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Structural Concrete - Hassoun

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866 Chapter 21 Beams Curved in Plan<br />

Figure 21.4<br />

Semicircular beam fixed at the supports.<br />

The load on the curved beam per unit length is equal to<br />

w ′ w(r sin θ)r sin θ dθ<br />

= = wr sin2 θ<br />

(21.10)<br />

2(rdθ)<br />

2<br />

2. Shearing force at A: For a uniform symmetrical load on the slab, the shearing force at A is<br />

equal to<br />

π∕2 ( )<br />

[ wr<br />

V A = V B = ∫<br />

0 2 sin2 θ (rdθ) = wr2 θ<br />

2 2 − 1 ]<br />

4 sin 2θ<br />

( ) π<br />

= wr 2 = 0.39wr 2 (21.11)<br />

8<br />

3. Bending moment at A: Taking moments about the line AB, the bending moment at A is<br />

equal to<br />

π∕2<br />

M A = M B = w ′ (rdθ)×(r sin θ)<br />

∫<br />

= ∫<br />

π∕2<br />

0<br />

0<br />

( ) wr<br />

2 sin2 θ (r sin θ)(rdθ) =− wr3<br />

3<br />

(21.12)

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