ML20093K767

Forwards Response to NRC Request for Addl Info on Category 1 Masonry Wall Design,Based on 840701 Telcon.Seb Allowable Stresses Parallel to Bed Joints Permitted

ML20093K767
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	10/16/1984
From:	Danni Smith COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
9326N, NUDOCS 8410180155
Download: ML20093K767 (11)

Text

,.

7 ~\\ Commonwealth Edison C

[

~

): one First Natirn?! Plual Chictgo. Ilknois s

( C 7 Address R ply to: Post Offica Box 767

~

j/ Chicago. Illinois 60690 October 16, 1984 Mr. Harold'R..Denton, Director

' Office of-Nuclear Reactor. Regulation U'S.. Nuclear. Regulatory Commission Washington, DC 20555

~

Subject:

Byron-Generating Station Units 1 and 2 Braidwood Generating Station Units 1 and 2 Masonry Walls NRC Docket Nos. 50-454/455 and 50-456/457 References (a):

November'30, 1981 letter from B. J. Youngblood to-L. 0. DelGeorge (b):

December 5, 1983 letter from T. R. Tramm to H. R.-'Denton

Dear Mr. Denton:

Reference (a) provided NRC' guidance for demonstrating the adequacy of masonry walls at Byron and Braidwood Stations..

Re'ference (b)-provided a report-which addressed points of

-information agreed to in.a conference call on July 1, 1983 regarding the design of Category I masonry = walls.

During the masonry wall final load check for Byron, it was found, for:a. limited number of walls, that modifications to meet the actual maximum stresses statement given in the Reference (b)' report

.were not feasible due. to' the late stage of construction.

For these cases, SEB allowable stresses have been used.

The enclosed report

-is2a copy of the Reference (b). report revised to reflect this change. -Marginal markings on pages 4,.9 and 10 indicate where revisions have occurred.

Please address further questions regarding this matter to this office.

One signed original and fiteen copies of this letter and the: enclosure are provided-for NRC review.

Verytrullyypurs,lf A F

^8410 g 55 PDR 0

4 Davia

. Smith A

PDR _

Nuclear Licensing Administrator

\\

l Y

9326N g

,..~:

f,

.2

-RESPONSE TO NRC REQUEST FOR ADDITION $L INFORMATION

.t ON MASONRY WALL DESIGN BASED ON TELEPHONE CONVERSATION OF JULY 1,1983 4

1.0 Introduction

~

~This ~ report covers the following additional information

.which was. requested by= the NRC during the telephone conference call on. July 1,11983.

The report:

A.

.Provides. the. calculation and basis of analysis for the masonry walls-considering the following:

-- 1) out-of plane load 2) in-plane interstory drift load

'3) the-effects of masonry column flexibility.

B.

Provides a.

description of. the design basis for reinforced masonry wall design.

-C.

. Identifies any structural cracks that exist in Byron

-Unit 1 walls with an explanation of their effect on the wall design.

'D.-

Verifies that Byron /Braidwood Stations' safety related masonry walls were constructed in accordance

with the criteria set forth in 1CCFR50 Appendix B.

2.0

~ Desian - and - Analysis Procedure for Unreinforced Concrete v

1 Masonry Walls-The 'following describes. the design criteria used. on the

~ Byron /Braidwood project which ~is more stringent than the one earlier submitted to the NRC with a letter from D.

L.

-Peoples of Commonwealth Edison to Darrell G.

Eisenhut of

.NRC, : dated July : - 1980.

Commonwealth Edison Company has voluntarily used this criteria in reassessment of the

. nuclear safety related masonry walls.

'2.1

. Analysis' Procedure 2.1;lL Determination-of-Dynamic Lateral Loads Concrete' masonry-walls have been analyzed based on conventional elastic methods.. Dynamic lateral loads ~have been determined ' by an equivalent static method. using the expression:

WD "'9W "W 9 W, a

P where:-

W Dynamic lateral load

=

D l.

. n

-e i.

?,

W

='

Weigh't'of'conciete masonry wall W

Wj'=-

Uniform -'or concentrated' attachment load on the wall ~

gW-Wall; acceleration-.using appropriate damping

=

values per Section 2.1.5 g". = ^

Peak. acceleration-for attachment : loads using appropriate damping values per Section 2.1.5

.2.1.2-

. Wall Frequency Calculations

~

~ The fundamental ~ frequency. calculations have been based on the plate theory for walls both with and without embedded steel columns.

In. developing the expression

.for c,.

! frequency calculations for walls with embedded. steel columns,- the finite _ element technique has been used which takes;into account the-column flexibility, the wall edge

-conditions' and.the wall a'spect ratios.

Appendix A

describes brieflyj the method used for development of the frequency equation and the wall edge conditions studied.

