Title:
Concrete Strength in Tied Columns
Author(s):
Shamim A. Sheikh, C. C. Yeh, and Shafik Khoury
Publication:
Structural Journal
Volume:
87
Issue:
4
Appears on pages(s):
379-385
Keywords:
axial loads; columns (supports); compression; flexural strength; moments; reinforced concrete; strength; stress-strain relationships; stress block; tied columns; Structural Research
DOI:
10.14359/2722
Date:
7/1/1990
Abstract:
The stress-strain curve of concrete in compression depends on several factors, including the size and shape of compressed concrete, types and intensity of stresses acting in different directions on concrete elements, and the presence of strain gradient. The strength of concrete has little effect on the behavior of sections under pure flexure and under flexure and low axial-load levels. For sections subjected to flexure and large axial loads, when concrete strength significantly influences section behavior, the strength of concrete in the specimens is believed to reduce with an increase in axial load level. Results from five 12 in. (305 mm) square and 9 ft (2.14 m) long column specimens are reported in this paper. Based on this and the results from previous research, a simple relationship is suggested in which the concrete strength is reduced from f'c at the balanced load to 0.85f'c for concentric compression. A second-degree parabolic stress-strain curve with strain at peak stress equal to 0.002 can be used for a reasonably accurate and conservative prediction of section capacity.