Title: Axial Load Behavior of LargeScale Spirally Reinforced HighStrength Concrete Columns

Author(s): Stephen Pessiki and Annette Pieroni

Publication: Structural Journal

Volume: 94

Issue: 3

Appears on pages(s): 304-314

Keywords: columns; confined concrete; ductility; high-strength concrete; spiral reinforcement;

DOI: 10.14359/482

Date: 5/1/1997

Abstract:
The axial load behavior of 8 largescale spirallyreinforced concrete columns was investigated. The 559 mm (22 in.) diameter columns were designed according to ACI 318 Code requirements and tested in concentric axial compression. The columns were made with concrete compressive strengths ranging from about 34.5 MPa to 69 MPa (5 to 10 ksi). The influence of concrete strength, longitudinal reinforcement, and spiral reinforcement size/pitch on the strength and ductility of the columns was evaluated. The higher strength concrete columns displayed less ductility than the lower strength concrete columns. Columns with a higher longitudinal reinforcement ratio were able to maintain peak resistance for a large displacement, but exhibited less ductility as compared to columns with a relatively lower longitudinal reinforcement ratio. For the columns tested in this study, an increase in the spiral size and pitch, while maintaining a constant volume of spiral reinforcement, lead to an increase in the column ductility. For the highstrength concrete columns, first cracking of the cover concrete was observed at a lower load relative to the peak load as compared to the lowstrength concrete columns. Two failure modes were observed in the 8 specimens tested. The lowerstrength concrete columns exhibited a bulging type failure mode, and the higher strength concrete columns exhibited an inclined failure plane.