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Reliability Related to Factor of Safety and Uncertainty
Many engineers have recognized that the value of the factor of safety of a geotechnical structure is less important than its reliability or the probability of failure. In this context "failure" is defined according to Leonards' well-known description as "unacceptable difference between expected and observed performance." Considering any type of structure or system for which a factor of safety can be computed, placing all the known and unknown uncertainties into the standard deviation of the factor of safety, and assuming that the factor of safety is normally or lognormally distributed, we can find the relation between the probability of failure, the expected value of the factor of safety, and the variance in the factor of safety. In addition to providing a quick graphic estimate of the probability of failure, the resulting plots reveal that, when the standard deviation exceeds approximately 0.3, increasing the expected value of the factor of safety has little effect on the probability of failure. In such cases reducing the uncertainty by better engineering is more effective in improving reliability than increasing the target factor of safety. The results apply to any type of structure and any mode of failure.
Reliability Related to Factor of Safety and Uncertainty
Many engineers have recognized that the value of the factor of safety of a geotechnical structure is less important than its reliability or the probability of failure. In this context "failure" is defined according to Leonards' well-known description as "unacceptable difference between expected and observed performance." Considering any type of structure or system for which a factor of safety can be computed, placing all the known and unknown uncertainties into the standard deviation of the factor of safety, and assuming that the factor of safety is normally or lognormally distributed, we can find the relation between the probability of failure, the expected value of the factor of safety, and the variance in the factor of safety. In addition to providing a quick graphic estimate of the probability of failure, the resulting plots reveal that, when the standard deviation exceeds approximately 0.3, increasing the expected value of the factor of safety has little effect on the probability of failure. In such cases reducing the uncertainty by better engineering is more effective in improving reliability than increasing the target factor of safety. The results apply to any type of structure and any mode of failure.
Reliability Related to Factor of Safety and Uncertainty
Christian, John T. (author) / Urzua, Alfredo (author)
International Foundation Congress and Equipment Expo 2009 ; 2009 ; Orlando, Florida, United States
2009-03-10
Conference paper
Electronic Resource
English
Reliability Related to Factor of Safety and Uncertainty
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