Title:
Story Stability and Minimum Bracing in RC Framed
Structures: A Genera l Approach
Author(s):
J. Dario Aristizabal-Ochoa
Publication:
Structural Journal
Volume:
92
Issue:
6
Appears on pages(s):
735-744
Keywords:
buildings; columns; earthquake-resistant design; lateral pres-sure;
moments; reinforced concrete; slenderness ratio; structural analysis.
DOI:
10.14359/9667
Date:
11/1/1995
Abstract:
An analytical method and closed-form formulas are presented by which the stability of an entire story of a framed structure can be analyzed directly. The proposed method and formulas are suitable for the calculation of the k-factor sway-magnification factor Ss, minimum interstory bracing, and column design in RC framed structures with rigid, semirigid, or flexible connections and with uninhibited or partially inhibited sidesway. The pro-posed method is simpler and more versatile than any other method avail-able, yielding results within I percent of the theoretical values for symmetrical rectangular frames and 3 percent for nonsymmetrical frames. The proposed method utilizes the axial loads in the columns obtained from a conventional first-order linear analysis to determine the critical axial load, the sway-magnification factor Ss, and minimum bracing at any level in multistory frames. The proposed method allows the designer to investigate the effects of interstory bracing, load patterns, changes in column geometry and cross-sectional properties, as well as flexural hinging (or degradation at the connections) on the stability response of framed structures, all with the help of a pocket calculator. To understand the proposed formulas and their range of applications, a comprehensive example already analyzed by MacGregor, 1 using both the ACI Code 2 and an analytical P-A iterative method is presented and the results compared to those of MacGregor