BRACED FRAMES WITH HYSTERETIC DISSIPATIVE DEVICES: SEISMIC RESPONSE AND DESIGN CRITERIA

The seismic behaviour of elastic braced frames with hysteretic dissipative devices is investigated. The analysis is carried out using a simplified single degree of freedom model that is deduced on the basis of an equivalence criterion between one-storey and multi-storey braced frames. The criterion allows one to characterise the structure by means of a few global parameters, such as the fundamental period of vibration, the ratio between the fundamental period and that of the correspondent unbraced frame, and the behaviour factor. The combined effect of design values of structural parameters and the energy frequency content of the input is stressed by evaluating the power spectral density of the stationary phase of the response. Consistent energy, displacement and strength response spectra are shown. The results elucidate the different behaviour of short and medium period structures with respect to the predominant period of ground motion. For each of the two classes, design criteria and guidelines for choosing the optimal values of the structural parameters are summarised. Four design examples are presented in order to demonstrate the effectiveness of the proposed criteria.