A numerical failure analysis of nano-filled ultra-high-performance fiber-reinforced concrete structures via a moving mesh approach

This work proposes a novel FE-based model for simulating crack propagation mechanisms in Ultra-HighPerformance Fiber-Reinforced Concrete (UHPFRC) structures (typically exhibiting compressive strength over 150 MPa and tensile strength around 10 MPa) enhanced with nanofillers under general loading conditions. This model combines synergistically a Moving Mesh (MM) technique with the Interaction Integral (M-integral) method, and the R-curve concept. In particular, the MM technique, based on the Arbitrary Lagrangian-Eulerian formulation, is used for tracking geometry changes of the computational domain caused by crack advance, thus avoiding massive re-meshing operations. In particular, a mesh regularization technique based on proper rezoning equations is used to ensure that the mesh points move consistently. The M-integral method is used for extracting the crack front variables (i.e., the Stress Intensity Factors (SIFs)), required for the computation of the mixed-mode crack growth direction. Finally, the well-known R-curve concept allows the ductile behavior of nano-enhanced UHPFRC beams to be captured in a LEFM setting. In particular, the crack growth resistance, regarded as a function of the crack extension, is numerically derived via a calibration procedure starting from the available experimental data. In addition, to assess the reliability and effectiveness of the proposed approach, the results of numerical simulations are compared with experimental outcomes reported in the literature.