Title:
Flexural Stiffness of Composite Columns Subjected to Bending about Minor Axis of Structural Steel Section Core
Author(s):
S. Ali Mirza and Timo K. Tikka
Publication:
Structural Journal
Volume:
96
Issue:
5
Appears on pages(s):
748-757
Keywords:
building codes; columns (supports); composite construction (concrete and steel); concretes; loads (forces); moments; slenderness; steel; stiffness; structural design
DOI:
10.14359/728
Date:
9/1/1999
Abstract:
ACI 318-95 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 that 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 computed from axial load-moment-curvature relationships. This study was undertaken to determine the influence of different 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 minor axis of the steel section in symmetrical sin-gle curvature under short-term loads. Approximately 12,000 simu-lated 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. A design equation for EI is proposed.