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05-03ChapGere.0013

05-03ChapGere.0013 - 2 Q Ib 5 3000 mm 3(67,500 mm 4(30 mm 5...

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Problem 5.8-9 A wood beam AB on simple supports with span length equal to 9 ft is subjected to a uniform load of intensity 120 lb/ft acting along the entire length of the beam and a concentrated load of magnitude 8800 lb acting at a point 3 ft from the right-hand support (see figure). The allowable stresses in bending and shear, respectively, are 2500 psi and 150 psi. (a) From the table in Appendix F, select the lightest beam that will support the loads (disregard the weight of the beam). (b) Taking into account the weight of the beam (weight density 35 lb/ft 3 ), verify that the selected beam is satisfactory, or, if it is not, select a new beam. Solution 5.8-9 SECTION 5.8 Shear Stresses in Rectangular Beams 333 (a) A LLOWABLE LOAD BASED UPON SHEAR IN GLUED JOINTS allow 0.3 MPa ( V newtons; P newtons) Q (30 mm)(10 mm)(10 mm) 3000 mm 3 ( N/mm 2 MPa) S OLVE FOR
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Unformatted text preview: 2 Q Ib 5 3000 mm 3 (67,500 mm 4 )(30 mm) 5 1 675 mm 2 t 5 VQ Ib Ê V 5 P 2 1 qL 2 5 P 2 1 1.6 N (b) A LLOWABLE LOAD BASED UPON BENDING STRESSES s allow 5 8 MPa ( P 5 newtons; M 5 N ? m) ( s 5 N/m 2 5 Pa) S OLVE FOR P: P 5 (56.25 3 10 2 6 ) s allow 2 1.6 5 (56.25 3 10 2 6 )(8 3 10 6 Pa) 2 1.6 5 450 2 1.6 5 448 N s 5 (0.08 P 1 0.128)(N ? m) 4.5 3 10 2 6 m 3 M max 5 PL 4 1 qL 2 8 5 0.08 P 1 0.128 (N ? m) s 5 M max S A B 8800 lb 120 lb/ft 9 ft 3 ft q 5 120 lb/ft P 5 8800 lb d 5 3 ft s allow 5 2500 psi t allow 5 150 psi R A 5 qL 2 1 P 3 Ê R B 5 qL 2 1 2 P 3 (a) D ISREGARDING THE WEIGHT OF THE BEAM V max 5 R B 5 6407 lb R B 5 540 lb 1 2 3 (8800 lb) 5 6407 lb R A 5 (120 lb / ft)(9 ft) 2 1 8800 lb 3 5 3473 lb A B P q L = 9 ft d R B R A V (lb) 3473 2753 ] 6047 ] 6407 (Continued) A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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