ML13323A471
| ML13323A471 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/30/1985 |
| From: | Southern California Edison Co |
| To: | |
| Shared Package | |
| ML13323A468 | List: |
| References | |
| NUDOCS 8509260273 | |
| Download: ML13323A471 (22) | |
Text
ENCLOSURE 4 BALANCE OF PLANT STRUCTURES SEISMIC REEVALUATION PROGRAM AS-BUILT REEVALUATION OF THE TURBINE BUILDING SOUTH EXTENSION SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 JUNE 1985 15R9260273 850924 PADOCK 05000206 0L PDR
~805 L)
- 1.
INTRODUCTION On April 30, 1982, the results of the seismic reevaluation of the turbine building and turbine generator pedestal were submitted to the NRC (Reference 1).
The submittal identified conceptual modifications consisting of addition of structural steel bracing, foundation changes, and miscellaneous modifications to the north extension, south extension, west heater platform, and east heater platform of the turbine building.
The-summary of these modifications are given in Section 5 of Reference 1.
By mid-1983 all of the modifications to the north, east, and west extensions, as well as the majority of the modifications to the south extension were completed. On December 23, 1983 the "Return To Service" (RTS) plan was submitted to the NRC (Reference 2).
The basis of the plan was to assure that structures, systems, and components necessary to achieve and maintain a hot standby condition have sufficient design margins to resist the postulated 0.67g modified Housner earthquake.
Since the failure of the south extension would not prevent the plant from reaching a safe shutdown condition, the conceptual modifications remaining in the south extension were not implemented during the RTS.
Since seismic withstand capacity of the south extension has been substantially increased by the modifications constructed to date, an analysis of the adequacy of this condition to sustain required seismic loads was performed. This report describes of the as-built condition of the south extension, including the modifications constructed to date except one brace (No. 43) and one foundation (No. 0).
The analysis methodology for evaluating the as-built withstand capability and the results of this analysis are also presented. It is shown that the as-is condition of the south turbine extension satisfies the seismic reevaluation criteria (Reference 3).
- 2.
SUMMARY
OF MODIFICATIONS IMPLEMENTED The following describe all of the proposed modifications to the south extension identified in Section 5.4 of Reference 1 and describe the current status of completion of each modification. Figure 1 shows the conceptual modifications identified in Reference 1. The as-built condition is depicted in Figure 2.
2.1 Structural Steel Bracing
- a. A wide flange W12X120 diagonal brace was designed for installation between the top of column N-6 and the bottom of column M-6.
STATUS:
Complete
- b. A wide flange Wl2xl2O diagonal brace was designed for installation between the top of column N-6 and the bottom of column P-6.
STATUS:
Complete
- c. A wide flange Wl2xl2O 'K" brace was designed for installation in the east-west direction between column M-6, M-7 and M-8.
STATUS:
Complete
- d. A wide flange Wl2xl2O diagonal brace was designed for installation between the top of column N-8 and the bottom of column M-8.
STATUS:
Complete
- e. A wide flange Wl2x12O diagonal brace was designed for installation between the top of column P-8 and the bottom of column N-8.
STATUS:
Complete
- I
- f. A wide flange Wl2xl20 diagonal brace was designed for installation between the top of column P-7 and the bottom of column P-6.
STATUS:
Complete
- g. A wide flange W12xl2O diagonal brace was designed for installation between the top of column P-6 to the concrete pier located east of column P-6.
STATUS:
The as-built analysis of the south extension showed that this modification is not required to satisfy the design margins.
2.2 Foundations
- a.
Along column line 6 a combined footing approximately 20 feet x 12 feet x 6 feet deep was designed for installation. The existing footings for columns M-6 and N-6 were structurally connected to the modified footing using rock bolts.
STATUS:
Complete
- b. Along column line 8, a combined footing approximately 20 feet x 12 feet x 6 feet deep was designed for installation. The existing footings for the columns M-8 and N-8 were structurally connected to the modified footing using rock,bolts.
STATUS:
Complete
- c. Along column lines P-6 to P-8 a combined footing was designed for installation. The existing footings for the columns P-6, P-7, and P-8 were structurally connected to the modified footing using rock bolts.
STATUS:
The as-built analysis of the south extension showed that this modification is not required to satisfy the design margin.
- d. A spread foundation was designed for installation east of column P-6.
STATUS:
The as-built analysis of the south extension showed that this modification is not required to satisfy the design margins.
(See item g in Section 2.1) of the deck slab. These shear plates were welded to the top flanges of the supporting beams and girders. Some of these welds were ground out and rewelded in order to assure transmitting of seismic forces to the structural frame.
