Seismic Analysis of Large-Scale Piping Systems for the JNES ... - NRC

DM4-2(2) (Restart):
This analysis considered the plasticity developed during DM4-1 and DM4-2(1). Comparisons for
the DM4-2(2) with restart regarding the displacement D2, D4, and acceleration A2 are provided
in Figure 4-28 through Figure 4-30. The overall shapes and the peak responses of the time
histories agree generally well between the test and the analysis, with a maximum peak difference
of about 6%. All response peaks in the time histories are under-predicted by the analysis. The
analytical time histories appear to be slightly less damped than the test. In addition, the analytical
time histories show some tendency that the responses are encapsulated within constant limits,
which may imply that the mono multi-linear kinematic hardening model may result in strain
shakedown for this level of input motions. The Fourier spectra of the test displacements show a
flat region for frequencies above 20 Hz, suggesting white noise was recorded in the test. Unlike
for tests DM2-1 and DM2-2, the white noise cannot be easily identified in the time histories
because the white noise is about 4~5 magnitudes smaller than the peak response. The dominant
responses, which are at a frequency of slightly less than 6 Hz, and most responses for frequencies
between 1~20 Hz compare especially well between the test and analysis. Both the test and the
analysis show discontinuities at around 1 Hz and 10 Hz in the Fourier spectra. The differences of
the displacement responses at the low frequencies reflect the difference in the residual
displacements and the overall shapes, and may be due to the baseline correction of the input
motions. The response spectra of the acceleration A2 for the test and analysis match very well.
The spectral response peaks are at a frequency of slightly less than 6 Hz, which is the same as the
input dominant frequency and close to the fundamental frequency of the pipe system (5.9 Hz
from test DM4-2(2)). The relative difference of the maximum spectra responses is only about 5%
(over-predicted by the analysis), comparing to the relative difference of about 6% of the PGA’s
(under-predicted by the analysis).
DM4-2(1) (Without Restart):
This analysis did not consider any plasticity developed previously. Comparisons for the DM4-
2(1) without restart regarding the displacement D2, D4, and acceleration A2 are provided in
Figure 4-31 through Figure 4-33. Compared to DM4-2(1) with restart, no significant difference
can be found for the various comparisons for this analysis, meaning that the previous plasticity
accumulation does not have a significant impact on the displacement and the acceleration
responses considered in the analysis.
DM4-2(2) (Without Restart):
This analysis did not consider any plasticity developed previously. Comparisons for the DM4-
2(2) without restart regarding the displacement D2, D4, and acceleration A2 are provided in
Figure 4-34 through Figure 4-36. Compared to DM4-2(2) with restart, no significant difference
can be found for the various comparisons for this analysis, meaning that the previous plasticity
accumulation does not have a significant impact on the displacement and the acceleration
responses considered in the analysis.
In summary, the comparisons of the piping system analyses of the design method confirmation
tests demonstrated that displacement and acceleration time history responses were predicted with
high accuracy, mostly within a maximum relative error of 10%. The analyses tend to overpredict
the responses for low level input motions while somewhat under-predict the responses for
high level input motions. The analyses are capable to capture closely the dominant frequency
content, in view of the Fourier spectra and response spectra. Major features in the Fourier spectra,
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