ML20010E528
| ML20010E528 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 08/10/1981 |
| From: | Baughman P, Chin S, Duffy W EARTHQUAKE ENGINEERING SYSTEMS, INC., YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20010E526 | List: |
| References | |
| BM-Y-VY-800161, BM-Y-VY-800161-R, BM-Y-VY-800161-R00, IEB-79-02, IEB-79-14, IEB-79-2, NUDOCS 8109040223 | |
| Download: ML20010E528 (22) | |
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- - :s t 10, l '. w l Rev. 0 FACTCR OF SAFliTY S TUDY FOR VERMONT YANKEE NUCl. EAR POWER STATION BASEPl. ATE FLEXIBII,ITY i
Prepared For Yankee Atonic lilectric Company 25 Research Drive Westborough, MA 01581 Prepared by Earthquake Engineering Systens, Inc.
600 Atlantic Avenue Boston, ifassachusetts 02210 Prepared By:
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PDR ADOCK 05000271 600 AtIavitic \\vence O
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e TABLE OF CONTENTS Page Introduction---------------
1 Baseplate Selection Process------------------ ____________..--2 TensionIsadin----------------------------------------------3 Moment Load!.ng-------------------------------
4 Calculation of Group Action------------------------~
5 Results------------------------------------------------------6 Conclusion---------------------------------------------------9 Reference.s--------------------------------------------------10 APPENDIX Table 1 Safety Factors (Tension Only)----------------------13 Table 2 Safety Factors (Moment Only)---
16 Table 3 Tension Load Magnification Factors--------------- -17 Table 4 Moment Load Magnification Factors------------------19
TN TROD'JCTION This report, prepared by Earthquake Engineering Systems, Inc., for Yankee Atomic E:tectric Company, summarized a study of the pipe support baseplates at the Vermont Yankee Nuclear Power Station.
Based upon reviews of several nuclear facilities, criteria have been developed by the Nuclear Regulatory Commission (NRC) that define the limits of pipe support operability (1)*.
Although anchor bolt safety factors of four or five are intended to be the final design and installation objectives, lesser margins may be acceptr.ble on an interim baser.
The purpose of this study was to determine whether baseplates which hao Deen designed for a safet', factor of four using rigid plate assumptions will still have at least a s.afety factor of two when baseplate flexibility is considered.
In addition, bolt load multipliers were determined for possibic use in evaluating flexi-bility effects under calculated piping reaction loads.
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- Numbers in parentheses indicate references at the end of the report.
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EASEPLATE SELECTION PROCESS e
Every as-built pipe support package was inspected, and c copy of each baseplate sketch obtained.
Dimensions and other pertinent information were checked to assure that each sketch was complete.
Once all the sketches were obtained, the baseplates were organ-ized by sorting them into groups having cor.inon characteristics, with an additional group of nonstandard bsseplates.
Nonstandard baseplates are those which cannot be analyzed using the EPLATE computer program.
All baseplates were accounted for by compliation of a master list which indicated the corresponding group for each baseplate.
In selecting a particular baseplate to be investigated, an attempt was made to find a plate which would behave in such a manner as to be an upper bound for a large number of plates.
Assessment of plates was based upon visual inspection making note of the number of bolts, bolt spacing, attachment location and type, as well as the plate flexibility.
In all, 34 plates were analyzed.
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l TENSION LOADING e
An analysis was performed on each baseplate selected to determine the effect of a direct tension load.
This load was calculated as the.aximum tension in the attachn.cnt, using rigid plate f
assump*. ions, which does not exceed the allowable pullout force in any of the anchor bolts.
With a non-eccentric attachment, all the j
anchor holts are at the maximum; however, in other cases the bolt force varies.
.Once the tension load was calculated, it was applied to a finite-
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element computer model of the baseplate (6).
Because a baseplate is flexible rather than rigid, as was assumed when determining'the i
applied tension load, there is a difference in the force distri-4 bution to the anchor bolts.
l At first, the tension load applied to a baseplate was based upon the allowable values of pullout specified for HILTI " Kwik-Bolt" stud anchors with the minimum embedment(2).
