NON-DIMENSIONAL PARAMETRIC ANALYSIS FOR THE SEISMIC RESPONSE OF DUAL MOMENT-RESISTING AND BUCKLING-RESTRAINED BRACED FRAMES

Buckling-restrained braces (BRBs) have proven to be very effective devices improving the seismic performance of existing and new building frames. They provide strength, stiffness and added damping to the structure, however, due to their low lateral post-elastic stiffness, their use may lead to excessive residual deformations which may hinder the building’s reparability. Moreover, excessive cumulative ductility demand in the BRBs may compromise the capability of withstanding multiple earthquakes. To overcome these drawbacks, BRB frames (BRBFs) can be coupled with moment-resisting frames (MRFs) to form a dual system. If properly designed, the MRF acts as a back-up frame and allows to control the residual drifts and optimize the performance of the BRBs. This paper attempts to provide insights into the performance and residual capacity of this type of dual systems and to shed light on the influence of the main BRB’s design parameters. A non-dimensional formulation of the equation of motion is derived and an extensive parametric study is carried out on a single-degree-of-freedom system subjected to a set of natural records with different characteristics and scaled to various intensity levels. This allows to investigate a wide range of configurations, considering different levels of the relative strength of the BRBF and MRF and their ductility demand, and to obtain useful information for the BRBs design.