ARC322 Homework 18 SOLUTION 2008

ARC322 Homework 18 SOLUTION 2008 - ARC322 Homework 18 . 15...

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ARC322 Homework 18 … 15 Points KEY 1. A 2x4 wall supports a 4x8 wood beam normal to the wall with a total load of 25,000 lb on the beam (1/2 of the load goes to the wall). Is the condition OK with respect to compression perpendicular to grain? 2 points The contact area between the 2x4 and the 4x8 is 3.5 in x 3.5 in = 12.25 in 2 The Load on this area P = 25,000 lb/2 = 12,500 lb f =P/A = 12,500 lb / 12.25 in 2 = 1020.41 lb/in 2 > 625 lb/in 2 … NOT OK 1 point 2. A 2x4 wall supports a DFLSS beam normal to the wall that carries a DL+LL of 75 lb/ft 2 . The beam simply spans 25 ft. The beams are spaced at 7ft OC. Is the system OK with respect to compression perpendicular to grain? 4 points First, we must design the beam. W = 75 lb/ft 2 x 7 ft x 25 ft = 13,125 lb M = WL/8 = 13,125 lb x 25 ft/8 = 41,016 ft-lb S = M/ f = (41,016 ft-lb x 12 in/ft)/1600 lb/in 2 = 307.62 in 3 Select a 6 x 20 S = 348.6 in 3 > 307.62 in 3 … OK 1 point The contact area between the 2x4 and the 6x20 is 3.5 in x 5.5 in = 19.25 in
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ARC322 Homework 18 SOLUTION 2008 - ARC322 Homework 18 . 15...

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