Global stability of axially loaded partially encased composite column with L-shaped section

Abstract

The partially encased composite (PEC) section consists of steel component and concrete partially encased between flanges. This paper investigates the global stability of partially encased composite column with L-shaped section (L-PEC column). Firstly, two experiments of the L-PEC column with unequal-leg under axially compressive load is reported. Their failure modes are mainly flexural buckling, concrete crushing and spalling. Secondly, the elastic buckling of the L-PEC columns is demonstrated through the buckling analysis of the FE models, and it is proved to be feasible that the normalized slenderness ratio λv is used to evaluate the reduction factors φ of L-PEC columns within the length-to-thickness ratio less than 4 instead of λuvω which is corresponding to flexural-torsional buckling mode. The elastic buckling of axially compressed members with L-shaped thick-walled PEC and homogeneous section is also discussed. Moreover, the parameter analysis of the nonlinear stability of the L-PEC columns is conducted, and the results indicate that the aspect ratio of the cross-section and length-to-thickness ratio of the shorter leg are also key factors affecting the stability of the L-PEC columns. Based on that, the design formulas are proposed, which take into account the effect of the aspect ratio and length-to-thickness ratio of the shorter leg. The formulas can be used to calculate the load-bearing capacity of the L-PEC columns with both equal- and unequal-leg L-shaped sections.