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Unformatted text preview: 1 EMA 3702 Mechanics of Materials First Hour Exam Date: 9/23/11 Name: ________________________________ PI#:__________________________________ 1. A structural steel (E = 30,000 ksi) bar with a rectangular cross section is bent over a rigid mandrel (R = 10 in.), as shown in the following figure. If the maximum fiber stress in the bar is not to exceed the yield strength ( y = 36 ksi) of the steel, determine the maximum allowable thickness h and M for the bar, if b = 2 in.. [30%] [Solution] (4.9) Hence, h = 0.024 in 3 12 bh I = 2.304 *10^-6 in^4 Based on Eq. (4-21) 1 , M EI EI Therefore M EI R M = 6.912 lb-in m c 2 2 all all m Ec h E or c Hence h E E 2 2. A foundation pile, which has been driven to a depth L in the earth, supports a vertical load Q, as shown in the following figure. Assume that this load is resisted by a frictional force f whose intensity varies parabolically 2 f kx . Here k , a constant, is to be found from the equilibrium of vertical forces. Here k , a constant, is to be found from the equilibrium of vertical forces....
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- Fall '11