ML19257A379
| ML19257A379 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 11/24/1979 |
| From: | WISS, JANNEY, ELSTNER & ASSOCIATES, INC. |
| To: | |
| Shared Package | |
| ML19257A371 | List: |
| References | |
| WJE-79731, NUDOCS 8001030893 | |
| Download: ML19257A379 (29) | |
Text
APPENDI K 5 EVALUATION OF TESTS OF TENSILE BOND STRENGTH W
or i
CONCRETE BLOCR TO FILL J
IN THE TROJAN NUCLEAR POWER PLANT p,
NEAR PORTLAND, OREGON E
WJE No. 79731
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WISS, JANNEY, ELSTNER AND ASSOCIATES, INC.
330 Pfingsten Road Northbrook, Illinois 60062 312/272-7400 jg}.7 102 November 24, 1979 8001030 P93
EVALUATION OF TESTS OF TENSILE BOND STRENGTH 0F CONCRETE BLOCK TO FILL W
1N THE i
s TROJAN NUCLEAR POWER PLANT s.
NEAR PORTLAND, OREGON y
a WJE No. 79731 n
e Y.
E November 24, 1979 i
s t
n INTRODUCTION e
I At the request of Mr. Don Broehl of the Portland General Electric a
n d
Company, an evaluation was =ade of the results of 15 tests on the com-A posite block and concrete fill walls in the Trojan Nuclear Power Plant.
s s
These tests, conducted by Northwest Testing Laboratories, were intended ij to provide a measure of the tensile bond strength between the block and e
3-fill.
I r[
Following the notice on November 19, 1979 to proceed, an inspection of the locations where the tests were performed was made on November 20, 1979 by Dr. John M. Hanson of Wiss, Janney, Elstner and Associates, Inc.
in the company of Mr. Frank Rogan of PGE. A copy of a letter from Northwest Testing Laboratories, dated November 19, 1979, summarizing the test results was received at this time, along with a copy of the test data and a set of photographs showing the locations of the tests and the pieces removed from the walls. 1927 103
At a subsequent meeting on November 20, 1979 with Mr. Don Brochi and others at the PGE office in Portland, background information relating to the tests was reviewed. We were instructed that this evcluation was to provide a review and interpretation of the test data, and was to be 97 k
limited to consideration of the tensile bond strength between the concrete s,
J block and central concrete fill of the composite walls in the Trojan a
Plant.
n e
Y.
E BACKGROUND 1
5 t
n Walls in the Auxiliary Building at the Trojan Plant may be sub-e jected to normal loads due to the reactions of piping or to seismic inertia aj forces. The walls which are considered in this evaluation consist of two A
wythes of concrete block joined by a concrete fill, as illustrated in s
S 0
Fig. 1.
t k
The concrete block in the walls are reported to typically be t
similar to corner block with two interior cells, except that the shell f
at one end is open. These block were manufactured under quality controls c
limiting the linear shrinkage to 0.05 percent and the density to between 130 and 135 lbs per cu ft.
The specified compressive strength of the concrete block was apparently 2000 psi. Cells within the block were filled with grout having a specified minimum compressive strength of 2000 psi.
The concrete fill between the two wythes of block varied in thickness.
Its specified compressive strength was 3000 psi.
No. 3 reinforcing bars serving as tension ties were required at 4-ft centers each way between the block wythes..
- N o. 3 TIES a
- c...
AT 4'
S P AC.l N G EACH WAY
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CELLS g
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3 5a N6" VARIES
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BLoCKI FILL l BLOCK Fig. 1 - Section through' walls 1927 105
Tests were conducted at nine selected locations on Levels 5 and 25 in the Auxiliary Building. The testing was carried out, as, illustrated in Fig. 2(a), by using a hollow-core drill with a diameter of approximately 12 in. to make a cylindrical cut on a horizontal W
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axis into the walls. This cut was made up to 1 in, deeper than the S.
junction between the block and the concrete fill. A horizontal pull-y a
out force, P, was subsequently applied using an hydraulic jack to the n
n e
y.
exposed surface of the core. In most of the tests, this force was E
applied by means of a 1-in. dia. expansion anchor set along the axis
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of the core. However, in three tests, the force was applied through e
three 3/4-in. dia. expansion anchors and a plate coupled to a 1-in. rod.
