Uncertainty in fatigue life prediction of structures subject to Gaussian loads

Anders Bengtsson and Igor Rychlik


Centre for Mathematical Sciences
Mathematical Statistics
Lund Institute of Technology,
Lund University,
2007

ISSN 1403-9338
Abstract:
In this report we shall concentrate on Gaussian (or close to Gaussian) loads acting on a structure. The goal is to compute a measure of risk for fatigue of a component during a specific time period and the so called ``safety index'' will be used to combine different types of uncertainties. The presented methodology can be applied in a more general situation of environmental loads which properties may vary with time of the year. The load is assumed to be ``locally'' stationary such that the mean load is constant (and taken to be zero) but the variance of a load can change slowly with time. Non-stationary hierarchical processes, separable into a stationary Gaussian process and a process describing the load amplitude and period, e.g. processes with Pierson-Moskowitz or JONSWAP spectrum, are treated in detail. The variability of a load, relevant for the fatigue accumulation process, will be described by means of rainflow cycles counted in the load. Moreover, common damage intensity approximations are reviewed and evaluated in a simulation study.