基于直接强度法的薄壁轴压构件局部屈曲临界荷载实用计算式

Practical formula of critical local buckling load of thin-walled members under axial compression based on direct strength method

为建立适用于直接强度法的局部屈曲临界荷载实用计算式,分析了用于计算薄壁轴压构件局部屈曲极限荷载的直接强度法和有效宽度法所建立的依据,明确了两种方法中局部屈曲临界荷载P_(cr,L)的物理意义,并提出了P_(cr,L)的选取准则。提出了考虑板组效应的P_(cr,L)实用计算式,并通过与广义梁软件GBTUL的精确值对比,验证P_(cr,L)实用计算式的精度,证实P_(cr,L)选取准则的正确性。基于文中的P_(cr,L)实用计算式和直接强度法计算C形轴压构件的极限荷载,进一步验证了P_(cr,L)实用计算式的精度,同时与GB 50018—2002《冷弯薄壁型钢结构技术规范》中公式计算结果进行对比。研究表明:采用直接强度法计算极限荷载时,应选取考虑板组效应的局部屈曲临界荷载计算式,文中的P_(cr,L)实用计算式的形式简单且具有较高的精度。

In order to propose a practical formula of critical local buckling load based on the direct strength method, the background and nature of the direct strength method and the effective width method for calculating the ultimate strength of local buckling of thin-walled members under axial compression are analyzed. Physical significance of local buckling load Por,L is revealed. Selection criteria on Por,L for the two methods is proposed. A practical formula of critical load Pcr,L ＇ considering plate-assembly effects, is proposed. The accuracy of the proposed formula is verified by comparing its results with the exact values computing by the general beam theory software, GBUTL. The correctness of the selection criteria is also confirmed by comparison. The ultimate loads of C-section thin-walled member are computed by the proposed formula and direct strength method. Comparison with numerical results indicates that the proposed method yields reasonable predictions for the critical load of local buckling. The superiority of the Pcr,L practical formula is shown by comparing with the values from the current national standard GB 50018--2002. The results show that the Pcr,L formula considering plate-assembly effects is required by the direct strength method, and the proposed formula is of simple form and of significantly improved accuracy.