不锈钢箱形截面轴心受压构件整体稳定性有限元研究

为研究不锈钢箱形截面轴心受压构件的整体稳定性,采用ANSYS软件对奥氏体和双相体两种不锈钢箱形截面轴心受压构件的整体稳定性进行了数值模拟,模拟中考虑了材料的非线性本构模型、构件的初始几何缺陷、残余应力的影响。重点通过不锈钢箱形截面构件在轴压作用下的荷载-位移曲线、截面应变发展情况及极限承载力对其整体稳定性能进行阐述。通过对比有限元模拟值、试验值以及根据规范计算的承载力,认为采用ANSYS软件能对不锈钢箱形截面轴心受压构件进行准确地模拟,残余应力对箱形截面的极限承载力影响较小,《钢结构设计规范》(GB 50017—2003)不适用于不锈钢整体稳定性设计。     

钢柱整体稳定性的数值分析方法研究

采用通用有限元软件ANSYS建立轴心受压钢构件有限元模型,对23个已有试验结果钢材焊接截面轴心受压柱的整体稳定受力特性进行有限元分析.详细地介绍了建立有限元模型的具体方法,并给出了分析其整体稳定特性的求解全过程,提出了输入构件几何初始缺陷和模拟截面残余应力的方法.通过将有限元计算结果与相应的试验结果进行对比,验证了本文建立的有限元模型的有效性.计算结果还表明,本方法不仅适用于普通钢材的轴心受压构件计算,而且适用于高强钢轴心受压构件承载力计算.     

高强度等边角钢轴心受压局部稳定的有限元分析和设计方法研究

随着钢结构的发展,高强度热轧等边角钢在钢结构中的应用逐渐增多,如输电铁塔和大跨度桁架等。然而由于强度的提高,较多数量角钢截面的等效宽厚比超过规范的限值,不满足局部稳定的要求。我国现行规范尚未对这一问题给出明确规定。运用通用有限元软件ANSYS建立有限元模型,准确模拟构件的残余应力和几何初始缺陷,对15个高强度热轧等边角钢轴心受压构件的局部稳定受力性能进行有限元分析,并与相应的试验结果进行对比。比较结果表明,建立的有限元模型能够准确模拟几何初始缺陷和残余应力对构件局部稳定受力性能的影响,从而准确地分析计算高强度热轧等边角钢轴心受压构件的局部稳定受力性能。利用已验证的有限元模型,对高强度热轧等边角钢轴心受压构件的局部稳定受力性能进行有限元参数分析,并与美国规范和欧洲规范的设计方法进行对比。结果得到:几何初始缺陷和残余应力对于高强度热轧等边角钢轴心受压构件局部稳定承载力的影响比普通钢材受压构件小;美国钢结构设计规范能够更准确的计算Q420等边角钢轴心受压构件的局部稳定承载力。     

激光焊接不锈钢工字形截面中长柱受力性能研究

为研究激光焊接奥氏体不锈钢工字形截面轴心受压中长柱的承载性能,对10根激光焊接不锈钢工字形薄柔截面中长柱进行轴心受压试验研究,结果表明,中长柱的破坏模式均为板件局部屈曲与构件整体弯曲屈曲的相关失稳。同时,基于残余应力试验,验证了已有激光焊接不锈钢工字形截面的残余应力分布模型。基于试验结果验证了有限元模型,对激光焊接不锈钢工字形截面轴心受压中长柱开展参数分析,研究了几何初始缺陷和残余应力对中长柱稳定承载力的影响,结果表明,残余应力是影响中长柱稳定承载力的主要因素。结合试验和有限元计算结果,对CECS 410:2015《不锈钢结构技术规程》中轴心受压构件稳定承载力设计公式的适用性进行评估,并考虑残余应力的影响修正了轴心受压构件整体稳定设计公式的计算系数。采用修正后计算系数的规范公式能准确计算激光焊接不锈钢工字形截面轴心受压构件的稳定承载力。     

