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OS-C501

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Offshore Standard DNV-<strong>OS</strong>-<strong>C501</strong>, November 2013<br />

App.J Method of estimation of characteristic strength – Page 249<br />

APPENDIX J METHOD OF ESTIMATION OF CHARACTERISTIC<br />

STRENGTH<br />

The characteristic strength is defined as the 2.5% quantile in the strength distribution. The method for<br />

estimating the characteristic strength is based on requiring the level of safety given in this standard to be met<br />

regardless of the number of available strength test data. Tabulated values of k m in Table 4-3, Table 4-4 and<br />

Table 4-5 in Sec.4 have been derived such that the confidence levels at which the characteristic strength in<br />

Sec.4 [2.4.5] is estimated, ensure that the same target reliability level is achieved. This level is achieved<br />

regardless of the available number of results from material testing or testing of components. It is noted that the<br />

necessary confidence level to achieve this varies with the number of available test results.<br />

The k m values have been obtained based on the results from probability analyses in which the reliability level<br />

is calculated for the case that a limited number of data for the strength is available and for the case that there is<br />

perfect knowledge of the strength (i.e. when an infinite number of test results would be available). k m has been<br />

obtained by adjusting the value of the characteristic strength for the case with a limited number of tests results<br />

such that the reliability level comes out the same as for the case with perfect knowledge.<br />

The method of analysis is described in:<br />

— Ronold, K. and Lotsberg, I.: On the Estimation of Characteristic S-N curves with Confidence. Marine<br />

Structures, vol. 27, 2012, pp. 29-44.<br />

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