Seismic Analysis of Large-Scale Piping Systems for the JNES ... - NRC
Seismic Analysis of Large-Scale Piping Systems for the JNES ... - NRC
Seismic Analysis of Large-Scale Piping Systems for the JNES ... - NRC
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With <strong>the</strong> internal pressure and gravity load applied, modal analyses <strong>of</strong> this piping model can<br />
provide an indication <strong>of</strong> <strong>the</strong> accuracy <strong>of</strong> this model. Using <strong>the</strong> hybrid multi-linear kinematic<br />
hardening material model, <strong>the</strong> frequencies <strong>of</strong> <strong>the</strong> first two modes were found to be 6.09 Hz and<br />
7.60 Hz, representing relative differences <strong>of</strong> -3.3% and -6.2% from <strong>the</strong> sine sweep tests,<br />
respectively. Using <strong>the</strong> mono multi-linear kinematic hardening material model, <strong>the</strong> frequencies<br />
<strong>of</strong> <strong>the</strong> first two modes were determined to be 5.88 Hz and 7.33 Hz, which represent -6.6% and -<br />
9.5% <strong>of</strong>f <strong>the</strong> values from <strong>the</strong> sine sweep tests, respectively. However, <strong>the</strong>se frequencies are<br />
considered to be acceptably accurate, especially when <strong>the</strong> hybrid multi-linear model is used <strong>for</strong><br />
<strong>the</strong> lower excitation tests (DM2-1 and DM2-2) and <strong>the</strong> mono multi-linear model is used <strong>for</strong> <strong>the</strong><br />
higher excitation tests (DM4-1, DM4-2(1), and DM4-2(2)), in which <strong>the</strong> fundamental frequencies<br />
were reported to be 5.9~6.0 Hz [<strong>JNES</strong> 2003].<br />
Responses to be compared between <strong>the</strong> analysis and <strong>the</strong> test are taken at or around Elbow 2, as<br />
indicated in Figure 4-15. Some <strong>of</strong> <strong>the</strong> nodes around this location were relocated slightly from <strong>the</strong><br />
regular 500 mm discretization, in order to make <strong>the</strong> comparisons at <strong>the</strong> same locations as <strong>the</strong><br />
instrumentation. Four responses are selected in this study <strong>for</strong> comparison, as described in <strong>the</strong><br />
following.<br />
• D2: a relative displacement measurement between nodes 30 and 34. This response is<br />
designated in this report as “D2TEST” or “D2,” indicating <strong>the</strong> test result or analytical<br />
result, respectively.<br />
• D4X: a displacement measurement in <strong>the</strong> test in <strong>the</strong> X direction at node 29, relative to <strong>the</strong><br />
shaking table top (reference node 1 in <strong>the</strong> FE model). This response is designated in this<br />
report as “D4TEST” or “DX29-1,” indicating <strong>the</strong> test results or analytical result,<br />
respectively.<br />
• A2X: an absolute acceleration measurement in <strong>the</strong> X direction at node 29. This response<br />
is designated in this report as “A2TEST” or “ACC29,” indicating <strong>the</strong> test result or<br />
analytical result, respectively.<br />
• S85: strain measurements at a location on <strong>the</strong> exterior surface <strong>of</strong> elbow 2, which are<br />
designated in <strong>the</strong> test by strain gauge SE2C-7A (axial) and SE2C-7H (hoop). The strain<br />
responses will be taken from <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> elbow model (to be described in <strong>the</strong> next<br />
subsection). The comparison will be made based on <strong>the</strong> strain ratcheting time history and<br />
<strong>the</strong> maximum strain range (typically determined in conjunction with fatigue analysis).<br />
In addition to <strong>the</strong>se responses that will be compared to <strong>the</strong> test results, <strong>the</strong> relative displacements<br />
and rotations between node 30 and node 34 are saved from <strong>the</strong> analyses <strong>of</strong> <strong>the</strong> system model and<br />
will be used as inputs to <strong>the</strong> elbow shell model.<br />
4.2.3.2 <strong>Analysis</strong> <strong>of</strong> <strong>the</strong> <strong>Piping</strong> System and Result Assessment<br />
Except <strong>for</strong> <strong>the</strong> two (elastic) allowable stress tests DM2-1 and DM2-2, <strong>the</strong> three elasto-plastic tests<br />
have significant accumulation <strong>of</strong> plasticity, which may change <strong>the</strong> dynamic properties <strong>for</strong> <strong>the</strong><br />
subsequent tests. There<strong>for</strong>e, attempts have been made in investigating <strong>the</strong> plasticity accumulation<br />
effect through <strong>the</strong> ANSYS restart option that can preserve <strong>the</strong> de<strong>for</strong>med model to <strong>the</strong> analysis <strong>of</strong><br />
next test. More specifically, <strong>the</strong> analyses <strong>of</strong> DM4-2(1) and DM4-2(2) were per<strong>for</strong>med using two<br />
approaches: (1) analyses using <strong>the</strong> initial unde<strong>for</strong>med piping system model and (2) analyses using<br />
<strong>the</strong> de<strong>for</strong>med piping system model.<br />
The results <strong>of</strong> <strong>the</strong> transient analyses <strong>of</strong> <strong>the</strong> five tests are compared to test results provided by<br />
<strong>JNES</strong>/NUPEC. For acceleration responses, <strong>the</strong> comparisons are made with time histories and<br />
response spectra with a damping ratio <strong>of</strong> 5%; while <strong>for</strong> displacement responses, <strong>the</strong> comparisons<br />
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