ARC322 Homework 20 SOLUTION

# ARC322 Homework 20 SOLUTION - ARC322 Points Key 1 A DFLSS...

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ARC322 Homework 20 26 Points Key 1. A DFLSS 6x18 wood beam spans 20 ft. It carries a DL+LL of 185lb/ft. Is it Ok in deflection based on L/240? 4 points 1 point dwg Deflection = 5WL 3 /384EI D = (5(3700 lb)(20 ft x 12 in/ft) 3 )/(384 x 1,600,000 lb/in 2 x 2456 in 4 ) = 0.169 in 2 points L/240 = (20 ft x 12 in/ft)/240 = 1 in > 0.169 in . .. OK 1 point 2. A DFLSS 4x8 wood beam cantilevers 8 ft. It carries a DL+LL of 200lb/ft. Is the 4x8 Ok where D is limited to L/240? 4 points 2 points dwg D = WL 3 /8EI = (1600 lb x (8 ft x 12 in/ft) 3 )/(8 x 1,900,000 lb/in 2 x 111.1 in 4 ) = 0.84 in 2 points L/240 = (8 ft x 12 in/ft)/240 = 0.4 in < 0.84 in . .. NOT OK 1 point Note: We selected 1,900,000 psi because it is a 4x8 (top part of the chart) Note: A 4x8 cantilever with an 8 ft arm is not even close to the rule of thumb. They were not required to select a correct member per the question … if they did 2 POINTS EC

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ARC322 HW#20 Page 2 3. Design a DFLSS wood beam that spans 22ft on an 8ft spacing and carries a DL of 65 lb/ft
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ARC322 Homework 20 SOLUTION - ARC322 Points Key 1 A DFLSS...

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