1. Introduction

For a structure subjected to random excitation such as swell, turbulent flow, or earthquake… the loading is not known deterministically, but is most often described by probabilistic or spectral information such as power spectral density. For linear structures it is possible to use a stochastic calculation method that makes it possible to determine the spectral densities of response power to these random excitations.

The function of the operator POST_DYNA_ALEA is to perform statistical analyses of the response power spectral density. It therefore provides probabilistic information on the structure’s response. The calculations of statistical parameters are carried out on the basis of the calculation of the spectral moments of the power spectral density under consideration.

These statistical parameters are: the standard deviation, the apparent frequency, the peak factor according to Vanmarcke’s definition, the mean maximum and the irregularity factor.

Note:

The operator POST_DYNA_ALEA, originally designed for the seismic approach, after a calculation with the operator DYNA_ALEA_MODAL [U4.56.06] ([bib1], [bib2]) , can also perform the operator’s post-treatments DYNA_SPEC_MODAL developed by the department TTA as part of the resorption of FLUSTRU. This operator calculates the response of a GV tube-type structure uniformly excited by a transverse flow.