An improved algorithm for parameter estimation suitable for mixed Weibull distributions

The shape of measured or design load spectra can vary considerably and therefore frequently cannot be approximated by simple distribution functions. The introduction of mixed Weibull distribution has thus been suggested. Compared to the extreme value distribution, the proposed distribution makes the extrapolation of load spectra and its scatter prediction much easier, especially in the case of variable operating conditions. The major drawback of mixed distributions in general is a complicated, and often impossible, calculation of unknown parameters. This article presents an improved algorithm for unknown parameter estimation. The algorithm is distribution-independent and consists of rough parameter estimation and optimization. Each component density is calculated separately. The solving of complicated systems of equations is not necessary. The proposed algorithm has been tested by analyzing load spectra resulting from in-the-field measurements.