Compressive and Flexural Behavior of RC Columns Laterally Prestressed by High-strength Steel Bars

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Title: Compressive and Flexural Behavior of RC Columns Laterally Prestressed by High-strength Steel Bars

Author(s): T. Hitaka, K. Sakino, T. Yamakawa, and A. Furukawa

Publication: Special Publication

Volume: 238

Issue:

Appears on pages(s): 429-446

Keywords: confined concrete; high-strength steel bar; moment - curvature analysis; prestress confinement; retrofit; ultimate moment

Date: 10/1/2006

Abstract:
A dry column confining method using high-strength steel bars proposed by one of the authors is applied to a total of 24 reinforced concrete columns. Two series of tests were conducted on these columns. Hoop steel ratio of the columns was 0.1%, typical of RC columns designed before the Japanese Building Code in 1981. These RC columns were laterally reinforced using 19 sets of four high-strength steel bars and L-shaped steel blocks that were attached around the column by tightening the high-strength steel bars. Five specimens were exposed to concentric compression. Uniform bending test was conducted on 19 specimens under constant axial load. High-strength steel bars were pre-tensioned before testing. The amount of pre-tension was controlled by strain in the bars. It was found that the new confining method is effective to increase ductility of the RC columns. Strength of a RC column increases in a proportional manner to the amount of pre-stress in high-strength steel bars. Strength estimation method is proposed. The measured strength varied between 93% to 116% of the calculated strength.