钢压弯构件弯扭屈曲的研究

本文简要介绍了近年来在西安冶金建筑学院完成的有关钢压弯构件弯扭屈曲研究的成果,包括以下几个方面;(1)确定钢压弯构件设计承载力的典型截面选择;(2)考虑钢材屈服非连续性或焊接残余应力影响时构件的非弹性弯扭屈曲;(3)单轴对称截面压弯构件的弯扭屈曲分析和试验研究;(4)双轴和单轴对称截面构件弯扭屈曲的实用相关公式;(5)绕截面弱轴弯曲的压弯构件的弯扭屈曲分析和试验;(6)冷弯薄壁型钢构件的非弹性弯扭屈曲的分析和试验。     

轴心受压杆件的弯扭屈曲

全面梳理了轴压杆弯扭屈曲的理论分析过程和工程应用方法。只有一个对称轴或无对称轴的截面,可能出现弯扭屈曲;当为双轴对称截面时,可能发生扭转屈曲;这时临界荷载可能小于通常的弯曲屈曲的欧拉临界荷载。根据弹性弯扭屈曲理论,GB 50017—2017《钢结构设计标准》给出了扭转屈曲和弯扭屈曲的设计公式。     

弹塑性工字形钢梁换算截面法的适用性

采用换算截面法将弹塑性工字形钢梁换算成纯弹性工字形钢梁来解决其弯扭屈曲的问题。应用ANSYS有限元软件,分别对弹塑性工字形钢梁和换算截面后的纯弹性工字形钢梁进行了弯扭屈曲分析。分析显示,两种截面的临界弯矩值相差很小,说明在对弹塑性工字形钢梁进行弯扭屈曲分析时,换算截面法非常适用。换算后的工字形钢梁为纯弹性的,有助于简化弹塑性工字形钢梁弯扭屈曲问题的分析过程。     

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。     

压弯杆件弯扭屈曲的换算长细比

冷弯薄壁型钢结构设计在计算单轴对称截面偏心压杆弯矩作用平面外的稳定时,采用了换算长细比的概念,并且把它推广到压弯杆件弯扭屈曲的计算。但是压弯杆件的弯扭屈曲可以包括偏心压杆的弯扭屈曲,而反之则否。所以上述推广存在一定问题,有时可     

钢异形柱压弯组合实用计算研究

在L形截面钢柱的弯扭屈曲一般性相关方程和轴心受压实用计算研究的基础上,对L形截面钢柱压弯组合承栽力实用计算方法进行研究,化简L形截面柱弯扭屈曲一般性相关方程,考虑柱缺陷影响,用梁柱理论分析得出L形截面柱压弯组合实用设计计算公式,并通过几组L形截面柱偏心受压承栽力试验,验证了计算公式。     

双轴对称楔形工字钢梁的弹性弯扭屈曲

本文利用基于板壳屈曲理论的有限元方法对楔形薄壁构件的弯扭屈曲进行了分析,对两种基于薄壁杆件理论的楔形工字钢梁弯扭屈曲分析方法进行了对比。基于较精确的楔形薄壁构件屈曲理论,对承受线性变化端弯矩作用的楔形梁的弯扭屈曲进行了大量分析,并提出了新的楔形工字钢梁临界弯矩计算公式。该公式形式与等截面梁的相同,便于工程应用。     

正六边形孔蜂窝钢梁的整体稳定研究

通过将双轴对称工字形截面的正六边形孔蜂窝梁的等效刚度代入当量实腹梁弯扭屈曲临界弯矩值的公式中,得到蜂窝梁的弯扭屈曲临界弯矩值公式。为考虑开孔引起的剪切变形对蜂窝梁弯扭屈曲临界荷载值的影响,并验证所得蜂窝梁弯扭屈曲临界荷载公式的正确性,通过与有限元软件计算同尺寸的蜂窝梁得到的弯扭屈曲临界弯矩相比较,证明了所推公式具有满足工程所需的精度。最后为方便工程应用,对蜂窝梁整体稳定性计算公式进行了改进。     