Frequency. calculations have' been based on moment of inertia' of an uncracked.section because the applied moments are always less than the moment capacities of uncracked section.-

'~

2.1. 3 '-

Material Property Variation Considerations Variation-in material properties.

which affects the I-stiffness of. the concrete masonry wall is accounted. for conservatively by assuming L the following. variation in the modulus of. elasticity "E,":

~

L A.

Hollow Units:

1000 f' - 600 f' c

B.

Solid / Grouted Units:: 1200 f' - 800 f' m

m t.

L In design,.the above variation in "E " is reflected by

[

, assuming 3 corresponding variation fn frequency.

The L.-

, j following. requency range.has-been.used.

-l t

Solid / Grouted Units' O.9f - 1.lf

.c Hollow Units.'

O.8f - 1.0f L

f where:-

f

,=

frequency. determined per requirements of Section 2.1.2 based on E,= 1000 fg 3.-

~

Modulus of elasticity for concrete masonry E,

=:

f'

=

Masonry compressive strength equal to 1350 psi t'

l 2.1.4 Effect of Wall Opening on Frequency Calculations-Frequency values have been mod'ified with the following adjustment factors to account for the openings in the wall.

Opening Area in Percent of Adjustment Total Wall Surface Area Factor 0 - 10%

1.00 10 - 20%

0.95 20 - 35%

0.90 35 - 45%

0.85 The adjustment factors are based on the results of the finite element analysis of a wall panel in which various locations and sizes of the openings were studied.

Also included in the study was-the effect of different boundary conditions for the wall panel.

2.1.5 Determination of Wall Accelerations ~and Accelerations for Attachment Loads A.

Wall Accelerations-1.

Damping values used:

2% OBE 4% SSE 2.

The design "g"

value has been determined by reading the largest value within the frequency range specified in Section 2.1.3 from the response spectra curves for each floor elevation at the top and bottom of the wall elevations and using the average of the two maximum values.

3.

The design value of "g" determined above has been increased by a modal participation factor equal to 1.05 to account for participation of higher modes when wall frequency is less than 33 cps.

The value of the modal participation factor has been determined by finite element modal analysis of typical wall panels.

B.

Accelerations for Attachment. Loads 1.

Damping values of 2% for OBE and 4% for SSE load combinations have been used for attachment load.

[-

2.

The peak "g"

value at each ' floor elevation corresponding to top and bottom of the wall elevations has been used to determine the design "g"

value by taking the average of the two "g" values.

0 2.2-Desian Procedure'for Out-of-Plane Loads

)

2.2.1 Concrete-masonry walls have been designed based on working : stress principles..

The design moments have been obtained.considering.a

12. inch wide beam strip.

The walls have been assumed as. simply ~ supported or horizon-tally' cantilevered, as applicable, with due consideration

.to the1 boundary conditions.

l 2.2.2

' S tructural-steel columns have been used to provide lateral support for-the masonry walls for out-of-plane loads,- thereby creating horizontally spanning conditions.

As. s_uch,- the walls have been designed for horizontally.

spanning beam strip moments.

A value of 36 psi has been

. permitted as the maximum value for the masonry. stress parallel to the bed joint during re-evaluation of-wall design for the-as-built conditions.

However, for' a

-limited number 'of wall panels, where modifications are R

not feasible - due to the late stage of construction, SEB

- allowable - - stresses parallel to the bed joints, as given

-in Tables 1 and 2, have been permitted.

'A parametric - study has been done to investigate the

.effect of column flexibility using different spacing and sizes of steel columns for various wall thicknesses.

This. study shows that'a typical wall, which has a ratio

~

of.- wall height to column spacing equal. to 2.0, and which has -been designed based on the above-mentioned procedure, is subjected to secondary moments in the vertical direction smaller than the cracking moments.

The struc'tural : steel columns which have been provided to

_act ' as.. lateral. support -for the~' masonry ~ wall are not

~.

subject. to any axial, load as the top connections of the columns have been provided with vertical slotted-holes.

2.213 No overstress factor ha's b'een used in the design of masonry' walls for. load combinations containing OBE-seismic - -loads which lis in compliance with SEB Interim Criteria,~Re'v. 1, July 1981.

f 2.2.4-

. Horizontal. joint reinforcem b has not been considered for calculating the flexural strength of the wall.

attach $ent load has

'2.2.5

The

• local pull-out' ef fect due to an been considered in the design.

..s..

s e.

-2.2.6 Out-of plane drift effects due to relative. displacement of one floor-with respect-to the other:nare not imposed on the Jmasonry walls at Byron /Braidwood Stations for the following reasons:

A.

There is a 1"

gap between the top of the walls and the underside of the floors above.

I.

'i

k

,

a:.

-1.

.B.

.The - top. connections: of the.. masonry lateral support steel columns are pinned connections.