After some preliminary work, however, it was decided that the allowables would be based 4
upon PHILLIPS " Red Head" concrete anchors (3), as this was the i'
basis of the original design.
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MOMENT LOADING Several baseplates were investigated to assess the impact of flexibility upon the load distribution to the anchor bolts under a moment loading.
Baseplate flexibility can be a greater factor in the anchor bolt load distribution for moment-resistant baseplates, as opposed to baseplates which are loaded in tension only.
This magnifies the difference between the assumed linear (rigid plate) and the actual non-linear (flexible plate) action.
In a manner similar to the method used in evaluation of the tension load cases, the external moment calculated was applied to a finite element computer model of the baseplate (6).
The externally applied moment was found by determining the maximum moment by rigid plate theory causing all anchor bolt loads to be equal to, or less than the allowable pullout 16ad.
Normally the bolt forces varied throughout the plate according to the distance from the attachment.
Allowable anchor bolt pullout was based upon available information from the Phillips Drill Company for " Red Head" concrete anchors (3).
Spacing reductions are from the same source.
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' CALCULATION OF GROUP ACTION Anchor bolt pullout capacities for HILTI " Kwik-Bolt" stud anchors under various spacing arrangements were calculated in two different ways.
The first approach was to assume that the anchor bolts all had a minimum embedment depth per reference 7 and reduce the anchor pullout capacity on a straight-line basis for bolt to bolt spacing less than the minimum required for full ancher efficiency.
When any anchor bolt is located so as to be within the minimum spacing distance of more than one contiguous anchor, each anchor had its allowabic pullout ~ reduced proportionately.
A group action procedure (4) was employed when the linear reduction method proved to be unsatisfactory.
Capacity was calculated from the concrete tensile strength of the projected net area of the stress cones radiating anchor embedment to the concrete surface.
Estimation of the projected areas was accomplished with either an approximate (equivalent squares) er an exact method as appropriate.
RESULTS The factor of safety for a base plate was calculated by dividing the ultimate bolt capacity by the bolt force from the computer analysis.
The ultimate capacity is based on the anchors now in place while the computer force derives from the allowables for the original installation and rigid plate assumptions.
The results are tabulated in Tables 1 to 4.
On the first calculation, 22 plates were analyzed.
The input attachment tension load was based on the ililti allowable.
The ultimate capacity is also the Hilti value.
Thus, the safety factor computed reflects the decrease from 4.0 due to plate flexibility and preload.
These results are tabulated in Table 1, Column A.
As can ta seen, 6 plates had a safety factor less than 2.0 indi-cating that the bolt forces were amplified more than twice over rigid plate assumptions.
The safety factors were then recalculated using the original Phillips bolts as the basis for the input attachment load.
The allowables were also reduced for spacing according to Reference 3.
Likewise, the Hilti ultimate capacities were reduced for spacing in accordance with Reference 2.
These results are tabulated in Column B of Table 1.
Because the original plate sorting was not f
done with bolt spacing in mind, another sort had to be made and 12 additional plates were selected for analysis.
Of the 34 plates, 21 had a safety factor less than 2.0.
For the 21 plates with safety factors less than 2.0, the ultimate Hilti capacity was
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' recalculated based on group action in accordance with Reference 4.
These results are shown in Column C of Table 1.
Of the 21 plates, 8 had safety factors less than 2.0.
For the 8 plates in Colman C still having safety factors less than 2.0, the group action calculation was repeated using the actual bolt embedments recorded during installation.
The safety factois are tabulated in Column D of Table 1.
Of the 8, two have safety factors less than 2.0.
Reference 4 gave an indication that in certain cases, the pull-out cone angle might be taken as greater than 90, citing a TVA paper, Reference 5.
For the final 2 plates, the cone angle required for a safety factor of 2.0 was calculated.
The angles are shown in Column E of Table 1.
They are based on minimum embedment.
Unfortunately, a review of Reference 5 shows it to be of no value in opening up the cone angle for the embedments being considered.
Six of the 34 tension cases were selected for moment load con-sideration.
The results are shown in Table 2.
The last two digits of the file name designation correspond to the file designation for the tension only case.
