Behavior Factor of Dual Concentrically Braced Systems Designed by Eurocode 8

In concentrically braced frames the low plastic redistribution capacity favours collapse configurations characterized by plastic deformations concentrated on a few storeys. The degrading character of the inelastic response of braces and the presence of scattered values of the storey overstrength factor further emphasize this behaviour. To improve the seismic response of these frames many researchers propose to couple concentrically braced frames with moment resisting frames. Despite the interest for the use of these dual structures the code procedures proposed for their design remain simplistic and not thoroughly investigated by researchers. To contribute to the knowledge of the effectiveness of these code procedures, several buildings with concentrically braced dual structure are designed here according to Eurocode 8. Their seismic response is obtained through incremental nonlinear dynamic analysis. The investigation aims to evaluate the correctness of the behaviour factor suggested in the Eurocode 8 and the effectiveness of the rules proposed for the application of the capacity design principles.