Strain Development and Hoop Strain Efficiency in FRP Confined Square Columns

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Title: Strain Development and Hoop Strain Efficiency in FRP Confined Square Columns

Author(s): Jason Barrington, David Dickson, Luke Bisby and Tim Stratford

Publication: Special Publication

Volume: 275

Issue:

Appears on pages(s): 1-20

Keywords: FRP, image correlation, reinforced concrete, square columns, strain efficiency, strengthening.

Date: 3/1/2011

Abstract:
The performance of FRP-wrapped square/rectangular columns depends on their corner radius, with larger corner radii resulting in superior confinement. However, the specific impacts of corner radius on the development of hoop strains in the FRP wraps are not well known. Most existing models for square FRP confined columns only indirectly consider the impacts of corner radius by inserting ‘shape’ factors into empirically calibrated models based on circular FRP confined columns. This approach cannot rationally account for the phenomena resulting from corner effects. This paper presents an investigation into the mechanics of square FRP confined concrete columns. It is shown that accounting for corner radius requires the inclusion of at least two modification factors: (1) a shape factor which accounts for the area of effectively confined concrete as well as the column’s side aspect ratio, and (2) a variable strain efficiency factor which accounts for the adverse effects of decreasing corner radius.