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Structural Concrete - Hassoun

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9.2 Design of One-Way Solid Slabs 327<br />

Figure 9.3 Moment coefficients for continuous beams and slabs (ACI Code,<br />

Section 6.5).<br />

support a quantity equal to Vb/3, where V is the shearing force calculated from the analysis and b<br />

is the width of the support:<br />

M f (at face of support) =M c (at centerline of support)− Vb<br />

(9.1)<br />

3<br />

In addition to moment, diagonal tension and development length of bars should also be<br />

checked for proper design.<br />

The conditions under which the moment coefficients for continuous beams and slabs, given<br />

in Fig. 9.3, should be used can be summarized as follows:<br />

1. Spans are approximately equal: Longer span ≤1.2 (shorter span).<br />

2. Loads are uniformly distributed.<br />

3. The ratio (live load/dead load) is less than or equal to 3.<br />

4. For slabs with spans less than or equal to 10 ft, negative bending moment at face of all supports<br />

is<br />

(<br />

1<br />

12<br />

)<br />

w u l 2 n.<br />

5. For an unrestrained discontinuous end at A, the coefficient is 0 at A and + 1 at B.<br />

11<br />

6. Shearing force at C is 1.15w u l n /2 and at the face of all other support is 1 w 2 ul n .<br />

7. M u = (coefficient) (w u ln) 2 and l n = clear span.

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