GATE 2026 CE (CE1) – Question 55
A bridge with an expected life of 50 years is designed for a flood of 10000 m$^3$/s corresponding to the return period of 100 years. The risk associated with this design is _____________ (*rounded off to two decimal places*).
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Correct answer: 0.38 to 0.40
Explanation
The risk is the probability that the design flood is exceeded at least once during the life of the structure: $1 - \left(1 - \frac{1}{T}\right)^n = 1 - (0.99)^{50} = 1 - 0.605 = 0.395$, which is 0.39 (0.395 sits right on the rounding boundary).