Compressive strength of high strength concrete-encased composite columns with noncompact and slender steel angles

Abstract

Concrete-encased steel angle (CEA) column is an encased composite column where structural angles are used for longitudinal and transverse reinforcements. In this study, the compressive behavior of CEA columns was investigated, focusing on the use of high-strength concrete and noncompact and slender steel angles. Ten CEA column specimens (concrete strength fc' = 33 and 66 MPa and steel yield strength Fy = 454–552 MPa) were tested under compressive loading. The section classification of steel angles and the spacing of transverse ties were considered as test variables. The tests showed that the cover concrete spalled off at peak loads and local buckling occurred in steel angles. Due to the use of high-strength concrete, the compressive strength (i.e., peak loads) was increased but the post-peak degradation behavior became steeper. The peak and residual strengths of CEA columns were examined focusing on the effects of cover failure, confinement by transverse ties, and local buckling of steel angles. Based on the results, empirical equations to estimate the peak and residual strengths were proposed and the validity was assessed by comparisons with the test results.