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/,t six of the nine locations, a second test was conducted, as n
d illustrated in Fig. 2(b), by extending the coring through the concrete g
5j fill and about 1 in. into the far block wythe. The procedure described t
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in the preceding paragraph, using a centrally located l<-in. dia, expan-t sion anchor embedded in the concrete fill, was then repeated to obtain e
s.
I a test at the junction of the fill and far wythe of block.
n C
REVIEW OF THE TEST DATA The letter from Northwest Testing Laboratories reporting the 15 test results is reproduced in the Appendix.
It is our understanding that documentation of the tests, including their location and a descrip-tion of the surfaces where the cores were broken under the applied pull-out loading, will be provided in a separate report.
. 1927 106
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I"4 EXP, ANCHOR
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FI RST TEST NEAR B LO CK"]
FAR BLOCK i
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SECOND T EST "A"
Fig. 2 - Pullout Tests 1927 107
The test data and photographs of the locations of the tests and the pieces removed from the walls were carefully reviewed and the r,esults of this review are summarized in Table 1.
In examining the test results, it should be noted that pullout W
i loads are not reported for two tests, Nos. 1 and 6, because they are not s
8' applicable to this evaluation.
J For the reasons given in Table 1, only three of the remaining n
),
13 tests were considered to provide a valid measure of the tensile bond E
strength at the block / fill interface. The other 10 tests are considered I
5 1
to Provide a lower bound esti= ate of the tensile bond strength, and for n
this reason these results are enclosed in parentheses.
a h
INTERPRETATION A
5 s
The application of the pullout load to the near block did not 0
f develop the tensile bond strength of the block / fill interface in any test a
[
except No. 3.
Rather, the strength was limited by conditions relating 5.
to the anchors and to stress distribution within the near block.
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n C
In Test No. 3, the strength was developed because the interface was only partially bonded, apparently as a result of lack of consolidation of the fill concrete.
Although only two of the tests intended to develop the tensile bond strength of the fill with the back block were considered to be valid, all of the other tests, except No. SA, provide a reasonable lower bound estimate of the strength. Test SA is excluded because the anchor split the core, and the remaining portion of the core was broken out with a wedge and hammer. The results of these tests, excluding No. SA,
~'-
1927 108
Table 1 - Review of Test Results Puliout Nominal Test Load (2)
Tensile 3)
Bond Strength Remarks Mark (l)
(lbs)
(psi) 1 Invalid test, because dore did not cut reinforcing bar in block.
2 9,820 (94)
Core sustained 5 cycles of applied nominal loading to 5000 lbs, before failing during first cycle while holding peak load. Test considen to be invalid because the core broke in the biock and not at the block / fill inter-face.
2A 17,670 (170)
Core sustained 11 cycles of nominal loading -
5 to 5000 lbs, 3 to 7500 lbs, and 3 t o 10,000 lbs - before splitting and breaking under increased loading. Test considered to be invalid because break occurred in fill concrete about 2 in. from block.
Splitting of core apparently caused by anchor bolt.
3 4,500 43 Failed before reaching intended peak load on first cycle. Valid because separation occurred at block / fill interface. Apparently fill con-crete did not bond to block on about one-half of interface.
4 7,120 (68)
Core sustained 5 cycles to 5000 lbs nominal loading and failed as peak load was reached during second cycle to 7500 lbs nominal loading.
Test not valid because break occurred in block.
4A 24,500 236 Core austained 11 cycles of nomiral loading, as described for Test No. 2A, before failure occurred under increased loading primarily at block / fill interface. Valid test, although the observation that the break surface departed from the block / fill interface around the peri-p ery of the core is considered to show that h
the applied tensile stress at the interface was higher at the center of the core than near the periphery.
5 4,730 (45)
Failed during fifth cycle after reaching peak nominal load of 5000 lbs. Test invalid, because break occurred in the block.
. 1927 109
Table 1 - Review of Test Results (Continued)
Pullout Nominal Test (2)
Tensile Bond Strength (3)
L Remarks Mark (1) s)
(psi) 5A 14,460 (139)
Core sustained 11 cycles of nominal loading, as described for Test No. 2A, before splitting under increased loading.
