Title:
Investigation of Minimum Longitudinal Reinforcement Requirements for Concrete Columns Using Present-Day Construction Materials
Author(s):
Paul H. Ziehl, Jeffrey E. Cloyd, and Michael E. Kreger
Publication:
Structural Journal
Volume:
101
Issue:
2
Appears on pages(s):
165-175
Keywords:
column; creep; high-performance concrete; high-strength concrete; reinforced concrete; reinforcement; shrinkage
DOI:
10.14359/13013
Date:
3/1/2004
Abstract:
A research project was conducted to assess the feasibility of reducing the current ACI Building Code and AASHTO Bridge Specification requirements for minimum longitudinal reinforcing steel in columns. The current code requirement is based primarily on research conducted in the 1920s and 1930s on concrete with a compressive strength generally less than 34.5 MPa (5000 psi). The investigation was conducted to determine the effects of present-day construction materials on minimum reinforcement requirements. A research program was carried out that included: 1) fabrication and long-term loading and monitoring of 24, 8-in. diameter by 4-ft long reinforced concrete column specimens; 2) fabrication of reduced-humidity enclosures for storage of all specimens throughout the test program; and 3) long-term monitoring of 14 unloaded companion specimens. Test variables included concrete strength and reinforcement ratio. All loaded specimens were subjected to a nominal compressive force of 0.40fc¢/Ag. The long-term response of concentrically loaded and unloaded specimens is presented in this paper, and measured responses are compared with predicted long-term responses based on recommendations from ACI Committee 209.