| dc.description.abstract | Fatigue design in offshore structures is based on S-N curves derived from tests on tubular joints where failure is defined as penetration of wall thickness. However, in practice, fatigue cracks are likely to continue to grow around the weld circumference after breaking through the wall and it has been found in certain circumstances that a significant residual life remained after through-thickness cracking.
The purpose of this thesis is to analyse and compare data to see if exists any correlation with different factors or parameters from different tubular joints and their residual life. This data of tubular joints was collected from several reports that have been done through years by different organizations and laboratories in which distinct testing conditions have been taken into account with the purpose to simulate the joints to be offshore. Some examples of the different parameters taking into considerations by these organizations and laboratories are e.g. type of joints, loading conditions, loading spectrums, environment, welding profile.
To analyse the data several evaluations of statistics were performed and with help of statistical software named “Statgraphics” different plots like probability distributions were realized in order to see which is the best fit for the data gathered, but not only plots were made there. Also, some regression analyses were executed for assessing if there exists any major influence or correlation between the different factors and the residual life.
Some basic designs of S-N curves and S-N curves with modified thickness as given on “DNVGL-RP-C203” [1] for the stages of failure of N1 and N3 were plotted and compared to the S-N curves in the “OTH 92 390” [2] report. For last, a comparison of the conclusions from the report of “Zhang and Wintle” [3] to the results of the data gathered was conducted. | |
