Braced frame

Members in a braced frame are not allowed to sway laterally (which can be done using shear wall or a diagonal steel sections, similar to a truss).

Ordinary concentric braced frames (OCBFs) do not have extensive requirements regarding members or connections, and are frequently used in areas of low seismic risk.

OCBF steel frame buildings originated in Chicago and reinforced concrete frames originated in Germany and France – areas where earthquakes were not an engineering consideration.

[1] Accordingly, special concentrically or eccentrically braced frames were later developed with extensive design requirements, and are frequently used in areas of high seismic risk.

The purpose of the concentrically- or eccentrically-braced design is to ensure adequate ductility (i.e., to stretch without breaking suddenly).