L形截面部分包覆钢-混凝土组合柱弱轴压弯整体稳定

Stability of partially encased composite steel and concrete column with L-shaped section under eccentric compression around minor axis

为了研究L形截面部分包覆钢-混凝土组合(PEC)柱的压弯稳定性能,对L形截面PEC柱进行了弱轴压弯试验和有限元分析。试验研究中设计并制作了3个L形PEC柱试件,变化参数为长细比和偏心距。试验结果表明:截面形状和主钢件分布的几何非对称性,以及混凝土材料拉压强度的非对等性,造成L形PEC柱在受力后截面中和轴的偏转,导致构件发生弯扭变形。有限元分析表明,L形截面的肢背或肢端受压对构件承载力有一定影响;长细比较小(即长细比为10~30)时,肢背受压的构件轴力-弯矩相关曲线具有大小偏心分界的特征,但长细比较大(即长细比大于60)时,整体失稳成为控制破坏模式,相关曲线向原点内凹。建议了L形PEC柱绕弱轴压弯时的整体稳定承载力计算公式,与试验和有限元参数分析结果对比表明:当长细比小于60时,建议公式可以适用,当长细比大于80时,建议公式偏不安全,需进一步改进后才能用于工程设计。

The global stability of partially encased composite steel-concrete column with L-shaped section(L-PEC column) under axial load and bending moment about minor axis is experimentally and numerically studied.Three L-shaped specimens were designed with different slenderness and eccentricity of axial load.The test results show that the geometrical asymmetry of the section and distribution of main steel area,as well as the non-equivalency of concrete material strength in compression and tension make the deflection of the sectional neutral axis of the L-PEC column after loaded,thus results in the flexural-torsional deformation.FEM analysis shows that compressive zone at tip or corner of the L-shaped section affects the capacity somewhat.For small slenderness ratio columns when tip compressed,there is a cut-off point at axial load-moment interactive curve to divide large and small eccentricity.While for large slenderness ratio columns,the global instability shall be predominant for failure mode and the curve is concave.An equation for global stability of axial load and moment about minor axis of L-PEC column is recommended.Compared with the results of the tests and FEM analysis,it is shown that the equation is applicative to L-PEC column with slenderness not greater than 60,while is unsafe to the column with slenderness greater than 80,so further study is necessary for engineering application.