ML20112B329
| ML20112B329 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 01/07/1985 |
| From: | Ehasz J EBASCO SERVICES, INC., LOUISIANA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20112B305 | List: |
| References | |
| OL, NUDOCS 8501100324 | |
| Download: ML20112B329 (67) | |
Text
-
Y Ol '
RELATED-' -,
=^ D;iCENcg JanuaryihI,^1985 C:' . p . ..
~ : ?, :;
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION .b- JUl g A10:27 t.ff n. 1 Before the Atomic Safety and Licensing K$paal" Board. l
%'licfMV:f.r In the Matter of )
)
LOUISIANA POWER & LIGHT COMPANY ) Docket No. 50-382 OL
)
(Waterford Steam Electric Station, )
Unit 3)
AFFIDAVIT OF JOSEPH L. EHASZ Q1. Please state your name, address, and occupation. ,
A1. My name is Joseph L. Ehasz. I am employed by Ebasco Services Incorporated (ESI), Two World Trade' Center, New York, New York 10048, as Chief Civil Engineer. A statement of my educational and professional qualifications is attached.
Q2. What has been your involvement in the Waterford 3 project?
A2. ESI, as Louisiana Power & Light Company's (LP&L) architect-engineer-for the Waterford 3 project, has designed the plant structural system and has general management respon-sibility for construction, including the placement of all
~
8501100324 850107 PDR ADOCK 050003B2 9 PDR
__f
c t safety-related concrete. I have been involved in the Waterford 3 project since the inception of the design of the plant.
Q3. Has ESI: analyzed the effects of the cracking in the Waterford 3 on the structural integrity of the basemat?
A3. Yes. Ebasco has studied closely and evaluated the results of the surface mapping and non-destructive testing (NDT) of the cracks. Ebasco has carefully studied the physical evidence of the cracks and evaluated this in light of the
. knowledge _of soil properties and construction sequence to develop an understanding of the causes f cracking.
Ebasco has developed, from the NDT, a theoretical model of the cracks which was used in evaluating the effect of the cracks on the structural integrity of the basemat. Using this ' J.,
model and mathematical analyses, ESI evaluated the effects of the cracks on the flexural and shear transfer capabilities of the basemat and the effects of the cracks on the dynamic re-sponse of the structure.
The results-of Ebasco's studies and analyses are described
'in the attached " Summary Evaluation - Structural Significance
~
of Basemat Nondestructive Testing Results," Revision 2, November 27, 1984 (Attachment 1).
._______J
- c Y Q4. Has ESI-come to a conclusion regarding the adequacy of the Waterford basemat?
A4. Yes. The Waterford 3 basemat cracks have been inten-sively studied for the past year and a half. Ebasco, as well as several consultants, have studied the physical location and geometry of the cracks and any ramifications on the structural integrity of the base mat which they could have. All have found them to be of no significance to the structural integrity of the basemat. The cracks have been mapped, measured and identified at depth by nondestructive testing means, the proba-ble mechanism of their generation has been identified, and cal-culations have been made to predict their effect on the perfor-mance of the mat. All of these studies and investigations have -
~
led to the same conclusion that the cracks are of no signifi- ' ,; ,
cance to the structural integrity of-the basemat and hence none to the safety of the plant under any of the postulated loading conditions.
As stated at page 23 of Attachment 1:
[We] conclude that the cracks in the Waterford 3.basemat, as defined by the nondestructive testing, have no adverse in-fluence on the structural integrity of the basemat. It is fully capable of func-tioning as required by the design in accor-dance with the pertinent codes.
, _ QS. Have you reviewed the affidavits submitted by the NRC Staff and Brookhaven National Laboratory to the Appeal Board on
. December 17, 1984, including the affidavit of John S. Ma and the views of John T. Chea as presented in Attachment 1 to the affidavit of James P. Knight?
.__f
, y .tI AS. Yes, I have.
. Q6. Are you in agreement with the conclusions of the NRC
-Staff and.'those of BNL?
A6. Yes, I agree with.the conclusions of basemat adequacy presented by the Staff and the Brookhaven National' Laboratory (BNL). In so doing, I concur with both the Staff and BNL in
.their disagreements with some of the views of Dr. Ma and Dr.
Chen.
Q7. To what extent do you disagree with the views of Dr. Ma?
A7. Dr. Ma makes a number of statements which are incon-
- sistent with'the-literature and the conventional body of engi- .
neering' knowledge, including papers he himself has cited. How- ',
ever, my principal disagreement is with what appears to be his primary concern,- that the cracks may significantly impair the capability for shear transfer of forces and the dynamic re-tsponse of the basemat might be significantly changed.
With' respect to shear transfer, Dr. Ma does not quantify-3'-
the extent to which he believes that shear transfer will be im-paired by the cracks, or even state positively that it will be a problem. Rather, he asserts, in general, with no attempt.to relate his concern specifically to the characteristics of the 7
sbasemat, that.a crack will reduce the ultimate shear transfer strength and increase the slip due to load (Ma affidavit, page 26),;and that'"there has not been.enough evidence to O
p -
l'
- g- Lt.
conclude that the existing cracks can be safely ignored" (Ma affidavit, .page 31). The specific design aspects of the
- basemat, however, preclude such effects, a conclusion which is reflected in the expert views of the NRC Staff, BNL, and Pro-fessor.Myle J. Holley, Jr.
The basis'of Dr.-Ma's concern appears to be a mis-reading of a paper which he cites by A. H. Mattock, et al.,
. published in the PCI Journal, March-April 1972 (Ma affidavit, page 26). The paper is attached hereto as Attachment 2.1/ The basis cited by Dr. Ma is a quote from.that paper that "'[a]
pre-existing crack along the shear plane will both reduce the
. ultimate shear. transfer strength and increase the slip at all
~
levels of load.'" ~(Attachment 2, page 74.) That quotation, however, applies '.o a case where there is no compressive force on the crack, which is definitely not the situation for the .
Waterford 3-basemat.
Dr.-Ma stopped short of noting that the-Mattock paper also reports on results of testing for, shear transfer across'a crack when there is compressive force on the~ crack,-such as ex--
ists'at Waterford 3. The Mattock paper states:
s In a heavily reinforced shear plane, or one subject to.a substantial externally applied normal. compressive stress, it is possible for the theoretical shear resistance due to
, friction and dowel effects to become-
- 1/ ~
~Dr.:Ma-has cited the; wrong title of-the paper. The' title
+
cited is a paper by Mattock, et al., which_ appeared in the July-August 1975-issue of PCI Journal, and which is not germane to this situation. Dr. Ma.is clearly referring to the.1972 paper (Attachment 2).
4 .
~
t
~._,,___ - -._. ~ ---.__ -. .-. - -,-,-. -. -
- p -u ^
-greater than the shear which would cause failure in an initially uncracked specimen having the same physical characteristics.
In such a case, the crack in.the shear plane " locks up" and the behavior and ulti-mate strength then.become the same as for an initially-uncracked specimen.
(Attachment 2, page 70; see also page 75.)
The key element here is that the behavior in an ini-tiallyferacked section can be the same as in an uncracked sec-
' tion if there is sufficient compressive force across the crack.
The behavior referred to in-the conclusion quoted by Dr. Ma is Lvalid only in a-section in which there is little or no com-
.pressive. force across the crack. Then there must be initial slip to engage the reinforcing steel and develop tension in it, which is the very basis of shear-friction action. As noted at -
page 22Hof Attachment 1 and at pages.21-22 of the July 18, 1984' -
BNL. Report, the Waterford basemat has substantial compressive force across the cracks due.to the externally applied soil and
~
water pressures. -Calculations were performed which showed that the: maximum-postulated shear was' easily transmitted across the cracksLutilizing tlue friction -resulting only from .the com-pressive' force present on~the. crack faces. No utilization of extra compressive force brought by the reinforcingLsteel being
. engaged;due to slight slipping of'the. crack ~ faces is required.
Thus, little cn no. slip will occur on the cracks due to trans-
~fer of shear under any of the designJfactored load conditions.
Dr.:Ma's stated concerns with the lessons learned in the 1971 San Fernando earthquake regarding effect on bridges g
l
.6 %
(Ma-affidavit, pages 17-18) has no bearing on the case at hand.
The problem with the bridges had to do with expansion joints 1
which were1unreinforced and which were responding to large rel-ative displacements high on a structure. The Waterford 3 basemat in-no way resembles this situation, as it is an inte-grated reinforced concrete structure which is structurally con-t'inuous, with no expansion joints, and is supported on soil.
Similarly, Dr. Ma also provides a misleadingly par-tial quotation from a paper by Price to indicate that the basemat should be free of cracks:
"[T]he primary requirement involved in mass concrete construction is that the completed structure is a monolithic mass that is free .
from cracks . . ." (Ma affidavit, page 30).
~~
However, the complete quotation, and indeed,~the article itself, clearly' indicates that the statement applies to dams ,
(which are not reinforced concrete structures), where freedom from cracks is-important. The statement has no applicability
-to reinforced concrete structures, such as the basemat, where l, cracking is anticipated.
L Q8. How do you disagree with Dr. Ma's concerns expressed at pages 16-18 and 31 that the cracks will cause deviations from-the predicted seismic response of the basemat?
A8. Dr. Ma's concern that.the seismic response will devi-ate because of the cracks, and that the significance of such deviation is not known (Ma affidavit, page 18), appears to l ;arise from his.asking us to assume "that the crack is wide and
- - D
a 1 there is no contact between concrete surfaces across a crack."
(Ma affidavit, page 17). Such an assumption is clearly errone-ous, as discussed above, because of the substantial compressive force across the cracks in the Waterford 3 basemat. Moreover, Dr. Ma does not identify the forces which would separate the faces of the crack to eliminate contact. In fact, there are no such forces. Further, actual measurements of cracks at surface and at depth show them to be of modest width.
Since it has been demonstrated that the shear behav-ior.of the mat will not be significantly affected by the cracks,-and since no significant increase in the flexure of the
- i. basemat will be caused by the cracks (Attachment 1, pages 15-16), it follows that the dynamic response of the mat
~
will.not be significantly affected by the presence of the 4 cracks. ,
~
Dr. Ma has noted that the dynamic response of the basemat was determined using a model which assumed that the mat-behaved as a single-monolithic structure. (Ma affidavit, page 16.) He noted that the model was valid with shallow cracks present, but questioned the validity of the model if the
. deeper cracks in the basemat are present. In fact, the basemat cracks do not invalidate the model. As discussed above, the i . cracks do not affect the shear and flexural behavior of the mat. The cracked mat therefore can be correctly assumed to act monolithically. Hence, the cracks have no significant effect on-dynamic response of the basemat. See_ Attachment 1, pages 16, 22-23.
c %-
A dynamic analysis performed by BNL is a demonstration of the.small effect that total _ elimination of the shear _ transfer capability in one~ element of the basemat could have. (Affida- l
- vit of Reich, et al., Attachment 1, Appendix D.) The analysis shows that-the response of the structures above the mat is vir--
tually~ unaffected, even by the assumption of such a fictitious loss of mat rigidity.
' Q9. Do you share Dr. Ma's concerns expressed at page 28 of-his: affidavit.about steel corrosion and durability?
A9. It'is not clear to me that Dr. Ma has-actually ex-
. pressed'such a concern'about the Waterford 3 mat specifically.
~
He discusses the general concepts of rebar corrosion and con- -
crete durability, but does not define any specific concerns ap- ' J,,
plicable to the basemat. In any event, the record is clear that we have no problems with corrosion and durability in the-Waterford 3 basemat.
The cracks as they exist at present are not leaking
~
any appreciable amount of water. At some spots,-a dampness marks the location of the crack, but otherwise the cracks are dry at-the surface. This indicates that there has'been a healing or. filling of the crack sufficient to prevent about a 50-foot' head of water from forcing water through them. Any.
water in'the cracks has become stagnant and alkaline in. nature, which makes it noncorrosive. Nevertheless, extensive studies
~
-were performed.to identify the corrosion hazard to the
_g_-
o A reinforcing steel in the mat and to ascertain if there would be any hazard to it during the life of the plant. ,
In his affidavit of September 27, 1983, submitted in support of LP&L's answer to the earlier motion to reopen on the basis of basemat cracks, William Gundaker, ESI Director of dor-rosion Engineering, reviewed and summarized these studies and the results and conclusions. He stated at page 6 of his affi-davit that ". . . I can state that there is no reason for me to believe that corrosion of the reinforcing steel in the concrete mat at Waterford 3 Nuclear Plant would occur to a degree that would have any significance." This statement was made after a series of chemical tests on the water which was extracted from a crack and from water which was extracted from the ground ~ad-
~~
jacent to the mat, and an examination of the results of these tests in light of a clear understanding of the potential causes ,
of corrosion in reinforcing steel embedded in concrete.
the have also looked at the experience with concrete struc-tures in the vicinity of the plant. Ebasco has put in place many concrete structures and foundations in the general area of the Waterford Plant in the last 50 years with no reported fail-ures due to corrosion of reinforcing steel. In all of these structures the general design and stress levels are about the same as those at Waterford.
