Advanced finite element modeling of textile-reinforced mortar strengthened masonry

Fabric-reinforced cementitious matrix (FRCM) strengthening is an innovative technology for effective reduction of seismic vulnerability of existing masonry and historical structures. At present, numerical modeling strategies for evaluation of the in- and out-of-plane performance of masonry structures strengthened with these composites are in their embryonic stage. The present chapter is aimed at presenting two alternative approaches to such strategies. In particular, a detailed 3D heterogeneous and an inexpensive homogenization approach are reviewed. In the first model, brick and mortar joints are meshed separately with 3D eight-noded elements, whereas FRCM is discretized using trusses (fiber grid) and 3D eight-noded elements (cementitious matrix). These 3D elements are made in all cases with a softening and damage behavior with plasticization, both in tension and compression, using the concrete damage plasticity model. In the homogenization approach, masonry is substituted with an equivalent nonlinear orthotropic material exhibiting softening. The elementary cell is discretized using a few triangular elastic elements (bricks) and holonomic interfaces (joints) in which all the nonlinearities are lumped. The FRCM reinforcement is applied to the homogenized masonry using equivalent trusses with limited tensile strength and fragile behavior, connecting adjoining rigid elements. Equivalent mechanical properties of the trusses can be eventually tuned accounting for FRCM debonding or rupture of the fibers. The pros and cons of the two numerical procedures are discussed with respect to their reliability in fitting experimental force-displacement curves and crack patterns, as well as to the rather different computational effort required by the two strategies.