ML20215B190
| ML20215B190 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/15/1987 |
| From: | Ashley G ABB IMPELL CORP. (FORMERLY IMPELL CORP.) |
| To: | |
| Shared Package | |
| ML20215B058 | List:
|
| References | |
| IM-P-002, IM-P-002-R00, IM-P-2, IM-P-2-R, NUDOCS 8706170251 | |
| Download: ML20215B190 (2) | |
Text
_
4 1
CLARIFICATION OF IMPELL CTH DESIGN VERIFICATION j
CRITERIA / METHODS FOR RESOLUTION OF CYGNA AUDIT CONCERNS I
j Seismic Load Combinations
)
i Prepared for:
Texas Utilities Electric Company-Prepared b):
Impell Corporation 0210-040/041 IM-P-002 Revision 0 I
i Prepared by: d. m Au Jug, S/f g/6 7 Approved by: [ [ M T -/ 5~- 3 7 o
$$0"$0$$k$$0
$5 A
c s~
~me
' CONCERN:
The: response spectrum analysis method provides seismic -
load'results which are unsigned. A concern has.been
. raised regarding the direction and magnitude of the -
critical. load combination of. gravity and seismic load.
r BACKGROUND:
The CPSES cable tray hanger design verification program
~
uses the gravity + seismic (G+S) combination method.
'This method is less corservatTve_-than the [Gl+1Sl-combination, method.
-DISCUSSION:
A representative cable tray system which contained a good'-
cross section of typical cable tray supports was
^
selected.
Time history.and The response;specresponse spectrum analyses-were run.
trum_ analysis results were combined with gravity using both G+S and lGl+lSl.
combination methods.
CONCLUSION:
This issue was resolved in the Impell calculation M-49 Rev. O. [1] The results-of thir calculation showed that:
the G+5 and IGj+ ISj envelope the results of the time history analysis, except_ for. two-instances.
In those two instances time history analysis results were higher than both G+S and lGl+lSi results.
This was due to the fact that tTie seismic ' response from.the time history analysis was higher than the response predicted by the response spectrum analysis, and hence not 'due to the ccmbination method. The slight underpredictions. (5-7%) thyt may result from the response spectrum analysis are compensated by the conservative broadening of the spectra.. For the_ remaining seismic responses (Gl+1Si values were more conservative than G+S however, _ G+S responses more accurately approached ~the time histiiry responses.
This calculation has shown that the G+S combination method is adequately conservative in ~
predicting the combination of gravity 'and seismic loadings for the verification of CPSES cable tray systems.
REFERENCES:
1)
Impe11 Calculation M-49, " Seismic Load Combination Study", Rev.-0, 2/2 m