Title: Flexural and Shear Strengthening of Concrete Beams Using New Triaxially Braided Ductile Fabric

Author(s): Nabil F. Grace, Wael F. Ragheb, and George Abdel-Sayed

Publication: Structural Journal

Volume: 100

Issue: 6

Appears on pages(s): 804-814

Keywords: concrete; ductility; fiber reinforcement; flexure; shear.

DOI: 10.14359/12847

Date: 11/1/2003

Abstract:
The effectiveness of a new triaxially braided ductile fabric designed specifically to be used for strengthening of concrete beams has been experimentally investigated. This fabric is pseudo-ductile and is a hybrid of different types of fibers. The fabric contains bundles of fibers triaxially braided in three directions (+45, 0, and –45 degrees). The 0-degree fibers are mainly used for flexural strengthening, while the +45- and –45-degree fibers are mainly used for shear strengthening. The fabric has a yield-equivalent strain value in the 0-degree direction close to the yield strain value of steel. Therefore, it has the potential to contribute significantly to the beam load before the yielding of the steel reinforcement of the strengthened beam without further sacrificing much of its ductility. In addition, the fabric is designed to exhibit a certain load-strain response in its 45-degree directions, allowing the optimum contribution to beam shear strength. Twelve reinforced concrete beams have been strengthened in flexure or shear using the new fabric. Similar beams have been strengthened with a carbon fiber sheet and one with a steel plate to compare their behavior with those strengthened with the new fabric. The beams were loaded in four-point bending until failure. The beams strengthened in flexure with the new fabric produced greater ductility than those strengthened with the carbon fiber sheet. The new fabric produced yield plateaus similar to those of the unstrengthened beams and also to that experienced by the steel plate. The test results of the beams strengthened in shear demonstrated that the fabric stretched before beam failure to strain values that were very close to its yield-equivalent strain value. This confirmed that the fabric strength was fully exploited.