The paper proposes some of the results of a research whose aim was to define a design procedure of HDR-based dissipating braces for the seismic protection of composite moment resisting space frames. Some of the results of an experimental campaign, carried out on a real scale single storey one bay-by-two bays mock-up of a steel-concrete composite space frame equipped with HDR-based dissipating devices, are shown. In the first part of the paper, the design procedure of the bare mock-up and the experimental campaign performed on the HDR devices are summarized. The second part of the paper reports the results of the dynamic characterization of the bare frame and of the equipped frame, performed with free vibration tests. Finally, the results of cyclic tests performed with sinusoidal displacement paths are compared with results provided by numerical calculations in order to validate a single degree of freedom model.