Delamination of FRP reinforced masonry pillars: numerical analyses and design considerations

In this communication, a heterogeneous, fully three-dimensional finite element model is presented, suitable to simulate delamination phenomena of FRP strips glued to masonry. Both mortar and bricks are modeled independently in tension and compression, through different isotropic damage variables and activation criteria. Reference is made to a masonry pillar, constituted by three Italian standard bricks and two mortar joints, reinforced by a perfectly-adherent FRP external sheet, and subjected to a conventional delamination test. The overall response in terms of reaction force versus tangential slip, and the three dimensional collapse mechanisms are investigated, induced by different boundary conditions and mechanical properties of the constituent materials. In particular, the dependence of nominal strength and overall ductility on FRP width is investigated. Numerical predictions are compared to those provided by the Italian recommendation CNR DT200, with the aim of highlighting pros and cons of design formulae.