Efficient implementation of an advanced bounding surface constitutive model for steel

Structural steel has gained increasingly relevance in the field of structural engineering due to its high ductility and high strength-to-weight ratio. Furthermore, different approaches were developed with a view to describing its plastic behaviour, on the basis of some peculiarities of the steel post-yielding response, such as the plateau, together with both kinematic and isotropic hardening, and its behaviour under cyclic loads. In this regard, the bounding surface theory was proven to be effective in a wide range of applications, involving different materials (i.e., soils, concrete and steel). Among the bounding surface constitutive models for steel, the SANISTEEL model revealed extremely promising, containing a robust analytical formulation, still not included into a finite element code and tested at the structural level. Hence, this work aims at describing the implementation procedure of the above mentioned uniaxial constitutive model in OpenSees focussing on the implementation procedure, and on the numerical procedure employed to limit the overshooting of the stress-dependent function. The implementation is validated against experimental tests and comparisons with the Updated Voce-Chaboche formulation. Furthermore, numerical simulation of the seismic response of a steel frame is presented. The implementation reveals, that SANISTEEL model is extremely capable to simulate the monotonic and cyclic response of structural steel.