Thus, plate FSS 102 in Table 2 is the same as FSS 2 in Table 1.
Safety factors tabu-lated in Columns F, G, H and J were calculated using the same assumptions as Table 1,
Columns B, C, D and E, respectively.
Of the six, two have safety factors under 2.0.
f As part of this study, flexibility magnification factors were calculated for potential use during later reanalysis.
For the I
34 tension cases and six moment cases, the load output from the finite element analysis was divided by the rigid plate toad.
These loads are listed in Tables 3 and 4.
Since these plate were picked to envelope groups of the standard plates, it is possible that~these factors can be conservatively used to hand calculate i
bolt loads from known pipe support reactions.
However, since the baseplate analysis is non-linear, the effect of the applied-load magnitude on the magnification factors needs to be investi-gated to assure nservatism.
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' CONCLUSION Of the 777 baseplates on safety related supports, 478 met the
" standard" criteria and were covered by this study.
Of the non-standard plates, many can probably be enveloped by the cases con-sidered herein.
However, a review of these plates showed that a detailed grouping effort is required to verify this opinion and some additional cases will probabl.y need to be analyzed.
These analyses will be more time constaing since the EPLATE computer program cannot be used.
In summary, for the 478 standard baseplates, and quite probably many of the 299 non-standard plates, the effects of flexibility and preload will not reduce the factor of safety against bolt pull-out to lower than 2.0, assuming that the plates were properly designed originally using rigid plate assumptions with a safety factor of at least 4.0.
It is our understanding that the two exceptions, FSS 14 and FSS 19, have been upgraded during the last plant refueling outage.
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LIST OF REFERENCES 1.
U.S. Nuclear Regulatory Commission, I.E.' Bulletin No. 79-02, Revision No. 1 (Supplement No. 1), " Pipe Support Base Plate Designs using Concrete Expansion Anchor Bolts", August 20, 1979.
2.
HILTI FASTENING SYSTEMS, Bulletin TR 111 " Summary Report -
Kwik-Bolt Testing Program", January 1974.
3.
ITT-PHILLIPS DRILL DIVISION, Catalog F-500 " Concrete Anchoring Handbook and Specifiers Guide", 1973 Edition.
4.
AMERICAN CONCRETE INSTITUTE, ACI Journal - August 1978, Pages 329 to 347, " Proposed Addition to:
Code Requirements for Nuclear Safety Related Structures (ACI 349-76)".
5.
TENNESSEE VALLEY AUTHORITY - CIVIL ENGINEERING BRANCH,
" Anchorage to Concrete" Research and Development Report No.
CEB 75-32, December 1976.
6.
EARTHQUAKE ENGINEERING SYSTEMS, INC., "EPLATE - A Nonlinear Finite Element Program for Analysis of Baseplates" Version 3.0, January 1980, Revised June 1980.
7.
Mercury Company's Concrete Expansion Anchor Removal and Replacement Installation Procedure, Revision 4, September 25, 1979.
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- APPENDIX i
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'CUIDE TO TABLE 1 (TENSION LOAD)
Values tabulated in columns A, B, C and D are safety factors which have been calculated on the basis of the assumptions stated below.
Columa A The tension load input tc the finite element program was based upon allowable values (2) of pullout for HILTI " Kwik-Bolt" stud anchors at' minimum embedment, with no reduction for close spacing.
Ultimate anchor pullout, for the safety factor calculation, was not reduced for closely spaced anchors.
The anchors were assumed to be at minimum embedment.
Column B PHILLIPS " Red Head" concrete anchor allowable pullout loads were the governing values in the computation of the tension load.
Reduction of the allowable pullout for close spacing was on a linear basis and followed the recommendations in the PHILLIPS catalog (3).
Ultimate anchor pu11out(2) was reduced on a straight-line basis for close spacing.
Minimum embedment depth was assumed.
Column C Required only if Column B is less than 2.0.
Input to the finite element model was the same as for column B (PHILLIPS allowable loads).
Ultimate anchor pullout was calculated by estimation of the concrete strength (4) for anchors with minimum embedment depth.
Column D Required only if Column C is less than 2.0.
