度单角钢轴压构件的稳定性能因其材料的屈服强度等力学性能改变而发生变化,因而在稳定设计及其相关研究中会遇到许多新的问题。针对这一现状,结合我国GB 50017-2003《钢结构设计规范》、美国钢结构设计规范ANSI/AISC 360-05和ASCE 10-97等三部规范,对设计规范中宽厚比限值规定的适用性、高强度角钢宽厚比限值制定的必要性、角钢构件长细比的计算,以及现有角钢轴压构件稳定计算的折减方法等问题进行了探讨和算例分析,基于稳定的基本理论和数据结果的对比分析,解释并给出了上述几个问题的确定性结论和需要注意的方面,为高强度单角钢轴压构件稳定设计方法的研究提供了参考。     

圆形钢管混凝土柱抗压强度

通过对24个钢管混凝土柱(CFST)施加轴向压力直到破坏的试验,以研究其性能。试验中考虑的变量包括钢管的长度、直径、强度和混凝土的强度。由于长细比较大,造成系列1中的所有组合柱发生整体弯曲屈曲而破坏。尽管系列2试验中的组合柱也经历了整体弯曲屈曲,但"短柱"的破坏是由混凝土压碎和钢管失效引起的。将试验结果与采用南非规范(SANS10162-1)和欧洲规范(EC4)计算得到的荷载值进行对比表明,2种规范结果均偏保守,对系列1试验,分别达到8.4%和13.6%,对系列2试验,分别达到10.5%和20.2%。压力与竖向变形曲线显示受压柱具有很好的延性。     

Interaction of bending and axial compression of stainless steel members

The paper deals with the buckling behaviour of stainless steel members with the main focus on developing design formulae for use in the latest version of the European Standard EN 1993-1-4: Eurocode 3-Design of steel structures-Part 1-4: General rules — Supplementary rules for stainless steel. Brussels; 2005.It is based on numerical simulations of single span members of various section type, which are subjected to axial compression and bending. Both flexural buckling and lateral-torsional buckling are dealt with so that the buckling behaviour of both I-sections and hollow sections can be covered.On the basis of these numerical results interaction factors have been derived in context with the design model for member design in Eurocode 3-1-1. For statistical evaluation the test results available from other authors have been used.The outcome of this investigation has been incorporated in the present EN 1993-1-4 as a recommendation in restricted form.     

960 MPa高强度钢材轴心受压构件局部稳定试验研究

针对960 MPa高强度钢材轴心受压构件的局部稳定性能,对4个箱形截面试件和4个工字形截面试件进行了轴心受压试验。分析了试件的局部稳定性能,并将试验结果与我国、美国和欧洲钢结构设计规范的相应设计计算结果进行了对比分析,研究各国规范对960 MPa高强度钢材轴心受压构件局部稳定性能设计计算的适用性。研究结果表明：当构件的板件宽厚比相同时,960 MPa高强度钢材构件的局部屈曲后强度要大于460 MPa高强度钢材构件,960 MPa高强度钢材构件应考虑钢材的屈曲后强度;我国现行钢结构设计规范中关于轴心受压构件局部屈曲应力的计算结果不适用于960 MPa高强度钢材构件;在试验钢材板件宽厚比范围内,960 MPa高强度钢材构件的局部屈曲承载力,采用美国规范和欧洲规范的设计计算结果较为准确。     

Buckling of steel shells subjected to non-uniform axial and pressure loading

The paper presents theoretical and numerical studies of the buckling of steel shells subjected simultaneously to axial and pressure loading. The type of combined non-uniform loading used for this analysis (horizontal pressure and wall frictional pressure which occurs in the silos) is given in the Eurocode 1 part 4. An Abaqus program was used to study the influence of the parameters affecting the strength of the shell. The results of this parametric study were used to develop a new semi-analytical method for the prediction of the critical stress of the stiffened and isotropic shells. The corresponding formulae are compared, in different examples of geometrical shells, with the results obtained by finite element simulation and by the formulae for buckling design given in recommendation EC3.     

