Title: Simplified Design Method for Ultimate Capacities of Circularly Confined High-Strength Concrete Columns
Author(s): S. Yuping and S. Kenji
Publication: Symposium Paper
Appears on pages(s): 571-586
Keywords: circular concrete column; confined concrete; confinement
concrete-filled steel tubular column; equivalent rectangular stress block;
pressure; tubed colu mn; ultimate curvature; ultim ate moment; ultimate stra
Confinement of concrete by transverse steels (tubes or spirals) is effective in improving ductility of high-strength concrete (HSC). While the circular transverse tubes or spirals can provide much stronger confinement to the compressed concrete than the rectilinear transverse steels (tubes or ties), and circular reinforced concrete column is widely used in building and civil structures, studies and information on the flexural behavior of circularly confined concrete columns are scarce. As a result, there is not yet a reliable ultimate capacity design method directly applicable to circular concrete columns in current design codes. In this paper, a simple ultimate capacity design method is proposed for the circularly confined HSC columns. This simple method utilizes an equivalent rectangular stress block for the compressed concrete in circular column section. Since expressions of the parameters definingu the stress block and the ultimate strain were developed based on an confinement model proposed by the authors, the proposed design method enables engineers to compute directly ultimate capacities of a circular column, and to evaluate the confinement effect of circular transverse steels on the ultimate capacities. The predicted ultimate moment and curvature agreed well with the experimental data of HSC columns confined by circular steel tube and circular concrete-filled steel tubular (CFT) columns available.