422_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

422_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

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Unformatted text preview: 05Ch05.qxd 9/24/08 416 4:59 AM Page 416 CHAPTER 5 Stresses in Beams (Basic Topics) LOADING DIAGRAM FOR ONE BALK Section modulus S qL2 b 8 Mmax S W total load ‹ wLbLc q b3 6 (8.0 kN/m)(3.0 m)2 8 9,000 N # m 16 MPa 562.5 * 10 Solving, bmin wLc 2 W 2Lb Mmax sallow b3 6 6 9,000 N # m 562.5 * 10 m3 and b3 0.150 m 6 m3 3375 * 10 6 m3 ; 150 mm (8.0 kPa)(2.0 m) 2 8.0 kN/m Problem 5.6-7 A floor system in a small building consists of wood planks supported by 2 in. (nominal width) joists spaced at distance s, measured from center to center (see figure). The span length L of each joist is 10.5 ft, the spacing s of the joists is 16 in., and the allowable bending stress in the wood is 1350 psi. The uniform floor load is 120 lb/ft2, which includes an allowance for the weight of the floor system itself. Calculate the required section modulus S for the joists, and then select a suitable joist size (surfaced lumber) from Appendix F, assuming that each joist may be represented as a simple beam carrying a uniform load. Planks s s L s Joists Solution 5.6-7 Floor joists Mmax qL2 8 Required S 1 (13.333 lb/in.)(126 in.)2 8 Mmax sallow 26,460 lb/in. 1350 psi 19.6 in.3 From Appendix F: Select 2 * 10 in. joists sallow 1350 psi L 10.5 ft 126 in. w floor load s spacing of joists q ws 120 lb/ft2 13.333 lb/in. 16 in. 0.8333 lb/in.2 26,460 lb-in. ; ; ...
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This note was uploaded on 12/22/2011 for the course MEEG 310 taught by Professor Staff during the Fall '11 term at University of Delaware.

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