Subsequently, a wedge was hammered between core and wall, causing separation at the block / fill interface.
Test not valid as stress causing separation is not known.
Not applicable, because wall was not composite 6
at this location.
7 15,890 (153)
Core sustained 16 cycles of nominal loading, including 11 cycles as described for Test No. 2A plus 3 cycles to 12,500 lbs and 3 cycles to 15,000 lbs, before failure under the first cycle of an increased nominal loading to 20,000 lbs. Test invalid, because break occurred mainly within block, although a small pertion of the piece thac pulled out crossed the interface and extended into the fill con-crete.
7A 21,790 (210)
Core sustained 23 cycles of nominal loading -
5 to 5000 lbs, 5 to 7500 lbs, 5 to 10,000 lbs, 5 to 15,000 lbs, and 3 to 20,000 lbs - before failure under increased loading. Test invalid, because break appears to have begun at the junction of the inside face of the block and the cell concrete, near the center of the core, and progressed outward through the block.
8 3,790 (36)
Failed before reaching intended peak load on first cycle. Test invalid because core broke in block. Result was low because of void in block cell concrete.
8A 14,850 143 Core sustained 19 cycles of nominal loading following the same pattern as in Test No. 7A, before failing just prior to reaching the intended peak load of 15,000 lbs in the 20th cycle. Valid test, because break occurred mainly along block / fill interface, although it did extend into the fill concrete on a small portion of the area.
Table 1 - Review of Test Results (Continued)
Pullout Nominal Tensile Test d(2)
Bond Strength (3)
Remarks Mark (1)
(lbs)
(psi) 9 15,000 (144)
Core sustained 17 cycles of nominal loading, following the same pattern as in Test No. 7A, before f ailing as peak loading was reached in the 18th cycle. Test invalid because core broke in block.
9A 21,790 (210)
Core sustained 21 cycles of nominal loading, following the same pattern as in Test No. 7A, before failing under increased loading. Tes:
invalid because core broke mainly in block, althcagh a small portion of the break surface occurred at block / fill interface. Core was apparently split by anchor bolt.
(Fill is not as thick as other locations.)
Notes:
(1) Tests 'ere conducted at nine locations, as indicated by the first number of the mark. At each location, designated by a number, the test was intended to apply a tensile stress to the interface between the back face of the near
~
block and the concrete fill. Where another test is indicated by the letter A, a second test was conducted at the same location. This test was intended to apply a tensile stress to the interface between the near face of the back block and the concrete fill.
(2) As reported in letter to PGE from Northwest Testing Laboratories dated
~
November 19, 1979.
(3) Determined assuming pullout load was uniformly distributed over 11.5 in. dia.
Values in parentheses are considered to be results of invalid tests, core.
although in every case they represent a lower bound estimate of the tensile bond strength at the block / fill interface.
}h2[-lll are plotted in Fig. 3.
The average bond strength developed in these 5 tests was 194 psi.
In assessing the 5 test results shown in Fig. 3, it may be noted that they have a characteristic variation that is expected in tests W
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dependent on the tensile strength of concrete.
Furthermore, the s.
average bond strength of 194 psi is approximately one-tenth of the a
n specified compressive strength of the ble:k, which is a reasonable value n
e y.
for tensile strength. This result is also consistent with the observa-E tion that the break surface in the valid tests, Nos. 4A and 8A, appeared g
5 t
to depend on the strength of the block concrete rather than the fill n
er concrete.
It is considered desirable to establish a basis for using these n
d test results within the framework of the provisions of the ACI Building g
sj
. Code Requirements for Reinforced Concrete (ACI 318-77) and the ACI e
i Building Code Requirements for Concrete Masonry Structures (ACI 531-79).
a t
e The conditions at the interface of the block and fill concrete S.
I are further considered to be similar to the conditions at a vertical n
construction joint in monolithic concrete construction. With s,!ficient reinforcement across the joint to accom=odate the internal force system, there is usually no need to provide any special treatment other than that the joint be cican and have some roughness.
In the Trojan walls, structural integrity of the interface is required, and the amount of reinforcement across the joint is nearly negligible.
In resisting shear, the provisions of ACI 318-77 allow the use of flexural members without shear reinforcement if the factored shear force, V,, does not exceed one-half the shear strength provided by the 1927 112
Ave.