'Q10. Do you find any significant disagreement among the various views presented, including those of Dr. Ma and Dr.
.Chen, on the cause of the basemat cracks?
.n
g7, . . . . . . .
\
t v
.'" i H; l YA10. No, I do not see any significant disagreement among '
the: current _ views put forth as to the cause of the cracks. All who h' ave expressed their views appear to agree that the primary cause was differential settlement of the basemat during con-
+
struction,'as well as the normally expected thermal shrinkage.
The causes for the cracking in the Waterford basemat have been determined to be from two interrelated reasons -- the j highly compre,ssible nature of the soil beneath the plant and the sequence of construction of the basemat.
MDua. soil beneath Waterford is a normally consolidated
-clay, silt and-!s'and mixture which'was laid down by water in the I-- -
<f0
.: Pleistocene Age.,.It is horizontally bedded and generally quite t , . . .
h dN).(ompr$s'sible when loads'inl excess of those which it has.experi-4 y ' -
enced in the past are impressed upon it. The Waterford mat,
'during the;edrly construction phases, imposed such loads upon ,
~
3 , Nit and'hence consolidation was..eapected and was experienced.
, .. 4 i
.The method of impressing this' load was controlled under engi-neering direction by strict! control.of the construction
.. ~~?:
l' q{shquencing pf the mat and superstructure.
w>, .
3 qThe=basemat, which is 267 feet by.380 ' feet,- was nec->
eaIarily.constructedbythe'sequentialplacementof60-footby 170-foot blocks. The-blocks.are structurally. continuous. The-E construct' ion sequence :resulted in a staged' consolidation of the
' Pleistocene 1 soils such that-the north and south ends of the mat-g ,
1 have? settled'more-thanithe' center where the construction.
~
'n started. Much of the settlement of each block occurred soon
- lj;
& l
. 1 er.
~
(($1)
JE pppA' Y D
e %
after concrete placement, with the rate of settlement tapering off with time. Thus, the first block of the basemat placed had experienced an initial settlement by the time an adjacent block was placed. The adjacent block was placed level with the pre-viously placed block,-and then underwent settlement starting at the level of the already partially settled first block. Thus, the second block had to undergo all of its settlement while the first block only had a percentage left to go. While the total settlement for each block was about equal, because placement of the basemat was done from the center outward to the north and south ends, the result was a mat which was finally convex up with the highest portion being at the center of the reactor building. Figure 2 of Attachment 1 illustrates this shape of the basemat.
The convexity of the basemat resulted in tensile ,
forces due to flexure at the top of the basemat in the middle section early in the life of the mat. This resulted in the cracking. As illustrated in Figure 2 of Attachment 1, the flexure was greatest around the reactor building centerline and was quite symmetric to the north and south. The cracking is predominantly in an east-west orientation and concentrated around the east-west reactor building centerline.
With the addition of superstructure loads, the flexure of the mat was reduced as it was stressed more in accordance with the final' loading conditions. This put the top of the mat in compression and closed up the cracks.
d
l
,- s-l
.Both Dr. Ma (Ma affidavit, page 1) and Dr. Chen have expressed disagreement with BNL on the cause of the cracking.
This is apparently because each of them has referred to an early conclusion of BNL (July 18,.1984, BNL Report, page 26) that the cracking was largely due to the placement of loads on the constructed basemat by construction of the plant super-
' structures prior to the placement of backfill. However, from discussions with BNL, it became apparent that BNL was initially under a mistaken impression about the sequence of construction.
After learning that'the soil backfill was not placed after con-struction of the superstructures, BNL modified its conclusion and now agrees that the ca.use of the cracking was primarily_due ,
to differential settlement during placement of the basemat (Af-r fidavit of Reich, et al., Attachment 1, page 3).
With all parties agreeing fundamentally on the cause .
of'the cracking, the only remaining difference of opinion seems to be_related to the precise soil mechansim which caused the.
differential settlement to occur.
. .Q11. What is ' tie difference of opinion regarding the soil mechanism leading to the differential settlement?
All. Contrary to the positions of Ebasco, the NRC Staff,
-and<BNL, _Dr. Ma and Dr. Chen suggest that the differential set-tlement may have been due to non-uniformity of the soil beneath-the basemat. Soil non-unifor$ity, however, is not necessary-for differential settlement of the' mat to have occurred. In-
, s-fact, as_I discussed in my answer to Question 10 above, even
-though the soil was relatively uniform, differential settlement was anticipated, and the construction sequences was planned to minimize and maintain symmetry of the differential settlement.
The postulation of non-uniform soil is contrary to the objective evidence. First, extensive preconstruction soil tests showed the soil beneath the basemat to be uniform. At the Waterford site, 74 soil borings were drilled. Of these, 22 were in the area of the basemat. Numerous soil tests were per-formed.on the Pleistocene clays, giving results that show simi-larity in grain size distribution and relative uniformity in strength, permeability, and compressibility. Following excava-tion, which exposed the upper several feet of the Pleistocene
~
'fo rmation, the soil was mapped in detail. The formation at foundation level consists of horizontally beddedilayers of ,
silts and clays. The conditions encountered compare very favorably with the data taken from the site borings. Mapping of the excavation disclosed no abnormalities or discontinuities
.in the-foundation materials.
Second, the relatively symmetric differential settle-ment experienced by the basemat is indicative of relatively uniform soils. Non-uniform soils would not lead to the-symmetric settlement pattern exhibited by the basemat with its carefully sequenced construction. It is not conceivable that such symmetric settlement would have occurred with non-uniform soils.
T
- c w 1 Finally, the cracking pattern itself was consistent
.with the symmetric ~ settlement which could not have occurred over non-uniform' soils. The pattern of cracking in plan is not a random one,_but rather a pronounced east west alignment strongl'y concentrated around the east west centerline of th6
, reactor building and somewhat symmetric with the centerline.
The' cracks are predominantly near or emanating from the top Laurface of the mat and are-all vertical as defined by non-destructive testing.(NDT) methods.
-Q12. Does it really matter whether the differential set-tlement occurred over uniform or non-uniform soils?
.A12. No, I do not believe so, because the differential -
4
' settlement.has essentially stopped. Dr. Ma appears to agree: ;
. . . . the possible major contributing fac-tors to the cause of the cracks would have '
, vanished and would not appear again. Ther-mal stress due'to the cement hydration pro-cess,.which might have produced the cracks, would not appear again. Stress resulting from' concrete' block construction sequences has leveled off. Stress associated with
~ differential settlements decreases as the settlements of soils became stabilized through soil _ consolidation. process. The significant groundwater level changes dur-ing construction would not reappear. (Ma affidavit, page 31).
. While Dr. Ma prefaced these observations with a~ recommendation that:the~ cracks be repaired, his stated reasons for believing 1that the causes of the cracks had vanished are unrelated to whether or not~the existing _ cracks are repaired.
4 3~
O
,- s Similarly, Dr. Chen at page 9 concluded that The plant foundation design, the "compen-sated" foundation concept, is sound and acceptable. The soil bearing capacity is adequate and the future settleuent should be negligible.
Our analyses, as confirmed by our monitoring of basemat
-settlement, show that future settlement of the basemat, if any, will be insignificant, irrespective of the uniformity or
.non-uniformity of the underlying soils. The existing cracks, caused primarily by the differential settlement which resulted in a convexity at the top of the basemat with commensurate ten-sile stresses over the top surface, have been closed by the placement of the plant superstructure deadload on the basemat.
The significance of these cracks on the structural adequacy of the basemat has been' determined, and it is no longer of signif-
.icance what the exact causes of the cracks were, other than to ,
determine that the causes are no longer active.
k% $EHASZ .D POSE @HL.
/
Subscribed and sworn to before me this' 7 -A day of January, 1985.
rub l
(( 6/ NOTARY. PUBLfC Josephine R. Bambara V Notary P btic. Saare el New York 5
My Commission Expires: gj),i ff'3j/f,0[5 Cert 4a+e f.les in New York Couetv Conmssion Expres March 30. 9 Pl, i
o s JOSEPH L. EHASZ Chief Consulting Civil Engineer EXPERIENCE SLMMARY Registered Professional Engineer in sixteen states with seventeen years of experience in civil ergineering, design ano construction aspects of major hydroelectric, fossil-fueled and nuclear generating stations. Major field of interest is in civil and geotechnical related aspects of power plant ,
structures; in particular the soil and rock mechanics design, analysis and construction of earthworks and foundations for dams, ambanlonents, and major plant facilities.
Reponsible to the Vice-President of Consulting Engineering for all technical, administrative and personnel aspects of the Consulting Civil Engineering and
-Earth Sciences Departments. Responsibilities have included direction of civil engineers as well as the soils engineering grow working on foundation engineering and desip features of hydroelectric and steam power stations; s@ervision of engineers working on all civil aspects of power stations as well as directirg engineers with respect to soils and field reconnaissance investigations, establishing foundation design criteria, establishing earthquake design criteria, engineering on design drawings and construction -
specifications.
Office assignments have included lead civ'il engineer on various hydroelec't'ric and steam electric power stations. Geotechnical experience includes design and analysis of difficult foundations, detailed stability and sectlement analyses for unusual subsurface conditions designing and analyzing large earth and rockfill dams and developing observation systems for earth and rockfill dass. Work includes establishing foundation design criteria for nuclear power plants, entailing both static and dynamic factors and considerations; the analysis of the various foundation types and the ef,fects on the dynamic considerations of the building components. Job engineering includes civil engineering features such as mannels, dikes, general foundation layout of steam electric stations, transmission lines and river crossings. Responsible for the engineering of a 15-mile make@ pipeline and associated reservoir and river punging facilities, including site investigation and reservoir embankment and spillway design. Responsibilities also included engineering on dam foreim hydroelectric projects involving detailed geotechnical studies, foundation evaluation and associated foundation treatments for a 500-foot arch dem and a 680-foot high rockfill and concrete gravity dam complex.
Field assipments have included supervision on field investigation, borings and' test pits for hydroelectric nuclear and steam electric plant sites; inspection of construction associated with waterfront. docking facilities; s@ervision and inspection on caisson construction, pile driving and pile load testing on various plant sites. Field s@ervision to establish criteria for controlled compacted backfill for soil bearing foundations and responsible charge of detailed seepage studies for pumped storage projects, ' including field assignments during initial filling of upper and lower reservoirs.
Responsible for site evaluation and grouting programs' developed for varied embankment dams as well as concrete dams.
p
. s 3 5EPH L. EHASZ REPRESENTATIVE EXPERIEPCE Client Project Size Fuel Cholla Unit Nos. 115 MW Coal Arizona Public Service 250 MW Company 1, 2, 3 & 4 250 MW 400 MW Dallas Power & Light Lake Hubbard Unit 375 MW Gas Company No. 1 Cedar Bayou Unit 750 MW es. Oil / Gas Houston Li@ ting &
Power Company Nos. 1 & 2 Brunner Island Unit 790 MW Coal Pennsylvania Power &
Light Company No. 3 Montour Unit 800 MW es. Coal-" -
Nos. 1 & 2 Bethel Unit No. 1 100 MW Gas 'J.,
Portland General Turbine Electric Company Harborton 200 MW , Gas
. Turbine .
Beaver 450 MW Gas Turbine United Illuminating Bridgeport Harbor 400 MW Coal Company Unit No. 3 Carolina Power & Light Shearon Harris Unit 960 MW es. Nuclear Company Nos. 1, 2, 3 & 4 St. Lucie Unit 890 MW ea. Nuclear l
Florida Power & Li@t Company Nos. 1 & 2 ,
Allens Crsek 1200 MW Nuclear Houston Li@ ting &
Power Company Unit No. 1 Waterford Unit No. 3 1165 MW Nuclear Louisiana Power & -
Light Company WPPSS Unit Nos. 3 & 5 1300 MW es. Nuclear Washirgton Public Power Staply System t
e L 0
. s .
33SEPH L. EHASZ EWLOYENT HISTDRY I
?
Ebssco Services Incorporated, New York, N.Y.; 1965 - Present -
o Chief Consulting Civil Engineer,1980 - Present '
-o Corporate Chief Civil Engineer, 1979-1980 o Assistant Chief Civil Engineer, 1977-1979 o S@ervising Engineer, 1971-1977 o Engineer, 1965-1971 Rutgers University, College of Engineering, Graduate School, New Jersey; 1964-1965 o Graduate Student and Teaching Assistant; Burns & Roe, Inc., Engineers and Constructors, New York, N.Y.; 1963-1964 o -Enginser EDLCATION
. Rutgers University, New Jersey - BSCE - 1963 ' J.,
Rutgers University, New Jersey - MSCE - 1965 REGISTRATIONS Professional Engineer - New Jersey, Alaska, Arizona, California, Florida,-
- Georgia, Louisiana, Michigan, Minnesota, New York, North Carolina, Pennsylvania, Texas, Washington and West Virginia.
