普通卷边槽钢的弹性畸变屈曲荷载

DISTORTIONAL BUCKLING LOADS OF COLD-FORMED LIPPED CHANNELS

畸变屈曲是控制冷弯型钢稳定设计的重要屈曲模式之一。该文以理论研究成果为基础,结合应用有限条屈曲分析程序,对冷弯卷边槽钢在偏心受压和纯弯曲下的弹性畸变屈曲荷载进行了深入细致的分析。首先基于对轴心受压和纯弯曲两种极端荷载情况下畸变屈曲荷载的参数分析,提出了屈曲临界半波长度和考虑翼缘自身剪切与畸变影响的修正参数的近似计算公式;接着对腹板提供给翼缘板的转动约束刚度进行了分析讨论,提出了精度较高的近似计算公式;利用以上结果,最后提出了冷弯卷边槽钢在偏心受压和纯弯曲下的弹性畸变屈曲荷载简化计算公式。简化公式具有足够的精度、便于手算、实用性强,可供工程设计人员和各国冷弯薄壁型钢设计规范修订相应内容时参考。

Distortional buckling is an important buckling mode governing the stability design of cold-formed steel channels. This paper presents a set of simple formulae for the elastic distortional buckling loads of cold-formed lipped channels subjected to eccentric compression or pure bending. These formulae are derived from an existing theoretical solution on the basis of parametric studies and with the assistance of finite strip buckling analyses. Firstly, results from parametric studies on the distortional buckling loads for the two extreme load cases of axial compression and pure bending are presented and interpreted, leading to approximate expressions for the buckling half-wavelength, in which a modification factor is included to account for the effect of the shear and distortional deformation of the flange section. The rotational restraint, provided by the web to the flange during buckling deformation, is then examined, and an enhanced approximate expression considering the rotational restraint is proposed. Based on these approximate expressions, two simplified formulae are finally presented to predict the elastic distortional buckling loads of cold-formed lipped channels subjected to eccentric compression and pure bending respectively. These formulae are shown to be accurate through comparisons with results from finite strip buckling analyses. They are easy to apply, and may be directly used in practical design and incorporated into future design codes and guidelines.