Experimental study on the bond behaviour of a transversely compressed mechanical anchorage system for externally bonded reinforcement

The use of Carbon Fibre-Reinforced Polymer (CFRP) laminates as Externally Bonded Reinforcement (EBR) has been widely used to strengthen concrete structures in flexure. In some strengthening applications special end-anchorage systems are required at the end of the FRP element in order to transfer the high shear stresses, typically developed between the FRP reinforcement and the concrete substrate, so as to avoid a premature FRP peeling-off failure. A typical anchorage system is the mechanical anchorage, where the laminate is transversely compressed through an anchorage plate, which is fixed to concrete with prestressed screws. The influence of laminate width and compressive stresses created by the anchorage system still requires better understanding. This paper aims at studying the experimental overall bond response of concrete elements strengthened with mechanically anchored EBR CFRP systems. For this purpose, 6 concrete blocks of 200x500x800 mm3 were strengthened with CFRP laminates of different widths using EBR technique; afterwards they were mechanically anchored to the concrete with different levels of transverse compression, and finally they were tested under a pull-out configuration until failure. The results of the investigation show the influence of the width of the laminate, the level of confinement on the bond strength and capacity of the system.This work was supported by FEDER funds through the Operational Program for Competitiveness Factors – COMPETE and National Funds through FCT (Portuguese Foundation for Science and Technology) under the project FRPLongDur POCI-01-0145-FEDER-016900 (FCT PTDC/ECMEST/1282/2014) and partly financed by the project POCI-01-0145-FEDER-007633. The first author acknowledges the Spanish Government (Ministerio de Educación, Cultura y Deporte) for the grant José Castillejo ref. CAS16/00288. The second author wish also to acknowledge the grant SFRH/BD/98309/2013 provided by FCT. Finally, the authors also like to thank the S&P Clever Reinforcement Ibérica Lda. company for providing the materials