中间加劲复杂卷边槽钢纯弯构件弹性畸变屈曲应力计算方法研究

为了研究中间加劲复杂卷边槽钢纯弯构件弹性畸变屈曲应力简化计算方法,采用有限条分析软件CUFSM对不同参数的复杂卷边槽钢、∑形复杂卷边槽钢以及腹板V形加劲复杂卷边槽钢各70个构件的畸变屈曲应力进行数值分析.在此基础上,借鉴现有板件局部屈曲应力的表达方式,引入畸变屈曲系数,经拟合分析提出上述构件畸变屈曲应力的简化计算公式,并将复杂卷边槽钢和腹板V形加劲复杂卷边槽钢的公式进行合并,对公式的有效性进行验证.     

冷弯薄壁卷边H型钢受弯构件局部屈曲分析

采用有限条软件CUFSM对200种不同截面几何参数的冷弯薄壁卷边H型钢在荷载作用下的局部屈曲应力进行计算,并利用构件的屈曲应力分析了不同的卷边宽厚比、截面宽高比、腹板高厚比、翼缘宽厚比对冷弯薄壁卷边H型钢局部屈曲性能的影响。在此基础上,提出了适用于求解冷弯薄壁卷边H型钢在荷载作用下局部屈曲应力的简化计算式,并将简化公式计算的结果与有限条法计算的结果进行对比,表明所提出的简化计算式具有很好的适用性和精确性。     

受弯的冷弯卷边槽钢畸变屈曲强度和其相关屈曲承载力

受弯的冷弯薄壁卷边槽钢基本上有板件局部屈曲,截面畸变屈曲和构件弯扭屈曲三种屈曲模式,随后有它们之间的相关屈曲。由于畸变屈曲模式对缺陷的敏感度高,因此其屈曲后强度提高的幅度远低于局部屈曲模式。但是与局部屈曲模式相比,畸变屈曲模式抵抗破坏的能力却很强。可以用有限单元法计算受弯卷边槽钢截面的畸变屈曲强度。本文介绍了澳大利亚-新西兰标准AS/NZS4600-2005,用手算法计算受弯卷边槽钢截面的弹性畸变屈曲应力,並用直接强度法计算其相关的屈曲承载力。     

冷弯薄壁卷边槽钢梁弹性畸变屈曲拟合计算

针对冷弯薄壁卷边槽钢纯弯梁,从现有文献中,选取具有代表性的截面形式,分析截面各种几何参数对弹性畸变屈曲临界应力fod的影响,并在此基础上拟合得到fod计算公式。该拟合公式物理意义明确,与有限条法计算结果进行对比,结果表明:所提出的公式具有较高工程精度,且简单实用、便于手算;该公式的运用,推进了直接强度法的实用化进程,亦可供工程设计人员参考。     

冷弯薄壁型钢构件的直接强度设计法

受压或受弯的冷弯薄壁卷边槽钢有板件局部屈曲，截面畸变屈曲和整体弯曲屈曲或弯扭屈曲三种模式。本文着重介绍板件的相关屈曲和计算截面畸变屈曲应力的方法并阐述了三种屈曲模式之间的相关关系。指出用传统的有效截面设计法计算受压和受弯冷弯薄壁卷边槽钢承载力的弊端，较详细地说明了用构件全截面计算的直接强度设计法。     

卷边槽形截面受弯构件畸变屈曲计算方法研究

采用能量法分析冷弯薄壁型钢卷边槽形开口截面受弯构件弹性畸变屈曲应力及其畸变屈曲稳定系数。通过与有限条法分析的畸变屈曲应力进行对比分析,表明建议的畸变屈曲应力计算公式具有较高的精度,通过简化计算得到畸变屈曲稳定系数计算公式及部分加劲板件的局部畸变屈曲统一计算公式;给出了卷边槽形截面受弯构件考虑畸变屈曲的稳定承载力计算方法。最后通过分析计算受弯构件试验的构件承载力并与试验结果进行对比,表明本文提出的计算方法是合理的,相对于现行GB 50018—2002《冷弯薄壁型钢结构技术规范》能更准确地计算受弯构件部分加劲板件屈曲稳定系数及卷边槽形截面构件的稳定承载力。     

板件中间加劲的复杂卷边槽钢轴压构件弹性畸变屈曲应力的实用计算法

为了研究板件中间加劲的复杂卷边槽钢轴压构件畸变屈曲临界应力的简便计算方法,应用有限条分析软件CUFSM对冷弯薄壁板件中间加劲的复杂卷边槽钢以及腹板中间V型加劲的复杂卷边槽钢共90个轴压构件进行数值模拟,分析各参数对构件弹性畸变屈曲临界应力的影响。经拟合分析,得出针对板件中间加劲的复杂卷边槽钢、腹板中间V型加劲的复杂卷边槽钢轴压构件的弹性畸变屈曲临界应力的简化计算公式,并验证该公式的有效性。     

冷弯薄壁C型钢绕强轴偏心受压构件的极限承载力

冷弯薄壁型钢结构多采用有效截面法对构件承载力进行计算,该方法计算繁杂且未考虑构件的畸变屈曲性能。直接强度法采用全截面计算各类参数,能够考虑各种单独屈曲模式及其相关屈曲对构件稳定性能的影响,但目前该方法并不能应用于压弯构件。对冷弯薄壁C形钢绕强轴偏压构件的稳定性能进行参数分析,探讨了构件长度、偏心距、腹板高厚比、翼缘宽厚比和卷边高厚比等因素对构件承载力的影响规律。结合有限元分析结果,基于轴压构件和纯弯构件的直接强度法公式,提出了冷弯薄壁型钢绕强轴偏压构件的极限承载力计算方法。     

