Post-buckling strength of rectangular concrete-filled steel tube panels

为研究矩形钢管混凝土壁板的屈曲后强度，根据平板的弹塑性屈曲理论并考虑残余应力的影响，确定了板件发生塑性屈曲、弹塑性屈曲和弹性屈曲的正则化界限宽厚比。采用试验验证的有限元模型进行了宽厚比为20~150、钢材屈服强度为275~960 MPa的矩形钢管混凝土壁板局部屈曲分析，以界限宽厚比为控制点，根据有限元结果拟合出了矩形钢管混凝土壁板的有效宽度计算式。研究结果表明：弹性屈曲板件的屈曲后强度提高程度显著高于弹塑性屈曲板件；屈曲后强度的提高程度与钢材屈服强度无明显相关性；与无面外约束钢板相比，混凝土的单侧约束作用可使板件的屈曲后强度普遍提高约50%；提出的矩形钢管混凝土壁板的正则化界限宽厚比和有效宽度计算式与试验结果吻合较好，有效宽度试验值比所提公式计算值平均增大7.2%，标准差为0.091。     

初始缺陷对矩形钢管混凝土柱壁板屈曲后强度的影响

为了研究焊接残余应力和几何初始缺陷对矩形钢管混凝土柱壁板屈曲后强度的影响,采用有限元软件ABAQUS进行参数分析,参数包括壁板的屈服强度、宽厚比、几何初始缺陷取值大小、是否施加几何初始缺陷和焊接残余应力,并考虑两者耦合作用,给出考虑焊接残余应力和几何初始缺陷后的矩形钢管混凝土柱壁板有效宽度计算公式,并与试验数据进行比较。结果表明:建立的有限元模型能较好地模拟壁板的局部屈曲和屈曲后行为,焊接残余应力和几何初始缺陷都会降低壁板屈曲后强度,且焊接残余应力的影响较大; 不同强度等级的钢材都需要考虑焊接残余应力和几何初始缺陷的影响,对于屈服强度大于460 MPa的高强钢材,当宽厚比大于65时,可以忽略几何初始缺陷的影响; 给出的有效宽度计算公式可以较为准确且偏保守地预测矩形钢管混凝土柱壁板屈曲后强度。     

基于壁板屈曲后强度的矩形钢管混凝土偏压承载力计算方法

为了准确计算大宽厚比矩形钢管混凝土短柱偏压承载力,通过有限元方法对非均匀受压单侧约束平板的屈曲性能进行了研究,给出了该类板件的弹性屈曲系数计算公式。以此为基础,结合有效宽度法,提出了基于壁板屈曲后强度的矩形钢管混凝土偏压承载力计算方法。为验证所提计算方法的准确性,建立了大宽厚比钢管混凝土短柱偏压试验数据库,并将该计算方法与各规范的计算方法进行了对比。结果表明:提出的两种大宽厚比矩形钢管混凝土偏压承载力计算方法具有较高的计算精度,计算结果与试验结果吻合良好,其中方法二能够准确地评估构件的偏压承载力,可用于大宽厚比矩形钢管混凝土短柱偏压承载力计算中。     

矩形高强钢管混凝土壁板弹塑性屈曲及宽厚比限值解析解

钢管混凝土壁板的局部屈曲可通过限制其宽厚比来避免.为了得到矩形高强钢管混凝土柱壁板的宽厚比限值,将其简化为受混凝土单侧约束板,以薄板的弹塑性局部屈曲理论为基础,采用Bleich近似计算方法和Ramberg-Osgood高强钢材本构模型,推导出了受单侧约束板在均布压应力作用下的弹塑性屈曲应力,得到了矩形高强钢管混凝土柱壁...     

矩形钢管混凝土柱T形加劲肋设计方法

基于钢板弹性屈曲理论,提出了矩形钢管混凝土柱内设置T形加劲肋的技术措施和设计方法。对于板件宽厚比较大的矩形钢管混凝土柱,沿钢管壁纵向设置T形加劲肋,由于T形加劲肋翼缘部分包裹于混凝土内部,充分发挥加劲肋与混凝土的共同工作性能,改善钢管壁局部屈曲性能。采用能量法并考虑内部混凝土对钢管壁的侧向支撑作用,基于均匀受压四边固支板简化计算模型,推导了内设置T形加劲肋的柱壁板件临界应力计算公式。通过控制钢管壁全截面有效,并考虑加劲肋界限刚度比影响,提出了矩形钢管混凝土柱的T形加劲肋刚度限值要求。结果表明:T形加劲肋与混凝土的共同工作显著改善了钢管壁的局部屈曲性能;对于大宽厚比矩形钢管混凝土柱,通过合理设计T形加劲肋,仍可使钢管壁全截面有效,即先发生屈服而不是局部屈曲。     

