A State-of-the-Art Review on Debonding Failures of FRP Laminates Externally Adhered to Concrete

Thomas H.-K Kang,Dong Joo Lee,Sanghee Kim,Joe Howell

doi:10.1007/s40069-012-0012-1

Abstract

There is significant concern in the engineering community regarding the safety and effectiveness of fiber-reinforced polymer (FRP) strengthening of RC structures because of the potential for brittle debonding failures. In this paper, previous research programs conducted by other researchers were reviewed in terms of the debonding failure of FRP laminates externally attached to concrete. This review article also discusses the influences on bond strength and failure modes as well as the existing experimental research and developed equations. Based on the review, several important conclusions were re-emphasized, including the finding that the bond transfer strength is proportional to the concrete compressive strength; that there is a certain bond development length that has to be exceeded; and that thinner adhesive layers in fact lower the chances of a concrete-adhesive interface failure. It is also found that there exist uncertainty and inaccuracy in the available models when compared with the experimental data and inconsistency among the models. This demonstrates the need for continuing research and compilation of data on the topic of FRP’s bond strength.

Highlights

Much of the concrete infrastructure in the world is aging beyond fifty years, and many of these structures are showing significant deterioration and distress
Buyukozturk et al.’s (2004) research revealed that that both failure load and ductility of pre-cracked reinforced concrete (RC) beams can be significantly increased through the addition of fiber-reinforced polymers (FRP) shear strengthening which helps the anchorage of FRP sheets used for flexural strengthening; one of the areas lacking an overall understanding is still the interface and bond between the FRP laminates and the concrete substrate
The results provided by Arduini et al (1997) confirmed the strengthening benefits provided by externally bonded FRPs, they highlighted the existence of sudden brittle failure mechanisms that must be considered

Summary

Introduction

Much of the concrete infrastructure in the world is aging beyond fifty years, and many of these structures are showing significant deterioration and distress. Existing experimental research shows that the theoretical high ultimate capacity of FRP strengthened reinforced concrete (RC) beams often cannot be achieved because of FRP plate debonding or horizontal cracking and subsequent loss of concrete cover below the reinforcing steel. This significantly reduces the strength enhancement provided by the FRP and can create brittle failures. Buyukozturk et al.’s (2004) research revealed that that both failure load and ductility of pre-cracked (in service) RC beams can be significantly increased through the addition of FRP shear strengthening which helps the anchorage of FRP sheets used for flexural strengthening; one of the areas lacking an overall understanding is still the interface and bond between the FRP laminates and the concrete substrate. The following sections review the previous research programs on the bond behavior of FRP laminates externally bonded to concrete and the currently available analytical expressions to predict the interface stresses and effective bond lengths

Previous Research on the Interface Bond of FRP Attached to Concrete

Bond-Related Analytical Models

Findings

Conclusions