Abstract
Service life prediction and the durability approval of randomly loaded structures, such as vehicles, is only possible if the loads acting upon the vehicle are known. Since the operating conditions as a rule vary during service life, load time histories represent non-stationary random processes. A direct treatment of non-stationary loads is not possible if the procedures currently used in automotive industry are applied. Individual operating conditions must be analysed separately. As a result, partial loading spectra are obtained. Afterwards the representative design spectrum is attained as an algebraic sum of partial spectra. This procedure is time consuming. The scope of this paper is to show that design spectrum can be extracted directly from non-stationary load time histories if the mixed Weibull distribution is applied.