Title: Experimental Study of Intermediate Crack Debonding in Fiber-Reinforced Polymer Strengthened Beams

Author(s): Owen Rosenboom and Sami H. Rizkalla

Publication: Structural Journal

Volume: 105

Issue: 1

Appears on pages(s): 41-50

Keywords: bond; cracking; debonding; fiber-reinforced concrete; prestressed.

DOI: 10.14359/19067

Date: 1/1/2008

Abstract:
Interface crack propagation of fiber-reinforced polymer (FRP)- strengthened reinforced or prestressed concrete flexural members is often initiated from the toes of the intermediate cracks and propagates toward the supports. This type of FRP delamination is commonly termed intermediate crack (IC) debonding and is common for flexural members with high shear span-to-depth ratios. This paper describes an experimental program where six 30 ft (9.14 m) long prestressed concrete bridge girders were tested monotonically to failure to evaluate the bond characteristics of carbon FRP (CFRP) strengthening systems. Four of the beams failed due to IC debonding, one failed due to FRP rupture, and the unstrengthened control girder failed due to concrete crushing. The results of this study were combined with the results from other tests in the literature to create a useful experimental database. The database was used to assess the analytical models currently available in the national code documents. The analysis indicated that the current models do not correlate well with the experimental database and the need for a new analytical model is highlighted. This paper briefly discusses a proposed model for IC debonding that predicts the measured values tested by other researchers well.