An international benchmark has been organized by EDF R&D during 2008–2010,
gathering 11 partners. Its main objective is to quantify the confidence in numerical
models. The built-up dynamical system considered is a pump actually in service in power
plants, considered in its work environment. Blind eigenfrequency numerical values relative
to the pump assembly fixed in concrete present a larger variability than the 5% rough
variability concerning the separate parts, essentially due to the modeling of the boundary
conditions and interfaces at macro level. For the nine first eigenmodes considered,
experimental-numerical correlation shows a frequency error less than 15% for the free
sub-structures and nearly 30% for the free five-component system. Though the first overall
modes are correctly identified, the frequency error is significantly larger for the
clamped pump assembly, with however MAC coefficients higher than 0.9 for two modes; but
the frequency error can be reduced to less than 9% for the four first modes after updating
procedure. A lesson to draw is that measurement information is needed to improve the
quality of theoretical built-up structure. After this benchmark, a more ambitious research
program will follow as a FUI project, gathering the observation of numerical and
experimental variabilities, updating model improvement and numerical quantification of the
total uncertainty.