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Structural Concrete - Hassoun

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476 Chapter 13 Footings<br />

6. Check the depth for one-way shear. Maximum shear occurs at a distance d = 31.5 in. from the<br />

interior face of column II (Fig. 13.26):<br />

V u1<br />

= 319.3 − 31.5 (42.38) =208.1 K<br />

12<br />

V<br />

d = u1<br />

φ(2λ √ f c ′ )b = 208.1 × 1000<br />

0.75(2 × 1 × √ = 24.4in.<br />

4000)(7.5 × 12)<br />

The effective depth provided is 31.5 in. > 24.4 in.; thus, the footing is adequate.<br />

7. Check depth for two-way shear (punching shear). For the interior column,<br />

( ) 4<br />

b 0 = 4(c + d) = (20 + 31.5) =17.17 ft<br />

12<br />

20 + 31.5<br />

c + d = = 4.29 ft<br />

12<br />

The shear V u1<br />

at a section d/2 from all sides of the column is equal to<br />

V u2<br />

= P u2 − q u (c + d) 2 = 524 − 5.65(4.29) 2 = 420 K<br />

d =<br />

V u2<br />

φ(4λ √ f ′ c )b 0<br />

=<br />

420(1000)<br />

0.75(4 × 1 × √ = 10.4in.

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