A Modification to HL-RF Method for Computation of Structural Reliability Index in Problems with Skew-distributed Variables

The Hasofer-Lind and Rackwitz-Fiessler (HL-RF) method in reliability analysis is a popular iterative method for obtaining the reliability index. However, in the cases of limit state functions with skew-distributed variables, HL-RF method may give inappropriate answers. This paper represents a modification to HL-RF method in order to improve its performance in such problems. Based on this modification, non-normal distributions are replaced with equivalent skew-normal distributions instead of equivalent normal distributions. By this modification, asymmetric non-normal distributions are not replaced with symmetric distributions anymore. It is demonstrated that this consideration of skewness of non-normal distributions improves the behavior of HL-RF method and makes the proposed method more reliable. This improvement is shown through illustrative examples.