Concentrically Braced Frames (CBFs) are a class of structures resisting lateral loads through a vertical concentric truss system. The axes of the members  are aligned concentrically at the joints. CBFs tend to be efficient in resisting lateral forces which allow high strength and stiffness. That lead to less favorable seismic response, low drift capacity and higher accelerations. Special Concentrically Braced Frames (SCBFs) are a special class of CBF which are proportioned and detailed to maximize inelastic drift capacity. This type of CBF system is defined only for structural steel and composite structures.  Proportioning and detailing rules for braces ensure adequate axial ductility, which translates into lateral drift capacity for the system. Special design and detailing rules for connections, beams, and columns attempt to preclude less ductile modes of response that might result in reduced lateral drift capacity.

Taken from a FB page source. 

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