Implementation and validation of a constitutive model for the cyclic behaviour of interface elements

A constitutive model developed for the simulation of the cyclic behaviour of interface elements is proposed. Its theoretical framework is fully based on the plasticity theory. Starting from an existing monotonic model, two new yield surfaces are introduced in order to include non-linear unloading/reloading behaviour in an accurate fashion. The motion of the unloading surfaces is controlled by a mixed hardening law and, by adopting appropriate evolution rules, it is possible to reproduce non-linear behaviour during unloading. Numerical results concerning the analysis of both uniaxial tests and masonry walls are presented and discussed as application and validation examples of the constitutive model.