火灾下蜂窝梁孔间腹板受剪弹性屈曲简化设计方法

Shear Buckling Strengths of Web-posts in a Castellated Steel Beam with Hexagonal Web Openings in a Fire

运用有限元方法研究了火灾下六边形孔蜂窝梁在竖向剪力作用下孔间腹板弹性屈曲问题。取孔间腹板的上半部作为隔离体,将蜂窝梁的孔间腹板等效为受水平剪力的楔形悬臂板。根据薄板受剪屈曲理论计算公式,通过屈曲系数k计算孔间腹板受剪屈曲承载力。运用有限元分析获得蜂窝梁竖向剪切屈曲承载力,通过反分析计算屈曲系数k。结果表明:k随着孔间腹板宽厚比和孔洞上方腹板高厚比的增大而非线性减小;随着孔间腹板高厚比的增大而线性增大;随着腹板厚度的增大而线性减小;随火灾升温基本保持不变。在参数分析的基础上,提出了火灾下六边形孔蜂窝梁受剪屈曲系数k的计算公式,简化了蜂窝梁孔间腹板屈曲承载力的设计过程。

Shear buckling behavior of web-post in a Castellated Steel Beam （CSB） with hexagonal web openings under vertical shear in a fire were investigated with finite element method. By stud- ying buckling behavior of the upper part of the web-post under horizontal shear force, the shear buckling problems of web-post could be replaced by those of a suspended wedge plate under horizontal shear force. The shear buckling strength of the wedge plate could be obtained, if the shear buckling coefficient k was provided. After obtaining the vertical shear buckling strength of a CSB by using finite element analysis, the shear buckling coefficient k was obtained by inverse analy- sis. Research results show that k decreases non-linearly with the increase of web-post width to thickness ratio and web height of Tee-section to thickness, k increases linearly with the increase of web-post height to thickness ratio. And it decreases linearly with web thickness, k is nearly kept consistent with elevated temperatures T in a fire. Practical calculating method for k in a fire is proposed as results of a systematic parameter analysis, which greatly simplifies the shear buckling design of web-post.