Bond = 19 4 psi 236
///
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(210)
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2A 4A 7A 8A 9A Test Mark Fig. 3 - Results of tests on far block interface 1927 113
concrete, 4 V, where $ is the strength reduction factor. This may be considered comparable to requiring a strength reduction factor of 1/2 4 where strength without reinforcement is required.
Since & for shear is specified to be 0.85 in the Code, the equivalent strength zy k
reduction factor is 0.425 for a flexural member without shear reinforce-S.
J ment. When shear is being resisted without reinforcement, the strength a
is dependent on internal tensile stress in the concrete.
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In our opinion, the conditions at the block / fill interface are E
[
more critical than for shear as considered in the previous paragraph.
t n
Based on the limited test data and our knowledge of the conditions in er the composite walls at the Trojan Plant, a strength reduction factor of aj 0.2 is judged to be appropriate.
On this basis, the maximum tension A
permitted across the block / fill interface under factored loads should s
S 0
be 0.2 x 194 = 39 psi, or say 40 psi, t
k By using a strength reduction factor of 0.2, it may be noted that t
the bond strength is taken to be slightly less than the bond strength of f
43 psi obtained in Test No. 3.
If there are other areas where there is e
little or no bond between the block and fill, they are believed to be small ano scattered, since the walls at the Trojan Plant were constructed under a quality control program that is understood to have required thorough consolidation of the fill concrete.
In addition, assuming that the ratio of factored to service loads is 1.5, the stress at the block / fill interface should not exceed about 25 psi.
It may be noted that this level of tensile stress is allowed normal to bed joints in masonry construction containing hollow units in ACI 531-79.
' 1927 ll4
Considering a cubical element at the block / fill interface, with one face parallel to the interface, states of stress varying from pure normal stress to pure saear stress are theoretically possible.
W The resistance of a monolithic mass of concrete to shear is greater g
s 3-than its resistance to tension.
Since the tests demonstrated that J
a the bond at the block / fill interface was comparable to the tensile n
n strength of the block concrete, it follows that tension at the inter-e Y.
E face will be more critical than shear. However, states of stress that I
include shear at the interface may have a principal tensile stress s
n 2
acting at an angle to the interface. By limiting the maximum principal a
tension at the interface to 40 psi, the potential for initiation of a
d a crack that might change its direction and propagate along the inter-A s
face is mitigated.
O f
In this regard, it should be recognized that application of I
a t
forces that cause stresses exceeding the tensile strength of the e
5, walls at their boundaries will cause cracking that may penetrate the S
block / fill interface.
In this state, the stress at the interface will be more dependent on local conditions; i.e.,
reinforcement in the wall or location of supports on the wall. However, limitation of the tensile af.ress under factored loads at the bliek/ fill interface to 40 psi, aloit,with consideration of the local effect of the crack-ing, is believed
.o be sufficient to assure integrity.
. 1927 115
CONCLUSIONS Review of test data obtained from core pullout tests on the composite block and fill concrete walls in the Trojan Nuclear Power 57 Plant has shown that a high level of bond exists at the block / fill I
S s.
interface when the construction is as intended by the project specifi-J a
cations. This bond strength is believed to be closely related to the n
E tensile' strength of the concrete in the block. The average bond in y.
E 5 tests selected as providing a reasonable measure of the bond strength 1
5 was 194 psi.
t D
e In view of the lack of bond encountered at one of the 13 locations r
a where tests of the interface were performed, as well as the recognition n
d that structural integrity is required in the ab.sence of reinforcement, A
s it is our opinion that a conservative strength reduction factor must be 5
0 t
applied to the bond strength. A value of 0.2 is recommended, which 1
a t
limits the tensile boad stress to 40 psi under factored loads. This e
3' limit is consistent with the level of tensile stress that is allowed in I
H concrete masonry construction.
Respectfully submitted, WISS, JANNEY, ELSTNER AND ASSOCIATES, INC.
4*A i
...*' 9#
'<b *...
