Unformatted text preview: 4. Assume that the beam in #3 is a simply supported beam and that its load is 3500 lb/ft. What is the length of the beam? Here, we need to stop and think a little … w = 3500 lb/ft … we don’t know W because we don’t know the length. But, we do know the maximum moment is 1,050,000 ftlb and we know f for A36 steel is 24,000 lb/in 2 … so … M = w L 2 /8 … rearranging L 2 = 8M/ w = (8 x 1,050,000 ftlb)/3500 lb/ft = 2400 ft L 2 = 2400 ft L = (2400 ft) 1/2 … using ½ exponent since MSWord doesn’t do square root symbols easily L = 48.99 ft … you could probably round to 49 ft if you want. 5. What is the bending stress on the beam? f = M/S = (1,050,000 ftlb x 12 in/ft)/531 in 3 = 23,728.81 lb/in 2 < 24,000 lb/in 2 … OK...
View
Full Document
 Winter '08
 McGavin
 Second moment of area, simply supported beam, maximum moment

Click to edit the document details