ML19291C514

Forwards Response to IE Bulletin 79-02,Revision 2, Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts. Concrete Expansion Anchor Baseplate Assemblies Have Been Designed for Min Factor of Safety Equal to 4.0

ML19291C514
Person / Time
Site:	Zimmer
Issue date:	01/04/1980
From:	Borgmann E CINCINNATI GAS & ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-02, IEB-79-2, NUDOCS 8001240529
Download: ML19291C514 (20)

Text

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. h THE CINCINNATI GAS & ELECTRIC COMPANY sm F CINCINN ATI. OHIO 4 5201 Jan. 4, 1980

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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, REV. 2, PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS, DOCKET 50-358 W.O. 57300, JOB E-5590, ITEM # 400 Gentlemen:

The attached document is being furnished in response to IE Bulletin 79-02, Rev. 2.

Included is the following:

Attachment (1) Response to IE Bulletin 79-02 Rev. 2.

We believe this information provides a complete response to NRC IE Bulletin 79-02 Rev. 2.

Very truly yours, THE CINCINNATI GAS fi ELECTRIC COMPANY fW &p a.

E.A. BORGMANN, SENIOR VICE PRESIDENT JCH/kjd ENCLOSURE NRC Office of Inspection and Enforcement cc:

Division of Reactor Inspection Programs }[93 2}]

Washington, D.C. 20555 -

T. Daniel (Region III, WHZ Site) J.R. Schott R.F. Scheibel H.C. Brinkmann S. Rurka H.E. Crail H.H. Shah K.K. Chitkara S.G. Salay W.D. Kaymire (pink)

W.W. Schwiers ATTN: Gen. File J.D. Flynn Q

8001240 -t ,

, , . , _ . . _ . - - . - . - - - - - . - - , - ~

. Attachment 1

. ~._ RESPONSE 'IO IE BULLETIN NO. 79-02 REV. 2.

ZBMER UNIT 1

2. Verify that the concrete expansion anchor bolts have the following minimum factor of safety between the bolt design

. load and the bolt ultimate capacity determined from static load tests (e.g., anchor bolt manufacturer's) which simulate the actual conditions of installation (i.e., type of con-crete and its strength properties):

a. Four - For wedge and sleeve type anchor bolts,

b. Five - For shell type anchor bolts.

The bolt ultimato capacity should account for the effects of shear-tension interaction, minimum edge distance and proper bolt spacing.

If the minimum factor of safety of four for wedge type anchor bolts and five for shell type anchors cannot be shown, then justification must be provided. The Bulletin factors of safety were intended for the maximum support load including the SSE. The NRC has not yet been provided adequate justi-fication that lower factors of safety are acceptable on a long term basis. Lower factors of safety are allowed on an. interim basis by the provisions of Supplement No. 1 to IE Bulletin No. 79-02. The use of reduced factors of safety in the factored load approach of ACI 349-76 has not yet been accepted by the NRC.

Response: Concrete expansion anchor baseplate assemblies for Zimmer, Unit 1, have been designed for a minimum factor of safety equal to 4.0 against manufacturer's recommended ultimate loads for the following piping load combinationc:

1) Normal

2) Upset .

A minimum factor of safety equal to 2.0 against manufacturer's recommended ultimate loads has been used for the following piping load combinationst

1) Emergency

2) Faulted 1793 212

.1

_ _ _ _ _ = . . _ _ . - - - . - . - - , . .- . . . . _ _ . ,, ., ..w. ,s__ g.

- -- -. ___. -- - _ - - - _ _ - - - . _ 5--.-- - . . _ _

It is emphasized that these are minimum f actors of saf ety, and in certain instances, factors of safety equal to 4.0

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or more have been realized under the emergency / faulted condi-tions due to the relatively light loads supported by the anchors and the use of standardized plate assemblies with high load carrying capacity compared to the applied loads.

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It is The Cincinnati Gas & Electric Company's opinion that factors of safety equal to 2.0 and 4.0 are justified for the emergency / faulted and normal / upset load conditions respec-tively for the following reasons:

1) The factors of safety are consistent with and conservative compared to the philosophy of and the structural accep-tance criteria specified in Sections 3.8.3 and 3.8.4 of the Nuclear Regulatory Commission's Standard Review Plans. .

2) The f actors of saf ety are consistent with the philosophy of ASME Section III tIo which saf ety related piping systems are designed.

