Elisa Bertolesi¹, Gabriele Milani², Bahman Ghiassi³, and Ernesto Grande⁴
1)  ICITECH, Universitat Politècnica de Valencia
Camino de Vera s/n 46022, Valencia (Spain)
e-mail: elber4@upv.es
2)  Dept. of Architecture, Built environment and Construction engineering ABC, Politecnico di Milano
Piazza Leonardo da Vinci 32, 20133, Milan (Italy)
e-mail: gabriele.milani@polimi.it
3)  Centre for Structural Engineering and Informatics, University of Nottingham
Coates Building, University Park NG7 2RD, Nottingham (UK)
e-mail: Bahman.Ghiassi@nottingham.ac.uk
4)  University Guglielmo Marconi, Department of Sustainability Engineering
via Plinio 44, 00193, Rome (Italy)
e-mail: e.grande@unimarconi.it

Keywords: Micro-modeling approach, Cohesive interface, Fiber Reinforced Cementitious Matrix material (FRCM), Numerical analysis, Concrete damage plasticity model.

Abstract. A novel advanced full 3D heterogeneous FE numerical model for the analysis of specimens made by a fragile material (e.g. concrete or masonry), reinforced with FRCM and subjected to standard debonding tests is discussed. The numerical approach relies into a micro-mechanical full 3D discretization of the FRCM reinforcing system. For the two cementitious matrix layers (external and internal) 8-noded brick elements exhibiting distinct damage and softening behavior in tension and compression are utilized, whereas for PBO elastic 3D elements are used, introducing an inelastic cohesive interface layer placed between the two layers of cementitious mortar and the PBO grid. In this way, all possible failure modes in FRCM strengthening systems can be properly reproduced, exception made for PBO tensile rupture, which is unlike in the majority of the existing experimental tests available. The model is preliminarily benchmarked utilizing some experimental results available in the technical literature, and relying into single lap shear testes performed on FRCM strengthening systems applied to a concrete substrate. Excellent agreement between the results obtained with the micro-mechanical numerical model proposed and experimental outcomes is observed, especially in the prediction of the initial stiffness, peak strength and post peak behavior.