Nonlinear analysis of conventional and buckling restrained braced frames under near field ground motions

In this study, nonlinear static and dynamic analyses were performed to compare the structural response of different type of moment resisting frame buildings with diagonally conventional braces (CBs) and buckling restrained braces (BRBs) subjected to near-field ground motions. For the purpose of this study, two bare frames having two equal 6 m bays and a total height of 20 m were selected as case studies. The existing steel frames were designed according to two different cases. They were referred to as a) ordinary moment-resisting frames (OMRF), designed without any provision for preventing the collapse due to storey mechanism and b) special moment-resisting frames (SMRF), designed to fail after the global mechanism occurred. Then, conventional and buckling-restrained braces were inserted in the bays of the existing frames. For the braced frame structures, diagonal type with three different configurations was used. For the earthquake excitation, artificial pulses that were equivalent to Northridge and Kobe records were taken into consideration. Capacity curve, interstorey drift index, global damage index, base shear, top shear, damage index and plastification were evaluated for each frame system. The results exhibited a substantial improvement in the earthquake performance of the frames with the incorporation of conventional and especially buckling-restrained braces.Keywords: Buckling-restrained brace, Diagonal brace, Earthquake, Frame, Nonlinear analysis, Structural response.