不锈钢方矩管压弯构件平面内稳定承载力理论研究

对不锈钢方矩管截面的平面内稳定承载力进行研究,对两种不同截面,两端铰接的方矩管压弯构件进行数值模拟,在有限元模型中考虑了不锈钢非线性本构关系,冷加工效应和构件的初始缺陷,并与已有的试验数据进行对比,结果验证了有限元模型的准确性。在此基础上,拟合出了适应于工程中常用不锈钢压弯构件截面和长细比的下限相关曲线公式以及计算不锈钢方矩管压弯构件平面内稳定承载力的线性相关算式。为了便于实际应用,该式在形式上与我国GB 50017—2003《钢结构设计规范》保持一致。     

高强钢材焊接工字形截面受压构件有限元分析

运用通用有限元软件ANSYS建立三维有限元模型,模拟两端铰接的高强钢材焊接工字形截面轴心受压与偏心受压的受力性能,并用国内外试验数据验证有限元模型的正确性。在有限元模型建立过程中,对不同强度等级(460,690,960MPa)的高强钢构件进行模拟,充分考虑多种非线性因素以保证模型的正确性。为了充分验证模型,对不同强度等级、构件长度、截面尺寸的构件进行有限元计算,将计算得到的极限承载力与试验结果对比。在此过程中,采用初弯曲等效模型与弯矩等效模型分别模拟轴心受压构件和偏心受压构件。结果表明:该有限元模型有足够的精度,可以较好地模拟实际构件受力性能。     

高强焊接圆钢管轴心受压整体稳定性能设计方法研究

关于高强度焊接圆钢管受力性能的研究尚处于起步阶段,我国《钢结构设计规范》(GB 50017—2003)中针对焊接圆钢管轴心受压构件的整体稳定设计方法缺乏足够的研究依据,因此有必要对焊接圆钢管的整体稳定性能进行深入研究。利用ANSYS有限元软件对试验试件进行数值模拟计算,基于验证模型,对不同强度等级钢材和不同截面尺寸的高强度焊接圆钢管受压构件进行有限元参数分析。通过与国内外规范进行对比,最终对高强度焊接圆钢管的整体稳定设计方法提出两种建议:一是对于高强度焊接圆钢管截面轴心受压整体稳定承载性能可按照我国《钢结构设计规范》(GB 50017—2003)或欧洲规范Eurocode 3的a类柱子曲线进行设计计算;二是基于我国《钢结构设计规范》(GB 50017—2003)和欧洲规范Eurocode 3中的柱子曲线的公式形式,更新柱子曲线的缺陷系数,给出了新的设计曲线。     

卷边C形截面不锈钢柱畸变屈曲直接强度法

为研究轴心受压卷边C形截面不锈钢柱的畸变屈曲承载力,采用ABAQUS软件对不锈钢轴压构件进行了非线性有限元模拟,并通过现有试验验证了有限元模型计算结果的准确性。弹性畸变屈曲荷载是采用直接强度法（DSM）的关键参数,首先研究了边界条件对构件承载力的影响,然后对比分析了现有轴心受压卷边C形截面不锈钢柱畸变屈曲承载力的计算方法与试验结果,发现BECQUE等提出的DSM公式与AISI中的畸变屈曲DSM公式均不能准确地预测卷边C形截面不锈钢构件的畸变屈曲承载力。最后,在大量有限元分析的基础上提出了轴心受压卷边C形截面不锈钢柱畸变屈曲承载力计算公式,并采用现有的试验结果验证了该公式的准确性。     