PROFESSIONAL AFFILIATIONS American Society of Civil Engineers American Concreto Institute l International Society of Soils & Foundation Engineers Internationsi Commission on Large Dams Casuilttee on Earthquakes )
-New Jersey Society of Professional Engineers i Rutgers Engineering Society
- Who's Who In Engineering (1982) e
-n,-~ ,-e,,-c.----,,,.,,-,+w-,--,--,-,,,n,,w-,,,-,-,,,---.--,--,-..w,,,n, - -,n-. _ - - -, . , . _ _ . _ _ _ - - - - - - - - - . '
4- .
3)SEPH L. EHASZ TEDelICAL PAPERS
" Static and Dynamic Properties of Alluvial Soils in the Western Coestal Plain i of Taiwan"; co-authored with K.Y.C. Chung; 7th Southeast Asian Geotechnical Conference; Hong Kong, November 1982
" Experience with Upstream Impermeable Membranes" leth ICOLD Congress, Rio de l Janeiro, May 1982
" Ash Pond Construction to Meet Performance Requirements"; co-authored with M Tenchin, ASE Convention & Exposition, New York, NY, May 1981 ;
" Foundation Movements - Prediction and Performance"; co-authored with M Pavone; 10th International Conference 'on Soil Mechanics and Foundation Engineerirg; Stockholm, Sweden,1981
" Dynamic Properties of Weathered Rock"; co-authored with I H Wong & K H Liu, 7th World Conference on Earthquake Engineering; Istanbul, Turkey; Sept 1980 , ._
" Probability of Liquefaction due to Earthquakes", co-authored with I H Chou, 7th World Conference on Earthquake Engineering; Istanbul, Turkey; Sept 1980 --
" Liquefaction Considerations in Nuclear Power Plant Design" ASE Specialty Conference on Structural Design of Nuclear Power Foundations, New Orleans, December 1975.
" Experience on Dams with Upstream Impermeable Membranes", Conference on Recent Developments in Design, Construction and Performance. of Embanierent Dems, University of California at Berkeley, June 1975.
" Compatibility of large Mat Design to Foundation Conditions," ASG National Structural Engineerirg Convention, New Orleans, April 1975.
"The Effects of Foundation Conditions on Plant Design," Atomic Industrial Forum, San Diego, December 1974.
" Implementation of Foundation Design Criteria", ASCE Specialty Conference on Structural Design of Nuclear Plant Facilities, Chicago, December 1973.
"Fotadation Design of the Waterford Nuclear Plant", ASCE Specialty Conference on Structural Design of Nuclear Power Facilities, December 1973.
" Civil Engineering Aspects of the Montour Steam Electric Station",
Pennsylvania Electric Association, October 1970.
" civil Engineering Aspects of Brunner Island Unit No. 3, Foundation and Circulating Water System", Pennsylvania Electric Association, May 1967.
~- -- - - . _ - ~ _ _ . _ . _
ATTACHMENT 1
s LoulSIANA ,. . a = ===
P Q W E R & Ll G Hn Tosume / ee.- = - sv 7eira.eace
' Mg g . caosiseees e November 28, 198A W3P84-3319- '
3-A1.16.07 A4.05-Director of Nuclear Isactor Regulation ATIN: Mr. Dennis M. Crutchfield, Asst. Director F*^ WS for Safety Assessment Division of Licensing NUC'En net,UdDS U.S. Nuclear Eagulatory Commission Washington, D. C. 20555 DEC 6 1984 d
SUBJECT:
[/
WATERPORD 3 SES ILN:-
ADDITIONAL INFORMATION ON 3ASEMAT _
HAIRLINE CRACKS
References:
Latter W3P84-3142, K. W. Cook to D. M. Crutchfield, dated November 7, 1984.
Dear Mr. Crutchfield:
The purpose of this letter is to supplement the-additional information provided in the referenced letter. This information was requested by the NRC and Brookhaven National Laboratory personnel at a meeting in Bethesda, Maryland on November 20, 1784 Attached is Revision 2 of the report entitled " Summary Evaluation Structural Significance of Basemat Nondestructive Testing Resulta". This revision addresses
- questions discussed among parties at the November 20, 1984 meeting. Further infor-mation regarding the degree of confidence in NDT results, probable causes of cracks, anchaai z for deep slip resistance, etc.narrow cracking, construction controls, shear considerations, Louisiana Power & Light remains firmly convinced that the cracks, as defined by NDT have no adverse affect on the structural integrity of the basemat. The basemac is fully capable of functioning as required by the design in accordance with the pertinent codes.
Very truly yours, f.hl- N Gy K. W. Cook Nuclear Support & Licensing Manager IGC:pic ATTACHMENI
_ _ _ __ _ __ . - - - - - - - - - - ---~
, Nr. D.M. Crutchfield
. Page 2 cc: E.L. Blake, W.H. Stevenson, G.W. Knighton, J.M. Knight, J.H. Wilson G.L. Constable Project Files, Adminingrative Support, LiC9asing Library
- i i
I 4
f 4
l l
l t 1 n
E 1
'd #
i i' I l
l LOUISIANA POWER AND LIGHT COMPANY WATERFORD STEAM ELECTRIC STATION UNIT NO. 3 -
SUMMARY
EVALUATION STRUCTURAL SIGNIFICANCE OF BASEMAT NONDESTRUCTIVE TESTING RESULTS REVISION 28 4
November 27, 1984 Ebesco Services Incorporated -
Two World Trade Center New York, NY 10048
- Includes revisions, clarifications and additions to the Revision 1 Report of November 1984 based on the November 20, 1984 seating with NRC staff and Brookhaven National 14boratory.
f
,, .' LOUISIANA POWER AND LIGHT COMPANY WATERFORD STIAM ELECTRIC STATION UNIT NO. 3
SUMMARY
EVALUATION STRUCTURAL SIGNIFICANCE OF BASIMAT NONDESTRUCTIVE TESTING RESULTS TABLE OF CONTENTS P_ age 1.0 PURPOSE I
2.0 SCOPE 1
3.0 BACKGROUND
1 4.0 NUT RESULTS
SUMMARY
2 5.0 PROBABLI~CAUSES OF CRACKS 9 ,
6.0 SIGNIFICANCE OF CRACKS AND EFFECTS ON STRUCTURAL INTEGRITY 13
7.0 CONCLUSION
23 .
REFERENCES 24 .
TABLE 1 -
SUMMARY
OF CRACKS WEST SIDE OF RCB TABLE 2 - FUMMARY OF CRACKS EAST. SIDE OF RCB TABLE 3 -
SUMMARY
OF CRACKS BENZATH RCB TABLE 4 -
SUMMARY
OF CRACKS IN RCB WALLS FIGURE 1 - BASEMAT CRACKS - PLAN VIEW FIGURE 2 - BASEMAT CURVATURE (From Reference 2)
APPENDIX 1 - REINFORCING STIEL STRESSES AS DEFINED BY CRACK WIDTH (CALCULATION) i f
^ ~~ ~ '~ ~ ~~ ~ '
"~~wubMn r6sti ed uunt~cOMynt
, WATER. FORD STEAM ELECTRIC STATION UNIT No. 3
SUMMARY
EVALUATION STRUCTURAL SIGNIFICANCE OF BASIMAT NONDESTRUCTIVE TESTING RESULTS' 1.0 PURPOSE The purpose of this report is to review the results of nondestructive testing (NUT) of Nuclear Plant Island Structure (NPIS) baseest cracks and to evaluate their significance with respect to the structural
, integrity of the NPIS.
2.0 SCOPE The scope of this report covers the following: '
- 1. Review and interpret data and results of NDT related to basemat as presented in the Muenow and Associates Inc. Report of October 1984 '--
sad Appendiz 6 of that report which was issued November 13, 1984. i
- 2. Evaluate the significance of the cracks on the structural integrity 1 of the NPIS basemat.
l
- 3. Study the crack patterns as defined by NDT, such as inclination, l depth, spacing, and width in order to determine the probable causes l of basemat and wall cracks.
3.0 BACKGROUND
An NDT program of the basemat cracks was performed by Muenow and Associates Inc. to determine the following:
- 1. Inclination of the cracks - whether the basenat cracks are vertical and/or diagonally inclined.
1 r
, s.u ~wmm m a us i i
.- j
. .. 2. Estiasta d:pth, length, and width of the bnocast cracko.
i As an auxiliary study, the depth of some cracks of the Reactor )
Containment Building (RCB) unil surfaces above the basemat was avsluated. .
l This NM examination was performed at the Waterford 3 Site mainly i during the months of July and August 1984 k 4.0 NM RESULTS SUMARY ;
l 4.1 CRACKS IN 3ASEMAT (Tables 1, 2 and 3)
The anjority of the cracks are oriented iin an east-west direction and located within a distance of thirty (30) feet from the east-west centerline of the RC3. Based on their appearance and nearness to each other they are grouped into 10 families:* 4 on the east side of the -
RCB and 6 on the west side of the RC3. Seven cracks beneath the RCB were also identified by N M , four of these cracks (Numbers 1, 4, 5 and ~-
, 7) appear to coincide with east-west cracks on either side of the RC3
)
and probably are interconnected (Figure 1). '.
Cthir cracks are oriented in a northeast / southwest or northwest /
southeast direction (diagonal cracks) and they are grouped into a total of 7 families. Of these families, 4 were evaluated by NDT: 3 in the northeast and 1 in the northwest corners of the RC3. These cracks are also referred to as East or West Diagonal cracks in the Muenow and
[ Associates, Inc. Report. Two of the cracks beneath the RC3 (Numbers 2 and 6) appear to coincide with the East or West Diagonal cracks and
- probably are interconnected (Figure 1).
- The grouping b' families is somewhat arbitrary and intended only to present L
, ca overview of the sat cracking. No analyses or conclusions are dependent upon the grouping.
t
, _ _ . . . _~ ,- -,,.,-+,w-r-
. - - - _= . . _ . _ _ _ _ _
6.1 HA.IRLINE CRACKS OF BASEMAT (Cant'd)
One crack, number 3, cypears to be ind2 pendent cf all ethers and is relatively short in length. '
Ebasco review indicates that within the above families of cracks, the' data show most cracks originate from the top surface of the basemat.
(top cracks), that a few noncontinuous cracks originate from the bottom surface of the baseest (bottom cracks), and a small number lie within g
^
the middle portion of the basemat (siddle cracks). I Tables 1 and 2 present a summary of the NDT ammination of the basemat cracks on each side of the RCD. This includes length, depth, group spacing and inclination of cracks which originate from the top surface of the baseest. In addition, a summary of cracks in the middle or near the bottom of the basemat is included.
Table 3 presents a summary of cracks beneath the RC3. These cracks are i oriented mainly in the E-W direction. -
4.1.1 Depth '
East-West Cracks Outside RCB The depth of the top cracks varies depending on the locations of the cracks. Generally, individual cracks do not extend intc the bottom region of reinforcing steel located approximately ten (10) feet depth from the top surface.
i The neutral axis for positive bending (tension at top surface of the beseest) is c=1-1=ced to be approrfestely 10'-6 from the top surface.
l The total basemat thickness is 12'-0.
The bottom cracks are found scatly in the vicinity of the east-west I
centerline of the RC3 and their depths range from 2 to 3 feet, seasured from the bottom of the basemat. Within this area a possible local interconnection between top and bottom cracks is indicated for Cracks J
, and Ke.
I 3
fl
.~
4.l.1 D oth (Cont'd)
I
. j East-West Cracks outside RCB (Cont'd)
The middle cracks are randomly distributsd. In general, they are not interconnected with top or bottom cracks.. . i
- Cracks Beneath the ECB !
l The interpretation of the crack depths beneath the ECB reflects the l
[ difficulties of extwi== the NUT technique to such long distances. '
Differing interpretations have identified these cracks as being noncontinuous and variable in depth, and also as being continuous and rather continuously extending to near the bottom of the basemat.
Dissonal Cracks (Northeast / Southwest and Northwest / Southeast)
The depth of these cracks, which in plan view run diagonally to the ,
)
i plant grid,'is generally less than six (6) feet. A few bottom and middle cracks are present, however, there are no indications of interconnection between the top ar.d bottom cracks.
4.1.2 Inclination All cracks in the baseast evaluated by NUr are essentially vertical.
In Page 2, of the Muenow and Associates, Inc. report it is stated that "there is no evidence of diagonal (shear) cracks; either occurring l
singularly or as a connection between two individual cracks within the I
areas investigated."
4.1.3 Length The cracks are variable in their length. The east-west cracks outside the ECB extend between the exterior wall of the RCB and the wet cooling tower walls. In the one case where visible and accessible for NDT examination, family VI cracks U, Y, X, the cracks extend to the area of the external walls of the NPIS. The diagonal cracks extend from the 4
- - _ - - - -)
.. 4.1.3 Lenath (Cont'd) exterior wall of the RC3 but end well before they reach the exterior
, wall of the NPIS. Whei the cracks intersect with a construction joint they so through the construction joint. It appears that there are 6 cracks that extend from the east to the west side of the. NPIS basemat since many'of the individual families located in three areas.(east, west and beneath the RCB) coincide and are probably joined.
4.1.4 Specina The east-west crack families have an average spacing of approximately 11'-0. The diagonal (north-east / southwest or northwest / southeast) crack families have an average spacing of approximately 15'-0 at the exterior wall of the RC3.