局部封闭和开口薄壁压弯构件的弯扭屈曲

单轴对称开口薄壁压弯构件在荷载作用于对称平面内时有可能发生弯扭屈曲。在这种情况下,其临界荷载总是低于平面内弯曲失稳破坏荷载,如果在构件的开口边加上缀板,使之形成若干断续的封闭截面,则弯扭屈曲临界荷载将显著提高,并有可能使破坏模式由弯扭屈曲转化为平面内弯曲失稳。本文提出了一种计算薄壁压弯构件弯扭屈曲荷载的方法,这种方法对局部封闭和开口截面都能适用。曾经做了213根具有不同长细比、偏心距、缀板间距(或无缀板)的冷弯薄壁型钢压杆试验,其结果与理论符合较好。     

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。     

Flexural-torsional buckling of shallow arches with open thin-walled section under uniform radial loads

An arch with an open thin-walled section that is subjected to a radial load uniformly distributed around the arch axis may suddenly buckle out of its plane of loading and fail in a flexural-torsional buckling mode. The classical flexural-torsional buckling load for an arch with an open thin-walled section under a uniform radial load has been obtained by a number of researchers, based on the consideration that the uniform radial load produces a uniform axial compressive force without in-plane bending prior to the occurrence of flexural-torsional buckling. This assumption is correct for deep arches. However, the uniform radial load may produce substantial bending actions in shallow arches prior to flexural-torsional buckling, and so the classical buckling analysis based on the assumption of uniform axial compression may produce incorrect flexural-torsional buckling loads for shallow arches. This paper investigates the flexural-torsional buckling of shallow arches with an open thin-walled section that are subjected to a radial load uniformly distributed around the arch axis. It is found that shallow arches under a uniform radial load are subjected to combined in-plane compressive and bending actions prior to flexural-torsional buckling, and that using the classical buckling solution for circular arches under uniform compression produces incorrect buckling loads for shallow arches. A rational finite element model is developed for the flexural-torsional buckling and postbuckling analysis of shallow arches with an open thin-walled section, which allows the buckling loads to be obtained correctly.     

Flexural-torsional buckling behavior of aluminum alloy beams

This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams (AAB). First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load-deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexural-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method (FEM) analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural-torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.     

美国哈特福德城体育馆网架结构失稳事故分析

本文对哈特福德城体育馆网架结构中的受压弦杆和腹杆作了分析，发现原设计者只计及了杆的弯曲屈曲，但是因支撑体系在杆的中点存在连接偏心，杆将发生弯扭屈曲，经计算15种压杆的弯扭屈曲荷载均远小于弯曲屈由荷载，致使屋盖结构塌落．     

铝合金梁弯扭稳定系数的试验研究及数值分析

本文依托国家标准《铝合金结构设计规范》编制研究项目,采用数值分析与试验相结合的手段研究了铝合金梁弯扭稳定系数的计算问题。首先根据铝合金材料的Ramberg-Osgood本构关系,近似地将梁屈曲时截面边缘纤维的切线模量应用于全截面,由此得出无缺陷铝合金梁弯扭稳定系数的计算式;接着采用有限元数值模拟技术,应用壳板单元结合材料的随动强化模型,并同时考虑构件的初始缺陷,对强硬化和弱硬化合金分别拟合出Perry-Robertson形式的铝合金梁弹塑性弯扭屈曲稳定系数计算公式;最后,针对梁弯扭屈曲时侧向扭转的特点,合理设计了一套试验装置,并进行了铝合金拉伸力学性能的测定和10根跨中受集中力作用的简支工字梁弯扭屈曲承载力的测定,通过与试验结果的比较,验证了拟合公式的正确性。     

上承式装配式公路钢桥悬臂推出法架设过程中稳定性研究

结合一座上承式装配式公路钢桥在采用悬臂推出法架设过程中发生的事故案例,基于钢结构弯扭屈曲理论,分析其失稳破坏机理,并通过有限元数值模拟技术,对架设过程中不同状态进行屈曲分析。计算结果表明:如果导梁桁架横向间距过小,即使在导梁搭上对岸摇滚后,仍有可能因为发生弯扭屈曲失稳而导致整个桥梁倒塌;增大导梁桁架横向间距能有效提高导梁结构的抗屈曲稳定承载力。     

