An eigendecomposition-based and mesh-sensitivity reduced constitutive model for nonlinear analysis of concrete structures under non-proportional cyclic loading

Emerging 3D printed concrete techniques has raised numerous possibilities in contemporary architectural creations that are often beyond the scope of prevailing structural design standards. Rigorous, three-dimensional, and nonlinear finite element analysis (NLFEA) with appropriate constitutive modelling of materials would be inevitable when analysing complex structures. However, many existing concrete models could hardly handle those structures' complicated behaviour, including crack-induced anisotropy, changeable stress transfer mechanisms, shear-slip and re-contact, mesh-size sensitivity, etc. Hence, this paper has developed a novel and experimentally validated constitutive model to tackle the above issues. The novel features include (1) highly robust total-strain formulation, (2) cyclic normal and tangential stress-strain responses, (3) a novel algorithm for uniquely fixing the 3D crack plane coordinate, (4) the equivalent strain transformation for modelling the axial-lateral strain interaction, (5) shear-slip and re-contact behaviour of cracks, and (6) mesh-size sensitivity mitigation. The proposed model was implemented into ABAQUS's user-subroutine and applied to simulate a full-scale column test with specimen height = 5 m. The tested column, subjected to a constant vertical load and a cyclic load in the horizontal direction, failed in shear. The simulation can capture the damage evolutions and hysteresis response of the tested column. Hence, the proposed modelling framework could serve as a basis for analysing and designing concrete structures with unconventional shapes under non-proportional loading.