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Structural Concrete - Hassoun

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450 Chapter 13 Footings<br />

4. Bending moment and steel reinforcement required.<br />

5. Bearing capacity of columns at their base and dowel requirements.<br />

6. Development length of bars.<br />

7. Differential settlement.<br />

These strength requirements are explained in the following sections.<br />

Reinforcing rebars placed in tow layers in a raft foundation.<br />

13.4.1 Size of Footings<br />

The area of the footings can be determined from the actual external loads (unfactored forces<br />

and moments) such that the allowable soil pressure is not exceeded. In general, for vertical<br />

loads<br />

total service load (including self − weight)<br />

Area of footing = (13.1)<br />

allowable soil pressure, q a<br />

or<br />

Area = P(total)<br />

q a<br />

where the total service load is the unfactored design load. Once the area is determined, a factored<br />

soil pressure is obtained by dividing the factored load, P u = 1.2D + 1.6L, by the area of the footing.

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