Elastic flexural-torsional buckling of thin-walled cantilevers

Previous studies by the authors revealed that the two representative theories with slight differences between, widely used in investigating the flexural-torsional buckling of thin-walled beams, have led to two different solutions in well-known literature for assessing critical loads of simply supported beams of monosymmetric cross section. With these two solutions, significant differences in critical loads may be found for these monosymmetric beams. Based on the classical variational principle for buckling analyses, a new theory on the flexural-torsional buckling of thin-walled members was proposed by the authors. In this paper, this new theory as well as the other two typical theories is employed to investigate the flexural-torsional buckling of cantilevers.This paper first gives a brief review and a careful comparative study on the flexural-torsional buckling of thin-walled cantilevers employing three different buckling theories. Differences between these theories are demonstrated with investigations on buckling of cantilevers under pure bending and two typical transverse loads. Explicit solutions, capable of considering variations of beam length and loading position along the vertical axis of cross section, are presented for predicting the critical loads of doubly symmetric cantilevers under two typical transverse loads. Advantages of presented solutions, such as good accuracy and ease of use, are exploited through the comparisons of critical results with those from existing solutions and finite element analyses.     

Prototype test on X-bracing panels using cold-formed lipped angles

The behavior and suitability of cold-formed lipped angle members for X-bracing with redundant have been studied. For the purpose, two full-scale panel tests were carried out. The first panel was designed so that the compression member would fail by buckling in flexural mode and the second panel in flexural-torsional mode. The members were designed using ASCE Manual No. 52. Theoretical aspects of least radius of gyration and buckling behavior of this bracing system have been discussed. The investigation on first panel, revealed that the member would buckle only in the flexural-torsional mode although flexural buckling would govern the design. The second panel test result showed that, the buckling mode and strength of the system for lipped angle sections can be predicted reasonably well.     

火灾下钢梁弯扭屈曲临界温度的计算方法

基于考虑横向荷载影响推导的钢梁整体失稳发生弯扭屈曲时临界弯矩的计算公式,引入高温下钢材的弹性模量随温度的折减系数,给出了火灾下钢梁整体失稳时临界温度的计算方法。研究表明,该方法计算结果与试验值吻合较好,满足结构抗火设计的精度要求。     

连续开孔实腹梁整体稳定性计算方法

为研究腹板开孔H型钢梁在纯弯荷载作用下的整体稳定性,采用翼缘和腹板刚度分离的方法,从理论上推导出带有连续正方形孔洞的H型钢梁的抗侧刚度、自由扭转刚度和翘曲刚度计算方法,得到其弯扭屈曲临界弯矩表达式。利用有限元软件ABAQUS对相同截面不同跨度的H型钢实腹梁在纯弯荷载作用下的弯扭屈曲临界弯矩进行分析,并将有限元模拟结果和规范计算结果进行对比。采用经验证的有限元模型对带有连续正方形孔洞的H型钢梁进行分析,并将有限元模拟结果与推导公式的计算结果进行对比。以现有规范为基础,推导出带有连续正方形孔洞的H型钢梁的弯扭屈曲临界弯矩实用计算公式。结果表明:连续开孔梁实用计算公式具有较高的精确度。     

复合荷载作用下双轴对称工字形悬臂梁的弯扭屈曲分析

基于能量变分法,推导了均布荷载和端部作用集中荷载下的双轴对称工字形截面悬臂钢梁的弯扭屈曲总势能方程,其中截面弯扭屈曲变形的位移和转角分别选用一项和无穷项傅里叶级数来表达模态试函数。根据最小势能原理无量纲化后,获得复合荷载作用下悬臂钢梁无量纲的临界荷载的解析解;通过无穷级数形式解答的无量纲临界弯矩的解析解进行收敛性分析,可得到精确解。应用ANSYS有限元分析软件进行数值模拟,对理论解进行数值对比。结果表明,复合荷载作用下悬臂钢梁的临界弯矩计算公式精度较高。