ML20090G684
| ML20090G684 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 07/16/1984 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 8986N, NUDOCS 8407250165 | |
| Download: ML20090G684 (10) | |
Text
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/^N Commonwealth Edison e
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) One First National Plaza. Chicago. Illinoss
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O J Address Reply to: Post Office Box 767
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/ Chicago, Illinois 60690 July 16, 1984 Mr. Harold R. Denton, Director Of fice of Nuclear Reactor Reguls Lion 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. 50-454/455/456/457 Reference (a):
March 22, 1984 letter from B. J. Youngblood to D. L. Farrar
Dear Mr. Denton:
This is to provide additional information regarding the design of Category I masonry walls at Byron and Braidwood Stations.
NRC review of this information should eliminate the need for License Condition 2 listed in the Byron SER.
In reference (a) the NRC requested additional information regarding masonry wall design.
Enclosed with this letter are responses to FSAR Questions 130.58, 130.59 and 130.60.
These responses will be incorporated into the FSAR in the next amendment.
Please direct further questions regarding this matter to this of fice.
One (1) signed original and fifteen (15) copies of this letter and the enclosures are provided for NRC review.
Very truly you f'
- n T.R. Tramm Nuclear Licensing Administrator Enclosures hh 0
E 8986N ggj I lI
B/B-FSAR QUESTION 130.58
" Paragraph 2.2.2 of the December 3, 1983 latter from T. R. Tramm to Harold R. Denton discusses a parametric study to investigate the effect of column flexibility.
Provide sufficient-information which would allow the staff to confirm that similarity does exist between the safety-related walls at Byron /Braidwood plants and those tested in the study.
This information should include, but not be limited to, such items as the basic assumptions and methods used in design, properties of materials, material property testing procedures, method of construction, and QA/QC requirements."
RESPONSE
As mentioned in our earlier response sent with the letter dated December 3, 1983, the masonry walls at Byron /Braidwood stations are not supported at the top and are provided with a 1-inch gap at the top.
Steel columns have been used to provide lateral support for out-of-plane loads.
As such, the walls have been designed for horizontally spanning beam strip moments.
A parametric study was performed to estimate the magnitude of vertical moments tesulting from the flexibility of the steel columns.
The possible variations in design parameters, such as column size, number of steel columns used in a wall, wall thickness, and length of wall, were considered by using more generalized design items A* and 1* which are described below and were also explained in Appendix A of the response dated December 3, 1983.
A*
= Ratio of total wall mass to the total mass of steel columns for a given wall.
= P,wt/P A ss I*
= Ratio of total wall rigidity to the rigidity provided by steel columns.
= E,wt /E I ss H/s = Ratio of block wall column height to block wall l
column spacing.
where:
h'
= height of wall or block wall column i
Q130.58-1
B/B-FSAR i
w
= width of wall t
= thickness of wall s
= spacing of block wall columns E,
= masonry modulus of elasticity E,
= steel modulus of elasticity P,
= masonry mass density P,
= Steel mass density
.A,
= total area of steel columns I,
= total moment of inertia of steel columns For a given ratio of h/w and h/s, plate vertical and horizontal moment coefficients can be generated for various valves of A*
and I*.
Of 236 unreinforced masonry walls at Byron Station Unit 1, 114 have been reviewed for the variations in A* and column aspect ratio h/s.
Due to the geometry and construction of three walls, use of the A* and I* approach is not appropriate.
These walls have been analyzed using the finite element method which considers the effect of column flexibility.
All the remaining walls have not been provided with block wall columns and, thus, are not subject to the effects of column flexibility.
The masonry walls at Byron Unit 2 and Braidwood Units 1 and 2 have similar geometry, have been designed using the same criteria, and have been constructed in accordance with the same specification.
Therefore, this review is valid for unrein-forced masonry walls at both Byron and Braidwood Stations.
Table Q130.58-1 gives the approximate breakdown of 114 unrein-forced masonry walls with block wall columns in different groups of A* and I* for various types of column aspect ratios (h/s).
Since the last reponse of December 3, 1983, all the 114 masonry walls at Byron Station Unit 1 were studied to determine the effect of column flexibility on the design of masonry walls.
For a given wall, plate vertical moments are calculated using finite element analysis, and the effect of column flexibility Q130.58-2
B/B-FSAR is evaluated by determinii.j if the moments in the vertical directier. are less than the cracking moments.
If so, the masonry wall design, based on calculation of design moments using a horizontally spanning beam strip between steel columns, is valid.
