The effect on the interfacial strength of the length/width ratio of FRP sheet bonded to concrete

Abstract

Fibre reinforced polymer laminates are commonly used for the retrofit of ailing reinforced concrete structures for both shear and flexure. Recent studies have been undertaken regarding bond behaviour, but these have not advanced significantly to apply in a general manner to FRP sheets. This paper presents the effect of the length/width ratio on the bond stress and strength between FRP laminates and concrete. The experimental and the theoretical study give the same effect of the length/width ratio. Experimental bond models were tested of 7 specimens with 3 bonding techniques and compared with predictions from finite element models. Mesh sensitivity studies were carried out for the FE modelling, and compatible crack patterns were observed between FE models and the experimental samples. The FE shows clearly the distribution of principal stress in the concrete and explains the failures observed in the experimental tests. This study shows that the width of CFRP sheet has more influence than the length. Also it can be concluded that increasing the CFRP sheet width leads to a propensity for concrete de-bonding. This also illustrates how existing expressions for bond strength match with the observed results. In general the results show that an increase in width provides more load capacity than a relative increase in length even some design methods do not interest to the effective of width/length sheet ratio.