Investigation on Applicability of Substitute Beam-Column Frame for Design of Reinforced Concrete Sway Frames
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Date
2012-09
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Addis Ababa University
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%.
Key Words: Sway frames, slender columns, substitute beam-column frame, ETABS, critical load, sway moment magnification, second-order analysis.
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Keywords
Sway Frames ;Slender Columns; Substitute Beam-Column Frame;ETABS; Critical Load; Sway Moment Magnification; Second-Order Analysis