FRP-Confinement of Hollow Concrete Cylinders and Prisms

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Title: FRP-Confinement of Hollow Concrete Cylinders and Prisms

Author(s): R. Modarelli, F. Micelli, and O. Manni

Publication: Special Publication

Volume: 230

Issue:

Appears on pages(s): 1029-1046

Keywords: FRP confinement; hollow-core columns; reinforced concrete

Date: 10/1/2005

Abstract:
The use of hollow-core reinforced concrete (RC) sections for bridge piers hasbecome a popular engineering practice to obtain a reduction of the self-weight(especially in seismic zones) and a better structural efficiency in terms of the strength/mass and stiffness/mass ratios. In contrast to this popularity in practice, scientificstudies on the mechanical behavior of such structural elements are limited.The use of Fiber Reinforced Polymer (FRP) materials for external confinement of hollowcore columns and piers is an almost unknown field at the moment. The research workpresented herein aims at evaluating the influence of various experimental parameterson the effectiveness of FRP jackets applied to hollow concrete columns.Hollow-core concrete prisms and cylinders were tested under uniaxial compression tostudy the stress-strain relationship before and after FRP jacketing. A range ofexperimental parameters were investigated: different concrete strength, type of fibers,number of wrap layers, column shape and dimensions, and for square and rectangularsections, the corner radius and the cross-sectional aspect ratio. Axial strain wasmeasured by LVDTs, while strains in the fibers were recorded by electrical straingauges.Circular columns wrapped with FRP showed a significant increase in terms of bothstrength and ultimate displacements. Results obtained by laboratory tests were closeto those recorded for FRP-confined concrete, which means that the increase in ultimateload was found to be comparable to that found in full circular sections. Rectangularcolumns showed a lower increase in ultimate capacity, compared to circular sections,even if the results related to ultimate axial displacement encourage adopting thistechnique for seismic retrofit to fulfill higher ductility requirements in both prismatic andcylindrical columns.