Since the allowable stresses perpendicular to the bed joints are approximately one-half of the allowable stresses parallel to the bed joints, the permissible values of plate vertical moment are determined by considering plate vertical cracking moments equal to one-half of the plate horizontal cracking moments.
The horizontal cracking muaents for hollow walls are based on the modulus of rupture determined by testing for the Clinton Power Station.
The modulus of rupture for solid masonry wall is obtained by adjusting the modulus of rupture of hollow block wall with a factor equal to the ratio of the SEB allowable stress for solid masonry to the SEB allowable stress for-hollow masonry.
Review of the actual plate vertical moments for the masonry walls at Byron Station Unit 1 indicates that all the masonry walls have actual plate vertical moments less than the vertical cracking moments based on the elastic analysis.
The vertical moments which are developed due to flexibility of the block wall columns do not affect the structural integrity of the walls.
Hence, the design of unreinforced masonry walls at Byron Station Units 1 and 2 and Braidwood Station Units 1 and 2, based on horizontally spanning beam strip moments, is acceptable.
s e
4 Q130.58-3 t
B/B-FSAR TABLE Q130.58-1
SUMMARY
OF MASONRY WALLS WITH STEEL COLUMNS BASED ON DESIGN PARAMETERS FOR BYRON UNIT 1 APPROXIMATE NUMBER OF MASONRY WALLS WITH STEEL COLUMNS TYPE OF GROUP 1 GROUP 2 GROUP 3 GROUP 4 ALL ASPECT A*>75 A*=38-75 A*=25-37 A*<25 VALUES RATIO h/s I*>500 I*=100-500 I*=50-99 I*<50 OF A* & I*
1 52.0 47 19 10 12 88
> 2. 0 2
6 8
2 3
19 53.0 3
> 3. 0 3
4 7
1 All All 56 27 12 19 114 Types Values L
+
t Q130.58-4 l
t
B/B-FSAR QUESTION l30.59 I'
" Paragraph 2.6.D.2 references static monotonic tests per-formed by various research organizations which form the basis for the statement that the average factor of safety is 5.6 under the OBE condition and 3.35 under the SSE condition.
Provide sufficient information to justify both the relevancy and applicability of the tests to the Byron /Braidwood safety-related masonry walls.
This infor-i mation should contain such details as the basic assumptions and modeling methods, properties of the material, material property testing procedures, and details of construction."
RESPONSE
Allowable Tensile Stresses Parallel to the Bed Joints
~
The project allowab1e stress parallel to the bed joints is in accordance with National Concrete Masonry Association's (NCMA), " Specification for the Design and Construction of Load Bearing Concrete Masonry."
Review of the background information regarding allowable tensile stresses parallel to the bed joints indicates that the allowable values have been established by doubling the allowable stresses perpendicular to the bed joints which are based on mortar tensile bond strength.
The stresses parallel to the bed joints are more a function of masonry unit strength than mortar.
As such, it is conservative to use double the vertical span values.
Table Q130.59-1 gives the summary of test results used to arrive at the value of modulus of rupture for he;izontally spanning walls and, hence, the tensile stress parallel to the bed joint.
The safety factors in the table have been calculated by dividing the actual modulus of rupture values by the allow-able stress values, 32 psi for Type N and O mortar, and 46 psi for Type M mortar.
For 15 concrete masonry walls with joint reinforcement, as is the case for masonry walls at Byron /Braidwood Stations, the safety factors averaged 5.6 for normal and OBE load com-binations, and 5.6/1.67 = 3.35 for SSE load combinations.
In addition, the test results for 43 walls containing no joint reinforcement indicate an average factor of safety of 5.3 for normal and OBE load combinations, and 5.3/1.67 = 3.17 for SSE load combinations.
These values are comparable but slightly less than those for walls with joint reinforcement.