John M. Hanson Project Manager
! ff,/ 0,5 Registered Professional Engineer j -
-. f,.~,:,, -
O i., ',
j f2, State of Oregon No. 10110
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- JMH:rg m
. 1927 116
9 O
O APPENDIX O
1927 117
NORTHWEST TESTING LABORATORIES 4115 N. MISSISSIPPI AVENuC P. O. BOX 17126 won.orstaverivs teonne
- ELD'NG CE*TIFICATIoM coast.tuction s=s action P O R T L A N D. O R E G O N 97217 so;6 TesTina mataniate insasetio" casu.cA6 maatvses PHTsscAL TEsTIMO November 19, 1979 Portland General Electric Company 121 S.W. Salmon Portland, Oregon 97204 Re: Trojon Nuclear Power Plant
~
Report Of: Composit Wall Masonry Block - Concrete Core Interface Bond Testing Load Application Equipment Test Loads were applied by a calibrated hydraulic jacking system consisting of the following: Encrpac hand pump (SN11754), Enerpac 30 Ton Ram (SN11752), Ashcraft 3000 Psig hydraulic gage (SN 11755), Ashcraft 6000 psig hydraulic gage (SN11757), Multi-Port hydraulic coupling and 25 feet of hydraulic hose.
. Test Site No.
Ulimate Failure Loads (Pounds)*
Gage used (PSI 6) 1 Not Applicable / Hit Rebar in Block 6000 7
.9820 6000 2A 17670 6000 3
4500 6000' 4
7120 6000 4A 24500 3000 5
4730 6000 5A 14460 6
Nct Applicable /Not Composit Wall 7
15890 6000 7A 21790 6000 8
3790 3000 8A 14850 3000 9
15000 3000 9A 21790 6000
- Note: Failure Loads determined by Mathmatical interpolation between adjacent calibration points.
1927 118
Portland General Electric Company Page
- Re: Trojan Nucelar Power Plant The test loading system, including hydraulic ram, couplings and pressure Certified gages were calibrated on a Tinius Olson Testing ~ Machine.
accuracy of this machine was established December 7,1978 by Cal-Cert Co.
By hand pumping, a wide range of loads were applied to the test machine.
This These loads along with the associated gage pressures were recorded.
was done for both the 3000 Psig PGE gage and the 6000 Psig Northwest Testing laboratory gage. Results of this calibaration follows:
Actual Load (pounds) from Tinius Olson 3000 PSIG Gage 6000 PSIG Gage 320 100 200 950 200 30 0 1,690 300 375 2,390 400 475 2,500 1430 500 5,000 800 875 7,500 1150 1225 e
1500 1575 10,000 12,500 1860 1925 15,000 2200 2275 17,500 2540 2625 22,000 2900 3000 22,500 beyond range 3350 25,000 beyond range 3725 27,500 beyond range 4075 30,000 beyond range 4425 Respectfully, NORTHWEST TESTING LABORATORIES, INC.
lL Charles R. Lane, P.E.
~
CRL/lz Report No. 211094 1927 119 I
ATTACHMENT 4 FIELD SURVEY OF CONCRETE WALLS, FLOOR SLABS AND STRUCTURAL STEEL A field survey of concrete walls, floor slabs, and structural steel at Trojan was conducted by two licensed civil engineers, one from Bechtel and one from PGE, and one PGE mechanical engineer who had detailed knowledge of the Trojan Plant piping systems.
The purpose of the field survey was to identify, for further detailed evaluation, specific installations where the loads from a safety-related pipe support were judged to be high relative to the capacity of the supporting structure.
In preparation for the field survey, preliminary calculations were made for typical structural configurations.
In addition, pipe support details for large pipelines were studied to deter-mine the range of possible loads. The original floor system design criteria had an allowance of 50 pounds per square foot to account for pipe loads and a 5000 pound load applied anywhere to beams to provide for lifting and pipe supports.
After studying this information, is was apparent that only certain adverse loading conditions could overstress the various structural members.
For example, weak axis bending, torsion or local distortion are the most likely adverse loading conditions for steel members.
For concrete walls and floor slabs, the most adverse loading condition is the normal load and bending moment at the base of a pipe support.
During the field survey, particular emphasis was placed on any area where such conditions could exist.
Multiple supports on a structural member was also of special interest.
The supports for the safety-related piping in the Containment, Auxiliary & Fuel Buildings, Main Steam Support Stracture, f
j
. to Supplement No. 2 Page 2 of 3 Emergency Diesel Generator Enclosure, Auxiliary Feedwater Pump Enclosure, and Intake Structure were inspected.
