拼合式冷弯薄壁型钢带翼缘十字形截面柱轴压承载力研究

Numerical Study on Cold-formed Steel Built-up Stiffened Cruciform Specimen Subjected to Axial Load

带翼缘十字形截面构件在轴心压力作用下可能发生弯曲屈曲和扭转屈曲。为研究拼合式冷弯薄壁型钢带翼缘十字形截面构件在轴心荷载作用下的破坏模式和极限承载力,设计了三种截面尺寸的拼合柱,利用有限元软件ABAQUS对不同长细比和螺栓间距的拼合柱进行了数值模拟。所研究的拼合柱的螺栓间距分别为150,300,450 mm,弯曲长细比范围为20~140,间隔为20。为考察拼合作用对此类拼合截面柱承载力的影响,将其与同尺寸的整体截面柱进行对比。数值分析结果表明:拼合柱的长细比决定了拼合式冷弯薄壁型钢带翼缘十字形截面柱失稳模式,当弯曲长细比小于换算长细比,即λ;<λ;时,拼合柱发生整体扭转失稳,反之,则发生整体弯曲失稳;长细比显著影响其极限承载力,相同截面尺寸下,极限承载力随着长细比增大而降低;增大螺栓间距会使试件刚度与稳定承载力下降,但在常见范围内降低幅度很小,且不影响失稳模式;由于拼合作用的影响,拼合截面柱对比相同尺寸的整体截面柱,其力学性能有所下降,且拼合作用对拼合柱扭转失稳承载力的影响比对弯曲失稳承载力的影响更显著。

Either flexural and torsional buckling may occur when a cold-formed steel built-up stiffened cruciform column subjected to axial compression. A numerical investigation was performed to study the failure modes and ultimate resistances of cold-formed steel thin-walled columns made from built-up stiffened cruciform sections. In the finite element simulations, built-up columns with three different cross-sectional sizes were designed and specimens with various slenderness ratios and bolt spacing were investigated. The range of the slenderness ratios of the specimens was from 20 to 140 at an interval of 20. Three bolt spacings of 150, 300, 450 mm were employed to study the built-up effect on compressive resistance of the specimens. The results show that the failure modes of such columns were dominated by their slenderness ratios. Overall torsional buckling occurred for specimens with λ;<λ;, while overall flexural buckling took place for specimens outside this range. The ultimate resistances were affected by the slenderness ratio, and the ultimate resistance of columns with the same cross-section size decreased as the slenderness ratio increased. The stiffness and ultimate bearing capacity of the column decreased when the bolt spacing increased, but such an effect was found insignificant within common bolt spacing ranges and the failure modes were not affected by the bolt spacing. The axial bearing performance of the built-up section columns was found to be inferior to their integral section column counterparts with same cross-sectional sizes, and this was more obvious for the columns failed by torsional buckling.