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Structural Concrete - Hassoun

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20.5 Special Requirements in Design of Structures Subjected to Earthquake Loads 835<br />

larger of h 1 or h 2<br />

0 ≥ 1<br />

6 (Clear span)<br />

18 in.<br />

s*≤<br />

s<br />

2<br />

h 1<br />

4<br />

h 2<br />

0<br />

4<br />

6d b<br />

s x<br />

s**≤<br />

6d b<br />

6 in.<br />

14 – h<br />

6 in. ≥ s x = 4 + x ≥ 4 in.<br />

3<br />

h 2<br />

d b<br />

A sh ≥<br />

0.3sb c<br />

0.09sb c<br />

A g<br />

A ch<br />

– 1<br />

f' c<br />

f yt<br />

f' c<br />

f yt<br />

≤ 4 in. (see 20.4.4.1 when cover > 4 in.)<br />

h 1<br />

Figure 20.21 Transverse reinforcement requirements for rectangular hoop reinforcement.<br />

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

4. Spacing of the transverse reinforcements along the length l 0 should satisfy the following:<br />

⎧h<br />

(h = minimum member dimension)<br />

⎪4 s ≤ ⎨6 × smallest longitudinal diameter bar<br />

(20.46)<br />

⎪<br />

⎩s 0<br />

Also,<br />

( ) 14 − hx<br />

4in. ≤ s 0 = 4 +<br />

≤ 6in. (20.47)<br />

3

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