ML19326C289
| ML19326C289 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 03/09/1970 |
| From: | ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19326C286 | List: |
| References | |
| NUDOCS 8004220847 | |
| Download: ML19326C289 (7) | |
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C SUPPLEMENT NO. 16 Table of Contents and Change Directions Content and Directions Additional Information for the
- Pages 5-F-6, Anchorage Zone Reinforcing in 5-F-7, 5-F-8, the Buttresses (In Appendix 5F 5-F-9, 5-F-10 of the PSAR, add these pages.)
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8004220 fY7 3-5-70 Supplement No. 16
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l ADDITIONAL INFORMATION FOR THE ANCHORAGE ZONE REINFORCING IN THE BUTTRESS ANALYSIS A. General The following information should be considered in conjunctiona with the information previously supplied in Arkansas Nuclear One. Supplement No. 15 to the PSAR.
The design of the Anchorage Zone reinforcing steel was based on the most conservative data on bursting forces.
This data was obtained from the Group H paper by S.J.
Taylor (Ref. 1) who included many theoretical and experi-mental results in his paper.
B.
Analytical Approach Based on Taylor's Paper (Ref. 1).
force is distributed along the length of the tendon,.betw the face of the beam and a point that is approximately the depeth of the beam away from the face.
Using this assumption, the bursting was considered to be distributed from the face of the buttress to a distance from the face that is approximately equaal to the depth of the buttress.
The tensile stress distribution resulting from the bursting force may be approximated by triangles as shown on Fig. 1.
f Table 1, the work by Zielinski &Refering to Reference 1, Page 5567, Rowe indicates that the peak bursting stress for a [fes i f
is the average cob
( As shown in Fig. 1) is.30 f wheere
=.7 c8nsideration.
s ve stress in the section under c predicted bursting stresses compared to the other analyticalT and experimental results shown in Table 1 of Ref.
1.
ratio of.7 is based on 1/2 the width of the' bearing plateThe a /a 1
i relative to outside of the buttress for the radial direction.the distance For the vertical direction, half the distance between the tendons was j
used.
A value of.35f was arbitrarily used for the maximum e
bursting stress to reduce any concern about the conservatism of the reinforcing specified by design.
The following equations.
',were used to obtain the bursting force:
f
.35f =.35 I
= Max. bursting stress
=
4b y
p F = Applied prestress force R ss.35 Ib}
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- 4ab R = Bursting force Note:
This force calculation assumes that the center-line stress distribution is constant throughout the section.
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E h/O VIE W SECTION A -A FIG. I C.
Cracked Buttress Analysis To verify the adequacy of the anchorage zone, a cracked buttress was assumed, and a separate analysis was made assuming a wedge shaped failure mechanism such as have been observed in concrete cylinder tests by Taylor (Ref. 1).
Figures 2 and 3 show some postulated crack patterns on the outside face of the buttress.
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Figure 4 chows tha postulctsd crcck patterne incide the buttress based on Figure 3.
As the force F is applied on the central wedge, it will have the tendency to create forces perpendicular to the applied force.
es The forces may be considered as the bursting forces.
The reinforcing steel confines all the outer blocks.
Section A, as shown below, provides one view of the simple system formed by the postulated cracks.
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R = Bursting force F/4 = Applied prestress force on quarter section f = p N = is the frictional force N = normal force exerted by the wedge p = coefficient of friction B = Included angle of the postulated failure plane For Equilibrium of the System:
fF
=0 x
.25F = N sin G + f cos G
. 25F = N (sin G +/.t cos G) f,F
=0 Equation 1 y
R = N cos G - f sin G R = N(cos G p sin G )
Equation 2 Solving for N in Equ. 1 and substituting into Equ. 2 i
R=.25F cos G -A sin G )
(sin G +p cos G )
Equation 3 l
The same solution will result if a similar solution is per-
- I formed for Fig.
2.
4 2
Equation 3 shows that the bursting force (R) is a function of the coefficient of friction (p ), the inclined angle (G) of the postulated failure and the applied grestress force.
The expected values of /1 =.75 and 6 = 45 will re-sult in a calculsted bursting force of.0358F (55 Kips).
It is expected that the ac.tual value would be less than 55 Kips, since the friction and shear on the plane is likely to be larger than.75 for the rough failure sur-faces observed in the tests mentioned.
As a very con o
servative limit, however, values of p =.50 and 6 = 30 were assumed.
This yields a bursting force of.165F (252 Kips).
The upper limit value of 252 Kips is very close to that calculated for 175F in the previous section where the formula was R M.25 (h) (4ab).
D.
Results and Conclusions The previous solution is assumed to be applicable to both the radial and the vertical directions.
In the real buttress, the amount oi vertical reinforcement is questionable, since the buttress is continuous and the assumed bursting forces are really not applicable.
