Seismic Research on Multistory Buckling Restrained Braced Steel Frame

Abstract:

To study the elasticplastic dynamic performance of multistory bucklingrestrained braced steel frame (BRBF) which modeled separately with rigid and pinned models, the bucklingrestrained brace (BRB) average horizontal force sharing ratio β and shearweight ratio CB were used as the main parameters, and the secondorder nonlinear elasticplastic dynamic analysis method was adopted. The research results are as follows: Maximum story drift distributes more evenly under the seismic fortification intensity, concentrates except for the first and top floor in the great or rare earthquake with the rigid model, focuses on the first floor particularly with the hinged column base from the pinned model, and additionally focuses on middle and upper layers affected by the second vibration mode. When β ≈30% under the great earthquake, the shear deformation dominates the structure and the first vibration mode is excellent; β≈60%, the second vibration mode participates in; β≈90%, the second vibration mode is remarkable. β value does not affect the seismic input energy when the fundamental period is set down, and the equivalent velocity VE is basically the same during the similar fundamental period; Meanwhile, VE values can be derived from elastic fundamental period and seismic wave energy spectra, which once again shows the effectiveness of seismic design based on energy balance method.

Key words:buckling restrained brace (BRB) average horizontal force sharing ratio; higher vibration mode; member performance requirement; seismic design based on energy balance method