冷弯薄壁型钢檩条两种稳定计算模式的比较

讨论国家规范GB50018-2002《冷弯薄壁型钢结构技术规范》“和欧盟规范EC3-1-3对冷弯薄壁型钢檩条承载能力的两种计算模式的差异：拉条和屋面板对檩条抗扭约束刚度及其整体稳定的重要影响,进行檩条畸变屈曲和翘曲应力的计算,评估工程实践中可滑动的卷边咬合式屋面板对檩条的抗扭约束刚度以及拉条的构造等对檩条的工况作用问题。对工程实践具有重要参考价值。     

冷弯薄壁型钢轴压构件畸变与整体相关屈曲承载力计算方法研究

基于我国《冷弯型钢结构技术规范》(征求意见稿)和北美规范及澳洲/新西兰规范中的直接强度法,利用国内外已有的试验数据,计算了60根破坏模式为畸变与整体相关屈曲的轴压试件以及50根破坏模式为畸变屈曲的轴压试件的承载力。通过计算值与试验值的对比分析表明：我国《冷弯型钢结构技术规范》(征求意见稿)中直接强度法所计算的轴压试件畸变与整体相关屈曲的承载力与试验值之比的平均值接近1.0,结果较为理想;计算所得的轴心受压试件畸变屈曲的承载力明显高于试验值,偏于不安全。基于上述结果,对《冷弯型钢结构技术规范》(征求意见稿)中直接强度法计算畸变屈曲的承载力提出了相应建议,即畸变与整体相关屈曲的承载力计算公式和畸变屈曲的承载力计算公式不应统一,应区别对待或给出附加核查条件,在计算畸变半波长度和畸变屈曲的承载力时,采用屈服荷载而非构件整体稳定承载力。     

考虑局部屈曲的矩形钢管混凝土轴压承载力计算方法

基于已有的试验研究与理论分析,给出了矩形钢管混凝土中钢管不出现局部屈曲时的最大宽厚比限值,同时提出大宽厚比下矩形钢管混凝土中考虑钢管屈曲的承载力计算方法。通过回归分析给出了矩形钢管混凝土轴压短柱、轴压中长柱的承载力简化计算公式,简化计算结果和大量试验结果进行对比,用试验结果验证了简化计算结果的正确性。同时,采用CECS、DBJ、EC4、LFRD及AIJ规程计算了矩形钢管混凝土承载力并和试验结果进行对比,对比结果表明:欧洲EC4规程、DBJ规程及简化计算结果与试验结果较为接近,所提出的简化计算公式不仅适用于普通宽厚比下矩形钢管混凝土承载力计算,且适用于大宽厚比下考虑局部屈曲时承载力计算,实现了普通壁厚和薄壁矩形钢管混凝土承载力计算公式的统一。     

卷边加强冷弯型钢梁局部和畸变屈曲

设计时,应重点考虑冷弯型钢构件的屈曲特性及其导致的有效性损失,以保证结构的经济性。数值模型改进后,能够反映考虑几何缺陷、材料非线性特性、后屈曲性能等因素的冷弯型钢梁的真实屈曲特性。针对侧向约束下冷成型Z型钢梁,采用已有的有限元模型,研究钢梁卷边及其与受压翼缘的相互作用对后屈曲特性的影响。利用卷边翼缘宽度比以及卷边倾角,观测局部屈曲、畸变屈曲和局部/畸变屈曲相互作用下截面抗弯刚度的变化。评估了EC3中适用于冷成型Z型钢梁局部和畸变屈曲的设计方法的有效性。总体而言,采用EC3计算的截面抗弯刚度并不保守。指出其中的不足并提出改进建议,改善卷边受压翼缘的失稳系数。     

不锈钢轴心受压柱弯曲屈曲承载力分析

为给我国《不锈钢结构技术规范》中轴心受压柱弯曲屈曲稳定部分的编制提供依据,对国外已有的同类构件的设计方法和试验研究数据进行搜集和对比。结果表明：目前的欧洲不锈钢结构设计规范和美国冷成型不锈钢结构设计规范中计算该类构件的公式均存在一定不足。依据搜集到的199个方管、矩形管、圆管、椭圆管、焊接H形钢和冷弯C型钢截面柱的试验数据,根据冷弯效应及残余应力对轴心受压构件稳定性能的影响,将构件依据截面形式分为A、B、C三类,其中方管、矩形管和冷弯C型钢为A类,圆管和椭圆管为B类,焊接H形钢为C类,三类轴心受压稳定曲线均采用Perry公式形式表达。与试验数据对比表明：采用三类曲线能较好地估算构件的稳定承载力且离散性较小。对提出的计算式进行可靠度分析,结果表明其可靠度指标β满足我国GB 50068-2001《建筑结构可靠度设计统一标准》的要求。     

Local and distortional buckling of cold-formed steel beams with edge-stiffened flanges

