Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Milan, Italy
Department of Engineering, University of Ferrara, Ferrara, Italy

A 3D homogenized FE limit analysis software for the prediction of collapse loads and failure mechanisms of masonry buildings reinforced with FRP strips is presented. A two step approach is adopted: in step I masonry homogenized failure surfaces are obtained through a kinematic FE approach in the representative element of volume (REV), constituted by a brick interconnected with its six neighbors. 8-noded rigid infinitely resistant parallelepiped elements interconnected with interfaces with frictional behavior and limited tensile and compressive strength are utilized to model the REV. A linear programming problem in few variables is obtained, suitable to recover masonry failure surfaces. In step II, homogenized surfaces are implemented in the novel FE kinematic limit analysis software for an inexpensive evaluation of collapse loads of entire buildings. Delamination is considered imposing to FRP-masonry interfaces a limited resistance in agreement with Italian code CNR-DT-200. Six noded rigid infinitely resistant 3D wedge shaped elements are used to model homogenized masonry, whereas for FRP three noded rigid elements are utilized. A two story small masonry house reinforced with FRP strips is analyzed to evaluate the increase of the load bearing capacity of the entire building due to the FRP.

Key words
Masonry, FRP strengthening, limit analysis, homogenization, 3D Finite Elements