3) Test data available today indicates that concrete expan-sion anchors will perform satisfactorily at load levels equal '.o oce-fourth and one-half t'.leir ultimate loads under dynamic conditions.

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. 4) Concrete expansion anchor ultimate loads r.: / directly with the square root of the concrete strength. Con-crete expansion anchors thereby achieve higher ultimate , . . ,

loads than recommended by manufacturers when the in-place concrete strength versus the nominal design strength is considered.

5) Test data has indicated that an elliptical interaction best defines the relationship for concrete expansion anchors under combined tension and shear. The expan-sion anchored baseplate assemblies for Zimmer, Unit 1, have been designed using a conservative straight line interaction based upon shear friction concepts. The straight line interaction provides substantial safety

, margins when compared to the actual elliptical interaction.

The Standard Review Plan structural acceptance criteria for normal and severe environmental loading combinations are working load levels (saf ety f actors between 1.6 and

2. 0) and are ultimate load levels (safety f actors between 1.0 and 1.25) for the extreme environmental and abnormal loading combinations. Normal and severe environmental loading combinations correspond to the normal / upset piping load combinations; while the extreme environmental and abnormal loading combinations correspond to the emergency /f aulted piping load combinations.

1793 214 3

Applying the philosophy of the Standard Review Plans, the

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allowable concrete expansion anchor load would be equal.

to the ultimate load f or the emergency and faulted load combinations. Theref ore, the current Nuclear Regulatory Commission position requiring a f actor of saf ety equal to 4.0 for the emergency and f aulted load combinations is not compatible with the Standard Review Plans, nor is it compat-ible with the design philosophy with which the structures supporting the expansion anchor plate assemblies have been designed. The factor of safety for a properly installed expansion anchor should be comparable to the factor of safety for the supporting structure.

Saf.ety related piping systems f or Zimmer , Unit 1, have been designed in accordance with ASME Section'III. This code recognizes that stresses in the piping system may approach yield under the emergency /f aulted load conditions. Therefore, the 4.0 factor of safety on the supporting system (expansion anchor baseplate assemblies) under the corresponding load combi na ti ons is not compatible with the piping system design philosophy.

.A survey of the dynamic test data on concrete expansion anchors indicates:

]793 215 4

Ng *

1) Concrete expansion anchors demonstrate negligible slip-s page (walking) under dynamic conditions at a load level equivalent to one-fourth the ultimate capacity of the anchor.

2) Noticeable anchor slippage (walking) does not occur

. in a concrete expansion anchor under dynamic conditions until the load level exceeds 60% of the ultimate capacity of the anchor.

An evaluation of published literat'ure and field test data obtained by The Cincinnati Gas & Electrfc Company on concrete expansion anchors indicates the capacity of expansion anchors can be conservatively assumed to vary 'directly with the square root of the concrete compressive strength, f'. Certain manufacturers have even recommended that the ultimate capacity varies directly with the concrete strength. The in-place concrete strengths are consistently higher than the nominal design strengths for the following reasons:

1) Concrete exhibits a minimum 10% strength gain af ter one year and continues to gain strength at a reduced rate beyond one year.

2) Concrete mix proportions have been conservatively estab-lished, and concrete cylinder strengths closely monitored.

Typical 28 and 90-day concrete cylinder breaks for s

]793 216

non-flyash and flyash mixes have average strengths in excess of 201 the nominal design strength. ,

Concrete expansion anchor ultimate loads have been based upon a nominal concrete strength, f', equal to 3500 psi.

Considering these factors, the in-place concrete strength for nominal 3500 psi cor. crete would be 4600 psi (3500 x 1.2 x 1.1) . This strength margin would result in a 15%

increase in the ultimate capacity of the concrete expansion anchors which is not accounted for in design. In addition, there are many areas such as the containment buildings and reactor buildings in which the nominal concrete design strength equals 5500 psi. A 44% increase in the ultimate capacity of the anchors would result in this situation.

Testa performed on individaal concrete expansion anchors and on concrete expansion anchored baseplate assemblies by the various expansion anchor manufacturers, and more recently by Teledyne-Brown Engineering, indicate that an elliptical interaction best defines expansion anchor capacity under combined tension and shear. The interaction equation would be of the following form:

(Tmax I +I V ) s 1.0 (1) max where:

V = Applied shear load.

1793 217 6

i N I T = Applied tension load.

V max = Maximum pure shear capacity f or an individual anchor or assembly.