STATUS:
Complete
- 3.
REEVALUATION CRITERIA AND METHODOLOGY The criteria followed for the reevaluation of the south extension are given in References 1 and 3. The analysis considered the occurrence of a 0.67g modified Housner earthquake in combination with normal plant operating loads, including the presence of the turbine gantry crane.
The basis of the mathematical model used is the three-dimensional finite element model developed in Reference 1. The turbine building complex is basically a frame structure supported by individual footings. There are no structural elements connecting the north, south, east, and west extensions, therefore, there is no interaction between the extensions.
For this reason, for the reevaluation presented herein, the north, east, and west extensions are removed from the mathematical model.
The models of the turbine generator and pedestal are included since some of the
- I south extension footings rest on the pedestal basement. The gantry crane is assumed to be parked at its normal plant operating location, that is on the south end of the south extension. The finite element idealization is given in Figure 3.
Linear elastic analysis methods are used for the computation of the static and dynamic responses. For the dynamic analysis response spectrum method is utilized.
The procedure followed to account for the effects of soil-structure interaction is consistent with Reference 1. Soil-structure interaction effects were taken into account by lumped parameter representation of the soil medium stiffness and damping. In computing the soil parameters, the footing geometry, structure inertia, total structural embedment, strain dependent properties of the foundation medium and forcing frequencies were considered as discussed in Reference 3. Because the supporting medium is a San Mateo sand deposit which is uniform and extends to a depth of approximately 1000 feet below the site, a frequency independent representation of soil stiffness and damping values was used. In addition, the effects of soil backfill conditions are included in the computations of lumped parameter soil structure interaction values as described in Reference 4.
0 The soil medium is represented in the three-dimensional finite element model by including three translational and two rotational linear spring stiffness values and their corresponding damping values. Although the composite modal damping values computed were as high as 51 percent, the maximum composite modal damping was conservatively limited to 20 percent for the response spectrum analysis.
The resulting structural seismic responses obtained from the response spectrum analysis consist of moments, shears, and displacements for the various elements that comprise the finite element model. These responses are then combined with the static analysis results for the evaluation of the structural members, the connections and the column anchorages.- The results of the calculations indicate that all structural elements in the as-built condition of the south extension satisfies the criteria set forth in References 1 and 3. Possible uplift in the footings are also evaluated.
- 4. DISCUSSION OF RESULTS In the present reevaluation, the member forces are computed both for the lower bound and upper bound soil conditions. In the majority of the cases, the lower bound soil parameters, reflecting the interpreted extreme soil backfill conditions (Reference 5), govern the evaluation.
The forces are then compared with the element forces presented in Reference 1. When the computed forces are less than or equal to those in Reference 1, the structural element (beam, column, or a connection) satisfies the seismic evaluation criteria. The majority of the evaluations fall into this category. Additional computations are performed to demonstrate that the element with the as-built forces satisfies the evaluation criteria, when the calculated forces are higher than those given in Reference 1.
Tables 1 through 6 show the summary of the evaluations performed.
For ease of reference the tables also contain the results of the member evaluations presented in Reference 1. The "remarks" column of each table describe the evaluation results of the as-built analysis described herein.
As is described in section 2.2, item c, the foundation modification combining footings P6, P7 and P8 is not constructed. Therefore the existing foundations were reviewed for the uplift loads from the newly installed bracing members. The dynamic analysis performed using the upperbound values of the soil parameters yielded forces on the footings which were less than the net downward forces in the columns. Therefore, the results of the upper bound analysis were acceptable for uplift considerations of the footings.
The selected footing evaluation indicated they met the acceptance criteria.
The bracing member forces calculated from the dynamic analysis performed using lower bound values of the soil parameters were evaluated in the similar manner for uplift considerations. All the structural column locations reviewed met the acceptance criteria except column location P6.
At column P6, the lower bound analysis yielded a total uplift load which was 4 percent greater than the total downward force on the footing. The effect of this unbalanced force on the rest of the structure was evaluated by performing a three dimensional static analysis. In this analysis the net unbalanced load of 7.8 kips at the column base was applied as an upward load to be redistributed and the resulting forces in the structural members were calculated. These members forces were superposed on the forces calculated from the dead load analysis and dynamic analyses.
All the members evaluated using these forces were found to be acceptable. Therefore, all the structural column footings were considered acceptable.