设平板加劲肋矩形钢管混凝土柱屈曲性能分析与设置原则研究

文中根据能量变分原理,采用瑞利-里兹法对设肋钢管混凝土钢管板件的局部屈曲性能进行研究,推导出设肋板件（刚性基层）屈曲系数,并在此基础上推导得到平板加劲肋的最小刚度要求。然后,对影响加劲肋最小截面刚度的因素进行分析,分析结果表明,加劲肋最小截面刚度和加劲肋面积与钢管壁板件面积的比值、管壁宽厚比、钢材屈服强度、钢管壁抗弯刚度有关;随着钢管壁宽厚比的增大,所需加劲肋最小抗弯刚度增大;随着加劲肋设置道数的增加,所需加劲肋最小抗弯刚度减小。最后,建立大量经试验验证了的ABAQUS有限元模型进行参数分析,数值计算参数分析结果较好地验证了文中所推导解析解的正确性。数值计算结果表明,当加劲肋的设置满足本文提出的最小刚度要求时,大宽厚比的钢管板件能够达到全截面有效,可按照我国相关规范进行承载力设计。     

PBL加劲型矩形钢管混凝土轴压柱局部屈曲性能分析

为研究开孔钢板连接件（PBL）加劲肋对矩形钢管混凝土轴压柱局部屈曲性能的影响,用能量法推导钢管屈曲系数计算公式,引入PBL和加劲肋相对刚度计算式并分析二者对屈曲模式的相互作用关系,讨论了PBL加劲型钢管的极限屈曲模式及其极限屈曲系数、最大相对宽厚比限值。结果表明:PBL加劲肋可明显改善钢管局部稳定性,钢管屈曲系数k随着PBL加劲肋刚度增加而增大,直至达到极限屈曲系数42.68;PBL连接件可减小板件纵向屈曲的波长,而加劲肋的影响作用与之相反;设置PBL加劲肋后,钢管的最大相对宽厚比限值可达184,并且板件屈曲后强度随宽厚比的变化曲线下降趋势减缓,强度值随着PBL刚度增加而逐渐提高。     

薄壁开孔矩形钢管轴压下局部稳定分析

局部屈曲是薄壁矩形钢管的一种主要屈曲模式,分析时应考虑板组间的相关作用。开孔后,将导致应力重分布,进而改变构件的屈曲性能。应用ANSYS有限元软件对薄壁开孔矩形钢管构件轴压下的局部屈曲性能进行了分析研究,讨论了板件宽厚比、翼缘腹板宽度比、开孔率等参数对局部屈曲性能的影响。     

矩形钢管混凝土柱管壁局部屈曲性能研究

对矩形钢管混凝土柱钢管壁的局部屈曲性能进行了分析研究。用有限条法计算出了各种应力梯度作用下管壁的局部屈曲临界应力σcr和局部屈曲系数k0 ,并将得到的屈曲系数代入到有效宽度统一法则中 ,得到了保证管壁不发生局部屈曲时板件的宽厚比、高厚比的限值表达式。分析结果与《矩形钢管混凝土结构技术规程》(CECS1 5 9:2 0 0 4)中限值的比较表明 ,规程的规定限值是可靠的     

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。     

Finite element analysis of local buckling behavior of steel plates in concrete-filled double steel plate composite shear walls

采用ABAQUS有限元软件对双钢板-混凝土组合剪力墙中外包钢板的局部屈曲行为进行了有限元模拟,分析外包钢板在轴压作用下的局部屈曲和屈曲后的受力性能。共开展了15个模型的有限元分析,模型的变化参数包括钢板的宽厚比和对拉钢筋的列数。分析结果表明：对于列间距和行间距相同的对拉钢筋布置方案,钢板局部屈曲始终发生在相邻两对拉钢筋之间;钢板发生屈曲后,与屈曲位置相邻的对拉钢筋承受较大的拉力,且对拉钢筋拉力随着对拉钢筋间距的减小而增大;增加对拉钢筋列数和减小钢板宽厚比可有效改善外包钢板的局部稳定性能,提高钢板的承载能力和变形能力;相比点约束,线约束对钢板局部屈曲的约束更为有效;无对拉钢筋模型、单列对拉钢筋模型和双列对拉钢筋模型达到屈服强度（345MPa）所需的最小宽厚比分别为25、30和37.5。     

