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Structural Concrete - Hassoun

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834 Chapter 20 Seismic Design of Reinforced <strong>Concrete</strong> Structures<br />

Clear space*<br />

≤ 3 in.<br />

≥ larger of 1 in.<br />

or 1.33 (max.<br />

agg. size)<br />

0.12<br />

ρ s ≥<br />

ε 1 0.45<br />

f' c<br />

f yh<br />

A g<br />

A ch<br />

– 1<br />

f' c<br />

f yh<br />

Figure 20.20 Transverse reinforcement requirements for spiral reinforcement.<br />

Courtesy of Portland Cement Association (Notes on ACI 318)<br />

h 2<br />

where<br />

f yt = yield stress of hoop reinforcement<br />

s = spacing of transverse reinforcement<br />

b c = cross-section dimension of column core measured center to center of confining reinforcement<br />

3. If the thickness of the concrete outside the confining transverse reinforcement exceeds 4 in.,<br />

additional transverse reinforcement should be provided at a spacing ≤ 12 in. <strong>Concrete</strong> cover<br />

on additional reinforcement should not exceed 4 in.

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