单轴对称工字钢梁的弹塑性稳定系数

Elastic-plastic stability factors of mono-symmetrical steel I-beam

工字钢梁在工业厂房中应用非常广泛,而平面外弯扭失稳是薄壁构件的主要失稳模式,比单独的扭转失稳和弯曲失稳要复杂的多。以往钢梁稳定研究主要集中在双轴对称截面,单轴对称截面的整体稳定性研究较少。为此,对承受跨中集中荷载和关于跨中对称的两点荷载的单轴对称工字钢梁进行了弹塑性弯扭屈曲分析,考虑初始变形和两种残余应力分布。通过算例分析得到不同截面尺寸和荷载作用点高度的稳定系数变化规律,以修正的ECCS公式为基础拟合得到了适用于单轴对称截面横向荷载作用下的弯扭屈曲稳定系数公式,该公式适用于的荷载作用点高度为剪心到上翼缘以上120 mm、截面宽高比为0.42~0.76范围内的单轴对称工字钢梁。与有限元计算结果对比表明,公式计算结果与有限元分析结果符合良好,且公式与有限元计算结果相比较为保守。

Steel I-beams are widely used in industrial plants, and out-of-plane bending and torsional instability is the main mode of instability for thin-walled components, which is much more complicated than torsional and bending instability alone. Previous studies on the stability of steel beams mainly focused on biaxially symmetrical sections, while the overall stability of uniaxially symmetrical sections was rarely studied. Elastic-plastic flexural-torsional buckling of mono-symmetrical steel I-beams subjected to mid-span concentrated loads and two-point loads with respect to mid-span symmetry was analyzed, initial geometrical imperfections and two types of residual stresses were considered. Through the analysis of a large number of mono-symmetrical beams, the changing rule of stability factors of different section sizes and height of loading were obtained. Based on the modified ECCS formulas, the stability factor formulas which were applied to mono-symmetrical and biaxial symmetrical steel I-beams were obtained. The formulas are suitable for load heights from shear center to 120 mm above the upper flange and width-to-height ratios between 0.42-0.76 mono-symmetrical steel I-beam. A comparison show that the results of formula are in good agreement with the results of finite element analysis, and the formula is more conservative.