However, to assure substantial conservatisq additional vertical reinforcement relative to Supplement 13 was I
provided.
,The stresses in the reinforcing steel due to the thermal gradient and the bursting forces for three locations are listed in Table 1.
The stresses in the vertical rebars from temperature effects are calculated by using an analy-sis similar to the ACl-505-54 (Specification for the De-i sign and Construction of Reinforced Concrete Chimneys).
The following table assumes that the prestress force and f
1 pressure force cancel each other.
TA8! E I
STECSS REINE DESIGN 1 DES /SN 2
.STA ESS DUE TO l.0C*
TYPE STEEL Bug $7/WS SURSTING IN THEAtMA/
BUTTRES DIRECTION STEESS STRESS gg,9,gy7 VE/ET
- 22,500 20,200 5,000 TOP Of ggg,7.
,g,ggg 84SE MAT 2AO/A!
24,600 23,060 TY'e VEET 22,500 20,200
/6,.300 j
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SUTTRESS HOE /Z.
/9, 70 0
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CONWALL g,dO/4!
24,600 29,000 BOTTOM VERT
- 22,500 20,200 l 2/,500 Of 2/MG HO2/Z.
/7,000 61%DE2
- ggpigz, g4,gno g3,000 3-5-70 5-F-9
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- iirst hcrizontal tendon stcrts at EL 341'-6" (6' - 6" above the mat).
C.
Last horizontal tendon ends at EL 511'-6" (3'-6" below ring girder).
Design 1 - Design based on data from paper by Taylor Design 2 - Design based on the wedge shaped failure mechanism of the I
buttress.
From Section B, considering the radial distance (a) as measured from the tendon centerline toward the center of the reactor building the ratio of a jg vill decreasc.
However, using the expression developed 1
by Leonhardt R =.3 F (1 - al/a)he use of the pr/ay* O an extreme uppe r and letting al limit of R =.3F will result.
T evious 1cgic is really not valid for a buttress, but this approach will only lead to calculated burstics strescca in the radial rebar under worst conditions of approxi-mately2/3 yield.
It may be concluded that the design of the reinforcing steel in the buttresses is sufficient to withstand the major predicted loads from the temperature cradient and the bursting forces, under both operating and cecident conditions.
E.
Test In order to investigate the behavior and verify the adequacy of the original and present anchorage zone reinforcing in the buttress, theThe applicant will participate in a full scale buttress test program.
specific objectives of this test program will be:
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To provide experimental evidence of the structural adequacy cf the reinforced buttresses for concrete containments which utill:e large force capacity prestressing tendons.
2.
To verify the capability of the buttress to withstand, during prestressing, an imbalance of end anchor loads.
3 To achieve a limited railure of a portion of the structure when the f 6
the vslue for dc. as defined by AcI 318-3 is larger than ich the buttress is designed.
l The test structure will be constructed to include the physical features of Arkansas Nuclear One, as well as alternate buttress designs to demon-strate the validity and margin in the design.
The test structure will simulate, within practical limits, the buttresses used on the actual l
, containment structure except where deviations r.re required to obtain l
The l
representative stress levels er to incorporate more conservatism.
test structure will have a concrete strength at the lover end of the
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l attengti. range, which is typical for actual containment structures, a
and the reinforcing steci vill be ASTM-615-68 dR60.
The tendons and end anchors will be supplied with a force capabil,ity equal to or greater than those supplied for the Arkansas Nuclear One containment. Of the
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twenty tendons supplied, sixteen will have an ultimate strength of approxicately 2.2 million pcunds and the other four will be used to apply a load of approximately 2.4 million pounds from each of the eight end anchors to the test structure.
Heat will be supplied to the test structure fro a fluid flowing through pipes placed on each side of the longitudinal axis of the test structure.
The outside faces of the test structure will be cooled. This combined technique will be used to simulate the temperature gradients for-winter operational and design accident conditions.
The details of the test procedure are presently under preparation by the Bechtel Corporation and it will be reviewed by their consultants.
The test procedure sequence of applying heat and stressing loads on the test structure will be similar to that for stressing an actual non-tainment structure during the winter and will also simulate the -tress loading of the containment structure during an accident condition.
At approximately three-month intervals after the initial short-term test, the test structure will be reheated to simulate the winter oper-ating gradient at which time additional readings will be taken.
Tt is anticipated that some test results will be available d'tring April 1970.
The buttress reinforcement will re=ain as shown in Supplement No.15 until justification is provided for reduced reinforcement.
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References 1.
Anchorage Bearing Stress, Group H. Paper 49 S. Taylor, Pages _ 563-576.
f 2[ Prestressed Concrete Design and Construction, F. leonhardt, Page 271.
1 5-F-11 3-5-70 Supplcment No. 16