460MPa级高强度钢材工字形截面轴心受压柱局部稳定有限元分析和设计方法研究

为研究标准屈服强度为460 MPa的高强度钢材工字形截面轴心受压柱的局部稳定受力性能,采用通用有限元软件ANSYS建立有限元模型,考虑残余应力和局部初始几何缺陷的影响,与已有的460 MPa高强度钢材工字形截面轴心受压柱试验进行对比分析,验证了有限元建模方法的正确性。利用经过验证的有限元模型,针对460 MPa高强度钢材工字形截面轴心受压柱的局部屈曲性能进行有限元参数分析,并将已有试验结果、有限元参数分析结果,与中国、美国和欧洲钢结构设计规范中的设计曲线进行对比,提出新的设计公式。结果表明:钢板厚度、钢板长宽比、局部初始几何缺陷幅值和残余压应力值对构件翼缘极限承载力的影响很小,但对翼缘局部屈曲承载力有较大影响;所提出的建议设计计算公式相对于中国、美国和欧洲钢结构设计规范中的设计计算方法,更加适用于460 MPa工字形截面轴心受压柱极限应力和局部屈曲应力的设计计算。     

不锈钢椭圆中空受压构件的结构响应

冷加工不锈钢椭圆中空截面结合了圆形中空截面和不锈钢的美感以及不同几何形状的横截面相对于两个主轴的结构功效。迄今为止,对这种横截面的构件尚没有结构设计指南,主要是产品相对较新,缺乏基础结构试验数据。对冷加工不锈钢椭圆空心截面受压构件的结构响应进行研究,提出设计建议。为获得结构性能的基础数据,进行一系列试验。首先,通过张拉试验建立基本的材料应力-应变关系。随后,通过短柱试验确定横截面的平均受压响应,通过弯曲试验获得极限承载力以确定不锈钢椭圆中空截面合理的弯曲曲线。对试件进行包括初始缺陷的几何性质测定。对试件的荷载位移响应进行记录并在文中给予介绍。与试验同步,进行了有限元模拟。如果有限元模拟的结果与试验结果不相符,将对个别关键参数进行进一步的研究,包括外形比例、横截面长细比和构件长细比。基于试验与数值分析结果,提出3组不锈钢椭圆中空截面受压限值以及椭圆中空截面柱合理弯曲曲线。     

不锈钢轴心受压构件稳定承载能力计算方法研究

国内外不锈钢材料力学性能的试验资料表明:不同牌号不锈钢材料的力学性能差别较大;同牌号不锈钢材料的力学性能也有一定差别,而材料力学性能变化对轴心受压不锈钢柱的稳定性系数的影响在国外典型不锈钢结构设计规范中均无明确的规定。基于经验证的有限元模型,计算了30种典型不锈钢材料的稳定系数曲线,采用修正正则化长细比概念对Perry公式及K&R公式进行改进,得到适用于常用不锈钢材料力学性能的轴心受压柱稳定系数表达式,并与国内外已有的试验数据进行对比,结果表明,此表达式具有较高的精度,可供我国不锈钢结构设计规程中轴心受压构件设计条文编制参考。     

冷弯薄壁型钢开口三肢拼合立柱轴压性能试验研究

对18根冷弯薄壁型钢开口三肢拼合立柱的轴压性能进行了试验研究,试件分为A、B两种截面类型：A类由3根冷弯薄壁C型钢拼合而成;B类由2根冷弯薄壁C型钢和1根U型钢拼合而成。得到了各试件的荷载-位移曲线和破坏特征,并将试验结果与中、美两国相关规范“有效宽度法”和“直接强度法”计算结果进行了初步对比分析。研究结果表明：两类截面长柱（LC）系列立柱的破坏特征分别为弯扭屈曲、弯曲屈曲,而中柱（MC）系列立柱A类截面为畸变屈曲、B类截面为畸变屈曲和弯曲屈曲,短柱（SC）系列立柱均为局部屈曲和畸变屈曲。AISI有效宽度法计算结果对于A、B两类截面LC系列立柱偏于安全;对于SC系列立柱则偏不安全;对于MC系列立柱吻合较好。AISI直接强度法计算结果对于A类截面LC和MC系列立柱偏于安全;对于SC系列立柱则偏不安全;对于B类截面立柱直接强度法计算结果与试验结果相差-16-5%~11-2%。《冷弯薄壁型钢结构技术规范》计算结果与试验结果相比,LC系列立柱偏于安全,而MC和SC系列立柱计算结果与试验结果吻合较好,相差分别为 -8.7%~4.7%和 -7.3%~13.7%。     

