Title:
Amplification Factor for Three-Dimensional RC Framed Structures: A Nonparadoxical Approach
Author(s):
J. Dario Aristizabal-Ochoa
Publication:
Structural Journal
Volume:
94
Issue:
5
Appears on pages(s):
538-548
Keywords:
buckling; building codes; columns (supports); construction types;
computer applications; frames; loads (forces); reinforced concrete; seismic
loads; steels; stability;
DOI:
10.14359/503
Date:
9/1/1997
Abstract:
An analytical method and the corresponding equations by which the stability of an entire story of 3-D framed structures can be analyzed directly are presented and derived. The proposed method is: 1) suitable for the calculation of the effective length k-factor for each column, the total critical load, and the sway-magnification factor ds of an entire story of real framed structures with rigid, semirigid, and simple connections and with sidesway uninhibited, partially inhibited, and totally inhibited; 2) straightforward and more versatile than any other method available, yielding conservative results within 1 percent and 4 percent of the theoretical values for symmetrical and non-symmetrical frames, respectively; and 3) limited to framed structures with columns of doubly-symmetrical cross section with their principal axes parallel to the global axes. The proposed stability approach allows the designer to investigate the effects of: 1) axial load pattern; 2) the variation in sizes and heights among the columns; 3) the topology or plan-layout of the columns; 4) floor torsion-sway caused by any asymmetry in the loading pattern, column layout, column sizes and heights and their reduction in the flexural-buckling capacity; 5) the columns' flexural and torsional end restraints; 6) flexural hinging or degradation at the columns' connections; and 7) bracings along the two horizontal and rotational directions of the floor plane on the stability response of framed structures, all with the help of a pocket calculator and using the axial loads in the columns obtained from a conventional first-order linear analysis. To understand the proposed approach and stability equations and their range of application, three comprehensive examples are presented in detail and the results compared to those obtained by other methods.