The Control Building and ESF Switchgear Enclosure were not inspected since drawings indicated the piping in these areas is small and incapable of overloading the structural elements to which the pipe supports are attached.
The following items were considered in identifying structures more heavily loaded relative to their capacity:
1.
Number of piping restraints on the structural element.
2.
Size of piping and piping restraints.
3.
Location and type of restraint reaction, i.e. tension, compression, bending or shear, and relationship to principal axes of the structural element.
4.
Dead load on the structural element.
5.
Live load, other than pipe restraint reaction, on the structural element.
~
6.
Seismic response of the structural element.
7.
Floor slab thickness, span to thickness ratio, and reinforcing for concrete slabs.
8.
Size of framing for braced systems, and span to depth ratio for ceam-girder systems.
Based on the allowances in the original design criteria de-scribed above, it was obvious that the majority of the supports could not contribute significantly to the overall loading of tne supporting structural elements and that resultant loads fell well within these design allowances.
1927 121
. to Supplement No. 2 Page 3 of 3 Such supporting structures were determined to be adequate by inspection.
The survey identified fourteen supports for further evaluation.
Of these 14 supports, 5 involved structural steel members and 9 involved concrete floor slabs.
No supports on concrete walls were identified for further evaluation.
1927 122
s.
ATTACHMENT 5 MORTAR BETWEEN WYTHES OF DOUBLE-BLOCK WALLS Recent inspections in the. field have found that some 14-in.
and 16-in. thick double block walls are not fully mortared between wythes.
This information contradicted information de-veloped from drilling for thru-bolting masonry walls which in-dicated approximately 90% mortar between wythes.
A review of construction records indicates that the above walls were erected during a limited time period in 1972.
As a result, walls constructed during that time period which rely upon mortar for interf ace shear transfer will be inspected. Where mortar is incomplete the inter-wythe space will be filled with non-shrink grout.
In performing a tensile-bond test of composite and mortared double-block wall interfaces in November 1979, PGE found one double-block shield wall at Elevation 5 ft in the Auxiliary Building where mortar was incomplete in the inter-wythe space along three courses of block.
This discovery led PGE to investigate whether there were any significant void areas in the mortar of the three mortared double block masonry walls which are major shear walls in the Control-Auxiliary-Fuel Building Complex.
Tests were done on these three walls (Control Building R-Line wall between Elevation 65 f t and 77 f t, Control Building N-Line wall between Elevation 65 ft and 77 ft and Auxiliary Building 46-Line wall between Elevation 61 ft and 77 ft).
Drilling of 1.5 inch cores into the inter-wythe space showed that i927 123
. to Supplement No. 2 Page 2 of 3 only one of these walls (the R-Line wall) had void areas in the mortar space.
The voids found in the R-Line wall and the test holes on all three walls were filled with non-shrink grout.
A check of QA records indicated that the R-Line wall was the only one of the three which was erected during 1972.
During similar tests on walls of the emergency diesel generator enclosures, the north wall (column line 45) was found to be mortared between wythes; however, the south wall (column line
- 52) was found to contain significant void spaces between wythes.
Construction records indicate that erection of these walls was completed in early 1973 and mid-1972, respectively.
Review of the construction contractual history provides an explanation for the lack of mortar between wythes of double-block walls erected in mid 1972.
The original architectural drawings upon which the contractors bid the work did not clearly indicate that mortar was to be placed in the nominal 3/8-in.
space between wythes of double block walls although the bid specifications required complete filling of all mortar joints.
However, the construction drawings issued in March 1972 clearly indicated that the inter-wythe space was to contain mortar.
In April 1972, before work was begun, the contractor indicated that his price was based on the bid drawing and had not included an allowance for the inter-wythe mortar, and he requested an adjustment in the contracted price for placement of this mortar to compensate for what he considered to be a change in design.
Erection of 16-in and 14-in.
thick double-block walls began in May 1972.
The adjustment in the contract was negotiated between PGE and the contractor 1927 124
. to Supplement No. 2 Page 3 of 3 and was settled in September 1972.
