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db = nominal diameter of bar, wire, or prestressing strand, in
Ach = cross-sectional area of a member measured to the outside edges of transverse reinforcement, in.2
f'c = specified comprehensive strength of concrete, psi
fyt = specified yield strength of transverse reinforcement,psi
Ag = gross area of the concrete section, in.2 For a hollow section, Ag is the area of the concrete only and does not include the area of the void(s)
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25.7.2 Ties
Ties , applies apply a closed loop of the deformed bar, which satisfies the rules:
Center-to-center spacing does not exceed the least of 16db of the longitudinal bar, 48db of the tie bar, and the smallest dimension of the member
Minimum The minimum diameter of the tie bar is controlled automatically according to ACI 25.7.2.2. Diameter The diameter of the tie bar is at least:
No. 3 enclosing No. 10 or smaller longitudinal bars
No. 4 enclosing No.11 or larger longitudinal bars or bundled longitudinal bars
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Anchorage of individual circular ties are is controlled according to ACI 25.7.2.4.1.
(a) Ends overlap by at least 6 in.
(b) Ends terminate with standard hooks in accordance with ACI 25.3.2 that engage a longitudinal bar
(c) Overlaps at ends of adjacent circular ties are staggered around the perimeter, enclosing the longitudinal bars
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Hoops consist of a closed tie or continuously wound tie, which can consist consisting of several reinforcement elements, each having seismic hooks at both ends.
The ends of the hoop reinforcement elements in hoops are anchored using seismic hooks that conform to ACI 25.3.4 and engage a longitudinal bar.
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