4.1.5 Width
~
The NDI evaluation has estimated the crack width to be less than
.007 in. and all the cracks are tight. Our recent field surface .-
measurement of crack L. done coincidentally with NDT examinations found ,
, the nazimum crack width to be .003 in. The crack was observed to be ,
filled with laitance and there was no actual open crack. Our field surface measurements in 1977 found the crack widths beneath the RCE to be between .002 and .005 in. Cracks of this width are commonly referred to as " hairline" cracks. Field Lassurements were made using a Bausch & Loeb optical comparator.
4.1.6 Evaluation of Confidence in NDT Results j As a result of a consideration of the techniques used in performing the NUT esamination of the baseast cracks and the procedures utilized in evaluating the dats derived from the NUI with respect to confidence in the accuracy of the reported crack information we cosclude:
l 1. Outside RC3 The ability to work close to the surface crack indication leads to a high confidence level in the location and orientation of the !
l 5
.-. _ _ . _ _ .. _ . _ _ _ _ _ _ _ - ~ . _ _ _ _ _ . . _ - - - - - - - - - - - . - - - I
.. - 4.1.'6 Evaluation af Confidence in NDT Resultn Cent'd) tested cracks. A somewhat lower, but still high, confidence level is associated with the location of the bottom of the cracks and a slightly lower confidence in the crack width seasurements.
'a. Location and'crientation of Crack The location and orientation of the cracks is dependent upon
{
the accuracy of the location of the transcucer and the accuracy and precision of the measurement of time. Since both of these i can be, and were, closely controlled and not subject to great variation or subjective interpretation there is high confidence that the location and orientation of the cracks are as defined by the NDT.
- b. Depth of Cracks Due to the divergence of the sound waves used in the testing, a precision of 1 ft in the location of the bottom of the cracks is recognized by Muenow(1} . This, since the cracks generally ettend dawn from the top of the sat, leads to a conclusion that the actual bottom of the crack can be as auch as one foot above -
the bottaa as defined in the Muenow Report, where the latter is defined at the center of the diversing cone. Therefore, the depth of the cracks outsi'de the RCB are no deeper than and could be as much as one foot less than the values reported by Muenow.
- c. Width of Crack The measurement of crack width is not an exact seasurement according to the Nuenow report, but is an estimate only.
Muenow assigns an accuracy of 20% to the value he reports (I 7 ails), which essentially means he is reporting the cracks (1) Muenow Report, p. 16 o
6
4.1.6 Evaluation af Crafidenen in NDT Reruits Cent'd)
- c. Width cf Crack (Cont'd) to be less than 8-1/2 mils. This together with the independent
, measurement of the surface crack width of 3 mils gives confidence that the cracks are all quite narrow (on the order of 5 mils).
- 2. Beneath RCB The technique used beneath the RCB involving greater distances from transducer to crack and requiring several reflections from the top and bottom of the sat results in a lower confidence level for some of the results derived therefrom.
- a. Location and Orientation of Cracks l
The location and orientation of cracks using a 60* transducer - '
and several reflections from the mat top and bottom is dependent upon the accuracy of the location of the transducer sad the measurement of time. Since these were closely controlled, the confidence in the NDT defined location and orientation is high.
- b. Depth of Crack The confidence level in the validity of the data defining the depth of cracks beneath the RCB is substantially below that for
, the cracks outside the RCB. There appears to be a large measure of subjective analysis and intuition injected into the
( interpretation of the raw data to deternine the crack depth.
i I
l 7 l l
+
6.1.6 Evalu.siton of C afidenca in NDT R9sulto Crnt'd) l
- 2. Beneath RCB (Cont'd)
- b. Depth of Crack (Cont'd) ,
'As with the 45' transducer data, the divergence of th'e sound waves causes a diminishing of the precision of the data. ,A i 2 to 2-1/2 ft precision is quoted by Muenow which any be enhanced by interpretation of frequency content and amplitude.
The precision quoted is open to question and the nature of the a=haarements is not clearly defined. While such r,finements are theoretically possible, they are not demonstrated, and hence must be discounted, resulting in less confidence in the accuracy of the depth of cracks as reported is valid. This
' lack of confidence renders uncertain whether tr cracks are traly as deep as reported.
However, for reasons cited earlier, whatever the uncertainty regarding interpretation of the crack depths, the cracks are ~
never deeper than reported.
j In summary, the location and orientation of the cracks, which are the aspects of greatest significance, are known with a high degree of confidence. The width and depth, which are of lesser significance, are known with a lesser confidence.
4.1.7 Crack Model for Evaluation As a result of this evaluation of the confidence in the reported NDT tasting and evaluation, the following model of the basemat cracks can be drawn 8
r
^ ^ - - - - - - - - - - - - - - - - ----
, ~6.1.7) Crack Mod d far Evaluatien (Cont'd) -
The basemat cracks cre vertical, er nearly so, and &cner:117 extend down from the top of the sat at locations where there are top surface indications of a crack. 'This orients them generally in an east-west direction.- They appear to extend in mariy cases almost completely across the ant. They extend down a variable depth', in some cases to the region of the bottom reinforcing steel. The actual depth of the cracks is questionable along auch of the length beneath the RCS, and I hence an assumption for conservatism will be made, in the evaluation of I their significance, that they extend from the top to the bottom of the mat. It is cautioned that this simplifying conservative assumption is demonstrably not the case for a significant portion of each crack and such assumption is ande simply for purposes of ease of evaluation. The crack widths are quite narrow, on the order of 5 mils, and, by visual observation at the top of the sat, filled with a laitance material and not open.
4.2 CRACKS IN RCS WALL -
Four hairline cracks on the exterior surface of the RC3 wall near the
$ basemat (Elev -35.O' ft) were evaluated using NDT. All of them were
. found to penetrate less than one (1) ft of the 10 f t wall thickness (Table 4).
5.0 PROBABLE CAUSES OF CRACKS l The causes of the top cracks were evaluated in 1977 and 1983 (Reference 1) and the conclusion was that they were mainly due to flasure of the baseest from initial loading (prior to the completion of superstructure). The NDT evaluation has determined th'at all of the top cracks are vertical, extremely narrow and do not generally extend below the neutral axis.
Although the predominant cause of cracks has been concluded to be flexure, other factors such as thermal and/or shrinkage strains probably contributed to their development. Also, the early placement of the lower portion of the RCB ring wall apparently influenced the 9
l f
... . . _ .. . . ,,c emw - ,
~
,- . cracking crientation as cvidenced by tha raJ:.a1 natura of the most northerly and southerly cracks.
5.1 CIACK FATTEtN r -
From the summary of' NUT results, it is clear that the top cracks are L
greater in number than the bottom cracks. This reflects that the crack pattern generally followed the basemat flexure, which was found to be predominantly convez shape throughout the construction stages. The top cracks are located primarily in an east-west band centered on the RC8 l centerline. This matches closely the area of ==w h = convex flexure of the basemat in the early stages of construction as shown on Figure 2.
i The causes for the convas flezure of the beseest during construction were the sequence of construction of the baseast blocks for the basemat sad the different rates of settlement of the foundation soil beneath each placement block. While the soil beneath che entire basemat is -
uniform, the loading imposed upon it was placed in segments at I
, different times (each placement block being a loading sessent). Thus, --
- the soil beneath each placement block followed the same time-consolidation curve but at a different location on the curve because of '
the different placing times. As a result, the differential settlement between the isst block placed and the first placed was greater than that between those placed earlier and the first. This caused a convex shape to the nat with the earliest blocks placed, at the center of the RC3, being at the top of the convez shape (see Fig. 2). The present convexity is very small being 2-1/2 inches over 380 feet. To prevent 4
any excessive or eccentric differential settlement of the basemat, engineering controls on the placement seguence of the superstructure i
were utilized. This assured nearly usiform superstructure dead loading on the sat at all times during construction.
e 10 fl
, a.u rausamu. cause.s un cxAuw wone c; 5.2 GACK WIDTH AND DEPTH The present crack widths are won within the anowable crack width of the ACI Codes. Section 1508.6, ACI 318-63 Code for control of cracking states that "....the avarage crack width at service load at the coecrete' surface of extreme tension edge, does not exceed 0.010 in, for exterior members..." Section 10.6.4, ACI 318-83 code Commentary for control of flazure cracking states that "...for interior and exterior exposure respectively, ... limiting crack widths of 0.016 and 0.013 in."
l
'!he NDT awa=4amtion performed at service load conditions has established the estimated crack width to be less than .007 in. and the l i
actual field measurements of crack "L" less than .003 in. When the '
basemat cracks were first observed under the RCB in mid-1977, the crack widths were observed to be between .002 and .005 in. The tensile stress in the top reinforcing steel which would correspond to these observed crack widths (approximately .005 in.) is sman, on the order -
of u kai, wen within the nuovable design limits (Appendix 1). The design yield strength of the reinforcing steel is 60 kai. '
In Reference 1 it was stated that "...The sat, as are an other '
reinforced concrete structures, is designed to carry loads and in so doing depends only on the compressive and shear strengths of concrete and the tensile strength of reinforcing steel. No credit is taken in the design for the tensile strength of concrete, . ..... Thus, as
- loading on the foundation met causes flexure and resultant tension of i
i the concrete, cracks are expected to form. This. cracking enables transfer of the tensile load from the concrete to the embedded l reinforcing steel as contemplated in the design of all steel reinforced concrete structures."
The positive and negative bending capacities of the sat are in no way I
diminished by the presence of the flexural cracks which are essentially
! vertical and which are of very modest width. Neither are the bending I
capacities in any way diminished by the depth of cracks, even if the cracks are assumed to extend completely thr.ush the sat thickness.
u r
l . 5.0 ' PROBABLE CAUSES OF CRACKS (Cont'd)
A sing 13 cyplication of band m moment sufficient to crack tha mat from .
the top surface down and to the small observed crack width would not of itself, produce as deep a crack as has been observed. Mechanises exist,. however, which in~ combi' n a.: ion with flexural. strains, can produce ,
deep, narrow cracks. One such mechanisa is the combination of flexural and thermal strains. The mat, a placement of concrete of substantial volume, will experience considerable temperature increase in the middle due to hydration of cement followed by cooldown over a lengthy period of time. This thermal cycle can result in substantial (on the order of
, several hundred psi) concrete tensile stresses in the middle and ,
1 compression stresses at the top and bottoa. These stresses in combination with flexural stresses can create a narrow crack extending to substantial depth.
During the early stages of construction the sat experienced time-varying relative displacements; i.e., time-varying flazural curvatures. As shown by Figure 2, flexural curvature of the sense that
'is associated with tensile strain at the top of the est was of a larger .
l angnitude at an earlier time than when the cracks were first observed and measured. Corresponding to these earlier larger sat curvatures, ,
there may have been larger crack widths than have been seasured at any time since the cracks were first discovered. Presently observed crack depths any reflect these possible earlier crack widths. As construction continued, the mat relative deflections changed, decreasing the curvature and tending to close the cracks.
If, as reasoned above, crack widths at the top of the sat were larger at an earlier time, present crack widths serve only to indicate the nazimum possible value of the present rebar tensile stress. If earlier crack width and associated rebar tensile stresses were substantially larger, and particularly if any rebar tensile yield strain was experienced. the present actual tensile stress must be less than implied by the present modest crack width and as estimated in Appendiz 1.
l 12
^ - - - ~~ ^
x m m i .u i ai s u m G onc a>
~ ^ ~ - - ^ ~ - - " ~ ~ ~ ^^ ^~
's.V There is no relichio $ suo far d .tcraining what actual ==*4=== valuen of crack widths and associated rebar strain may have occurred during
- early stages of the met construction. Different mechanisms have been identified which could account for the presently observed very modest crack widths together with substantial crack depths. A mechanise ;
. involving thermal strains can explain the presently observed condition !
without postulating earlier crack widths wider than at present. The other mechanism involves only flazure and postulates larger crack I widths at an earlier time in the construction sequence. The actus1 sequence of events probably involves both of these mechanisms but the stress / strain conditic.as during construction are of no consequence to the safety of the structure in its comp 1sted state.
I The validity of the construction process,. including the sat '
displacement monitoring program, is evidenced by the completed
- structure not by crack widths and associated reber stresses during the early construction stages. The earlier conditions are not relevant to -
the structural integrity of the completed structure, bat they serve to f
explain, qualitatively, the depth of cracking. ~
5.3 WALI CIACKS *
, The cracks in RCB walls are found to be superficial by NDI and, therefore, appear to be caused by shrinkage. These cracks are '
apparently not related to adjacent basemat cracks, which were caused by i mat flazure.
l 6.0 SIGNIFICANCE OF CIACKS AND EFFECTS ON STRUCTURAL INTEGRITY The following conclusions are of importance in the determination of the significance of the cracks in the Waterford 3 basemat and their effect upon the structural integrity of the basemat:
- 1. The cracks are flerural cracks probably influenced in some cases with thermal strains. The consistent vertical orientation of the
. cracks is the evidence of this.
h 5 13 4
-.__. _ _ _ _ _ . _ .. _ _ _ _ _ _.____ _ Q
. 6.0' 'IGNIFICANCE OF CRACKS AND EFFECTS ON STRUCTUR_AL INTEGRITY (Ccat'd)
- 2. There are no inclined cracks within the basemat. This provides
-evidence that no excessive diagonal tension, hence no azcassive shear, exists or has existed within the basemat.
l l
- 3. There are no through cracks from top to bottom of the baseast with the possible exception of a very few localized areas. The cracks -
are primarily extending down from the top surface of the basemat.
