Experimental Study on Short Concrete Columns with External Steel Collars

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Title: Experimental Study on Short Concrete Columns with External Steel Collars

Author(s): Jianhua Liu, Robert G. Driver, and Adam S. Lubell

Publication: Structural Journal

Volume: 108

Issue: 3

Appears on pages(s): 360-369

Keywords: collars; columns; cyclic loading; ductility; rehabilitation; repair; steel; strengthening

Date: 5/1/2011

Abstract:
Previous research has shown that deficient reinforced concrete columns can be rehabilitated or strengthened by using external steel collars to provide confinement. This technique can improve both the axial and flexural strengths of a column and enhance its overall ductility. The use of steel collars is investigated for short reinforced concrete columns subjected to combined axial and cyclic lateral loading through full-scale experiments. Ten cantilever columns, including two control columns and eight rehabilitated columns confined by steel collars, were tested. Parameters considered in the experimental program include collar spacing, collar stiffness, longitudinal reinforcement ratio, axial compression ratio, pretension of collar bolts, and shear span-depth ratio. One of the control columns was tested to failure and then repaired to study the feasibility of using external steel collars on previously damaged columns. The experimental results show excellent improvements in ductility, strength, and energy dissipation capacity of the columns due to the presence of the collars, demonstrating that the system has great promise as an effective rehabilitation technique for deficient short reinforced concrete columns.