The tension load is the same as in column C.
Calculation of ultimate anchor capacity considered the strength of concrete for actual depth anchor embedments.
Column E Required only if Column D is less than 2.0.
Internal failure cone angle (DEG) required to give safety factor of 2.0 based on concrete strength at minimum embedment.
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TABLE 1 (TENSION ONLY)
Case No.
Support No.
A B
C D
E FSS 1 4 1A HPCI-H63 3.09 3.38 NA NA NA FSS 2 HPCI-H82 7.70 2.10 NA NA NA FSS 3 CST-H40A 3.83 2.51 NA NA NA FSS 4 RHR-H173 2.65 3.32 NA NA NA FSS 5 4 5A CS-H46 2.52 2.32 NA NA NA FSS 6 RHR-HD200B 2.99 3.88 NA NA NA FSS 7 HPCI-H82 3.30 3.21 NA NA NA FSS 8 HPCI-HD254 3.17 3.91 NA NA NA FSS 9 RHR-H162 2.02 1.76 1.64 3.15 NA FSS 10 RCW-HD127 1.84 2.06 NA NA NA FSS 11 CS-HD67C 2.20 1.37 2.62 NA NA FSS 12 RnR-H195 2.26 1.32 2.30 NA NA FSS 13 ACSP-H27 1.58 1.96 2.05 NA NA FSS 14 RSW-H201 1.04 1.35 1.14 1.34 1090 FSS 15 RCW-H107 1.24 1.07 1.67 1.99 960 FSS 16 RSW-HD225B 2.30 3.45 NA NA NA FSS 17 RHR-H185 3.33 2.54 NA Nt FSS 18 RSW-H807 1.97 1.20 1.97 3.39 NA i
l FSS 19 CST-H15 3.04 0.30 2.00 NA NA FSS 20 HPCI-HD28 2.20 2.72 NA NA NA FSS 21 RHR-H129 2.51 3.22 NA NA NA FSS 22 RCW-H100 1.95 0.51 2.22 NA NA l a-
TABLE 1 (1 NSION ONLY) continued Case No.
Support No.
A B
C D
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USS 23 CST-H21 NA 1.69 3.19 NA NA FSS 24 CS-H64 NA 1.90 3.33 NA NA FSS 25 CS-H53 NA 2.22 NA NA NA FSS 27 RSW-t'181 NA 0.81 2.20 NA NA FSS 28 CUW-H31 NA 1.79 2.62 6A FSS 29 CST-HD25 NA 2.01 NA NA FSS 31 CST-H67 NA 2.16 NA NA FSS 32 CUW-H31 NA 1.73 3.41 NA FSS 33 HPCI-HD81C NA 0.76 1.95 3.11 NA FSS 34 RCW-HP115C NA 1.12 2.79 NA NA FSS 35 RCW-H153 NA 1.39 2.01 NA FSS 37 RHR-H197 NA 2.07 NA NA
- much less than 2.0 by inspection Note:
Cases 26, 30 and 36 are omitted as they are non-standard plates.
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'dUIDE TO THE USE OF TABLE 2 (MOMENT)
Values tabulated in columns F, G S H are safety factors calcu-lated from the output data of the finite element computer model.
Input for this program was calniated under the assumption that PHILLIPS " Red Head" concrete anchor (3) al'owable pullout values controlled the value of the moment loading.
Ultimate anchor pullout was calculated on the basis of the assumptions stated below.
Column F Ultimate anchor pu11out(2) was reduced on a straight-line basis for close spacing.
Minimum embedment depth was assumed.
Column G Concrete strength (group action) determined ultimate pullout.
Minimum embedment depth was assumed.
Column H Actual embedment depth is used.
Otherwise the assumptions are the same as in Column G.
Column J Internal failure cone angle (DEG) required to give safety factor of 2.0 based on concrete strength at minimum embedment.
TABLE 2 (MOMENT)
File Name Support No.