- This is evidence that the cracks are primarily the result of
, flasure and that the flexure was of an upward convez nature which agrees with the observed deformations of the baseast during construction.
4, Presently there is virtually no water seepage or wetness present at any of the observed cracks and the amount of water seepage in the past has been minimal causing only a wetness of the basemat in the immediate vicinity of the cracks. The cracks are believed to have
- filled with a laitance derived from the parent concrete asterial.
The general stress condition at the top of the basemat has become compression since the occurrence of the original cracking. This 4
condition will not change during cornal operation, hence, the -
continued =inf ant water seepage condition during the operation of the plant is assured. Therefore, the amount of water seepage presently meets, and will continue to meet, the original design intent for minimal water leakage.
4
- 5. The width of the cracks indicates a low present rebar stress (Appendiz 1).
- 6. The crack pattern is predominantly in an east-west direction (Figure 1), localized in a band running east-west sad centered near i
the RCE centerline. This band is within the region subjected to 14 0
. e
,, .6.h SIGNIFM B CE OF CRACKS AND EFFECTS ON STRUCTURAL INTEGRITY (Cont'd) the most extreme convez curvature during the early stages of
) construction (Figure 2). This evidence indicates that.the cracks resalted from early settlements of the basemat occurring during ylscament or shortly thereafter. The cracks lying in a northeasterly or northwesterly direction were influenced by the rigidity of the early placements of the RCB wall.
!. 7. The cracks in the RCE wall are shallow, shrinkage induced and are not related to the cracks in the basemat. The existence of cracks 4: in the basemat and the wall at the same, or nearly the same, U
f location appears to be coincidence.
33 0
- 8. The concrete quality is uniform and there are no significant voids and/or honeycombs within the mat. This indicates that the concrete
, consolidation was more than adequate during construction. The con. rete strength is indicated to be 5,000 to 7,000 psi by NDr.
,,. which is higher than the required design strength of 4,000 psi and
.w hich is consistent with the strengths seasured during the construction inspections. ,
i FLEXURAL CONSIDERATIONS 4
, s i
4 It is well known'that load-induced tensile stresses result in cracks in concrete aesbers. This point is readily acknowledged and accepted
! 4 in concrete design. Current design' procedures.... use reinforcing
, steel, not only to carry the tensile forces, but to obtain an adequate
' crack distribution and a reasonable limit on crack width."(1)
The cracka in the Waterford 3 foundation >basemat are to be expected f
considerina the flexural situation.. They have no negative effect on the structural integrity or strength of the basemat or on the ability a
z .
e .
(1) Causes, Evaluation, and Repair of Crac'esi in Concrete Structures - ACI 224 ACI Journal - May-June 1984, Paragraph 1.J.9.
F
.. 6.0 SIGNIFICANCE OF CRACKS AND EFFECTS ON STRUCTURAL INTEGRITY (Ccat'd) cf the basemat to resist adequately any d: sign load combinations, nor can they significantly alter the design response of the structure to seismic vibrations. The cracks, being quite narrow and tight, win not increase the flexure of the basemat and hence vi u not cause any '
additionaltransier.ofloadtobuildingmembersthanthatalready
- accounted for is the design.
Reinforced concrete members subjected to flexural loads are designed to accept cr=aH a= of the concrete in the tension zone. The ACI code for design of reinforced concrete structures states that " tensile strength of concrete is to be neglected in flexural calculations,"( and that i
au tensile stresses are to be directed to the steel reinforcing. This is normal concrete cracked section analysis and the concrete must crack !
since it has a low tensile strain at fracture. Therefore, the steel is the structural component in the cracked tension zone.
ifhen reversal of stresses occur and a previously cracked tension zone '
becomes subjected to compressive forces, the cracks close and the adjacent sides of the cracks bear against each ot.her. The concrete' crack surfaces in the 'diu:erford 3 basemat are weh able to bear against ,
each other since they are tight and have been fined with laitance acd under flexural loading the basemat will react the same as a normal concrete cracked section. Therefore, the flexural strength has experienced no degradation for bending in either direction and no significant increase in the flexure of,the basemat win occur.
SHEAR CONSIDERt.TIONS 1
f
'"If a (vertical) plane under consideration is an existing crack or interface, failure usuany involves slippage or relative movement along (2) Suilding Code Requirements for Reinforced Concrete, ACI 318-63, .
Paragraph 1503(e). >
i 16 l
- - - - - . - - - - - - I
. .- :.......c;.. N.-- a .c m.,
~
c.us.s va anknivu, UcrEGRITY iCcac'd)
, , the crack cr plane."( "If an initicily cracked specimen io tectcd, l shear can be transmitted only if lateral confinement or transverse I
steel exists. The irregula'rities of the surfaces of the two sides of the crack ride up on each other and this tends to open the crack and create forces in the transverse steel ...... In a heavily reinforced i_
' shear plane ^or one subjected to a normal compressive stress, the' shear resistance due to friction and dowel action may reach the shear '
corresponding to failure of an initially uncracked specimen having the same characteristics. In such a case the crack locks and the behavior and at th are similar to those for an initially uncracked I section." }
The Waterford basemat vertical cracks are both heavily reinforced and under " compressive stress."(5) In addition they are very narrow, do not extend through the baseest, and are filled with laitance.
Essentially they are " locked." In actuality, they resemble construction joints and respond similarly. -
l The Potential for " Shear Slip" on Mac Crack Planes If vertical shear on the basemat crack planes could produce " shear '
slip" (ie, a step change in vertical deflection across the crack plane), and if such shear slip were large, it would be appropriate to
-(3) The Shear Strength of Reinforced Members - ACI-ASCE 4261-74, ACI Manual of Concrete Fractice, 1983, Part 4, Paragraph 2.2.2. !
i
.(4) Ibid - Paragraph 2.2.2b. I (5)- Review of Waterford 3 Basemat Analysis Structural Analysis Division, Dept. of Nuclear Energy, Brookhaven National Laboratory, July 18, 1984,
- p. 21.
17 0
. 6.0' SIGNIFICANCE OF CRACKS AND EFFECTS ON STRUCTURAL INTEGRI (Cont'd) .
inve:tigate its possible significance to the dynamic response of the structure. For the reascas discussed below there is no basis for believing that slip will occur. ;
I f
Beckaround Renardina Shear Strenath and Shear Slip on Crack Planes I The matter of shear strength along a crack plane, or a potential cr'ack !
plane, has been relevant to reinforced concrete design. This is of interest primarily at the junctions of precast concrete seabers (where large shear forces must be transferred across such planes), in short reinforced concrete (R/C) brackets (where large shear forces sometimes accompanied by tensile forces must be transmitted across such planes),
and in 1/C asebranes subjected to concurrent large shear and tensile forces acting on transverse crack planes. In contrast, for beams and slabs designed to resist internal transverse shear force and bending moments rather than membrane forces, the question of shear strength across potential transverse crack planes normally does not arise.
Also, the evaluation of shear resistance across these planes is not normally a part of the design process. This is true even though transverse (flexural) cracks can develop in beams and slabs, ,
particularly when there are bending soment reversals. It may be noted that provisions for shear reinforcement focus on inclined crack planes. The requirements for such reinforcement any be satisfied by transverse bars (which do not cross any potential transverse crack) and such a reinforcing pattern is acceptable for very substantial magnitudes of transverse shear stress. The validity of this practice for conventional besas and slabs reflects (a) the absence of large '
tension forces on actual or potential crack planes, which could imply large crack widths; and (b) the great shear strength and slip !
I resistance along a crack plane if the crack is closed (or of small initial width), and if " clasping" (compression) force of adequate 18 rz
1 l
l , , magnitud3 is cvailabic. This compre:sion farca any be providad eith r
! by the compression component of a bending soment acting on the section, l by tension (flexural) steel crossing the section, by both, or by an externally applied compressioc force.
Much of the present understanding of shear strength and slip on crack planes was developed by research studies stimulated by the design of 1
, R/C containment shells for nuclear power plants. Such shells are subjected to very large membrane forces (i.e., large tension and shear forces) acting on transverse crack planes. The tensile forces can cause cracks of substantial width, and both shear strength and shear slip are matters of design interest. This is a very different l
condition than exists in the Waterford 3 basemat, but some of the results of the research on the membrane problem are relevant to this discussion of the basemat. In particular, we refer to a report of tests conducted at Cornell University (Reference 3), which for crack planes with initial crack widths of 0.01 in., and subjected to cycles
~
~
of shear stress reversals of about + 180 pai, demonstrated the following results:
- 1) clasping forces developed in the bars that were used to restrain ,
crack width growth did not exceed 20 percent of the applied shear !
force; and
, l
- 2) total slip, after 25 cycles of shaar reversal, did not exceed 0.01 in.
l It should be noted that the clamping forces developed here were from reinforcing steel responding to the shear slip displacement, an active )
clasping force only present when slip occurs.
i l
Baseast Strength and Slip Resistance on Cesek Plaaes The cracks in the basemat are predominantly east-west oriented, and are everywhere less than 0.01 inch in width. Of major impo cance is the 19 f
... - e . . . . . . . .a . a c..J..~ ~a.. ., dre-ws - alw 6 6 1me. A Ai (O~e nc Q~)
e l
fc:t that tha crack planeo cre ll2.t, t subjected to any tenzile farco. ;
Indeed there is a very . substantial compression force (exerted by soil I and water pressure on the north and south boundaries of the mat and the ,
unlis above), which is conservatively neglected for purposes of computing shaar strength on the crack plane. With regard to its j influence on slip, the effect of this compression force, conservatively '
ignored for strength, is particularly relevant and will be accounted for. Any north-south banding soment, whether positive or negative, which may be acting on the crack plane does not diminish the shear strength of the crack plane. Sending soment which causes tension force in the bottom rebars aust cause an equal and opposite compression force in the top few feet of the section. Similarly, bending soment which causes tension force in the top rebars must cause an equal and opposite compression force in the bottom few feet of the section. Thus, diminished resistance in the botton (or top) is offset by an enhanced resistance in the top (or bottom).
In the regions of interest the top rebers are ill 6 6", i.e., 3.12 2
in /ft, and the minimum bottom rebars are ill G 6" + #11 6 12", i.e., --
4.68 in /ft.' Over a representative crack plane length (50 ft) the maximum total shear forces on any crack plane are found at either end '
of the East-West running cracks. The maximum total shear forces on these 50 ft representative lengths correspond to the following values:
Total Unit Leadina Condition Shear Force Shear Force 1.5 x Gravity Load 42 K/ft 27 psi 1.1 x E-W EQ* 96 K/ft 61 psi
-1.1 x Vert EQ 5 K/ft 3 pai 1.1 (Vert EQ + E-W EQ) 101 K/ft 64 pai 1.5 Gravity + 1.1 (Vert EQ + E-W EQ) 143 K/ft 91 psi
- N-S EQ (earthquake) gives smaller shear forces.
l l
l 20 l J
f
. - < - e , , - - - - -
w-.. - . . , - - , . - , . , - - , , - .---en,----..,.,_------a . . , , , , , ---- ~ . - - - - - - - - ~ - - - - - - - - - -
6*.0 SIGNIFICANCE OF CRACKS AND EFFECTS 04 STRUCTUR/* IN EGRITY (Cont'd)'
It should be noted that averaging of forces over a 50 ft crack length !
is very conservative since this is only about 4 times the sat thickness. The average shear forces'would decrease rapidly vith !
increase in the crack' length considered. It also should be noted that the corresponding shear forces on any other 50 f t length of any o': hor cracks are less than the values tabulated above. !
Shear Capacities Using shear provisions of Section 11.7.4, ACI-1983, shear strength of the entire section is given by:
Y=
- V, = 4 A,g fy a where V = available shear strength at section -
- = strength reduction factor = 0.8S V, = nominal shear strength A,g = area of shear-friction reinforcement .
f y = specified yield strength of reinforcement = 60 kai
- = coefficient of friction = 1.4 A A
= correction factor related to unit weight of concrete = 1.0 therefore, V = 0.85 (3.12 + 4.68) 60 x 1.4 x 1.0 = 556.9 K/ft I
which corresponds to na average unit shear strength of:
y = 556.900 = 352 psi 12x11x12
{
1 Recause the rebars are concentrated near the top and bottom of the section, rather than distributed throughout the depth of the section we conservatively reduce the above shear capacity by 50 percent, i.e., to 278 K/ft. This is 1.9 times the 143 K/f t shear demand.
