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Notation
Mn = nominal flexural strength at section, in.-lb
Mnb = nominal flexural strength of beam including slab where in tension, framing into joint, in.-lb
Mnc = nominal flexural strength of column framing into joint, calculated for factored axial force, consistent with the direction of lateral forces considered, resulting in lowest flexural strength in.-lb
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The columns of special moment frames are considered as part of the seismic-force resisting system. The subject of this title is to reduce the possibility of yielding in columns of special moment frames. Columns not stronger than beams increased likelihood of inelastic action. The worst possible case is when all columns in a given story have flexural yielding at both ends. In this case, it creates a column failure mechanism to cause collapse. In order to avoid this situation, the minimum flexural strength of colums control given in ACI 18.7.3 should be satisfy.
The flexural strenghts of the columns shall satisfy ACI Eq.(18.7.3.2),
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18.7—Columns of special moment frames
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