Civil Engineering Reference
In-Depth Information
Fig. 15.9
Comparison of the undamped response spectra of the load function: Idealized load
functions for B747 versus Phantom RSK-LL
The statements made above are universally valid and not specific to one specific
system. It remains to be clarified whether the comparison of the results are as clear
for real structures. To answer this question, a simplified 3D computational model of
a convoy containment in accordance with Fig.
15.10
is loaded with the load
function for the Boeing 747 and also with the function according to RSK-LL.
Then the time response of the accelerations at different locations within the
secondary shielding is calculated. Subsequently floor response spectra are
established for different damping ratios using these time responses.
As an example Fig.
15.11
compares a chosen spectrum for a typical damping
ratio of 4 %, which describes the situation for the interior at a height of approx.
20 m. Depending on the frequency range the design accelerations are up to four
times higher for an excitation due to a commercial aircraft than for the Phantom
according to the RSK-LL, in extreme cases up to eight times higher. In order to
make a reliable statement about the protection status of German nuclear power
plants, especially of convoy facilities, continued research is necessary on the effects
on component integrity, an important element in the chain of evidence. It should be
noted however that the first approximations made here lies on the safe side. The
calculations are based on a simplified model and assume a linear system. Due to
the local destruction (formation of cracks) in the impact area, however, a significant
portion of the energy is consumed and not transferred into the building, such that
with respect to the induced vibrations in a realistic non-linear examination of the
impact area a reduction of the floor response spectra is to be expected.
