mason_constitutive_model

MASON (Masonry Advanced Softening cONtact) is a contact constitutive model for masonry joints developed within the framework of multi-surface plasticity for DEM analyses. It combines three yield surfaces — a tension cut-off, a Coulomb friction surface in shear, and an elliptical compression cap. Tensile and shear strengths soften exponentially after the peak, governed by the mode-I and mode-II fracture energies, while the dilatancy associated with shear sliding decays exponentially. Mode-dependent unloading and reloading rules, including secant-type degraded unloading, govern the cyclic response — reproducing hysteresis, pinching, and stiffness degradation, and attenuating spurious high-frequency content at re-contact in dynamic analyses. The model is implemented as a user-defined contact model in 3DEC 9.0 for both rigid and deformable blocks, and has been validated across scales — from joint-level tests through components (cross-vault, gable walls to collapse) to the building scale (TUD-BUILD-1) — under monotonic, cyclic, and dynamic loading with a single parameter set transferred without recalibration. The implementation is released openly.