3 2.3-

'Desian Procedure for-In-plane Loads

~In-plane drift effects. have.been. evaluated for the masonry walls with the following conditions:

A.

As : mentioned -in. our earlier ' responses, masonry walls are not.part of' the primary vertical or lateral load -

. resisting.

system.

They are.

non-load

bearing,

' interior partition walls.

L'~

'.y B~

LIn-plane' -interstory drif t is an imposed displacement on a masonry wall, and the resultant in plane. load is, therefore,

-a function of the in plane shear 4-__

stiffness of the masonry wall.

.The Lin-plane _- stiffness. is unpredictable, therefore a

strain criteria, rather -than. stress criteria, is more reliable for evaluating. drif t effects.

In-plane shear strain under SSE load condition is limited to 10.001'~ in./in. This allowable strain corresponds to initi -

~

-ation of cracking in masonry, and not the failure of the wall. -Therefore, the criteria is conservative.

The ac'tual maximum shear. strain in safety related masonry

walls. at Byron /Braidwood under SSE conditions is

- 0.0004"/." which corresponds to the maximum strain in the 1 reinforced concrete shear walls.

This strain is signifi-cantly less than 0.001"/"'.

-2;4-Combined-Effect of Out-of-Plane and In-plane Loads The walls have been designed independently for in-plane and out-of-plane loads and. no combined effect has been considered.

However, the increace in stresses-due to simultaneous application of loads due to two horizontal accelerations. will be compensated because the actual stresses in each direction for the safety-related masonry walls at Byron /Braidwood Stations are low.

'. 4:

-Table-.lLindicates the maximum values of actual stresses as compared to the project allowable stresses and SEB allowable - stresses.-

See discussion of allowable stresses in Section 2.6.

(

2.5~

Loads and Load Combinations

=The.-

loads and load combinations used for-the

?

safety-related walls are.in agreement with the loads and I

load combinations of SEB Interim Criteria, Rev.

1.

As

' earlier mentioned in our

-responses, there are no safety-related concrete masonry walls at Byron /Braidwood

+<

4 r

.i.-

~.

Stations-which are subject. to-accident pipe reaction-(Y )'-

et-impingement-(Y ) or missile' impact (Y,).

r 3

f 2.6 Allowable Stretses A.

The - safety-related concrete. masonry walls-for. Byron /

L Braidwood ~ Stations have been designed using NCMA-1979 allowable stresses corresponding to the special insp'ection. category.

-Commonwealth Edison. Company's QA/QC procedures for the construction of safety related concrete masonry walls ensure compliance with

- the. inspection requirements of-the SEB

Interim, Criteria, Rev. 1, July 1981.

B.

Table 1,. attached, gives a comparison of the allow-able-stresses as used for the Byron /Braidwood i.

Stations vs. SEB allowable stresses, both for OBE and-

'SSE load combinations.

C.

The. allowable stresses used for the Byron /Braidwood Stations -are in ~. agreement with the Byron /Braidwood

.FSAR and SER.

i D.~ -SEB allowable stresses and project allowable stresses.

are compared as follows:.-

- 1.'

The. project.; allowable. tensile stress perpendi-cular to the bed joints due to -out-of plane loads-f is - lower under / OBE. load combinations and exceeds

.SEB" values by_19% to 25% under SSE load.

The above; increases in SEB1 allowable tensile

. stress perpendicular.to the bed joints under SSE load combinati'cns are not critical because all L

the safety -related walls at Byron /Braidwood span L

-horizontally..

L.

2. - The project allowable tensil'e stress parallel to

-the_ bed joints due to out-of plane loads exceeds ACI 531-79 value by-4% under.OBE load combina-tions-and 3%.to 16% under SSE. load combinations.

?

~,.

~ above increases'\\ n SEB-allowable tensile The i

p l stress parallel to the bed., jointst are not a

g concern. because. the maximumTactual. stress under.

OBE or SSE load combinations is only' 48% of SEB allowable value for. hollow blockwalls.and 32% for i

solid' blockwalls.

Moreover,;shbrizontal. joint reinforcement which has been zignored in the

. design :does contribute towards the flexural 3

L strength of' the wall.

Also, the project allowable stress has an average factor of safety l:

of

'5.6 against failure loads under OBE load combinations - and 3.35 (5.6/1.67) under the SSE m

L t

_._.,.,..._,..,..,,,__,___,__'i. -.... _.... _..

J.a x

, 7.. -

~

load. combinations..

The: failure - loads are based-on. static monotonic, tests performed in the past i by.various research organizations.

" ~

3.

The project. allowable: shear stress is-lower-under

~

f OBE ' : load. : combinations and exceeds SEB. value by

- 10% - under J SSE load combinations.