6.0
,, SIGNIFICANCE OF CRACKS AND EFFECTS OU STRUCTURAL INTEGRITY (Cent'd) i It 10 c10cr that tha shear strength alens th3 cr:ck picna, even ignoring the inescapable active compression force, is such in excess of l the demand. '
Slip Resistance t
As reported in Reference 3, for an initial crack vidth of 0.01 inches, and cycles of shear stress reversal to 180 psi a slip of about 0.004 in. was developed at the end of tne first cycle increasing to 0.01 in. '
after 25 cycles. Moreover the nazimum clasping force developed during this cycling was only 20 percent of the applied shear force. In the sat we are interested in an applied shear stress of 91 psi, for which a 20 percent clamping force would be 18 pai.
The compression acting on the cracked section, due to horizontal soil and water pressure on the sat and walls, is 50 psi. Based on the finite =1===nt model, this compression exists in all areas of the -
basemat during earthquake loading conditions with the small exception
, of a very narrow band immediately adjacent to the north and south wal.1.s. It is not credible that this compression stress, reduced as may be reasonable for the effect of an earthquake, would not still be substantially in excess of 18 pai. This means that more than the !
required clamping pressure of 18 psi is available from the outset i.e., no robar tension is required to provide the required clamping force. Since, the clamping force is a passive force, the friction resulting from it is available without shear slip and is a static friction.
O l
i I
l 22 1
e
____ ------ -- k
..o; 7. ;.. < . m.h v c muu eu
. er:.uis va sini t.tuRAL LyrEGurY (ccat'd) {
Th3 conclusica that 10 drawn that the chear r:ciatanck cero:s the cr:ck is a state of static friction wherein the available static friction must be overcome prior to the occurance of any shear slip. Since the l available friction is s't least equal.to and undoubtedly for.in excess l
. .of"the applied shear stress we conclude that the shear-resistance would develop without any significant slip. Therefore, there is no change in the rigidity of the sat and no effect upon the dynamic response of. the basemat to the earthquake.
7.0 CONCLUSION
Considering each of the above items individually and in concert, we conclude that the cracks in the Waterford 3 baseast, as defined by the nondsatructive testing, have no adverse influence on the structural
, integrity of the basemat. It is fully capable of functioning as required by the design in accordance with the pertinent codes.
M S
4 O
l 23
, _ _ . . . _ _ , _ _ _ . . _ . - - - _ _ - - . - - - - - - - - - - - - - 0
~~
, ii.:r sNCEs ,
. 1. Affidavit cf Jcseph L Ehasa, Ebarco 5:Wicco .~.acarporated, cubmittcd before the Atomic Safety and Licensing Appeal Board, USNRC, September 1983.
- 2. _"NPIS Wall Hairline Crack Evaluation," by Ebasco Services Incorporated, April 1984.
- 3. J P Laible,1 N White, and P Gergely, " Experimental Investigation of Seismic Shear Transfer Across Cracks in Concrete Nuclear Containment Yessels," ACI SP S3-3, Reinforced Concrete Structures in Seismic Zones, 1977.
M e
+-
l l
l
)
1 24 l
l 1
- . . . ~ . . ._. .-_ .._... _ , _ . _ . . - . . , _ _ _ . . _ . . _ _ _ . . _ . _ _ _ _ . _ . _____._ _ ___
TJJ6LE 1 - SUHHARY CF CAACKS WEST SIDE OF RCB -
I Tep Crrck Pr senes af Subsurfacn Cercko (Se7 Notom)
. Botton Crack Middle Cr&ck Test Length Depth (ft.) Family 8elow Through _.
Family Crack I.D. Lines (exposed) Specina Botton Re-bar Botton Re-bar in His Max Average
- 1 A 7 7'- 6 1 2 2
- e a g a 7 9'- 0 2 3 3 * * *
- C 12 16'- 6 1 3 2 * *
- v
+10' * *
- v i.
- II D 5 6'- 0 2 5 4
- een a v:
E 1 2'- 0 3 3 3 e e se g:
F 6 9'- 0 4 10 3 en te .
- g C 4 6'- 0 1 5 4 e e a ,
116' 1
III 1 4 5'- 0 7 10 8 ** **
- v-
! H 6 9'- 0 5 10 8 ** **
- v; j J 20 28'- 0 3 12 9 een eene en ,
i K 10 13'- 0 3 11 8 ** *ee a ,
110' i
IV L 10 28'- 0 6 10 8 ** **
- v.
i +8' 1
1
.i i
i i Notes *None j ** Presence of crack is not probable since only at one or two test line location (s).
- n** Presence of crack is probable since indication at several test locations but not interconnected with top cra
.; ****Sintlar to *** except probably interconnected with top crack.
l (sh'ect1of2)
TABLE 1 -
SUMMARY
OF CRI.CKS WEST StDE CF RCS (Colt'd)
Top Crack Persemen af Subshrfacn cercko (Sea Not20)
- 4 . Botton Crack Middle Crack .
Test Length Depth (f t.) Family Below Through .
F=t ly Crack I.D. Lines (exposed) Spacing Botton Re-bar Botton Re-bar Inclinati Min Max Average
- 1 a vertical.
V H 4 6'- 0 4 5 4 e a a vertical' N 3 5'- 0 2 6 3 2 3 5'- 0 1 3 2 e a a ve rtical 8 *
- vertical.
3' 9 12'- 0 1 5 2
, * **
- vertical P 9 14'- 0 8 10 9
- e a
- vertical
. R 1 2'- 0 2 2 2
- *
- vertical Q 3 8'- 0 3 5 4 i e a e vertical S 3 4'- 0 4 4 4 e ama
- vertical; T 14 20'- 0 3 10 6 e a
- vertical; Y 3 6'- 0 1 1 1 t
+ 6' 9 14'- 0 2 10 5 * **
- ve rt icali l v1 U e a a .srtical i V. 5 13'- 0 2 5 *3 .
- *
- v rtical.
i X 22 25'- 0(+) 1 5 3 VII West piagonal 19 27'- 0 1 4 3 as a**
- verticatl
[
N tes: *None l
- Presence of crack is not probable since only at one.or two test line location (s). ,
I *** Presence of crack is probable since indication at several test locations but not interconnected with top crack.
- asimilar to *** except probably interconnected with top crack.
l i
'i (Sheet 2 of 2)
- 8
TABLE 2 - St49ERY CF CRACKS EAST SIDE CF RCS -
- Tap Crrck Pr seacq af Subsurfaca Crrcko (Sen Notbn)
Botton Crack Middle Crack .
Test Length Depth (ft.) Family Below Through .
! Family Crack I.D. Lines (exposed) Spacing Botton Re-bar Botton Re-bar I n.
! Min Has Average
. Aa 4 6'- 0 1 1 1 e e e v.
le .Be-Ce 5 6'- 0 1 4 3 * *
- vi De 2 4'- 9 1 1 1 * *
- v. i le 2 3'- 0 3 3 3 * *
- v; 110' I
IIe Ee 4 4'- 6 1 1 1 e e a y, Fe 8 12'- 0 2 10 6
- een e y, t
i
+13' i IIIe He 5 6'- 0 2 '3 2 ** * ** v..
- Je 5 7'- 0 2 4 3 see a se y, Le 8 13'- 0 3 12 7 een ne a y, i
i 111'
- IVe Ke 15 26' .O ~ 4 12 8 ee name a y,;
il 116'
- Del 3 4'- 0 1 1 1 *
- e ve-Ve De3 15- 23'- 0 1 6 3- e e e ,, l l
De4 5 10'- 0 1 1 1 e a me ye, l
l 115' l
Notes *None
- Presence of crack is not probabit since only at one or two test line location (s).
! *** Pres nce of crack in probable since indicqtion let several test locations but not interconnected with top cra l ****Sintlar to *** except probably interconnected with top crack.
op n k s c i...
TABLE 2 -
SUMMARY
OF CRACKS EAST SIDE CF RCB (Colt'd) . ,
T;ep Crack Pr-senen of Sybaurfaco Crock 6 kSea Notan)
Botton Crack Middle Crack Test Length Depth (ft.) Family Below Through ..
Family Crack I.D. Lines (exposed) Spacing Botton Re-bar Botton Re-bar Inc Min Has Average '
vie De5 17 24'-0 1 10 3 een a ese ye.
De6 5 7'-3 2 6 4 e* a e ve,
+ 15' De7 9 12'- 0 1 6 3 e na ese y,-
VIIe De8 8 10'- 0 1 3 2 e ese ese ,,
De9 11 15'- 0 1 5 2 en a one ye.
\
Notes *None eePresence of crack te not probable since only at one or two Esat line location (s).
e** Presence of crack ta probable af ac.e indication at several test locations but not interconnected with top cra
- Similar to *** except probably interconnected with top crack.
, (Skeet 2of2)
)
TABLE 3 -
SUMMARY
CF CRACKS BENEATH RCB Correlation. Spacing -
Crack I.D. with 1977 Mapping Depth Inclination 0 C.L. RCB -
None 6 (Note 1) Variable Vertical 18' None
" =
2 (Note 1) 12' .
.1 Yes
- 9 7 Partial 6'
3 Yes 9'
5 Partial 13' 4 Yes Average Spacing = 11' N:te 1 - This crack was not identified during 1977 mapping of cracke beneatle RCB.
(Sheet l'of 1)
K-_--
TABLE 4 -'
SUMMARY
CP CRACKS IN RCB WALLS .
Cerck I.D. Ta-t Litm Maximum Dept cf Panetrntion (ft.) Irelinatita Remarks.
RCs 1 3 1 Perpendicular . Wall thickness .= 10
. to wall surface RCB 2 3 1 Perpendicular Wall thicknesi = 10i to wall surface ,
RCB 3 3 1 Perpendicular ' Wall thickness = 10; to wall surface .
MCB 4 3 1 Perpendicular Wall thicknesa = 10' to wall surface i
(Sheet 1 of 1)
APPENDIX 1 REINFORCING STEEL STRESS AS DEFINED BY CPACK WIDTH Gergely & Lutz Eq'uation ("Causes, Evaluation and Repair of Cracks in Concrete," AC1 224 AC1 Journal May-June 1984, p. 218). .
3
~
w a 0.076 A dA y z 10 f,
Ay = 6 x 8.5 = $1 in d = 10.5 = 1.04 10.125 d
e
= 4.25 in w = 5 mils (crack width) ,
4 f, = 10,500 psi = 10.5 kai -
i i
(Sheet 1 of 1) c
W I
. i 32 s=
. . . . - 3 gl 9
o i n a.
at 1
, . i Ij.
~ ,
.,i . ,, .
i .
.. i. -
i
- i. _
- e. i.
O,
[ i. iej
.I ._
m,
._ .i. . ,,
._.,,.. 7., -. _ _.._ , .
l //
- j
. i ,. ,
L
- . . .. i <, , -
a u .: , ,:
.p,.
~.
-4 ,
. "~~- .w- i,
. . . ,r~, , m . +
.. .s. . - , a
.c..
c.
. h:4 i .: -
c i , ,
y .4, -. n g~
- -5 &. .,
1 .- 'I
&fe a F1
/ '
i, i .j a i : rf:.V- t9-
< .. ,i3. n,.r,e
/5 i:
~d i:),
t I lb c,d b l@ .I s ./ -
i I , T i,3 cm.r l.
r i ,., -y a i..
s
,e .,* . a. . , 3 j --
s .. . . .- - - - -
i s, 1, .
.ii 1,._e
- l.. i, i uj I
. i
,. @ - 3 I
I j # I *.~I' 4 I Id **.
.,3.....--.g 4
. _ - . -. . _ _ _. - _q - -
, r. M.: , +
J r.] 3 p %,.-' ..-
,. ; ! i,:' g,,i,i .i
~c-
_.__ ..v: p _==
e ,. 3 i s 5t
- l3>,i
- i L
2-.
2 l i :q
. ?. n' .
,.i%:. J ,i. 1._,i ,
a, Q- .
. _ ,.,l 7. .
u
,o s v,. i_ .
- u._ s-,- .-- ..
.i r; -t o T'-
-3 3.... .. . _
' : 1 -+,
= i ,, f,' g.[ g s
x
.. 1r,--,< p. !,r_tt.v.":: .. . . w,:e =>
\ ;+ . . _ ,. . ...g -
- I ,
t .
c- r E S 3 @a 32 *g
- y
. ; j e e
..s .
N l.' *,.s
.,s A or: ik . .
. .: 1
. t .c- , !
i.1 g l;.,2. T I - b h.._ h.
.'*s)." = .
2- l t- - - - - -
v.
- ! ! , !; ' ,. 5
. !l ;
I ef*
- f o .
4+
- Ii
, 7A e e f ;. e ,jt -)
t a. ~ i. .
.2-il j -
i
- 4.L.:.
!i i t i I
- 'th.l-?H ,
,; ,L
- - _ . _ _ _ _ _ _ . _--r.___. .
.w. - ..
