ML19291B095

Responds to IE Bulletin 79-02, Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts. Forwards Evaluation of Analysis Procedures for Design of Expansion Anchored Plates in Concrete by Sargent & Lundy Engineers

ML19291B095
Person / Time
Site:	Zimmer
Issue date:	07/06/1979
From:	Borgmann E CINCINNATI GAS & ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 7908290368
Download: ML19291B095 (6)

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THE CINCINNATI GAS & ELECTRIC COMPANY sIK~ 7 CINCIN N ATI.OHto 45201 July 6, 1979 J ^i.5 17 *.^"".

U.S. Regulatory Commission Office of Inspection and Enforcement Region III 7999 Roosevelt Road Glen Ellyn, Illinois 60137 ATTN: Mr. James G. Keppler Regional Director RE: WM. H. ZIMMER NUCLEAR POWER STATION - UNIT 1 IE BULLETIN 79-02, PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS, DOCKET 50-358 W.0. 57300, JOB E-5590, ITEN 400 Gentlemen:

The attached documents are being furnished in response to IE Bulletii.s 79-02 and 79-02 Rev. 1.

Included are the following:

Attachment (1) Response to IE Bulletins 79-02 and 79-02 Rev. 1.

Attachment (2) Evaluation of analysis procedures for the design of expansion plates in concrete, dated May 31, 1979.

We believe this information provides a complete response to NRC IE Bulletins 79-02 and 79-02 Rev. 1.

Very truly yours, THE CINCINNATI GAS & ELECTRIC COMPANY h __~

E.A. BORGMANN, SEN E PRESIDENT JCH/kjd ENCLOSURE cc: NRC Office of Inspection and Enforcement Division of Reactor Inspection Programs Washington, D.C. 20555 _

2',3 R.F. Scheibel J.D. Flynn W.W. Schwiers s 2012 S. Rurka J.R. Schott K.K. Chitkara W.D. Wa ire H.C. Brinkmann General File .

I84 S.G. Sa ay H.E. Crail g

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RESPONSE TO IE BULLETIN NO. 79-02 REV. 1 ZIMMER - UNIT 1 CINCINNATI GAS & ELECTRIC COMPANY

1. The pipe support baseplates for Zimmer Unit 1 have been designed based upon rigid plate theory. Cincinnati Gas & Electric Company has evaluated the rigid plate analysis procedure compared with flexi-ble plate analysis procedure, and has concluded that the design of expansion anchored plate assemlbies using rigid plate theory provides factors of safety ranging from a minimum of 4.0 to a maximum of 8.7 against manufacturer's recommended ultimate failure loads. It has been shown in the attached report, entitled, "Evauluation of Analysis Pro-cedures for the Design of Expansion Anchored Plates in Concrete," dated May 31, 1979, that, when the flexibility of the expansion anchored base-plate assembly, in conjunction with the load versus displacement behavior of the expansion anchor, is accounted for in a finite element. solution, the " prying action" forces are largely relieved, and the flexible plate solution approaches the rigid plate solution. This has been concluded for the typical expansion anchor assemblies used to support mechanical components for Zimer Unit 1 for various expansion anchor types, embedment depths, pre-load levels and applied load patterns which may typically be encountered in such installations. It is, therefore, Cincinnati Gas & Electric Company's opinion that adequate margin exists in the present design of expansion an-chored plate assemblies to accomodate the effect of the flexibility of the baseplate assemblies as required by the Nuclear Regulatory Comission.

The load-displacement curves illustrated in the attached report were ob-tained from field tests at several nuclear stations currently under con-struction, and are judged to be conservative. Cincinnati Gas & Electric Company will participate in a comprehensive static testing program2 for 012~N '6' concrete expansion anchors under the direction of an Independent Testing

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Laboratory to verify these load-displacement curves.

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Also, the test program will include testing to failure flexible expansion anchored plate assemblies designed using rigid plate theory, and demonstrat-ing that the failure load equals or exceeds four (4) times the design load.

The static test program to verify the load-displacememt curves and ultimate loads will encompass the following combination of variables:

a) bransion anchor types

1) Wedge type anchors

2) Self-drilling type ancP. ors b) Anchor diameter

1) 1/4"

2) 3/3"

3) 1/2"

4) 5/8"

5) 3/4"

6) 1" c) Embedment depth 1/2 anchor diameters d) Embedment material

1) Concrete-F{=3500psiand5500 psi

2) Masonry mortar - ASTM 270, Type M and Type N In addition, this testing program will also assess the long term preload relaxation characteristics of wedge and self-drilling type anchors.

