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(CIVL181)CIVL181_sample final.pdf
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CIVL 181 Sample Final Examination


Problem 1 (20%)

Circle T (true) or F (false) for each of the following statements. A correct answer will score 2 points; whereas one point will be deducted for each incorrect answer.


T F If the cost of a perfect test is higher than the value of perfect information, then one should not conduct any other test at all.

T F When designing a structure, one can only calculate the probability of collapse but cannot change it, as engineers have no control over random loads such as strong wind.

T F If the daily maximum wind speed, X, follows a normal distribution, then
follows a log-normal distribution.

T F If a return period of 500 years is used to design against earthquake load, and a return period of 200 years is used to design against wind load, then there is at least 0.005 probability that the design load will be exceeded by either wind or earthquake in a given year.

T F If the arrival of storms follows a Poisson process with mean arrival rate , then the inter-arrival time between storms follows an exponential distribution with its mean being 1/.

T F A 95% confidence interval for the true mean () denotes a range of values that will contain at least 95% of the time.

T F Decision tree analysis can be applied only to discrete random variables with several outcomes, for which a decision tree can be drawn. It does not incorporate continuous random variables.

T F The utility function can have a negative slope for a risk-aversive person.

T F Fault tree can be used to help in determining probabilities which will be then input into an event tree to determine the probability of various scenarios associated with an initial failure event

T F Monte Carlo simulation can be used if a non-linear function Y of several random variables is involved and P(Y > y0) is needed for some number y0.
*

Problem 2 (20%)

During the water shortage problem in the 1960s, sea water was used widely to produce concrete. It was believed that salt content in the sea water might cause an early deterioration of concrete, resulting in dangerous buildings. The Building Department started to investigate this problem by collecting concrete samples from buildings constructed during that period of time and measuring their strength and salt content, as shown in the table.

Sample
Concrete Strength (N/mm2)
Salt content (% by weight)

1
30
9

2
27
5

3
28
5

4
31
9

5
29
5

6
30
1

7
27
1

8
31
1

9
27
9

10
29
5





(a) Estimate the coefficient of variation of concrete strength of buildings constructed in the 60s.

(b) Determine the linear regression relationship between concrete strength and salt content based on the above 10 samples.

(c) Determine whether salt content is a cause for deteriorating