Debonding mechanisms in FRP plated unreinforced masonry under out-of-plane loading

Of major concern is the out of plane strength of unreinforced masonry (URM) structures subjected to seismic loads. Through tests and numerical simulations, this article shows that the application of externally bonded (EB) fibre reinforced polymer (FRP) plates to URM members can substantially increase the out of plane strength. Of fundamental importance to the behaviour of EB FRP plated masonry is the plate debonding mechanism as this affects not only the ultimate strength but also the ability to absorb energy. A numerical procedure, which can simulate plate debonding in EB FRP plated masonry, is first described. The developed numerical program is then: used to explain the mechanism of debonding and the parameters that affect this debonding mechanism; compared with plated beam tests first reported in this paper; and used to illustrate the plate debonding mechanism and the substantial increases in out of plane strength that can be achieved.