ARC322 Quiz 14 2008 KEY

ARC322 Quiz 14 2008 KEY - purposes may not be valid You...

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ARC322 Quiz 14 … 14 Points Name _______________________________ What is E for a 4x8 DFL No 1 beam? 1,700,000 lb/in 2 What three stresses would need to be resolved for the beam/reaction shown in the photo at the right at the reaction? A Shear Stress B Compression perpendicular to grain in the beam C Compression parallel to grain in the double 2x Is a wane generally of concern structurally for lumber? No, since it is usually a minor surface feature Is a split generally of concern structurally for lumber? Yes, because it could lead to very low shear failure parallel to grain You have specified 4x8 DFLSS wood beams on a project. While on the job site, you learn from the framer that the contractor bought 8x8 beams and sawed them into 4x8’s. What is the concern that you should have? What should you do? 2 points This is a potentially a big problem because the quality of the wood is no longer known and the values used for calculation
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Unformatted text preview: purposes may not be valid. You should consult with the building official and structural engineer on this issue. A DFL No 1 2x4 column rests on top of a DFLSS 4x8 simple wood beam that spans 12 ft. The column carries a load of 7,000 lb. Sketches are not required. A Calculate the compression stress parallel to grain in the column for the above condition. Is it OK? 3 points f = P/A = 7000 lb/(1.5 in x 3.5 in) = 1333 lb/in 2 < 1700 lb/in 2 … OK B Calculate the compression stress perpendicular to grain in the beam for the above condition. Is it OK? 3 points Note … we use the 2x4 column size because it is the area that is pushing down on the beam … f = P/A = 7000 lb/(1.5 in x 3.5 in) = 1333 lb/in 2 > 625 lb/in 2 … NOT OK...
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This note was uploaded on 03/30/2008 for the course ARC 322 taught by Professor Mcgavin during the Winter '08 term at Cal Poly Pomona.

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