Q130.59-1
B/B-FSAR TABLE Q130.59-1 FLEXURAL STRENGTH HORIZONTAL SPAN, NONREINFORCED CONCRETE MASONRY WALLS MODULUS SAFETY OF RUPTURE FACTOR MORTAR LOADING NET AREA ACTUAL /
CONSTRUCTION TYPE TYPE psf (psi)
ALLOWABLE 8-inch Monowythe N
Uniform 127 102 4.13 Hollow, 3-Core N
Uniform 136 141 4.41 (Reference 1)
N Uniform 127 132 4.13 N
Uniform 169 176 5.50 N
Uniform 173 180 5.63 O
Uniform 123 128 4.00 0
Uniform 158 164 5.13 8-inch Monowythe N
Uniform 149 155 4.84 Hollow Joint N
Uniform 160 166 5.19 Reinforced 0 16 inch N
Uniform 193 201 6.28 center to' center O
Uniform 150 156 4.88 (Reference 1)
O Uniform 186 193 6.03 8-inch Monowythe N
Uniform 203 211 6.59 Hollow Joint N
Uniform 196 204 6.38 Reinforced 0 8 inch O
Uniform 202 210 6.56
. center to center O
Uniform 195 203 6.34 (Reference 1) 8-inch Monowythe N
1/4 pt 56 58 1.81 Hollow (Reference 2)
N 1/4 pt 38 39 1.22 N
1/4 pt 61 63 1.97 N
1/4 pt 60 62 1.94 N
1/4 pt 69 71 2.22 N
1/4 pt 93 96 3.00 l
8-inch Monowythe M
Center 199 217 4.72 Hollow, 2-Core M
Center 176 192 4.17 (Reference 3)
M Center 151 165 3.59 4-2-4 Cavity Wall, M
Center 111 210 4.57 Hollow Units M
Center 135 255 5.54 (Reference 3)
M Center 95 180 3.91 s
l-Q130.59-2 a
v B/B-FSAR TABLE Q130.59-1 (Cont'd)
I' MODULUS SAFETY OF RUPTURE FACTOR MORTAR LOADING NET AREA ACTUAL /
1 CONSTRUCTION TYPE TYPE psf (psi)
ALLOWABLE 8-inch Monowythe M
Center 159 173 3.76 Hollow 2-Core M
Center 159 173 3.76 Joint Reinforced M
Center 191 208 4.52 6 8" center to center (Reference 3) 4-2-4 Cavity of M
Center 159 300 6.52 Hollow Units Tied M
Center 159 300 6.52 with Joint M
Center 159 300 6.52 Reinforced @ 8" center to center (Reference 3) 4-inch Hollow N
Center 138 365 11.41 Monowythe N
Center 157 415 12.97 (Reference 4)
N Center 101 268 8.38 8-inch Hollow M
Center 268 202 4.39 Monowythe M
Center 314 237 5.15 (Reference 4)
M Center 314 237 5.15 8-inch Hollow N
Center 277 210 6.56 Monowythe N
Center 314 237 7.41 (Reference 4)
N Center 314 237 7.41 8-inch Hollow O
Center 259 195 6.09 Monowythe O
Center 277 210 6.56 (Reference 4)
O Center 277 210 6.56 8-inch Hollow M
Center 268 202 4.39 Monowythe M
Center 297 224 4.87 (Reference 4)
M Center 277 210 4.56 8-inch Hollow N
Center 277 210 6.56 Monowythe N
Center 259 195 6.09 (Reference 4)
N Center 297 224 7.00 8-inch Hollow 0
Center 360 271 8.45 Monowythe O
Center 297 224 7.00 (Reference 4)
O Center 268 202 6.31 Q130.59-3
. ~
- B/B-FSAR TABLE Q130.59-1 (Cont'd)
MODULUS SAFETY OF RUPTURE FACTOR MORTAR LOADING NET AREA ACTUAL /
CONSTRUCTION TYPE TYPE psf (psi)
ALLOWABLE 12-inch Hollow N'
Center 352 142 4.44 Monowythe N
Center 314 127 3.97 (Reference 4)
N Center 333 134 4.19 a)
Total number of tests without joint reinforcement = 43 Average safety factor (SF) = 5.3 b)
Total number of tests with joint reinforcement = 15 Average safety factor (SF) = 5.6
REFERENCES:
1.
Hedstrom, R.
O.,
Load Tests of Patterned Concrete Masonry Walls," Proceedings, American Concrete Institute, Vol.
57, p. 1265, 1961.
2.
Fishburn, Cyrus C.,
"Effect of Mortar Properties on Strength of Masonry Monograph 36," National Bureau of Standards, 1961.
3.
Cox, F. W.,
and Ennenga, J.
L., Transverse Strength of Concrete Block Walls, " Proceedings," ACI, Vol. 54,
- p. 951, 1958.
4.
Livingston, A.
R., Mangotich, E.,
and Dikkers, R.
" Flexural Strength of Hollow Unit Concrete Masonry Walls in the Horizontal Span," Technical Report No. 62, NCMA, 1958.
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e BRAIDWOOD-FSAR QUESTION 130.60
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" Provide the report on the survey of the structural cracks that:exi'st in the Braidwood Units 1 and 2 safety related walls with explanation of their origin and of their effects on the wall design strength and structural integrity."
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RESPONSE
The survey and_ evaluation of the structural cracks in the Braidwood Station masonry walls will\\be completed in April 1985.
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