Seismic response and behaviour factor of dual eccentrically braced systems designed by Eurocode 8

The authors consider dual structures constituted by eccentrically braced frames and moment-resisting frames and design these structures according to rules that are the natural extension of those proposed in Eurocode 8 for dual structures constituted by concentrically braced frames and moment resisting frames. The procedure considers that the dual eccentrically braced structures may be designed by means of a single value of the behaviour factor and that the lateral forces are distributed between the braced and moment resisting frames according to their lateral stiffness. Further, a new design procedure is proposed, which slightly modifies that of Eurocode 8 in order to fill gaps and make the new procedure consistent with the intent of the code. In order to evaluate the effectiveness of the rules proposed for the application of the capacity design principles and the adequacy of the behaviour factor, the seismic response of the designed systems determined through incremental non-linear dynamic analysis is examined. To ensure the general validity of the results, the designed buildings are considered to be founded on hard or soft soil and are characterised by different values of the link length and number of storeys.