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categoryهندسة مدنية
schoolبكالوريوس
event_available2026-07-13
السؤال
Transcribed Image Text:
If two loads are applied to a cantilever beam as shown in the accompanying drawing, the bending moment at 0 due to the
loads is a1X1 + 22x2.
X₁
+
a₁
X2
↓
a2
0
(a) Suppose that X1 and X2 are independent rv's with means 6 and 12 kips, respectively, and standard deviations
1.3 and 2.6 kip, respectively. If a₁ = 5 ft and a2 = 10 ft, what is the expected bending moment and what is the
standard deviation of the bending moment? (Round your standard deviation to three decimal places.)
expected bending moment
standard deviation
kip-ft
kip-ft
(b) If X1 and X2 are normally distributed, what is the probability that the bending moment will exceed 75 kip-ft?
(Round your answer to four decimal places.)
(c) Suppose the positions of the two loads are random variables. Denoting them by A1 and A2, assume that these
variables have means of 5 and 10 ft, respectively, that each has a standard deviation of 0.5, and that all A's and
Xi's are independent of one another. What is the expected moment now?
kip-ft
(d) For the situation of part (c), what is the variance of the bending moment? (Round your answer to two decimal
places.)
kip-ft2
(e) If the situation is as described in part (a) except that Corr(X1, X2) = 0.5 (so that the two loads are not
independent), what is the variance of the bending moment?
kip-ft²
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