It should be noted that a large portion of the uplift load on the bracing members during DBE is generated because of the conservative method of modeling of the gantry crane on the parking structure outside of the south extension on the southside. The gantry crane is free to roll on the crane girders. The wheels of the gantry crane are not structurally connected to the crane rail girder. However, for the finite element model the legs of the crane were modeled as pin connected to the crane rail girders. Because of this conservative way of modeling, the east-west rocking mode of the crane about the north-south axis generates a large portion of the tensile load in the bracing members. In reality, the gantry crane may lift up during an east-west excitation. An independent stability analysis of the gantry crane performed previously had indicated that large margins of safety exist against the crane overturning even if the crane legs lift up.
Therefore, the column footing P6 is acceptable. The columns and footings of the parking structure, R6 and R8, were evaluated for the compressive loads only, sinre it was concluded that due to lifting of the legs of the crane, these columns can not be subjected to a tensile load.
The maximum lateral displacements of the south extension structure and the turbine/generator pedestal, as shown in Table 7, were calculated using the response spectrum analysis method. Two independent analyses were performed corresponding to the lowerbound and the upperbound values of the soil parameters. The lowerbound analysis yielded larger lateral displacements. As shown in Table 7 the maximum combined SRSS displacement of the Turbine/Generator Pedestal and the South Extension deck is 1.11 inches.
This is smaller than the 1.50 inches of the seismic gap available between the two structures, therefore is acceptable.
- 5.
CONCLUSIONS Based on the results of the reevaluation of the south turbine building extension with the modifications installed, it is concluded that the existing south extension, satisfies the seismic reevaluation criteria without further modification. Therefore, the additional conceptual modifications identified in Reference 1 need not be implemented to satisfy the design margins.
REFERENCES
- 1. to the letter from K. P. Baskin to D. M. Crutchfield, dated April 30, 1982, "Balance of Plant Structures Seismic Reevaluation Program, Turbine Building and Turbine Generator Pedestal, San Onofre Nuclear Generating Station, Unit 1".
- 2. Enclosure to letter from M. 0. Medford to D. M. Crutchfield, dated December 23, 1983, "Docket Number 50-206, Return to Service Plan, Seismic Reevaluation Program, San Onofre Nuclear Generating Station, Unit 1".
- 3.
Enclosure to letter from K. P. Baskin to D. M. Crutchfield, dated February 23, 1981, "Balance of Plant Structures Seismic Reevaluation Criteria, San Onofre Nuclear Generating Station, Unit 1".
- 4.
Enclosure to letter from K. P. Baskin to D. M. Crutchfield, dated April 18, 1983, "Soil Backfill Conditions, Chapters 1, 2, & 3".
Enclosure to letter from R. W. Krieger to D. M. Crutchfield, dated September 1, 1983, "Soil Backfill Conditions, Chapters 4 & 5".
Enclosure to letter from M. 0. Medford to D. M. Crutchfield, "Addendum 3 to the Report on Soil Backfill Conditions; Shear Modulus Values used in Soil Structure Interaction Studies SONGS 1".
P6-P7 36 W-N6 -
"E" P6-N6 37 MS-N8 -
"F" M6-N6 38 P6-P8 - "D" N6-M7'-MB 39-40 HB-ES 41
- 8-P8 42 P6 Outside 43 FOUNDATION/
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- , AREA 7
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- 400, IA A
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f FOUNDiATION SD" FOUNDATION IF' EXtSTING FOOTINGS NOT SHOWN Figure 1. Conceptual and Foundation Modifications in South Extension of Turbine Building (Reference 1)
U N
.7-FOUNDATIONOE in/7 Ex of
- b Bui
,'4B I%427 A-sO FOUNDATION a Fm Figure 2. As-Built Bracing and Foundation Modifications In South Extension of Turbine Building
Il Figure 3. Mathematical Model used in the Analyses of the South Extension of Turbine Building
TABLE I SOUTH EXTENSIO@ BRACING STRESS EVALUATION SEP EVALUATION FROM REFERENCE 1 TABLE 32 (1982)
EVALUATN(95
-vo soo/v CV I
RZ4ARK fre-mr
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0 754 20:92 2.9K
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13-7R 187 A
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41
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P6 -T,41 Whi~' Xj 12 A.5 IA* 7 Mf7-:-7-16 j'
4X W27_9 35113 7D'
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fa a CALCULATED AxIAl. STWEss, osl
- 2. fas Ai.LowAetf AAIAL Smess, 1(sl
- 5.,c sAfry A~cTO, ropA AXfij.. COMPORESS10A' NOTE A:
SEP LOADS HIGHER, MEMBER OK.
TABLE 4 SOUTH EXTENSION BOLTED CONNECTION EVALUATION SEP EVALUATION FROM REFERENCE 1,
TABLE 35 (1982)
EVALUATION (1985)
RF ECS A^ CEE CR TE#r/A RAFkfA RK 5 avrRCewF/OU4RE #0.