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。     

剪切作用下冷弯槽钢的弹性屈曲

研究与腹板平行的纯剪切荷载作用下包含翼缘和卷边的整个槽钢截面的弹性屈曲,并给出了解决方案。采用样条有限条法(SFSM)对纯剪切作用下的薄壁槽钢进行弹性屈曲分析,以获得截面的弹性屈曲载荷(Vcr)。利用剪切屈曲载荷计算用于截面设计的腹板的剪切屈曲系数(KV)。主要变量为翼缘宽度、构件长度和卷边尺寸。边界条件为两端简支。根据分析结果绘制交互作用曲线,可作为设计指南,使得设计人员不用样条有限条法(SF-SM)软件也能够预测弹性屈曲剪切系数(KV)。给出了不同的翼缘宽度、构件长度和卷边尺寸下构件的典型屈曲模态。包括局部屈曲和翼缘屈曲,畸变屈曲和截面扭曲。     

不同斜卷边檩条的局部屈曲和畸变屈曲

利用Hancock的简化模型分析了卷边槽形、卷边Z形檩条的畸变屈曲,用有限元方法计算了卷边槽形、卷边Z形檩条的畸变屈曲荷载以及翼缘局部屈曲系数,研究了卷边角度对畸变屈曲荷载的影响,提出斜卷边加劲板的屈曲系数取值以及屈曲系数关于卷边角度变化的公式。经对比验证,在卷边角度40°～90°的范围内,误差在2%以内。可供实际设计参考。     

RL型截面冷弯薄壁型钢的畸变屈曲荷载算式

为了对RL型截面冷弯薄壁型钢的畸变屈曲作进一步研究,以既有研究成果为基础,根据广义梁理论推导了两端简支和固支边界条件下RL型截面冷弯薄壁型钢的畸变屈曲荷载计算式。通过求解矩阵的广义特征值,利用推导的算式计算RL型截面型钢构件在轴压、绕弱轴和强轴弯曲下的畸变屈曲荷载和屈曲半波长,并与有限条软件CUFSM分析结果和既有理论公式的解相比,结果表明所得算式具有较高的精度。公式推导过程和结论可以为工程设计和进一步研究中计算畸变屈曲荷载提供参考。     

Distortional buckling of thin-walled inclined lipped channel beams bending about the minor axis

Based on the Generalised Beam Theory (GBT), two computing models are presented to analyse the distortional critical stress of cold-formed thin-walled inclined lipped channel beams bending about the minor axis. The computing model of rigid-body motion ignores the transverse bending deformation of the flange. However, the bending deformation of the flange is accounted for in the transverse bending computing model. Based on the transverse bending computing model, this paper puts up a simple method to take into account the in-plane bending of the flange. The results given by the rigid-body motion computing model does not correlate as well as those given by the transverse bending computing model with the results available in the literature. The accuracy of the transverse bending computing model is verified through comparison of its results with the known results. The comparisons demonstrate the importance of the bending deformation of the flange on the distortional buckling of cold-formed thin-walled channel beams bending about the minor axis.     

Distortional buckling of thin-walled inclined lipped channel beams bending about the minor axis

Based on the Generalised Beam Theory (GBT), two computing models are presented to analyse the distortional critical stress of cold-formed thin-walled inclined lipped channel beams bending about the minor axis. The computing model of rigid-body motion ignores the transverse bending deformation of the flange. However, the bending deformation of the flange is accounted for in the transverse bending computing model. Based on the transverse bending computing model, this paper puts up a simple method to take into account the in-plane bending of the flange. The results given by the rigid-body motion computing model does not correlate as well as those given by the transverse bending computing model with the results available in the literature. The accuracy of the transverse bending computing model is verified through comparison of its results with the known results. The comparisons demonstrate the importance of the bending deformation of the flange on the distortional buckling of cold-formed thin-walled channel beams bending about the minor axis.     

Compression tests of high strength cold-formed steel channels with buckling interaction

This paper describes a series of compression tests conducted on cold-formed simple lipped channels and lipped channels with intermediate stiffeners in the flanges and web fabricated from high strength steel plate of thickness 0.6 and 0.8 mm with the nominal yield stress 560 MPa. A range of lengths of lipped channel sections were tested to failure with both ends of the column fixed with a special capping to prevent local failure of column ends and influence from the shift of centroid during testing. The high strength cold-formed steel channel sections of intermediate lengths generally displayed a significant interaction between local and distortional buckling. A noticeable interaction between local and overall buckling was also observed for the long columns. A significant post-buckling strength reserve was shown for those sections that showed interaction between local and distortional or overall buckling. Simple design strength formulas in the Direct Strength Method for the thin-walled cold-formed steel sections failing in the mixed mode of local and distortional buckling have been studied. The strengths predicted by the strength formulas proposed are compared with the test results for verification.     

Study on distortional buckling performance of cold-formed thin-walled steel flexural Members with stiffeners in the flange

This paper presents a finite strip program CUFSM used to calculate and analyze the elastic distortional buckling of cold-formed thin-walled steel flexural members with stiffeners in the flange, which has different sectional geometric parameters. According to the classical buckling stress formula, the distortional buckling coefficient of the flange can be calculated so as to analyze the influence of changed sectional geometric parameters on it. On this basis, this study provides a simplified formula of distortional buckling stress to calculate 40 members with different sections which are selected from the Technical Code of Cold-Formed Thin-Wall Steel Structures of China but not contained in this paper. Compared with the analysis results of CUFSM, it shows that the two simplified formulas have quite high accuracy and wide applicability for general members provided by the specification. So it is suggested that they can be used for engineering design and standard revision.