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Unformatted text preview: ) ln( ) , ( == (520) For both Equation 519 and 520 the limit state is reached when R=Q and failure will occurs when g(R,Q)<0. Reliability index. The reliability index is a simple method of expressing the probability of failure using function g(R, Q) (Eq. 520). The frequency distribution of g(R,Q) would look similar to the curve shown in Figure 53. Figure 53. Definition of Reliability Index, β for lognormal Distributions of R and Q Evident from the curve is that if the standard deviation is small or the mean value is located further to the right, the probability of failure will be smaller. The reliability index β , is defined as the number of standard deviations, ξ g , between the mean value, g (average), and the origin, or: g g ξ β = (521)...
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 Spring '11
 Hass
 Normal Distribution, Probability, Standard Deviation, probability density curve, probability density functions, reliability index

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