Investigation on applicability of substitute beam-column frame for design of reinforced concrete sway frames

Abstract

The paper deals with the evaluation of the sway frame moment magnification provision for the design of slender reinforced concrete columns in sway frames according to EBCS 2: 1995.

A special feature of the moment magnification method in EBCS 2: 1995 is the introduction of the concept of substitute frame for the determination of the storey buckling load. The evaluation is carried out by comparing the magnified column moment with the corresponding values obtained from the more rigorous second order iterative P-Δ second order analysis.

The magnified column moments are also compared with the corresponding values determined using the ACI’s sway moment magnification provision. The results of the evaluation show that the sway moment magnification method according to EBCS 2: 1995 yields design moments close to the iterative P-Δ solutions. However, the results lie on the unsafe side and the percentage deviation is found to be the highest for irregular frames.

Keywords: Sway frames, slender columns, substitute beam-column frame, ETABS, critical load, sway moment magnification, second-order analysis