05-04ChapGere.0002 - figure. The poles are being designed...

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Solution 5.9-2 Log bridge SECTION 5.9 Shear Stresses in Circular Beams 339 Diameter d 5 300 mm s allow 5 7.0 MPa t allow 5 0.75 MPa Find allowable load W (a) B ASED UPON BENDING STRESS Maximum moment occurs when wheel is at midspan ( x 5 L /2). 5 0.625 W 1 664.1 (N ? m) ( W 5 newtons) M max 5 S s allow 5 (2.651 3 10 2 3 m 3 )(7.0 MPa) 5 18,560 N ? m [ 0.625 W 1 664.1 5 18,560 W 5 28,600 N 5 28.6 kN S 5 p d 3 32 5 2.651 3 10 2 3 m 3 M max 5 WL 4 1 qL 2 8 5 W 4 (2.5 m) 1 1 8 (850 N / m)(2.5 m) 2 (b) B ASED UPON SHEAR STRESS Maximum shear force occurs when wheel is adjacent to support ( x 5 0). 5 W 1 1062.5 N ( W 5 newtons) 5 39,760 N [ W 1 1062.5 N 5 39,760 N W 5 38,700 N 5 38.7 kN V max 5 3 A t allow 4 5 3 4 (0.070686 m 2 )(0.75 MPa) t max 5 4 V max 3 A A 5 p d 2 4 5 0.070686 m 2 V max 5 W 1 qL 2 5 W 1 1 2 (850 N / m)(2.5 m) W L = 2.5 m x q = 850 N/m Problem 5.9-3 A sign for an automobile service station is supported by two aluminum poles of hollow circular cross section, as shown in the
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Unformatted text preview: figure. The poles are being designed to resist a wind pressure of 75 lb/ft 2 against the full area of the sign. The dimensions of the poles and sign are h 1 5 20 ft, h 2 5 5 ft, and b 5 10 ft. To prevent buckling of the walls of the poles, the thickness t is specified as one-tenth the outside diameter d . (a) Determine the minimum required diameter of the poles based upon an allowable bending stress of 7500 psi in the aluminum. (b) Determine the minimum required diameter based upon an allowable shear stress of 2000 psi. d t = b h 2 h 1 Wind load d 10 A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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This note was uploaded on 09/20/2009 for the course COE 3001 taught by Professor Armanios during the Spring '08 term at Georgia Institute of Technology.

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