Title:
Confinement of High-Strength Concrete Columns
Author(s):
Shamim A. Sheikh, Dharmendra V. Shah, and Shafik S. Khoury
Publication:
Structural Journal
Volume:
91
Issue:
1
Appears on pages(s):
100-111
Keywords:
axial loads; columns (supports); confined concrete; ductility; earthquakes; energy; high-strength concretes; hinges (structural); Structural Research
DOI:
10.14359/4483
Date:
1/1/1994
Abstract:
High-strength concrete (HSC) with compressive strength of 8000 psi (55 Mpa) or higher is commonly used in columns at present. However, very little is known about its behavior under large inelastic deformations, particularly when subjected to severe earthquakes, and most building codes do not provide the required design guidelines. Results from four high-strength concrete specimens, three nonprismatic and one prismatic, tested under constant axial load and cyclic lateral loads simulating earthquake forces are presented here and compared with similar specimens of normal strength concrete (NSC). Concrete strength varied between 4500 and 8500 psi (31 and 59 Mpa). Relevant provisions of the ACI Building Code are evaluated in light of the test data. Increase in the lateral steel contents resulted in an almost proportional increase in ductility and energy-absorption capacity of confined high-strength concrete, just as in the case of normal strength concrete. The required amount of confining steel appears to be proportional to the strength of concrete for a certain column performance if the axial load is measured in terms of PMIV[sub o]D rather than as a fraction of f [sub c] prime> AMIV[sub g]D. Usable compressive strain in the range of 0.01 to 0.02, and curvature ductility factors as high as 16, were observed in confined high-strength concrete columns.