Behavior and Strength of Partially Encased Composite Columns with Built-up Shapes

摘要

A comprehensive study has been conducted to investigate the behavior and strength of a new type of partially encased composite column made with thin-walled, welded I-section, stiffened with transverse links. Concrete is poured between the flanges of the steel section. The paper describes and presents the results of the testing of five large-size 6003600 mm short column specimens. Failure of all specimens was due to local buckling of the flange plates along with concrete crushing. Transverse stresses measured in the steel section were found to be small and did not impair the axial compressive strength of the steel section. High stresses, however, developed in the transverse links as a result of the lateral expansion of the concrete. The study also shows that closer link spacing and the use of additional reinforcements can improve the post-ultimate load behavior. A comparison is made with test results obtained in previous studies on smaller specimens and an improved formula for predicting the column axial load capacity accounting for local flange buckling and the variation of the concrete strength with column size is proposed for design application.