High-Strength Concrete Columns Confined with Spirals

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Title: High-Strength Concrete Columns Confined with Spirals

Author(s): Lonnie A. Marvel and Riyadh A. Hindi

Publication: Special Publication

Volume: 293

Issue:

Appears on pages(s): 1-14

Keywords: axial loading; cross spirals; ductility; concrete, high-strength; spiral reinforcement.

Date: 10/4/2013

Abstract:
This paper experimentally investigates the behavior of high-strength reinforced concrete columns confined using a new cross spiral confinement technique. The new cross spiral confinement technique uses two opposing spirals to confine circular concrete columns enhancing their strength and ductility, and increasing spiral spacing to facilitate the flow of fresh concrete. The new confinement arrangement is experimentally evaluated and compared to the conventional single spiral confinement arrangement. Twenty-one circular high-strength reinforced concrete columns with four different spiral spacings and longitudinal reinforcement ratios were tested under monotonic axial loading. Seven specimens utilized the conventional single spiral confinement, used as control specimens, while the remaining specimens utilized the new cross spiral arrangement. The new arrangement enables an increase in spiral spacing while maintaining the same volumetric confinement ratio as the conventional. Alternatively, doubling the volumetric confinement ratio without violating ACI 318-081 requirement for minimum spiral spacing. The study showed that the new cross spiral arrangement with the same volumetric confinement ratio as the conventional spiral obtained similar ultimate stress values while it attained about a twenty percent increase in ultimate displacement. The cross spiral confinement using twice the volumetric confinement ratio greatly outperformed the conventional spiral in all aspects.