. ,,,n,--. .,
o .
g maa r [k.Eo
- 5. a . s
! 13-C 2
? N -
! E ig E@#
.' 8 1 l n f i
, { $ REACTOR BUILDING i .>-
1 2 -
- 8.0 i # ,.[
p 1.0 " ~ ~ ~ ~ ~
JUN.~ '78
- Q'% ' '~
N . .
l' g q poa.4 ArR. 7s -
= - 2.0 4 e i 8
- u- 3.0
- a '
i < &
O 380'4 l
1 h
m i
N S CROSS-SECTION OF BASEMAT t I
\
1 NOTES:
l VERTICAL EMAGGERATSON = 300 DIFFERENTIAL SETTLEMENT IS FROM DAY OF PLACING AND 8NCLUDES SETTLEMENTS AT VERY EARLY AGES OF EACH CONCRETE PLACEMENT l
l s
J N y Z
" ,1 the extruded cimeret). The ma- 20 percent of the force from the C A D TD A I NI\ I I\N CCCD l JI Li\ I '
chine is unlocked from the strand other end w'as lost due to friction.
The adjacent lane is also done and at c joint and locked on to strands ct the beginning of the next slab.- the jacks moved to start on a new ! RE'INFORCED CONCRETE- .
AKH 6
- 8. Tiehars are ' depressed into the slab.
c<merete with a wheel type device 11. With the stressing completed, the - i and a plastic parting strip in. 24 ft. kmg angle is removed. A stalled . to form a longitudinal second 1-beam 6 in. high is fitted jcint. After the finishing machine into place adjacent to the one al- Alan H.' Mattock
~
uninnity or wnhingian passes, metal caps are placed on ready there and ' connected via 8"" ""hi"8'*"
the top of the 1-beam and the an- dowels. Extension rods are con- .
gle to build them up to the 6 in, nected to the strand chucks which Neil M. Hawkins are exposed on the oppasite side uninnity or wnh;ngion pavement thickness. The adjacent 5"" *"hi"8'*"
concrete is hand finished and where the angle used to be. The curing applied. 3-ft. length of blockout is then ~
concreted and after it gains ade-
- 9. The concrete is then allowed to ,
gain strength. If the pavement is quate strength is post-tensioned Shotos how concrete strength, shear planc espected to shrink or contract it against the main slab with torque nuts on the ends of the extension characteristics, reinforcensent, antl glirect stress may be necessary to apply more than one step of post. tensioning rods. a[cci the shear transfer strength of reinforce ($
to prevent tensile cracks imm oc. 12. After the bhickouts are filled and concrete. Fun (laincntal behaolor of test specimens curring. If the concrete remains at post tensioned only one small ggg/g7 foa([ Is reporic([, an($ bij polbCses to cXp[ain ibc close to its placement temperature opening between the two I-heams gc7ido or arc (7coc 7 pet . lt a.s conchulc(l f hat for several days it is possible to is all that remains to accommo-date length changes of the slabs. shear-friction proolsions of ACl 318-71 gioc a apply full inst tensioning when g consert atioc csfitnate of shear-transfer strength the concrete reaches 3000 psi Foamed.in. place polyurethane is compressive strength (2 to 3 used to fill the opening. k heloto the state (lliinit of 800 psi. A ticsign equation days). Overall a very efilcient operation can 6 to (leticlop higher shear transfer strength
- 10. A gang of four lacks with 10-in. be effected. The two major areas of j is presente(l.
throw is lowered from a mobile concem are getting well consolidated .
cart into the blockouts at the end crmerete at the joints and in determin- l of a slab and a jack is positioned ing the time for teusioning. The ten- e on the end of each strand in one sioning operation is relatively simple ,
lanc. Each strand is then pulled and gwes no pmblems. Filling the gaps to 40 kips. Since this load will with concrete will require some care .
- 4. Direct stresses acting parallel and :n elongate the strand approximately but it shouki he fairly simple since each Test prolrraria transverse to the sl car plane. 8 i 40 in. in a 500 ft. slab, the jacks requires only about 1% cu. yd. of con. Shear transfer acmss a definite plane The influence of the first three fac- h would have to be regripped sev- crete. must fmjuently be considered in the tors has been studied in testsm of mon. O cril times. The gang wouki then Other agencies are encouraged to design of precast cuncrete connee- olithically cast " push-ofi" specimens as he moved to the adjacent lane place additional slahs in order to im, tions"m. A continuing study of the seen in Fig.1(a). *I'ests"* to study the g and that completed. Next the pmvc paving techniques and to de. 8
("et"rs affecting shear transfer strength influence of direct stresses acting paral.
jacks are moved to the other end velop additional design criteria. The is m pmgress at the University of lel and transverse to the shear plane y
of the slab and the strands are FilWA is developing specifications for Washington. Factors so far included in were made on the " pull-ofr* and mmi-pulled just a few inches to bring cimstructing additional sections and de study are as follows: iIied push-off specimens shown in Figs.
that end to full force since about these will be available upon request. ,
- 1. The characteristics of the shear 1(b) and 1(c) respectively. In all cases.
plane the shear transfer reinforcement
- 2. flhe characteristics of the rein- emsses the shear plane at right angics Disrunion of tress paper is incited.
forcement and is securely anchored so that it can Please fortcard sjour discussion to PCI Ileadquarters by July 1 '). T1# "*ne shcoNIs dn. cIop sts yseld strength in temism.
to pernit publication in the July-August 1972 issue of the PCI JOUltNAl 2 - _______________ - _________-____
nine I. Test pn! gram p ~ Shear Transfer P Rollers t Test Specimen Number 1 r Reinforcement i series Description type of tests f- ~1 I i
. ' 1 Push-off tests of initially uncracked A 13 O specimens. Reinforcement size con-g ant, sp cing varies. f',~4000 psi,
.. r. l l
I- - -
' Push-off tests of initially cracked spec- A 6
--(n -fl
. i I s g l 2 imens. Reinforcement size constant,
, , I h ....[
l ,I l spacing' varies. f' ~4000 psi, f, ~50 ksi.
l l ._- l l
. l l
- 3 Push-off tests of initially cracked spec- A 5 l I imens. Reinforcement size varies, U
s acing constant. f',~4'000 psi, f,~50
- - -l- - --- -- --
' ' l l l
\ Shear 8 l l l 4 Pu.h-off tests of initially cracked A 5 specimens. Higher strength reinforce-Pione O Steei ment, f,~66 ksi. Reinforcement size Brackef constant, spacing varies. f',~4000 psi.
5 Push-off tests of initially cracked A 5 P P P specimens. i_ow strength concrete, f;~2500 psi. Reinforcement size con-(a) (b) (c) stant, spacing varies. f,~50 ksi.
g 6 Push-off tests of both initially cracked A 4 Fig. i. Sincar transfer test specimens:(a) gnuslansf; (Is) pullasf;(c) modifini passis-<>f I and uncracked specimens. Dowel ac-g tion destroyed by short rubber sleeves i on reinforcement across shear plane.
[ f;~4000 psi, f,~ 50 kei.
7 P Additional reinforcement is providn! mal stress. The test program is sum- ,
s c ens. Re nfor nt sz an tway from the shear planc, to prevent mariecd in Tahic 1. spacing varies. *f' ~5000 psi, f*~50 ksi.
faihires other than along the shear The specimens were snhjectnl to plane. 'Ihe length and width of the monotonic loailing to failure. In all ,
8 Pull-off tests of initially cracked B 6 shear planes were 10 x 5 in.,12 x 4% cases, slip along the shear ptme was specimens. Reinforcement size and in., and 12 x 6 in. (approx. 25 x 13 cm, meamrni, and in some instances the spacing varies. f;~5000 psi, f,~50 30 x 12 cm, and 30 x 15 cm) in the lateral separati<m at the shcar plane was ,
ksi, push-oII, pull-oII and modifini pmb-off also meamred. Cracks were marked on 9 Modified push-off tests of initially C 6 specimens respectively. When loaded the faces of the specimens as they de. uncracked specimens. Reinforcement concentrically by a force P, the shear velopnl. Detailnl data for Scrk s I to 6 size constant, spacing varies. Angle r<long the shear plane is equal to P in have already been publishedm. The 0 varies (0,15*, 30*, 45*). f',~5500 psi, the pmh-oII and pull-off specimens. In data for Series 7 to 10 are summarized f,=52 ksi.
the modilini pmh-oIT specimens, the in Tahics 2 and 3. l'or ennvenience, the o m<rnt s ic force P puninces a shcar nitimate shear strengths are espn ssed
. 10 Modified push-off tests of . .tially sni C 10 cracked specimens. Reinforcement size fon e P im o along the shcar planc and as average shear stresses o,,, obtaincil .
constant, spacing varies. Angle 0 var-a . ...npu un e n,,. mal fon c r sin a hv ilividing the ultimate shear 7,ir"'
ies (0.15*, 30*, 45*,60* 75*). f' ~4000
- a. . ,w it sh. ar planc. Sa .blin rot V., by the an a of the shcar plane led i and 6000 psi, f,~52 ksi.
values of a ucie mni to give different (<l is the length of the shear plane and -
ratios of shear stress to tramverse vor. la its width).
g(, ..,., , , ., ,. . , , , , , -
57 3
U .
5 7 !"E.! Q E & E E4 0 2 E O nJ #
- .9 e5 =- jf f- Ew
- nsgEs-E 2. g a E..s.E a qa5.1=
2 .g gy sag.a mm t.f "k as o
- s. 2, x-E.e c3 n ...... -- n
.g- .
':Err-ll="]}8.E.553.E,ag s w s.
i e.x = am e R,g = g,;&i
,a [n.
g *b 8 f s. 2 g ;,. *$--
u m '- b b '* L V- k,3-
- n s5 g T. a
-g=g=os .
R.N=n = = g, h I'[h ,E h 82b~~033.32Bj2E,E,b.k~
N iF E- ~
E Y a [ > .5 l
5
-8fE8 Me a8E ET .E IS : a g s Ri =og E -.
.8D2.j,3.2ga.rg a;_ ag. ......
wwwwww wwwwww E5E
- g e
- 5. ;E.MEoR a AEEg a gg ::r . ;;. . g.
- : ["~ T 4 5.. sE :. ! r g' 's.g:E.5'=*
n
,2n- I" *$, "
ea ,o e. e , s.
E s .=o 5.- a g Ei E E: < ,g. B s'
= Ea .R* 2,ag ,,f.,Cs.r . ,a ., E.!
F.= o " E r
~
, e t
o13Es:sa-x. .=..o" g- _
= -.. e. 8 8.= -. s -=a}a:u eEr : ,
~z ao
- - o g- a n a < em g ge
> "' a 5 TE www ww mww ww $ wB
- 'a u* = ct ~=
.k S .% 3 E d 25'532.
e,_2 E 2.. <? x= s.- , ,&= {4 E. E.x5.-. B-
- 3. sE.1 E- s.;E.
- .E S a a I-gw r= go, Eg -
sssigslap5239
-s
- ~
@*R -
a90ss32ga32s'a>EQFIF 7 o 2 9 s E Er,sLBTFG g 5 E lr a g ra p; :o
.o n .- s - -see .- a s. y 53.
E =s' [ g & f m" I f 5 [ EE'5I?
! $ ,s2 ga c. $ [ a$ # E 5. 3! .
- $$$ $EEsst y En k eE" s E. !' - 2 a s=Ee . 666uuu e66uu-w -
[2.oageoR c , =n=g. g$. g- =va4=s1 3 *,
,a5e. 4 . e * =
- 4 u. c. "s' r 5 Ef"
- ~ 5 - g* h R $ gib"3!,3Ishh,5 5, E !: ~'= ' E E -
..((I
.c I
.k e -- ,
- = 3 s 5 5' "'E s " E [
"g. E'E" 28T823 28T828 ,"-'a Ei0 3a E E 3. " rs-H.5E-Es-;c E .C57 " J" i e 83E888 SEEEEE -
E e-
- E. R.e e- i E A6 = m* m n ~ e s :.s -e 5 a.c a =2 a, .m =
r ,a5. s s< e- o. - . , = e. = c. , - =
5-=
a a. a r a. a. a...w M e s, *s .= '5-
=.s.e.-s .,
r, x = a. "' "-
=.
.w-w.sesEE s E ,e,r we~s.E
= . ja = 2.
ilEI!-l'g=1.g,s
=..,. "9,$!.l.e..!..5 N..,.,..... "*3l5 iOii E-
!. E555EE RHHE 11 P .
. Tchte 3. Test data, Series 9 and 10 Reinforcement Concrete
. yield strength, pf, + ex,, v.,
[ Specimen number'"
Angle e, Number of point, f,, f'.
psi pf,,
psi o x,,
psi psi psi Failure type
- g deg. bars
- ksi G 9.1 45 10 52.4 5500 800 2460 3260 2460 S' 9.2 30 12 52.2 - 5500 956 1480 2436 2560 S 9.3 15 12 52.3 3940 976 406 1382 1515 S 9.4 0 12 53.7 3940 985 0 985 1389 S 9.5 30 8 51.0 6440 623 1655 2278 2870 S 9.6 30 4 51.0 6440 312 1600 1912 2770 S 10.1 75 6 51.8 3450 475 3220 3695 862 C 10.2 75 6 52.0 4390 476 3920 43 % 1049 C 10.3 60 8 51.8 3450 632 2780 3412 1610 C 10.4 60 8 53.0 4390 648 3060 3708 1770 C 10.5 45 10 52.7 4630 805 2265 3070 2265 S' 10.6 30 12 52.0 4630 954 1250 2204 2165 S i 10.7 15 12 52.4 4020 962 387 1349 1445 S i
10.8 0 12 53.7 4020 985 0 985 1115 S 10.9 30 8 51.0 5800 623 1490 2113 2S90 S 10.10 30 4 51.0 5800 312 813 1125 1410 S-l t
l 1. Specimens of Series 9 were initially uncracked; specimens of Series 10 were cracked along the shear plane before test.-
l 2. All reinforcing bars were No. 3's arranged in pairs crossing the shear plane.
