ML20062K234
| ML20062K234 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 08/09/1982 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 4707N, NUDOCS 8208170096 | |
| Download: ML20062K234 (9) | |
Text
-,
7-Commonwealth Edison one First National Plata. Chicago, lihnok C
O-Address Reply to: PEOffIce Box 767
~
Chicago Illinois 60690 Augus t 9, 1982 Mr. Harold R.
Denton, Director Of fice o f Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Pipe Support Anchor Plates NRC Docket Nos. 50-454, 50-455, 50-456 and 50-457 Reference (a)
July 6, 1982 letter from B. J.
Youngblood to L. O. DelGeorge
Dear Mr. Denton:
This is to provide advance copies of responses to FSAR questions regarding the flexibility of baseplates for pipe supports at Byron and Braidwood.
This information will be included in the FSAR at the next amendment.
Enclosed with this letter are responses to questions 110.71 and 110.72 which were transmitted in reference (a).
NRC review of this information should close Outstanding Item 5 of the Byron /Braidwood FSAR.
Please direct further questions regarding this matter to this office.
One signed original and fif teen (15) copies of this letter are provided for your review.
Very truly yours, f
l&W T. R.
Tramm Nuclear Licensing Administrator p oi 4707N 8208170096 820809
~'
PDR ADOCK 05000454 A
PDR i
Res ponse 110. 71 The Commonwealth Edison Company has accounted f or the ef-f ects of the baseplate flexibility on forces in the expansion anchors by extensive finite element studies.
The flexible plate was modeled by plate elements and the anchors were modeled by tr uss elements.
A bilinear load displacement curve f or the an-chors idealizing the load displacement behavior observed in tests was used in the analysis.
The supporting concrete was modeled by one way canpression springs.
Nonlinearity was introduced in the analysis by the nonlinear behavior of the concrete springs and the bilinear load displacement behavior of the expansion anchors.
A constant stiff ness method was used to solve this nonlinear problem.
The details of this analysis procedure are discussed in Ref erende 1.
The f ollowing discussion briefly sum-narizes how the effect of plate flexibility was considered in x
the design.
There are two possible ef f ects of the baseplate flexibility 1
on the f orces in the expansion anchors as f ollows:
l (1)
Prying action (2)
Unequal distribution of forces anong anchors based on the geometric configuration of anchors with respect to the applied loads.
Q110. 71-1 n
Commonwealth Edison Company's analysis procedure has con-sidered the effect of both these f actors on the f orces in expan-sion anchors.
As a result of this analysis, amplification f actors f or use in the design of expansion anchor plates were developed.
These amplification f actors correlate the anchor forces deter-mined by the nonlinear flex ble plate analysis to the forces determined by a conventional rigid plate analysis.
The amplification f actors were computed as f ollows:
)
(1)
Pure tension and pure moment was applied on the anchor plate assembly so that at least one anchor was stressed to its ultimate load capacity, Pu.
A nonlinear approach described above accounting for plate flexibility was used f or the analysis.
l
( 2)
For the same plate assembly and same load, the anchor f orce was calculated using a rigid plate analysis.
( 3)
The ratio of the anchor force obtained by the nonlinear finite element approach to that obtained by the rigid plate analysis approach is defined as the anplification f actor.
Q110. 71-2
The amplification f actors were determined for the Byron /
Braidwood specific plates varying the expansion anchor configura-tion and the plate size.
The loading conditions considered were the direct tension and pure moment in the critical direction.
An enveloping value of the amplification f actors for each plate size and anchor configuration thus obtained was used in the design.
A separate study had confirmed that the mnplification f actors for a combination of direct tension and moment will f all within the enveloping value of mnplification f actors.
The flexible plate test program which was conducted by Wiss, Janney, Elstner & Associates indicated an anplification f actor of 1.15 to 1.20.
These anplification f actors were reported at ul timate load.
The analytical assessment for the same assemblies predicted the anplification f actor to be 1.0.
The residual load of 15 to 20% which was observed during the WJE test is not attri-buted to base plate flexibility or prying action eff ects because the plate corner displacements which were monitored during the tests showed that the corners had lif ted and were not in contact with concrete at ultimate load.
Thus amplification of anchor force due to plate flexibility or prying action is not possible.
This residual in anchor load measurement is attributed to the behavior of the testing equipment at the ultimate load levels.
The tests did establish that prying action in base plate assem-blies with expansion anchors is insignificant as compared to pl at e ass e:.bli es wi th ri gi d bol ts.
According to analytical studies reported i:. Reference 1, the anplification factor was expected 0110. 71-3
to be 2.1 with rigid bolts.
The test results have substantiated that the rigid bolt behavior is not the true behavior and that the pr ying eff ect is relieved due to the flexible load-displacement characteristics of expansion anchors.
i Ref erence (1)
" Evaluation of Analysis Procedures for the Design of Expansion Anchored Plates in Concrete,"
l May 31, 1979.
Part of Commonwealth Edison Company's j
r response to IE Bulletin 79-02 transmitted by C.
Reed to J. G. Keppler dated July 5, 1979.
x e
Q110.71-4
Response 110. 72 Examples of three expansion anchor plate assemblies are pro vi ded.
The square plates are with four and eight anchors and the rectangular plate is with six anchors.
The maximum ap-plied load on the assemblies and the corresponding anchor forces obtained by the rigid plate analysis and the flexible plate analy-sis are tabulated.
The amplification f actors as defined in response to Question 110. 71 are also tabulated.
The larger of the computed amplification f actors f or each plate assembly is used as the design amplification f actor.
\\
e
-- - ~-
AMPLIFICATION FACTORS FOR TYPICAL EXPANSION ANCHOR BASE PLATES WITH hTDGE TYPE ANCHORS Max. Anchor Max. Anchor Reaction Reaction Plate Anchor (Flexible Plate (Rigid Plate)
Amplification No.
Ass em bly Load Analysis)
Analysis)
Factor 1
12x12x1/2 in 33.6 k (tension) 8.4 8.4 1.0 4 anchors 1/2" 159. 2 i n-k (moment) 7.43 8.4 1.0 l 2 9x15xl/2 in 33.7 k (t ension)
'7.0 5.62 1.25 i
/
l 6 anchors 1/2" 199 i n-k (moment) 7.0 6.62 1.06 l
l 3
21x 21x 7/8 in 114 k (tension) 16.0 14.25 1.12 l
8 anchors 3/4" 90 0 i n-k (moment) 16.0 14.7 1.09 o
Y i
o i
1 PO
12" g-15a
=
0 0
L o
o o
d 12" ga O
o o
37 0
't Plate No. 2 Plate No. 1 9x15xl/2 in 12x12x3/4 in 6 anchors 1/2" 4 anchors 3/4" 21"
=
=
o o
o I,
21" o
o o
o o
Plate No. 3 21x21x7/8 in 8 anchors 3/4" 1
Q110. 72 -3
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