High Damping Rubber (HDR), commonly used for seismic isolation devices, may also be used to produce passive dissipation devices. HDR-based devices have a number of advantages: they are recentering, they can withstanding a large number of cycle and moreover they can dissipate energy even under low excitations, such in the case of frequent earthquakes or wind actions. This paper presents a validation of a nonlinear viscoelastic model for HDR-based dampers already proposed by the same authors, by means of comparisons with experimental tests carried out on a full scale steel-concrete composite mock-up. The paper firstly describes the real scale mock-up and its characterization, in the elastic displacement range, carried out by means of fr...