Improvement of equivalent component approach for reliability analyses of series systems

The present study proposes an improved equivalent component approach to evaluate the system reliability of series systems. An analytical expression is derived to evaluate the unit normal vector, in the context of the first-order reliability method, associated with the equivalent component. This improves the computational efficiency for determining the correlation coefficients between the system and equivalent components in the equivalent component approach. An adaptive combining process is also proposed, whereby the two components with the highest correlation coefficient are combined at each combining step. The accuracy and efficiency of the improved equivalent component approach are demonstrated for series systems with equally and unequally correlated components. Finally, the improved equivalent component approach is illustrated through the system reliability analysis of a pressurized steel pipeline segment containing ten active corrosion defects.