T

= Maximum pure tension capaci ty f or an individual max ~~_.

anchor or assembly.

x = Exponent greater than 1.0 This equation can be reduced to:

T*

( T )'* + ( V y ) 5 ( Tmax ) (

The test data indicates that the ratio of T max to Vmax v ries from 0.80 to 1.2.

The design of expansion anchored baseplate assemblies for Zimmer, Unit 1, have been designed using a straight line interaction based upon the shear friction concepts using a coefficient of f riction .p. equal to 0.7. The resulting interaction curve is:

T + 1. 4 V $ Tmax It can be seen by inspection that the straight line inter-action curve will result in smaller allowable loads than the elliptical interaction for all circumstances in which the ratio of Tmax D Y max is less than 1.4 because the expo-nont, x, has been conservatively taken as 1.0. Attached are several typical ultimate shear tension interaction curves 1793 218 7

x i comparing the elliptical interaction determined by tests conducted by Teledyne-Brown Engineering with the otraight

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line interaction used in design. e-The Cincinnati Gas & Electric Company has committed to per-forming a comprehensive static and dynamic testing program for concrete expansion anchors under the direction of an Independent Testing Laboratory. It is anticipated this testing program will demonstrate the ability of concrete expansion anchors to satisf actorily carry normal / upset and emergency /f aulted loads using f actors of saf ety equal to 4.0 and 2.0 against manuf acturer's recommended ultimate loads, respectively. The results of this testing program -

will be available and reported to the Nuclear Regulatory

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Commission upon completion.

1793 2I9 8

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5. Determine the extent that expansion anchor bolt were used in concrete block (masonry) walls to attach piping supports in Seismic Category 1 systems (or safety related systems as defined by Revision 1 of IE Bulletin No. 79-02). If expansion anchor bolts were used in concrete block walls: '

a. Provide a list of the systems involved. with the number of supports, type of anchor bolt, line sine, and whether these supports are accessible during normal plant operation.

Response:. Small bore safety related piping systems have been attached to concrete masonry walls using concrete expansion anchors. The location and magnitude of these hanger loads have been documented and verified.

The capacity of the concrete masonry walls has been checked for these attached loads.

b.

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Describe in detail any design consideration used to -

account for this type of installation.

Response: The use of concrete expansion anchors in

' concrete masonry walls. at Zimmer, Unit 1, has been

, restricted to solid and grouted concrete masonry walls, and to the attachment of small loads, typically less than 500 pounds. Items falling under this category, for example, are small bore piping, electrical junction boxes and conduit. Heavier loads ha7e not been permitted to be attached to concrete masonry walls, nor have concrete expansion anchors been used in hollow concrete masonry walls.

All concrete masonry walls have been designed for a concentrated live load of 180 pounds applied on one-foot wide horizontal beam strips, spanning the length _of i/93 220 9

's. ,

the wall over its entire height. The 180 pound concen-

. trated live load has been placed on the beam strips

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to envelope the maximum resultant moment and shear.

Items actually attached to concrete masonry walls have been verified by field survey, and a final load check conducted to assure the adequacy of the walls to carry

,the applied loads.

c. Provide a detailed evaluation of the capability of the supports, including the anchor bolts, and block wall to meet the design loads. The evaluation must describe how the allowable loads on anchor bolts in concrete block walls were determined and also what analytical method was used to determine the integrity of the block walls under the imposed loads. Also describe the acceptance criteria, including the numerical values, used to perform this evaluation. Review the deficiencies identified in the Information Notice on the pipe supports and walls at Trojan to determine if a similar situation exists at your f acility with regard to supports using anchor bolts in concrete block walls.

Response: The allowable design loads for expansion anchors in concrete masonry walls have been determined by static tests conducted at various units currently under construction. The anchors in these tests were installed in solid concrete masonry units and in the masonry mortar joints. The ultimate loads for concrete expansion anchors installed in concrete masonry walls have, thereby, been established as approxima.tely one-half of the corresponding allowables in plain concrete.

The following concrete masonry units were used at Zimmer, Unit 1:

1793 221 10

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1) Solid concrete masonry a) Masonry units - ASTM C145, Type N-I blocks, having --

a minimum net compressive strte.gth equal to 1800 psi.

b) Mortar - ASTM C270, Type N, having a minimum com-pressive strength equal to 750 psi rt 28 days.