Shear buckling characteristics of cold-formed steel channel beams

Cold-formed steel members are increasingly used as primary structural elements in the building industries around the world due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. However, their shear capacities are determined based on conservative design rules. For the shear design of LCB web panels, their elastic shear buckling strength must be determined accurately including the potential post-buckling strength. Currently the elastic shear buckling coefficients of LCB web panels are determined by assuming conservatively that the web panels are simply supported at the junction between their flange and web elements. Hence finite element analyses were conducted to investigate the elastic shear buckling behavior of LCBs. An improved equation for the higher elastic shear buckling coefficient of LCBs was proposed based on finite element analysis results and included in the ultimate shear capacity equations of the North American cold-formed steel codes. Finite element analyses show that relatively short span LCBs without flange restraints are subjected to a new combined shear and flange distortion action due to the unbalanced shear flow. They also show that significant post-buckling strength is available for LCBs subjected to shear. New equations were also proposed in which post-buckling strength of LCBs was included.     

Elastic shear buckling characteristics of LiteSteel beams

LiteSteel beam (LSB) is a new cold-formed steel hollow flange channel beam. The unique LSB section is produced by a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. To date, limited research has been undertaken on the shear buckling behaviour of LSBs with torsionally rigid, rectangular hollow flanges. For the shear design of LSB web panels, their elastic shear buckling strength must be determined accurately including the potential post-buckling strength. Currently the elastic shear buckling coefficients of web panels are determined by assuming conservatively that the web panels are simply supported at the junction between the flange and web elements. Therefore finite element analyses were carried out to investigate the elastic shear buckling behaviour of LSB sections including the effect of true support conditions at the junction between their flange and web elements. An improved equation for the higher elastic shear buckling coefficient of LSBs was developed and included in the shear capacity equations of Australian cold-formed steel codes. Predicted ultimate shear capacity results were compared with available experimental results, both of which showed considerable improvement to the shear capacities of LSBs. A study on the shear flow distribution of LSBs was also undertaken prior to the elastic buckling analysis study. This paper presents the details of this investigation and the results including the shear flow distribution of LSBs.     

Analytical calculation of local buckling and post-buckling behavior of isotropic and orthotropic stiffened panels

A methodology for the analytical assessment of local buckling and post-buckling behavior of isotropic and orthotropic stiffened plates is presented. The approach considers the stiffened panel segment located between two stiffeners, while the remaining panel is replaced by equivalent transverse and rotational springs of varying stiffness, which act as elastic edge supports. A two-dimensional Ritz displacement function (pb-2 Ritz) is utilized in the solution of the local buckling problem of isotropic and laminated symmetric composite panels with arbitrary edge boundary conditions. The buckling analysis of the segment provides an accurate and conservative prediction of the panel local buckling behavior. Consequently, the developed methodology is extended in the prediction of the post-buckling response of stiffened panels of which the skin has undergone local buckling. Of high importance for the calculation of the post-buckling behavior is the selection of appropriate boundary conditions for the structural members analyzed. A comparison of the present methodology results to respective finite element (FE) results has shown a satisfactory agreement.     

夹层板轴向受压时屈曲后性能的有限元分析

以Narayan Pokharel,Mahen Mahendran试验[1]模型为研究依据,用有限元法对受单向轴向压力作用的夹层板进行了屈曲以及屈曲后性能分析。根据Winter公式计算出了板件的有效宽度,并与有限元计算结果以及试验结果进行比较,发现当夹层板宽厚比较大时,Winter公式过高地估计了板件的有效宽度,结果是偏于不安全的。最后,提出了有效宽度的建议公式。     

Finite element analysis and design of sandwich panels subject to local buckling effects

Past research into the local buckling behaviour of fully profiled sandwich panels has been based on polyurethane foams and thicker lower grade steels. The Australian sandwich panels use polystyrene foam and thinner and high strength steels, which are bonded together using separate adhesives. Therefore a research project on Australian sandwich panels was undertaken using experimental and finite element analyses. The experimental study on 50 foam-supported steel plate elements and associated finite element analyses produced a large database for sandwich panels subject to local buckling effects, but revealed the inadequacy of conventional effective width formulae for panels with slender plates. It confirmed that these design rules could not be extended to slender plates in their present form. In this research, experimental and numerical results were used to improve the design rules. This paper presents the details of experimental and finite element analyses, their results and the improved design rules.