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Notation
Ag = gross area of concrete section, in2
As= area of nonprestressed longitudinal tension reinforcement, in2
Ec = modulus of elasticity of concrete, psi
Es = modulus of elasticity of reinforcement, psi
fc' = specified compressive strength of concrete, psi
fy = specified yield strength for nonprestressed reinforcement, psi
Mu= factored moment at section, in.-lb
β = ratio of long to short dimentions; clear spans for two-way slabs, sides of column, concentrated load or reaction area; or sides of a footing
γs = factor used to determine the portion of reinforcement located in center band of footing
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According to ACI 18.13.2.1, the provisions of ACI 18.13 should apply to structures assigned to Seismic Design Category D,E or F.
According to ACI 18.13.2.2, Longitudinal reinforcement of columns and structural walls resisting earthquake effects should extend into the footing, mat or pile cap, and should be fully developed for tension at the interface.
According to ACI 18.13.2.3, if the column is designed assuming a fixed-end, it should satisfy ACI 18.13.2.2 requirements. Also, if hooks are required, longitudinal reinforcement resisting flexure should have 90-degree hooks near the bottom of the foundation with the free end of the bars oriented toward the center of the column.