冷弯薄壁卷边槽钢绕弱轴偏心受压构件承载力试验研究

Experimental study on behavior of lipped channel beam-columns under axial compression and minor-axis bending

为研究C型冷弯薄壁型钢压弯构件稳定性能,特别是其畸变屈曲性能,设计了38个冷弯薄壁卷边槽钢(C型钢)绕弱轴偏心受压短柱和中长柱试件,对其进行承载力试验,分析其破坏模式、极限承载力和变形性能。研究结果表明:正偏心受压试件的破坏主要由畸变屈曲模式控制,而典型的负偏心受压试件的破坏则主要受局部屈曲控制。对于中长柱试件,破坏还包含与整体屈曲的相关屈曲特征。正偏心受压试件承载力随腹板高厚比的增加而提高,而负偏心受压试件则呈现相反的规律。将试验结果和其他已有的试验研究数据与按GB 50018—2002《冷弯薄壁型钢结构技术规范》和北美(加拿大)规范S 136-12计算的试件承载力进行了对比,结果表明:对于负偏心受压构件,当应力不均匀系数ζ(截面上最小应力与最大应力的比值)趋于0并偏向负值(偏心距较大)时,随着ζ的减小,GB 50018—2002计算值与试验值的误差呈现逐渐增大的趋势,明显偏于不安全,当ζ≥-1.6时,按S 136-12对构件承载力的预估偏于安全;对于正偏心受压构件,当ζ≥-0.2时,GB 50018—2002和S 136-12对构件承载力的预估在多数情况下偏于保守,但其计算值离散性较大。

In order to obtain an in-depth understanding on behavior of lipped channel beam-columns, especially distortional buckling behavior, a total of 38 specimens including short and intermediate specimens were tested to investigate the failure mode, load-carrying capacity and deformation characteristic of the cold-formed channel beamcolumns under axial compression and minor-axis bending. It is revealed that the primary failure mode of beam-columns under axial compression and positive minor-axis bending is distortional buckling, whereas local buckling is the dominant failure mode of beam-columns under axial compression and negative minor-axis bending. The distortionalglobal or local-global interaction buckling is the distinguished characteristic for intermediate specimens. The results also show that the ultimate strength of beam-columns under axial compression and positive minor-axis bending increases as the increase of the width-thickness ratio of webs, whereas the opposite regularity is observed for beam-columns under axial compression and negative minor-axis bending. Based on the test results of this study and the other two investigations, the current design methods including the effective width method in GB 50018--2002 and S136-12 were evaluated. For beam-columns under axial compression and negative minor-axis bending, it is noted that the bearing capacity predicted by GB50018-2002 becomes unconservative as the decrease of （ （the ratio of minimum to maximum stress in the cross section） when ζ approaches to 0 and is negative and the predicted results from S 136-12 are conservative in the case that （ is not less than - 1.6. For beam-columns under axial compression and positive minor-axis bending, both GB 50018-2002 and S136-12 can provide the conservative predictions for the uhimate strengths of beam-columns with a large discrepancy for the case that ζ is not less than- 0.2.