Fiber-reinforced polymer (FRP) composite strips are bonded to the tension side of reinforced concrete (RC) beams to increase the load-carrying capacity of the structural elements. The weak link in the strengthening application is the debonding of the FRP strip at a strain level below that corresponding to the tensile failure of the composite. Thus, the design of the strengthened RC beam requires the definition of the debonding strain εfd of the FRP to perform cross-sectional analysis. The strain εfd is greater than the strain εdeb corresponding to the FRP debonding in single-lap tests, which are used to study the debonding phenomenon at the small scale. The difference between εfd and εdeb stems from the presence of multiple cracks along the beam that trigger the interaction of debonding forces in opposite directions and the effect of the curvature of the beam and associated presence of friction interfacial stresses. This paper presents a unique experimental investigation of the debonding phenomenon in strengthened RC beams. The RC beams are strengthened with the same area of fiber but using either two lower density composite sheets or one layer of higher density sheet. In both cases FRP anchors are used at the end of the FRP strips. A series of mirrors are used to capture images of the bottom face of the beam using digital image correlation (DIC). DIC analysis allows to investigate the debonding mechanism by studying the distribution of the strain component in the direction of the FRP fibers at different load levels and its relationship with the location of the flexural cracks. For comparison, the results of single-lap tests of the same FRP strips bonded to concrete prisms cast from the same batch of concrete used to construct the RC beams are presented. Ultimately, the goal of this work is to advance the knowledge on the bond mechanism at the structural scale and discuss the accuracy of the debonding strain used in international codes and guidelines.
Mirror DIC: A New Insight on the Debonding in FRP-Strengthened Beams
D'Antino, Tommaso;Focacci, Francesco;
2026-01-01
Abstract
Fiber-reinforced polymer (FRP) composite strips are bonded to the tension side of reinforced concrete (RC) beams to increase the load-carrying capacity of the structural elements. The weak link in the strengthening application is the debonding of the FRP strip at a strain level below that corresponding to the tensile failure of the composite. Thus, the design of the strengthened RC beam requires the definition of the debonding strain εfd of the FRP to perform cross-sectional analysis. The strain εfd is greater than the strain εdeb corresponding to the FRP debonding in single-lap tests, which are used to study the debonding phenomenon at the small scale. The difference between εfd and εdeb stems from the presence of multiple cracks along the beam that trigger the interaction of debonding forces in opposite directions and the effect of the curvature of the beam and associated presence of friction interfacial stresses. This paper presents a unique experimental investigation of the debonding phenomenon in strengthened RC beams. The RC beams are strengthened with the same area of fiber but using either two lower density composite sheets or one layer of higher density sheet. In both cases FRP anchors are used at the end of the FRP strips. A series of mirrors are used to capture images of the bottom face of the beam using digital image correlation (DIC). DIC analysis allows to investigate the debonding mechanism by studying the distribution of the strain component in the direction of the FRP fibers at different load levels and its relationship with the location of the flexural cracks. For comparison, the results of single-lap tests of the same FRP strips bonded to concrete prisms cast from the same batch of concrete used to construct the RC beams are presented. Ultimately, the goal of this work is to advance the knowledge on the bond mechanism at the structural scale and discuss the accuracy of the debonding strain used in international codes and guidelines.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
