Deriving probability density functions for degree of bending (DoB) in axially loaded tubular K-joints

Publish Year: 1394
نوع سند: مقاله کنفرانسی
زبان: English
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ICCE10_1185

تاریخ نمایه سازی: 19 تیر 1394

Abstract:

Fatigue life of tubular joints in offshore structures is not only dependent on the value of hotspot stress, but is also significantly influenced by the through-the-thickness stress distribution characterized by the degree of bending (DoB). The DoB exhibits considerable scatter calling for greater emphasis in accurate determination of its governing probability distribution which is a crucial input for the fatigue reliability analysis of a tubular joint. Although the tubular Kjoints are commonly found in offshore jacket structures, as far as the authors are aware, no comprehensive research has been carried out on the probability distribution of DoBs in tubular K-joints. What has been used so far as the probability distribution of DoBs in reliability analyses is mainly based on assumptions and limited observations, especially in terms of distribution parameters. In the present paper, results of parametric equations available for the calculation of DoBs have been used to develop probability distribution models for DoBs in axially loaded tubular K-joints. Based on a parametric study, a set of samples was prepared and density histograms were generated for these samples using Freedman-Diaconis method. Ten different probability density functions were fitted to these histograms. The maximum likelihood method was utilized to determine the parameters of fitted distributions. In each case, Kolmogorov-Smirnov test was used to evaluate the goodness of fit. It was concluded that generalized extreme value, gamma, log-logistic, and Birnbaum-Saunders distributions are the best probability models for DoBch, DoBch0, DoBch45, and DoBch180 in axially loaded tubular Kjoints, respectively

Keywords:

Tubular K-joint , Fatigue reliability analysis , Degree of Bending (DoB) , Probability density function (PDF) , Kolmogorov-Smirnov goodness-of-fit test

Authors

Hamid Ahmadi

Faculty of Civil Engineering, University of Tabriz, Tabriz ۵۱۶۶۶۱۶۴۷۱, Iran

Amirreza Ghaffari

Faculty of Civil Engineering, University of Tabriz, Tabriz ۵۱۶۶۶۱۶۴۷۱, Iran