INVESTIGATION ON APPLICABILITY OF SUBSTITUTE BEAM-COLUMN FRAME FOR DESIGN OF REINFORCED CONCRETE SWAY FRAMES

Abstract

Although Ethiopian Building Code Standard, EBCS-2, is based on the Eurocode, EC-2, there are some
clear differences between the two codes, most notably, with respect to the provisions for the design of slender columns in
sway frames. The provision in the EBCS -2 for columns in sway frames is based on the American concrete institute, ACI;
however, the former introduces the concept of the substitute frame, which is not in the ACI, to determine the stiffness of
columns for the determination of the critical load, Ncr, thereby the sway moment magnification factor. This research is
thus intended to investigate the suitability of the substitute frame for the intended purpose by comparing the design
internal actions obtained based on the ACI and EBCS sway moment magnification provisions with the iterative P-Δ
second order analysis, which is believed to be a more realistic approach, by taking different types of building frames
subjected to different loading conditions. The results of the investigation reveal that, though the results are on the unsafe
side, the provision in EBCS-2 yields design moments close to the iterative P-Δ second order analysis, except for the case
of frames with vertical irregularities where it deviates by 6.4%.