A three-dimensional meso-scale approach to the fracture analysis of ultrahigh performance concrete based on micropolar peridynamics

A three-dimensional (3D) meso-scale approach is proposed to simulate the fracture of ultrahigh performance concrete (UHPC) within the framework of peridynamics (PD). Micropolar PD, as an improved form of bond-based PD, is adopted to model the cementitious matrix. A PD constitutive model considering strain-hardening and strain-softening is introduced to simulate the mechanical behavior of UHPC. To improve the computational efficiency, a semi-discrete technique is employed to simulate the fibers. Meanwhile, to compensate for the drawbacks of the semi-discrete technique in analyzing fiber deformation, the effects of fiber inclination and end deformation on the fiber-matrix interface are incorporated into the fiber pullout model. In the analysis of cracking in UHPC, uniaxial tensile and uniaxial compressive tests were simulated to calibrate the proposed 3D PD model. Then, mode I fracture and mixed-mode fracture of UHPC beams under three-point bending were simulated. Satisfactory agreement is achieved between PD analysis and experimental observations in terms of crack paths and load-displacement curves. Additionally, the numerical results show that the random distribution of fibers has a stronger impact on the 3D fracture surface for mixed-mode fracture compared to mode I fracture.