Experimental assessment of bonded FRP-to-steel interfaces

Abstract

The use of bonded fibre-reinforced polymer (FRP) materials for the repair of civil infrastructure is becoming well established. The majority of applications are 'bond critical'; that is, the dominate limit state is affected by the FRP debonding from the substrate. Considerable research has been conducted on the behaviour of FRP bonded to a concrete substrate; however, there is a growing interest in using FRP bonded to a steel substrate. In the former case, bond behaviour is dominated by cohesive failure in the concrete substrate; in the latter, bond is dominated by adhesive behaviour. As a result of not needing to consider substrate failure in the case of FRP-to-steel applications, the FRP may be utilised much more efficiently, provided bond can be maintained. This paper briefly reviews factors affecting bond of FRP-to-steel and presents a relatively simple laboratory test method for assessing bond performance. The method is well suited to comparing performance of different applications, surface preparations, environmental exposures and so on, but also yields quantitative data in the form of the steadystate energy release rate useful for modelling and designing FRP-to-steel bonded interfaces.

Fatigue behavior of damaged steel beams repaired with CFRP strips

“…Debonding resulted in the stress transfer from the CFRP moving away from the notch and was evidenced by the relatively constant distribution of stress across a longer length of debonded CFRP 'bridging' the notch. The CFRP debonding strain was approximately 3300 µε which is consistent with observations from other studies using the same CFRP/adhesive system on a steel substrate [29]. The maximum adhesive stress developed occurred between Gage 3 (38 mm) and Gage 4 (76 mm) at an applied load of 66.7 kN.…”

A State-of-the-Art Review on Structural Strengthening Techniques with FRPs: Effectiveness, Shortcomings, and Future Research Directions

“…Some studies indicate that the impact of fiber shawls is less pronounced in filled columns compared to hollow columns. This effect is also observable in hollow columns, with GFRP being less effective than CFRP [ 78 , 80 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 ]. El-Sayed [ 121 ] discovered that the shear strength of concrete beams, wrapped by CFRP sheets, increases in parallel with the ultimate stiffness and strength of the control beam and the reduction in the ductility of a RC beam.…”

Editorial

“…This first issue contains papers on strengthening wrought iron 1 (until recently a problem area because of the unique laminar structure of wrought iron), adhesive bonding of FRP to steel structures 2,3 (which requires excellent surface preparation and produces a variety of stress concentrations that must be carefully considered at the design stage), the behaviour of carbon fibre and aramid tendons 4,5 (a very promising area for new build) and long-term environmental effects on FRP joints 6 . The authors are all prominent in the area of FRP research.…”