The economic use of cold-formed steel members means that buckling and the possible loss of effectiveness it produces are important features of design. The prediction of the true buckling behaviour of cold-formed steel beams accounting for all governing features such as geometrical imperfections, material nonlinearity, postbuckling etc. has been possible with the development of advanced numerical modelling. The FE models developed in previous research have been used in this paper to investigate the effect of edge stiffeners (lips) and their interaction with compression flanges on the postbuckling of laterally restrained cold-formed Z-section beams. Depending on the lip size-to-flange width ratio and angle of inclination of the edge stiffener, the cross-sectional bending resistance varied and transitions between local, distortional and combined local/distortional buckling were observed. The suitability of the design treatments available in Eurocode 3 (EC3) for local and distortional buckling of cold-formed Z-section beams was assessed. Overall, the EC3 predictions for cross-sectional bending resistances were unconservative. Some shortcomings were identified and some suggestions for improvements were made. This included improvements in plate buckling factors for edge-stiffened compression flanges.     

碳纤维复合材料加固圆形中空截面钢管梁设计

将碳纤维复合材料(CFRP)薄板粘结在圆形中空截面(CHS)钢管表面是一种提高截面结构性能的新方法。CFRP薄板用于钢管截面加固,设计时需了解其对钢材圆形截面的限制能力。该文给出了用CFRP加固CHS钢管抗弯能力的估算方法。CFRP箍环对管壁的约束能够减少局部纵弯失稳的影响。设计时将CFRP箍环的弹性模量作为纵向CFRP弹性模量的一部分,以此考虑CFRP箍环的影响。纵向CFRP将管壁的局部纵弯失稳的影响降至最低,最终增加钢管的局部抗弯刚度和强度。对现有设计准则,尤其是AS/NZS4600(2005),AS4100(1998)和EC3中所包含的加固影响参数进行了讨论。考虑了不同CFRP数量、纤维箍环弹性模量和钢材屈服强度对加固的影响。采用CFRP-CHS钢管的强度曲线和参数类型来描述其强度提高程度。     

Design of CFRP-strengthened steel CHS tubular beams

External bonding of carbon fibre reinforced polymer (CFRP) sheets to the periphery of steel circular hollow sections (CHS) is a relatively new technique for structurally improving such sections. Design of CFRP sheets for strengthening tubular steel sections necessitates the prediction of the capacity of confined steel circular sections. This paper presents a design method for evaluating the capacity of CFRP-strengthened steel CHS subjected to bending. The hoop FRP reduces the effect of local buckling by restraining the tube wall. The influence of hoop CFRP is considered in the proposed method by taking its modulus of elasticity as a proportion of the elastic modulus of longitudinal CFRP. The excitation of the longitudinal CFRP minimises the effect of local buckling in the tube wall, which ultimately increases the local flexural stiffness and strength of the tube. The inclusion of the effects of strengthening parameters in current design rules, notably the Australian Standards AS/NZS 4600 (2005) and AS 4100 (1998) and the European Standard EC 3, is discussed. The strengthening effects considered here are those that arise from varying amount of CFRP, modulus of elasticity of the hoop fibre and steel yield strength. Strength curves for composite CFRP-steel CHS are provided to illustrate the extent of enhancement with the type of the parameter.     

高强度钢材工字形截面轴心受压短柱局部稳定试验研究

针对高强度钢材焊接工字形截面轴心受压短柱的局部稳定性能,对9个Q460C工字形截面短柱进行轴心受压试验,分析试件局部屈曲应力、极限应力随板件宽厚比的变化规律,研究翼缘、腹板嵌固系数的取值。此外,将屈曲应力、极限应力试验结果与我国、美国和欧洲钢结构设计规范的相应设计计算结果进行对比分析,研究相应规范对于高强度钢材的适用性。结果表明：翼缘的嵌固系数可取为定值1.0,腹板的嵌固系数不宜取为定值;GB 50017-2003《钢结构设计规范》中关于高强度钢材工字形截面短柱的局部屈曲应力的计算结果是不合理的;AISC 360-05规范的极限应力计算值误差较大,但偏于保守;Eurocode 3规范的极限应力计算值与试验值较为接近,但大部分计算结果较试验值偏大。为此,建议提出新的公式计算工字形截面短柱的局部屈曲应力,而对Eurocode 3规范关于工字形截面短柱的极限应力计算公式进行修正,使其能适用于Q460C高强度钢材。     