The results of the static test program will be available for review by the

, Nuclear Regulatory Commission upon completion.

2. Cincinnati Gas & Electric Company has verified that concrete expansion anchor bolts have been designed using a minimum factor safety of 4.0 be-tween the bolt design load and the bolt ultimate capacity detennined 2012 M7

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. from manufacturer's static data for wedge and self-drilling type anchors.

91is factor of safety has been traditionally recommended by manufacturers of both wedge and self-drilling type expansion anchors for static loads.

3. The dynamic / cyclic loads for which the pipe support baseplates have been designed were obtained from either a response spectrum or time history method of aralysis, and, therefore, properly accounts for any dynamic

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load factors. The concrete expansion anchor design allowables were based upon maintaining a minimum factor of safety of 4.0 between the dynamic / .

cyclic design loads, corresponding to an OBE event, and the bolt ultimate capacity, as determined from manufacturer's static load that data for wedge and self-drilling type anchors. Cincinnati Gas & Electric Company will participate in a comprehensive dynamic test program under the di-rection of an Independent Testing Laboratory to verify the dynamic be-havior of wedge and self-drilling type expansion anchors. These tests will be perfonned on rigid plate expansion anchored assemblies under the following dynamic conditions:

a) Pipe transient cyclic loads b) OBE seismic loads The results of the dynamic test program will be available for review by the Nuclear Regulatory Comission upon completion.

4. A mixture of wedge and self-drilling type concrete expansion anchors have been used in safety related areas at Zimer Unit 1. The minimum embedment length for wedge type anchors is 4-1/2 anchor diameters. Self-drilling expansion anchors were used only on a limited basis in safety related areas prior to 1976. All concrete expansion anchors were specified to be installed at Zimer Unit 1 in accordance with manufacturer's recomendations.

Cincinnati Gas & Electric Company will inspect wedge and self-drilling

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type expansion anchors supporting safety related piping in which the cal-culated factor of safety ( ultimate anchor capacity divided by the cal-culated applied load ) is less than or equal to 10, at Zinner, Unit 1, to assure confonnance to manufacturer's installation recommendations.

Wedge type expansion anchors will be inspected to verify the following items:

a) Minimum test torque level b) Minimum embedment length c) Expansion anchor size Expansion anchors which do not meet the required test torque value will be retorqued to the installation value and n! inspected within seven days to assure that relaxation has not exceeded the required test torque value.

Expansion anchors which do not have the correct embedment length or size will be reanalyzed and, if inadequate to support the design loads, will be replaced, or the expansion anchored plate assembly modified accordingly to support the design loads.

Manufacturers of self-drilling concrete expansion anchors typically have not specified initial installation torque values. The torquing of a self-drilling anchor does not seat the anchor in the concrete hole, and, thereby, minimize anchor displacement as in the case of wedge and sleeve type anchors.

Cincinnati Gas & Electric Company, however, will participate in a test pro-gram for self-drilling type expansion anchors under the direction of an In-dependent Testing Laboratory to determine appropriate installation and test torque levels to assure that the preload in the self-drilling expansion anchors is greater than or equal to the design loads.

A random sample of self-drilling expansion anchored assemblies supporting safety related piping will be inspected by applying the test torque to the individual anchors.

The self-drilling 2 012 2 A '

expansion anchors will be inspected subsequent to the application

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e of the test torque to assure that the shell of the self-drilling expansion anchor is no? in contact with the back of the expansion anchor baseplate. Self-drilling expansion anchors which are in contact with the back of the expansion anchor base-

. plate will either be replaced with a wedge type anchor, or the expansion anchored plate assembly modified accordingly to support the design. loads.

Future expansion anchor installations at Zimmer Unit 1 will consist of wedge type only, with an embedment length equal to 4 anchor diameters.

These anchors will be installed in accordance with approved QA/QC pro-cedures, and the design load for these anchors will be less that the specified anchor preload.

The results of Cincinnati Gas & Electric Company's verificaton of existing expansion anchor installations at Zimer Unit 1 will be avail-able for review by the Nuclear Regulatory Commission upon completion.

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Attachment (2)

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EVALUATION OF ANALYSIS PROCEDURES TOR THE

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DESIGN OF EXPANSION ANCHORED PLATES IN CONCRETE

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PREPARED BY: OM REVIEWED BY: M  %

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APPROVED BY: ( '

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May 31, 1979

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DUPLICATE DOCUMENT Sargent & L 2 0 'i 2 q.-

c: j Entire document previously Chicago, eintered into system under:

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4 No. of pages: fyl._