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ch01-03 stress & strain & properties

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01 Solutions 46060 5/6/10 2:43 PM Page 12<br />

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*1–20. Determine the resultant internal loadings acting<br />

on the cross section through point D. Assume the reactions<br />

at the supports A and B are vertical.<br />

6 kip/ft<br />

6 kip/ft<br />

Referring to the FBD of the entire beam, Fig. a,<br />

a+©M B = 0; 1 2 (6)(6)(2) + 1 2 (6)(6)(10) - A y(12) = 0 A y = 18.0 kip<br />

A<br />

C<br />

3 ft 3 ft<br />

D<br />

6 ft<br />

B<br />

Referring to the FBD of this segment, Fig. b,<br />

: + ©F x = 0; N D = 0<br />

Ans.<br />

+ c ©F y = 0; 18.0 - 1 2 (6)(6) - V D = 0 V D = 0<br />

Ans.<br />

a+©M A = 0; M D - 18.0 (2) = 0 M D = 36.0 kip # ft<br />

Ans.<br />

•1–21. The forged steel cl<strong>amp</strong> exerts a force of F = 900 N<br />

on the wooden block. Determine the resultant internal<br />

loadings acting on section a–a passing through point A.<br />

200 mm<br />

F 900 N<br />

Internal Loadings: Referring to the free-body diagram of the section of the cl<strong>amp</strong><br />

shown in Fig. a,<br />

©F y¿ = 0; 900 cos 30° - N a - a = 0 N a - a = 779 N<br />

©F x¿ = 0; V a - a - 900 sin 30° = 0 V a - a = 450 N<br />

Ans.<br />

Ans.<br />

30<br />

A<br />

a<br />

F 900 N<br />

a+©M A = 0; 900(0.2) - M a - a = 0 M a - a = 180 N # m<br />

Ans.<br />

a<br />

12

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