Development of a consistent buckling design procedure for tapered columns

EC3–EN 1993-1-1 provides several methodologies for the stability verification of members and frames. When dealing with the verification of non-uniform members in general, with tapered cross-section, irregular distribution of restraints, non-linear axis, castellated, etc., the code mentions the possibility of carrying out a verification based on 2nd order theory; however, several difficulties are noted when doing so, in particular when the benefit of plasticity should be taken into consideration.Other than this, there are yet no guidelines on how to apply standardized, easily reproducible rules as those contained in Section 6.3.1 to 6.3.3 of the code to non-uniform members. As a result, practical safety verifications for these members are often carried out using conservative assumptions, not accounting for the advantages non-uniform members provide. In this paper, firstly, available approaches for the stability verification of non-uniform members are discussed. An Ayrton–Perry formulation is then derived for the case of non-uniform columns. Finally, and followed by a numerical parametric study covering a range of slenderness, cross-sections and fabrication process, a design proposal is made for the relevant case of in-plane flexural buckling of linearly tapered columns subject to constant axial force. The proposal is consistent with current rules for uniform columns provided in EC3-1-1, i.e., clause 6.3.1.     

中外钢结构设计规范安全度设置水平的比较研究

本文选择了国内外几本有代表性的钢结构设计规范,包括中国《钢结构设计规范》GB50017-2003和《美国钢结构建筑物荷载及抗力系数设计规范》LRFD-2001及欧洲钢结构试行标准EC3—1993,从相当安全系数的角度,对三本规范中的轴心受拉、轴心受压、梁受弯、偏心受压等基本构件在承载能力极限状态下的强度或稳定性的相当安全系数,进行了计算分析和比较,获得了中外钢结构设计规范安全度水平差异的定量数据,提出了调整我国钢结构设计规范基本构件的安全度设置水平的有关建议,可供我国钢结构设计规范今后修订时参考。     

非加劲钢板剪力墙弹塑性设计研究

为解决钢板剪力墙难以应用国内规范设计的问题,采用有限元软件ANSYS对钢板剪力墙在剪切荷载作用下的弹塑性屈曲性能进行分析,系统比较初始缺陷、宽高比和高厚比等参数对钢板剪力墙弹塑性屈曲性能的影响,提出衡量弹塑性屈曲性能的合理参数。通过数值模拟,并结合现有规范,提出钢板剪力墙弹塑性稳定的实用设计公式。与有限元计算结果的比较表明,该公式精度良好,且便于应用。     

轴向压力下多边形管柱局部屈曲的稳定性研究

对多边形薄壁钢管柱的局部屈曲进行试验研究。对3种不同截面形式(八边形、十二边形和十六边形)的6根柱进行轴向压缩试验。对于每种截面,均考虑其长细比和宽厚比的影响,并且在试验前精确测量材料的几何缺陷。试验结果显示材料的局部屈曲破坏形式取决于其截面形状。此外,材料的长细比是影响局部屈曲的主要因素。依据22组多边形薄壁钢管柱的轴心压缩试验结果对ASCE48-05、EC3、Migita和Fukumoto设计方程局部屈曲性能的预测结果进行评估。指出设计方程的缺点,Loov方程使用基于极限应力概念的新参数对方程进行了调整,使其能够适用于多边形管柱。与试验结果进行对比分析验证了新建方程的准确性。     

Stability investigation of local buckling behavior of tubular polygon columns under concentric compression

This paper presents experimental tests conducted to investigate the local buckling behavior of thin-walled tubular polygon steel columns. The experimental program consists of six stub columns with three different cross-sections, octagonal (eight-sided), dodecagonal (twelve-sided) and hexdecagonal (sixteen-sided), tested under concentric compression. For each cross-section, two values of the plate slenderness ratio (plate width-to-thickness ratio) are considered. Accurate measurements of geometrical imperfections are taken prior to the test. The experimental results show that the local buckling mode of failure depends on the type of the cross-section. Moreover, the plate slenderness ratio is the main factor controlling the local buckling capacity. Design equations provided in the ASCE 48-05, the EC3 and Migita and Fukumoto to predict the local buckling capacity of tubular polygons are evaluated against experimental results of 22 polygons tested under concentric compression available in the literature. Based on drawbacks observed in the design equations, the Loov's equation developed on basis of the ultimate stress concept is adjusted with new fitting parameters to fit for tubular polygon columns. The accuracy of the new equation is evaluated through a comparison with the experimental results.