A 3D cohesive-frictional coupled interface model for mesoscale simulation of steel fibre-reinforced concrete

A 3D mesoscale finite element modelling approach is developed for simulating complicated damage and fracture behaviour in steel fibre-reinforced concrete (SFRC) with explicit modelling of fibre–matrix interfaces. In this approach, a new 3D four-noded cohesive-frictional coupled interface element is developed to model the nonlinear interfacial bond-slip behaviour, supplemented by a kinematic multiple-point-constraint (kMPC) algorithm to simulate the wrapping effect of the mortar around the fibres. They are implemented as a user-defined element (UEL) and a user-defined MPC subroutine in ABAQUS, respectively. Three cohesive-frictional constitutive relationships are proposed to describe the nonlinear bond-slip behaviour of different fibre–matrix compositions. The new approach is validated by single fibre pullout tests, direct tensile tests and three-point bending tests of SFRC specimens with randomly distributed fibres. The results show that the new approach is capable of effectively capturing typical failure mechanisms in SFRC, such as fibre yielding, matrix failure, and fibre–matrix debonding and slipping.