F G
H J
FSS 102 HPCI-H82 1.89 2.08 NA NA FSS 106 RHR-HD200B 2.66 NA NA NA I
FSS 109 RHR-H162 1.43 1.72 3.32 NA FSS 114 RSW-H201 0.08 0.68 0.76 1240 FSS 119 CST-H15 0.23 1.70 1.27*
970 FSS 127 RSW-H181 0.79 2.20 NA NA
- This is less than Column G because actual embedment is less than the minimum per Reference 7.
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TABLE 3
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TENSIC1 LOAD MAGNIFICATION FACTORS CASE NO.
RIGID PL LOAD FLEXIBLE PL LOAD FLEX / RIGID FSS 1 6 1A 4.05 KIPS 6.243 KIPS 1.54 FSS 2 1.955 KIPS 3.59 KIPS 1.84 FSS 3 1.352 KIPS 2.14 KIPS 1.58 FSS 4 1.015 KIPS 1.955 KIPS 1.93 FSS 5 6 5A 4.406 KIPS 7.99 KIPS 1.81 FSS 6 2.125 KIPS 3.63 KIPS 1.71 FSS 7 2.125 KIPS 3.515 KIPS 1.65 FSS 8 2.125 KIPS 3.603 KIPS 1.70 FSS 9 2.125 KIPS 4.822 KIPS 2.27 FSS 10 2.125 KIPS 5.03 KIPS 2.37 FSS 11 3.74 KIPS 8.25 KIPS 2.21 FSS 12 4.46 KIPS 8.826 KIPS 1.98 FSS 13 3.708 KIPS 10.49 KIPS 2.83 FSS 14 2.125 KIPS 8.36 KIPS 3.93 FSS 15 4.072 KIPS 13.955 KIPS 3.43 FSS 16 4.46 KIPS 8.643 KIPS 1.94 FSS 17 4.46 KIPS 7.03 KIPS 1.58 FSS 18 2.125 KIPS 5.08 KIPS 2.39 FSS 19 3.36 KIPS 5.77 KIPS 1.72 FSS 20 1.42 KIPS 3.215 KIPS 2.26 l
FSS 21 4.46 KIPS 7.97 KIPS 1.79 FSS 22 4.46 KIPS 10.54 KIPS 2.36 FSS 23 3.7? KIPS 6.715 KIPS 1.80 FSS 24 3.88 KIPS 6.77 KIPS 1.74 l
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't TABLE 3 (continued)
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c, TENSION LOAD MAGNIFICATION FACTORS CASE NO.
RIGID PL LOAD FLEXIBLE PL LOAD FLEX / RIGID FSS 25 4.017 KIPS 6.464 KIPS 1.61 FSS 26 NA NA NA FSS 27 1.806 KIPS 3.42 KIPS 1.89 FSS 28 1.881 KIPS 3.44 KIPS 1.83 FSS 29 3.59 KIPS 5.644 KIPS 1.57 FSS 30 NA NA NA FSS 31 3.69 KIPS 6.80 KIPS 1.84 FSS 32 1.72 KIPS 3.391 KIPS 1.97 FSS 33 1.998 KIPS 3.388 KIPS 1.70 FSS 34 3.57 KIPS 6.671 KIPS 1.87 FSS 35 3.708 KIPS 8.851 KIPS 2.39 FSS 36 NA NA NA FSS 37 3.626 KIPS 6.921 KIPS 1.91 l
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TABLE 4 MOMENT LOAD MAGNIFICATION FACTORS CASE NO.
RIGID PL LOAD FLEXIBLE PL LOAD FLEX / RIGID FSS 102 1.955 KIPS 3.985 KIPS 2.04 FSS 106
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2.125 KIPS 5.292 KIPS 2.49 FSS 109 2.125 KIPS 5.923 KIPS 2.79 FSS 114 2.125 KIPS 14.06 KIPS 6.62 FSS 119 3.36 KIPS 7.509 KIPS 2.23 FSS 127 1.806 KIPS 3.492 KIPS 1.93 r
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.s NOTE:
It should be noted that piping overstress will not he considered a problem because of the conservative ARS we are using for the analysis, Pipe supports though, will be modified if necessary, to account for higher support reactions.
The design criteria for pipe supports is presently not available. The basic code used in this evaluation will be AISC with no increase for SSE condition.
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