2) Grouted concrete masonry y a) Masonry units - ASTM C90, Type N-I blocks, having a minimum net compressive strength equal to 1800 psi.

b) Mortar - ASTM C270, Type N, having a minimum compres-sive strength equal to 750 psi at 28 days. '

c) . Grout - Conforming to ASTM C476.

The concrete masonry walls at Zimmer, Unit 1, have been designed using elastic techniques. The allowable stresses in concrete masonry walls are in accordance with the National Concrete Masonry Association Specifications for Non-Reinforced Concrete Masonry. These stresses are:

1793 222 11 .

s,

.s .

Type N

'. Allowable Stress Mortar Shear 23 psi Tension in flexure normal 27 psi to bed joints Tension in flexure parallel 54 psi to bed joints These allowable stresses are based upon a factor of safety equal to approximately 3.0 against ultimate stresses.

No overstress has been permitted for OBE load combinations.

For SSE loading combinations,.the resultant factor of safety is equal to approximately 2.0 against ultimate stresses.

Concrete expansion anchor baseplate assemblies in concrete masonry walls have been analyzed using rigid plate theory.

The Cincinnati Gas & Electric Company has previously demon-strated that the rigid plate analysis procedure provides results compatible with a flexible plate analysis at the ultimate loading conditions when the ef f ects of expansion anchor flexibility and baseplate flexibility are properly accounted for.

The Cincinnati Gas & Electric Company has reviewed the deficiencies identified in IE Bulletin 79-28 concerning the adequacy of concrete masonry walls to support attached items at the Trojan plant, and has determined that a similar situa-tion does not exist at Zimmer, Unit 1.

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d. Describe the results of testing of anchor bolts in concrete block walls and your plans an'd schedule for any further action.

Res ponse: Tests have been performed on the capacity =*

of concrete expansion anchors in concrete masonry walls on several plants currently under construction. These static tests have indicated that the ultimate capacity of e.pansion anchors in solid and grouted concrete masonry walls is more than 50% of their corresponding capacity in plain concrete. The Cincinnati Gas & Electric Company has committed to participate in a comprehensive static and dynamic test program to substantiate the behavior of expansion anchors in concrete masonry walls.

These tests will include:

,1) Static load tests on individual anchors.

2) Load relaxation tests on individual anchors.

3) Dynamic tests on individual anchors under the following conditions:

a) Pipe transient cyclic loads, b) OBE and SSE seismic loads.

The test program will encompass the f ollowing combination of variables:

1) Expansion anchor types .

a) Wedge type anchors 1793 224 13

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b) Self-drilling type-anchors

2) Anchor diameters . _ . . _ _ _ . . _ . .

a) 3/8" b) 1/2" c) 5/8" d) 3/4"

3) Embedment Depth 1/2 anchor diameters

4) Embedment material a) Masonry units - ASTM C145, Type N-I blocks t' Masonry mortar - ACTM C270, Type N The results of the static and dynamic test program for concrete expansion anchors in concrete masonry will be available and reported to the Nuclear Regulatory Commission upon completion. .

e

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6. Determine the extent that pipe supports with expansion anchor bolts used structural steel shapes instead of base plates. The systems and lines reviewed must be

~ 02, consistent with the criteria of IE Bulletin No. 79 Revision 1. If expansion anchor bolts were used as described above, verify that the anchor bolt and structural steel shapes in these supports were included in the actions performed for the Bulletin. If these supports cannot be verified to have been included in the Bulletin actions:

a. Provide a list of the systems involved, with the number of supports, type of anchor bolt, line size, and whether the supports are accessible during normal plant operation.

b. Provide a detailed evaluation of the adequacy of the anchor bolt design and installation. The evaluation should address the assumed distribution of loads on the anchor bolts. The e' valuation can be based on the results of previous anchor bolt testing and/or analysis which substantsates operability of the affected system,

c. Describe your plans and schedule for any further action necessary to assure the affected systems meet Technical Specific'ations operability require-ments in the event of an SSE.

Response: Concrete expansion anchors have been used to attach structural steel shapes to concrete walls to support safety related piping systems. Structural angles have been the predominant steel shape used.

These structural shapes have been used to' support rela-tively light loads, less than 1,000 pounds, and have been included in the expansion anchor field verification programs in accordance with the criteria set forth in IE Bulletin 79-02, Revision 1.

1793 226 15

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SHEAR TENSION INTERACTION FOR 5/ f' $ PHILLIPS SELF- DRILLING ANCHOR

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