Title:
Flexural Stiffness of Composite Columns Subjected to Major Axis Bending
Author(s):
S. Ali Mirza and Timo K. Tikka
Publication:
Structural Journal
Volume:
96
Issue:
1
Appears on pages(s):
19-28
Keywords:
building codes; columns (supports); composite construction (concrete and steel); concrete; loads (forces); moments; slenderness ratio; steels; stiffness; structural design
DOI:
10.14359/592
Date:
1/1/1999
Abstract:
The ACI Building Code permits a moment magnifier approach for design of slender composite steel-concrete columns. This approach is strongly influenced by the effective flexural stiffness (EI) of the column which varies due to cracking, creep, and nonlinearity of the concrete stress- strain curve among other factors. However, the EI expressions given in ACI 318-95 are approximate when compared with the values of EI derived from axial load-moment-curvature relationships. The study reported herein was undertaken to determine the influence of a full range of variables on EI of slender tied rectangular composite columns in which steel shapes are encased in concrete. The columns studied were subjected to bending about the major axis of the steel section in symmetrical single curvature under short term loads. Approximately 12,000 simulated columns, each with a different combination of variables, were used to generate the stiffness data. The EI expressions were then developed for use in slender composite column designs. Two design equations are proposed in this paper.