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 14039338

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. Nonstationary
hierarchical processes, separable into a stationary Gaussian process and
a process describing the load amplitude and period, e.g. processes with
PiersonMoskowitz 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.