Because of this dispute and the evidence we found, we have less confidence that the inter-wythe space is properly mortared in walls built between April and September 1972.
Although mortar should have been placed between the wythes in compliance with the drawings through the entire period, we recognize that contractural disagreements between contractors and construction management are sometimes raflected in the quality of the work.
Since testing of two of the walls constructed during the period between April and September 1972 disclosed some large voids in the inter-wythe mortar, we are proceeding to test all double-wythe walls built during l
this period to verify the adequacy of mortar in the inter-wythe space.
Where voids are found, they will be filled with non-shrink grout, as have all voids found to date.
1 Mortared double wythe masonry walls built during the period from May through September 1972 are listed on the attached table.
1927 125
. to Supplement No. 2 TABLE 5-1 Mortared Double Wythe Walls Erected Mid-1972 Column Between Masonry Building Elevation Line Lines Inspection Date Control 61/65 R
41-46 6/27/72 1
Auxiliary 5
46 D-E 6/13/72 Emergency 45 52 U-S' 6/29/72 Diesel 45 52 X'-Z 7/10/72 6/29/72 Generator 45 52-W' Room ESF 69 46 U-Y' 6/9/72 Switchgear 69 51 X'-Y' 6/9/72 69 51 X'-Y' 6/9/72 6/9/72 69 51-W' 1927 126
ATTACHMENT 6 APPLICABILITY OF THE 1.8E LOAD COMBINATION In response to a question from the NRC staff, this dis-cussion will explain why the equation found in Section 3.8.1.3.2.1 of the FSAR, which requires that " structural ele-ments carrying mainly earthquake forces, such as equipment supports" be designed for 1.8 times the OBE loading is not applicable to the design of walls in the Trojan Plant, but rather is applicable only to the design of concrete pedestals for equipment.
Section 3.8.1.3.2.1 contains a list of equations which are ap-plicable to all Category I concrete structures.
It is logical to assume that the additional equation cited above was not included within that list because it was intended to apply only to a limited subcategory of concrete structures, i.e.,
those " carrying mainly earthquake forces, such as equipment supports."
It is appropriate to apply a higher load f actor to equipment supports than to walls because tha seismic capability of the equipment support could more directly affect the performance of an important piece of equipment.
Earthquake forces are one of the main forces normally considered in the design of equipment pedestals.
This is not the case for walls supporting piping where piping dead loads and thermal loads are generally much more significant than their seismic contribution.
Further, the piping supports, being spread along a run, are inherently more forgiving if one should fail.
Hence, the safety f actor need not be as conservative for piping as for equipment supports which are directly dependent on pedestal integrity to maintain functional capability.
We 1927 127
O
. to Supplement No. 2 Page 2 of 3 believe this is the basis for the additional conservatism for equipment supports.
We have researched the origin of this equation and its application in the design of supporting structures in other plants licensed in the period during which 'frojan was licensed.
This research did not conclusively establish the origin of this equation for Trojan nor did it provide a precise definition of the specific structural elements to which it should be applied.
However, the research did develop some useful infor-mation reflecting how the Atomic Energy Commission ("AEC")
may have interpreted the equation at the time Trojan was being licensed.
A paper, dated August 11, 1970, entitled,
" Seismic Design Criteria for Nuclear Power Plants", written for the AEC contains a load combination which includes the 1.8E factor for the design of concrete equipment pedestals.
This paper does not contain any other reference to the use of a 1.8 factor for OBE loads.
Therefore, in the absence of further evidence, it would appear that when Trojan was being licensed, the AEC would have interpreted the equation in Section 3.8.1.3.2.1 of the FSAR to only be applicable to concrete equipment pedestals.
We have reviewed the design of concrete Category I equipment supports at Trojan and have found only six supports where this lead equation would be applicable, i.e., only six concrete pedestals.
These are supports for the containment spray pumps, RHR pumps, and RHR heat exchangers.
We have analyzed these supports using the equation containing the 1927 128
. to Supplement No. 2 Page 3 of 3 1.8 E loading combination and have found that they satisfy the acceptance criteria.
It should be noted that major equipment supports such as for the reactor vessel, steam generators, etc, are structural steel and, therefore, the subject load equation is not applicable.
For the above reasons, we believe that the referenced equa-tion has been appropriately applied for Trojan.
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