A numerical imperfection sensitivity study of cold-formed thin-walled tubular steel columns at uniform elevated temperatures

A numerical study is carried out on cold-formed rectangular hollow section columns to evaluate the sensitivity of column failure strength to initial imperfections, stress–strain relationships and to assess the existing design methods. It is shown that the magnitude of initial local buckling imperfection has a significant effect on the ultimate strength of short columns where failure is predominantly local buckling. Its effect on long columns is relatively small. Similarly the magnitude of initial global imperfection has more influence on the ultimate strength of a long column, whose failure is governed by global buckling, than on short columns, where local buckling controls. The shape of the stress–strain relationship of cold-formed steel will have noticeable effect on the column failure load. Current design methods, for high temperatures in ENV1993-1-2 and for ambient temperature in ENV1993-1-3, can provide a valid basis of calculation but modification will be necessary, depending on the exact model of stress–strain relationship of cold-formed steel at elevated temperatures.     

Structural performance of cold-formed high strength stainless steel columns

This paper describes an accurate finite element model for the structural performance of cold-formed high strength stainless steel columns. The finite element analysis was conducted on duplex stainless steel columns having square and rectangular hollow sections. The columns were compressed between fixed ends at different column lengths. The effects of initial local and overall geometric imperfections have been taken into consideration in the finite element model. The material nonlinearity of the flat and corner portions of the high strength stainless steel sections were carefully incorporated in the model. The column strengths and failure modes as well as the load-shortening curves of the columns were obtained using the finite element model. Furthermore, the effect of residual stresses in the columns was studied. The nonlinear finite element model was verified against experimental results. An extensive parametric study was carried out using the verified finite element model to study the effects of cross-section geometries on the strength and behaviour of cold-formed high strength stainless steel columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The results of the parametric study showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally conservative for cold-formed high strength stainless steel square and rectangular hollow section columns, but unconservative for some of the short columns.     

Buckling analysis of high strength stainless steel stiffened and unstiffened slender hollow section columns

This paper investigates the buckling behaviour of cold-formed high strength stainless steel stiffened and unstiffened slender square and rectangular hollow section columns. The high strength duplex material is austenitic-ferritic stainless steel approximately equivalent to EN 1.4462 and UNS S31803. The columns were compressed between fixed ends at different column lengths. A nonlinear finite element model has been developed to investigate the behaviour of stiffened slender square and rectangular hollow section columns. The column strengths, load-shortening curves as well as failure modes were predicted for the stiffened and unstiffened slender hollow section columns. An extensive parametric study was conducted to study the effects of cross-section geometries on the strength and behaviour of the stiffened and unstiffened columns. The investigation has shown that the high strength stainless steel stiffened slender hollow section columns offer a considerable increase in the column strength over that of the unstiffened slender hollow section columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the three specifications are generally conservative for the cold-formed stainless steel unstiffened slender square and rectangular hollow section columns, but slightly unconservative for the stiffened slender square and rectangular hollow section columns.     

Tests of cold-formed high strength stainless steel compression members

The paper describes a test program on cold-formed high strength stainless steel compression members. The duplex stainless steel having the yield stress and tensile strength up to 750 and 850 MPa, respectively, was investigated. The material properties of the test specimens were obtained from tensile coupon and stub column tests. The test specimens were cold-rolled into square and rectangular hollow sections. The specimens were compressed between fixed ends at different column lengths. The initial overall geometric imperfections of the column specimens were measured. The strength and behaviour of cold-formed high strength stainless steel columns were investigated. The test strengths were compared with the design strengths predicted using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures. Generally, it is shown that the design strengths predicted by the three specifications are conservative for the cold-formed high strength stainless steel columns. In addition, reliability analysis was performed to evaluate the current design rules.     

