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Structural Concrete - Hassoun

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13.5 Plain <strong>Concrete</strong> Footings 463<br />

c + d = 18 + 19.5 = 37.5 in. = 3.125 ft<br />

V u2<br />

= P u − q u (c + d) 2 = 614 − 6.14(3.125) 2 = 554 K<br />

V u2<br />

Required d 1 =<br />

4φλ( √ f cb ′ 0 )<br />

Required d 2 =<br />

0.75<br />

554(1000)<br />

=<br />

(4)(0.75)(1) √ = 19.5 in. (β = 1; Eq. 13.9)<br />

4000(150)<br />

( 40 × 19.5<br />

150<br />

= 10.8in. (not critical)<br />

554(1000)<br />

) √<br />

+ 2 ( 4000)(150)<br />

(α s = 40 for interior columns.) Thus, the assumed depth is adequate. Two or more trials may be<br />

needed to reach an acceptable d that is close to the assumed one.<br />

5. Check depth due to one-way shear action: The critical section is at a distance d from the face of<br />

the column:<br />

( L<br />

Distance from edge of footing =<br />

2 − c )<br />

2 − d = 2.625 ft<br />

The depth required for one-way shear is<br />

V u1<br />

d =<br />

(0.75)(2)λ √ f c ′ b<br />

V u1<br />

= 6.14 ×(2.625)(10) =161.2K<br />

161.2(1000)<br />

=<br />

(0.75)(2)(1)( √ = 14.2 in.

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