/E CV VA /VC YE'S wo E
A 8c1 44 7RowS
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N A
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NOTE A,
8C4 44 4AnWS 17.1 91.8 49&
x NO A
8C5 44 3ows
(..4 36.7 51
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. Vc - CA4 C//LATED SH'FARA, r/PS
- 2. V'A -
4101AeLZ 5N/AR, K/PS 3, Sy*-SA#-ETY FACTOR FOR SHEAR NOTE A:
SEP LOADS HIGHER, CONNECTION OK NOTE B:
AS-BUILT LOADS MARGINALLY HIGHER, CONNECTION OK BY INSPECTION
TABLE 5 SOUTH NS COLUMN EVALUATION SPEVALUATION FROM REFERENCE 1, TABLE 36 (1982)
E PRESENT EVALUATION (1985, esp P v P f
Mpx My Mpy Mt f &
70of
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-4 04 04 OR 04Y e
- I)
A NO o I Fo tbx Fbn fby Fb y RcRe RA RAfc YEs
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45
)1Z4 vl3o 1.67 16.14 15.40
.D 5.17 27.0 1.01 l.ro' 1.5e X
Nae A
M-8 4s l24xI3o I-.6T 16.14 15.40 22.0 5.17 2T.o 1.01 1,40 1.5 o
N-G 45 N"Arw i0 6.32 14.60 8.59 21.3 4.23 27.0 0.98 I.6o 1.8 NO A
N-7 N'ISO 4.49 15.99 9.04 22.0 4.74 27.0 0.84 1.60 1.90 Cz l5
,Ilo 9.13 14.45 8.9 20.97 4.85 27.0 1.77 1.60 1.14 x
NOT-T P-45 24 100 271lo.
31Gs tooeo t3 zo5
- 1..o I..1 y
AMr-C, S.F.\\.t4 P-'7 45 Nq:4\\x130 4.94 15.98 9.28 22.0 5.5 7 7.0 I.OG 1.60 1.51 X
m a
P-8
- 5 N240oo 8.78 14.5I 6.99 19.09 5.5-1 Z.0 1.77 1.(00 1.24 X
onN eSF R-.
s 24x130 9.43 14.10 12.J9 22.0 0-7I 2.0 I.15 1.4o 1.39 X
Jflt' A R-8 45 N24A 130.
9.43 16.10 1 2.9 22.0 O.7 27.0 1.15
- 1. 6O 1.39
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2 I4x T38 785 7oZ 153C 203 I,
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.5.- oveRAI SAs r y FACrOR 4* s FQ Fpbwr, e.* SEE A/SC 6r'L COW6TRJ/CrloAe MA NUAL 1980, k5; Pp Py Myp ETC.-
KIPS OR klp
- INCHES POOT TAES (DEsIGIvATEo BY
'SUPERSCR/PTS)
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Py 1.18 A
/.47 Wpy NOTE A:
SEP LOADS HIGHER, MEMBER OK BY INSPECTION NOTE 8:
AS-BUILT LOADS MARGINALLY HIGHER, MEMBER OK BY INSPECTION NOTE C:
AS-BUILT LOADS HIGHER, MEMBER OK
TABLE.6 SOUTH EXTENS
- COLUMN ANCHORAGE EVALUATION PRESENT SEP EVALUATION FROM REFERENCE 1, TABLE 37 (1982)
EVALUATION (1985)
I REF NO.gR tsRr~O jCb FA~f b
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27 r 044 7-sEE sAffioN 5-A( /8
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- 4.
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JELi r 3054 c
NOTE A:
SEP LOADS HIGHER, ANCHORAGE OK NOTE B:
AS-BUILT LOADS MARGINALLY HIGHER.,4CHORAGE OK BY INSPECTION NOTE C:
AS-BUILT LOADS HIGHER, ANCHORAGrJ OK
TABLE 7 SOUTH EXTENSION -
DISPLACEMENTS MAXIMUM DISPLACEMENT DISPLACEMENTS LOCATION DIRECTION (INCHES)
REMARKS Northwest Corner of the North-South 0.582 Displacements O.K.
South Ext. Deck East-West 0.328 Northwest Corner of the North-South 0.543 Displacements O.K.
South Ext. Deck East-West 0.328 Southeast Corner of the North-South 0.946 Displacements O.K.
Turbine Pedestal Deck East-West 0.608 Southeast Corner of the North-South 0.946 Displacements O.K.
Turbine Pedestal Deck East-West 0.608 SRSS Combined Displacement North-South 1.11 Displacements O.K.
Turbine Pedestal Deck With South Ext. Deck