05-02ChapGere.0004

05-02ChapGere.0004 - 2 q 5 W 2 L b 5 wL c 2 Section modulus...

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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 uni- form floor load is 120 lb/ft 2 , 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 car- rying a uniform load. Solution 5.6-7 Floor joists SECTION 5.6 Design of Beams 307 L OADING DIAGRAM FOR ONE BALK W 5 total load 5 wL b L c 5 8.0 kN/m 5 (8.0 kPa)(2.0 m)
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Unformatted text preview: 2 q 5 W 2 L b 5 wL c 2 Section modulus Solving, b min 5 0.150 m 5 150 mm b 3 6 5 562.5 3 10 2 6 m 3 and b 3 5 3375 3 10 2 6 m 3 S 5 M max s allow 5 9,000 N ? m 16 MPa 5 562.5 3 10 2 6 m 3 M max 5 qL 2 b 8 5 (8.0 kN / m)(3.0 m) 2 8 5 9,000 N ? m S 5 b 3 6 L b 5 3.0 m b b q 5 8.0 kN/m Joists Planks s s s L s allow 5 1350 psi L 5 10.5 ft 5 126 in. w 5 floor load 5 120 lb/ft 2 5 0.8333 lb/in. 2 s 5 spacing of joists 5 16 in. q 5 ws 5 13.333 lb/in. Required From Appendix F: Select 2 3 10 in. joists S 5 M max s allow 5 26,460 lb / in. 1350 psi 5 19.6 in. 3 M max 5 qL 2 8 5 1 8 (13.333 lb / in.)(126 in.) 2 5 26,460 lb-in. q L 5 10.5 ft A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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