冷弯薄壁卷边槽钢轴心受压构件承载力计算的折减强度法

为了研究冷弯薄壁卷边槽钢轴心受压构件的极限承载力,对15根轴心受压的冷弯薄壁卷边槽钢进行了破坏性试验,并采用有限元分析方法对试件进行模拟分析,有限元计算结果与试验结果吻合良好,验证了有限元方法的有效性,然后对典型截面构件进行大量的有限元参数分析。研究结果表明：冷弯薄壁卷边槽钢轴心受压构件的极限承载力随着构件翼缘宽厚比、腹板高厚比、长细比以及钢材强度的增大而减小。通过参数分析得到了考虑局部屈曲、整体屈曲和畸变屈曲影响的构件屈服强度折减系数,提出了冷弯薄壁卷边槽钢轴心受压构件承载力计算的折减强度法及其相应计算公式,且通过试验验证了本文折减强度法计算卷边槽钢轴心受压构件极限承载力的适用性。     

焊接不锈钢工字形截面受弯构件整体稳定与设计方法

总结了作者在清华大学完成的一批焊接不锈钢梁在弯矩荷载作用下的整体稳定性能试验,试验以试件的长细比为主要变化参数,对8根工字形截面梁进行了研究.试验的材料是奥氏体型316冷轧板,材料应力-应变关系通过拉伸试验获得;同时采用有限元软件ANSYS建立包含初始缺陷的有限元模型,对试件的极限承载力和荷载-变形关系进行分析,并与试验结果进行了对比,以证明有限元分析的合理性和适用性,为进一步研究奠定基础.同时,还将试验结果与欧洲规范和作者的建议设计方法进行了对比.分析结果表明:通过合理建模的有限元分析结果与试验结果吻合良好,有限元分析能够合理的模拟焊接不锈钢梁的整体稳定性能,作者所建议的设计方法的计算结果与欧洲规范相近,能够应用于工程设计并保证足够安全.     

Design of cold-formed steel unequal angle compression members

Cold-formed steel unequal angles are non-symmetric sections. The design procedure of non-symmetric sections subjected to axial compression load could be quite difficult. The unequal angle columns may fail by different buckling modes, such as local, flexural and flexural–torsional buckling as well as interaction of these buckling modes. The purpose of this study is to investigate the behaviour and design of cold-formed steel unequal angle columns. A nonlinear finite element analysis was conducted to investigate the strength and behaviour of unequal angle columns. The measured initial local and overall geometric imperfections as well as the material properties of the angle specimens were included in the finite element model. The finite element analysis was performed on fixed-ended columns for different lengths ranged from stub to long columns. It is demonstrated that the finite element model closely predicted the experimental ultimate loads and the behaviour of cold-formed steel unequal angle columns. Hence, the model was used for an extensive parametric study of cross-section geometries. The column strengths obtained from the parametric study were compared with the design strengths calculated using the North American Specification for cold-formed steel structural members. It is shown that the current design rules are generally unconservative for short and intermediate column lengths for the unequal angles. Therefore, design rules of cold-formed steel unequal angle columns are proposed.     

高强冷弯薄壁型钢轴压柱畸变屈曲研究

550MPa高强冷弯薄壁型钢卷边槽形截面轴压柱发生畸变屈曲时会出现三种模式（O—O,O-I,I—I）,考虑材料和几何双重非线性的有限元法对三种畸变屈曲模式的构件承载力、变形模式、畸变屈曲应力、横截面应力的分布等相关性能进行比较分析,可看出三种畸变屈曲模式诸性能存在较大不同,同时畸变屈曲与局部屈曲、整体屈曲在相关性能方面也存在不同。采用直接强度法对畸变屈曲轴压柱极限承载力进行计算,计算结果与试验结果较吻合,故在计算畸变屈曲轴压柱极限承载力时建议采用直接强度法．