However, the 1 maximum-! actual shear stress due to ou t-plane loads or in-plane ' inertia loads on.any - masonry wall at : Byron /Braidwood-is only 30%

of SEB a l l o w a b l e 1 v a l u e -- u'n d e r OBE -load combinations and

-23%-under:SSE~ load' combinations.

I

-i'

'3.0

.Desian and Analysis Procedure for -Reinforced Masonry

- Walls; 13. l'~-

Like unreidforced ; masonry walls at-Byron /Braidwood

. Stations, l safety-related < reinforced masonry walls also

- havel been used E as 'non-load' bearing, interior partition

. walls.-

. These walls zhave been - separated from the floor

- above by. a gap i to avoid any transfer of _ vertical loads on

the walls.

These L walls have also not been considered as partxof shear. wall-' system for : Category I structures.-

In addition,- these~-. walls have been separated :from' the

=

building concrete or ' steel columns by a gap filled with compressible._ material-running. vertically the full height

' of the wall.

L3.2:

' Reinforced -masonry walls have. been analyzed using the

same procedure? ' as.

described ~

in Section 2.1 for unreinforced masonry walls; Like unreinforced masonry

~ walls, 'the. majority of o i-hese walls hasalso been designed

- spanning -horizontally utilizing masonry support - steel-

' columns as lateral; supports,: whenever - necessary.

Based

~

on : the analysis the. walls have been reinforced for -the

-actual forces f both vertically and horizontally.

As a minimum, these. walls have : been provided' with the minimum flexurallreinforcement-requirement.of ACI 531-79.

st'resses'_ per-ACI ' 531-79 have been used for

' AllowableD

. design ofireinforced masonry.

H Mis'cellaneous Design Infctmation 4.0-

- Af Vertical seismic ' acceleration is less than 1.0g for all of-the safety related L walls, thus causing no net.

tension onLthe walls.

' i:

B.-

Thel materials,.

testing, analysis,

design, E

construction-and_

inspection of safety related concrete ~ masonry walls for Byron /Braidwood. Stations xk

are indgeneral agreement with the Uniform Building

- Code-1979.

4

.')

e,.

e

--,r-9 nr

-s-es e &e---ee-e.

--#zoen..-+.

e+w-ev--

w-

<-.-.-*..w..e-m--..---e.

--er--

-w

---r w-*

5.0 Effect of Cracks on Design of Concrete Masonry Walls All safety-related masonry walls will be surveyed for the presence of structural cracks.

At Byron Station approxi-mately 15% of the walls have been surveyed and no signi-ficant cracks have been found.

It is anticipated that the entire survey will be complete by November 18, 1983.

6.0 Construction of Masonry Walls All safety-related masonry walls at Byron /Braidwood Stations are identified as such on design drawings and have been constructed to the requirements of a safety '

related specification.

The resulting wall construction meets the criteria set forth in 10CFR50, Appendix B.

t E

S

/

o O

9 9

~

f E

e D

e 0.

~

c,.

<., - i TABLE 1 Compa'rison of Actual-Maximum concrete Masonry Stresses Vs.'

j l

SEB and Byron /Braidwood Project Allowable Stresses s

Hollow Block Construction fm ".1,350 psi M

= 2,500 psi o

Normal and OBE Load Combinations SSE Load Combinations!

Lyron/

Byron /

Actual Braidwood SEB*

Actual Braidwood SEB*

Stress Maximum Project Allowable Maximum Project Allodable Stress Allowable Stress Stress Allowable Stress (psi)

Stress (psi)

(psi)

(psi)

Stress (psi)

(psi) d Tension Parallel to 8

Bed Joint 7

f 24 46 50 36 77 75 t

t

=-

r%

Tension Perpend.icular

~^

to Bed Joint f

12 23 25 12 38 32 t

~

12 34 40 12 57 52 Shear fy, 4r * <-

R-

• Used only where modifications were not feasible due to the late stage of construction.

m.. m

~

['**

. TABLE 2 c

Comp 5trison of Actual. Maximum Concrete Masonry Stresses vs.

SEB and Byron /Braidwood Project Allowable Stresses Solid Block Construction f' = 1,350 psi Mo = 2,500 psi Normal and OBE Load Combinations SSE Load Combinations B'ron/

Byron /

y

-Actual Braidwood SEB*

Actual Braidwood SEB*

Maximum Project Allowable Maximum Project Allowable Stress Stress Allowable Stress Stress Allowable Stress (psi)

Stress (psi)

(psi)

(psi)

Stress (psi)

(psi) b Tension Parallel to

?

Bed Joint 24 78 75 36 130 112 ft s

Tension Perpendicular to Bed Joint f 12 39 40 12 65 52 t

Shear f

12 34 40 12 57 52

~

y

• Used only where modifications were not feasible due to the late stage of construction.

g im

.. l