Environmental Load Direction and Reliability Bounds

Abstract

A procedure is presented for estimating reliability bounds for the probability of failure of members sensitive to load directionality effects. The property of multivariate extreme value distributions that zero values of all pairwise correlations imply statistical idependence among the variates is first used to obtain rough estimates of failure probabilities. More refined estimates are then obtained by using expressions for lower and upper bounds for the probabilities, which entail the use of univariate and bivariate probability distributions. In the latter, information is used on the pairwise correlation of load data corresponding to the various directions. In well-behaved wind climates the assumption that data corresponding to any two octants are shown to be mutually uncorrelated results in the overestimation of failure probabilities by a fctor of about two or less.