Design Equation for the Axial Capacity of Partially Encased Non-Compact Columns

This paper describes the research program that has been performed to develop and validate design equations for the axial capacity of partially encased composite columns made with three plate built-up steel shapes. The width-to-thickness ratio of the plate elements in these columns exceeds the limit for non-compact section and local buckling had to be examined for bare steel columns carrying construction loads as well as for composite sections. Potentially adverse effects of the loading sequence in actual columns and the confinement and creep of the concrete on the column axial load capacity were also examined in the study. Design equations are proposed for the bare steel columns and the composite columns.