- 3. S = shear; C = compression.
m o
. ' ! i ,
't r - rl 6 r ,k ehl is eer s oa e. ah /snn es
- n. h p s s er i hi e c gei6 f mrf e ht e
efpet ch tg h
ak n v 6 nhl shht c gt tg ii tah er s
n' ie jL ie e o h d cpe nol or n6 et mh a e e 0
o nt d e n ee h a0 t
5 5 wh h wat 3
t tgk o es v gi er t
i vh tr iwi t
s r t ohelnp 1
h ,s det wm e m ad (3 f ic enc f e ol a d e h r wa nt mer rh t
o - _ _ _ _ _ ~
p g e c o gf o s nb r e mhi oh trh s s- ws cndt i en ht mi fo at s v le a er n eg e kh diwtn0 a is h pn ci i b
u ind l t oeae w ,.l b ish ih epe meipnd p Wl o o
, s n
h er e5 p e i h t cgr at r s l 0 r e s r di ,tef s p o c 4 ,
a m 0 , m s
s nd ph ei s t
f e y )2bf s i
m u pihn e forcetu otse amcpt omf iou oetlymh s is ter r 5 2 is k o y.,i
, cw tat s fo lmpt d/i ns f mTat i s
l a 0 i@ l o r p hl hhi c ! it s c ts n a mrh n gisd eafh nwt eahgas t 0 + f 5 n i pi ewf,l peliml e hi ied .n a .,t s
e ief r o gf o k n
, ig el t e , ~
i o nfo g
we etn0timet s s tent 5 y ml o h s l f ) -
f e r pd es o is ,hs n t h pht rhAee1 f g a e r tr t ah is tat hg s s p
i t tg r et
.ht m6 e 4 led rmh esI .fo l ht o ie r
( s n
s c( s teh e s e nk e t y I ycetnenmn) e i e r ma 2
l t
a e n
S e
i%g oos ,
- t. !
w!a ts r
m t r
a ts ewfkd osi r
mah wwiys c te ust e e h a 0 t 5t sh tr lS T .,
l a
e S g f
,L c
E o p , a t
n n n a -a en2 e - nnfieag t - - s gyn) ge n nh lT ; o , c r
e ce e r rhI nai t si emr ie y cit c nr wied ninbi uit F
s
,y m,re emfot ef , e nggi n
r r n f o pah c e%nc at a F is p g
.,l
.,l c ph c r omi ne e ea ei icSteh nn p g n
9 phs lO- 0 g o
o ,a
,i t 4
C s ee2, s )m a e1n5 t r t s g 2 0 fo l e 4 fo r r H . i r s c n a pf o dt a w s p cn t t
e e einAr a nmh c e n w S s 0 i I
i s
e teh e .f oh s h ht eei eh r r r s wdt ao U ie 4 o ,f l c r s ocl bt ,
a e n mh iP re ni rh irbyh e d w 'i .ng pdn r
t n ei5 t e = o o ir a s t .h i a t l t s v n e S s 9 wb a S lf r t
r: ghl eoe t ne( o3 c ,h
( A.
h apint e ef e r n s h)Pc 2 g
. .,t gg n i o
t t
y r p r
ohdh t et o s g
a i E"nhi a.,I p f t 3 , e3 ai g 3i( s F g o
o g
o o o .g e r
r r
n f na o ev
,e nri t m ay N .o gpi on er s t
t 5 g . g o
r o
o, o
, o. o r ;s
, t 1 a n r yNia r.i 1
m yiofnah/e a ono s cw e ra( eh oic n n )m t
s le e )
/
hl r ic cr eb rtat pcd r trs tev e S Natn 7 is g n e r myz n e p ;
gr n a eaerh "' he t
y h at e 't s od h ( n i
r f et eeb a ab e r is I t ndi2 a1 n e ngnrh "
pua nga m (.n e re*o"n i
n et et hs al r t t
s s nz n.o ce a
r ra m h et nc ai3s ,3 h gh a " . ei i
l a e c " t ch e r gd hte't ' ee tet i e a n n iFmli a I hh e CThf ygi hF a w r oii cv t oai n I" f unmhh ct em"d m i ii5 wo f I
C P
i [- j*
. I o d o n
- ~ o+ ~ - - s a ht
.S /, d e e o i l T k n o e n
S E j/ c oi o s ,
, r I
.T F dO
/ 8 c r p ly o r o f
p r
e
- - ~
d k
e a
e s h n s e F sl o O 7 ek fo* ier it ah s
t e
t n
a is k
c o m em hi
- s c ei o nc I t
ss 0 c r I 4 t c L c o / in n a' n e 1
r SI O ne 5 np l
L .n c r a oi
- ly s U
P-e n S U
/f f al pp cw f, la i
m o
gfo
/ r I 2 zg e it I
. - - ,' ~ ~ _ 1jl o t
n e ac is i n at i
n -
sin e si c p chs mhs + s. ann
_7- mi i
ee 3 r
e op r a 0 gi r
p s I d i c 0 l 0/ e e s p m rh SBs 0 S id i -
' k n c o 0is 2 fg ot n
o 4 i (
P nt e
+ akc
- o. *
,, oi c
r p 0k 00 o i
eo rl n
I S
> g e t m e c a o / 2 y e r
4 a T
.f
- i. c r
i
,f e sl e loh
' 5, d) ht k gc S y s y
@f ier it s I'
I g, is p n ar ec 3 T E
so
,tn I mf e P bi rl l aa
/,\ Si n ei
.~
i S /, +
in b( r tl s ia rt F
F 3 O-iet r n ao s
4 o o
pu u
_t n
f y
ei 3
v c 1 a r f r
T o o P f n H e io i S o f ni S zg t T
E ' / d 'arr na U s ie isi n c o 0 ig sht t t I P r e r opa I o 2
v n F j '+f r u o S Bs t e h.
t F d e ch c tr t
e s O 'l ke +
a
- c fs itc - - - _ _ - f Er e H ie s o ./ f a o M o
o o
o o
o o
o 0
o #
o
. l S r cr e n oo +f ba n 4 2 o g s 4 2 3 ma l
U / o 4 i i P SU / i t
)
is igt r
a p
_ - _ ~ - g
_ /j i r ( F p
o o n o o o a o o # o o V
' o.
r i
o, ' s r .
2 5 i g
O F G d
n' .
3 'A' I i I I l l 3 3 greater thaN their yield point, i.e., strb5. iclosely for the tests / of initially un . '
UNCRACKED hankning had occurred. His b quita crackal L pmh-off specimem f reported; g _ ~' INITI ALLY CRACF f f) -
m
! possible, as the' yieki platenis of the . here, and also'for tests of larger initial- '
o higher strength reinforcement was mnt ly uncracked composite push-off speci- .
- Push-of f tests, .
- 8 8200
- sider:.bly simrter than that of the in- mem reported by Amlerson*. In the
' 08D88 I '
~
termediate grade - reinforcement. It ' pmh-off test, direct cumpressive stresses '
o ' - -Push-of f tests,
,e'+
o
' therefore appears conservative to as . exist ' parallel to the shear plane, aml *** - - S e, s 2 a 3 o_
same that the relationship between pf, ~ these were taken into account in the +- +
rud e, is the same for higher strength calculation. '
- v. *+, ,
reinforcement as for intermediate grade Using this meilwxl of calculation, an eoo - , _ ~
' +
reinforcement, provided the yiekt analytical study was made of the influ. (psi) f +#
e.
strength does not exceed 66 kst . ence on shear transfer strength of direct .
o
. Slam paraHel to de shear planc. Fmm ,+% ull,off tests, Concrete strength. %e effect of varia.
t.:m m cimerete strength on tim shear these calcidat, o ns it appearnl that if a direct tens.um stress emted parallel to o P Series 7 W[\ pull-off tests, -
4oo ._ _ _
. strength of initially cracked pmh-off de shear plaim, dien de slu ar trandn Ses8 specimens is illmtrated in Fig. 4. %e strength would increase more slowly, o specimens of Series 2 and 5 were iden, as pf, was increased, than in the pmh- 200 -
f _
tical in all respects except for cimerete f strength. Series 2 having 4000 psi (281 "E '' .Nts where a direct compresuve paraHel to de slmar plane. i i I l l l ) g g kgf/cm ) concrete and Series 5 hav-2 ".2
" clusion was disturbing Imm the o 200 400 soo soo o 2o0 400 soo soo sooo ing 2500 psi (176 kgf/cm )2 concrete. da.' *"".gnn s pinnt 4 view, since in many p gj gp,;)
For vilues of2 pf, below almut 600 psi practical situations there is a direct ten-(42 kgf/cm ) the concrete strength
" "' P* '*0 '* 0
- d * ' P" ? ' Fig. 5 Elect on shear transfer strength of direct stress acting paralici to the shear does not appear to affect the shear was dierefme decidal to study this g p,
tramfer strength. For higher vahics of a Pn>blem with pull-off tests nsi(ig speci-pf, the shear strength is lower for the nens of tie tygm shown n,i Fig < W>L ;
lower strength concrete. %e concrete %e shear is applied to the shear plane strength therefore appears to set an i upper limit value of pf,, below which by a cimcentne tension force acting on the relatiomhip between o, and pf, es-de specimen dmmgh peel Inaden hohn! to longittulinal reniforcitig liars tablished for 4000 psi mnerete wouhl embeddal in the specimen on either is ytrimental to shear tramfer strength parallel to the shear plane may fic ig-hok! for any strength of concrete equal side of de . hear planc. In dicsc speci. in nntiaHy unnacLed concrete. Ilow. nored m design for shear tramfer,if the to or greater than the strength being """'
- di"'C' '"* I"" '"" I"' P '*b mgn u hasal on du n4atiimship he- i w""k"duc' '
- k>
' " 'a" nductmn
""' .'""". ini ade P tween e, and pf, obtainn! in tests of nmsidered, and above which the shear lel to de shear planc, de avnage in_ "yicsion contributu, m of the mnerete, nutially cracked specnnens.
strength increases at a lesser rate for tensity of which is alumt half the inten-and the rate of increase in o, wnh m-the concrete strength being considernl. sity of the applied shear stress, in the en,ase in pf, is appmximately the same Direct stress transverse to the shear i
%.is change .m behav.ior is discussed ,
in both the pull-off and pmh-off tests. plane. The effect of cinnpressive direct compressive stress existed paral- is indicates that the mellux! of calcu- stresses acting transverse to the shear Direct stress parallel to the shear plane. lel to the shear planc, the average in- I lo.n pmgmsed catham is fauhy and plane was studied in Series 9 and 10.
in an earlier reportm a metlwxt was temity of which was equal to that of nuot k extragelated to the case of blodified push-off specimens were used, '
proposed for the calculation of the the applied shear stress. the pull-off test. as simwn in Fig.1(c). He depth of shen transfer strength of initially un- .
uh.unate shear strengths of die For specimens cracked along the the block-outs in the specimens was cracked concrete. %is was based on pull-off and push-off specimens are shear plane Ix4 ore being loadal in adjmted so that the kngth of the shear the average shear and normal stresses shear, the shear strengths of the pmh- plane joining their ends nmained om-acting on . a nincrete element in the annparnt in Fig. 5. For initiaHy un- ,
rra< Led specimens, the pull-off tests off and the pull-off specmiens are es- stant as the angle e varied. A system of sh. .n plu - an.1 made me ..f the f.nl. sentially the same for any given vaine mllers on the top of the specimen per-ne, ..o.t i. f .. . e. ie p,"g-nl bs gne lower shear strengths than the nI p/r flhis is important practically, mittal separations to develop, even for
/. .
- 10, . pc. h pn.t enl the er pmh e.fi ints. imbrating that a direct amec it indicates that direct stresses relatively large applied loads. %e spec-latumlup hehren r, and pf, sny - tenuon sinws paraHel to die shear planc .
6- PCI Journal ] lttarch-April 1972 03
.- s .
i load. slip relationships were not influ- tr,, + p/g was greater than 0.3/' and ' .
, , g' i . '*
Series 10 g enced by the value of pf, until immedi : the ratio of a3, to pf, was sinm{iane.
Initiolly crocked, t ately prior to failure, omly greater than 1.1 (An imtialh .
Modified push-Off tests _ . sigiiilicant deformations of the pre. cracknl specimen hasing a n . p/,
j '
/. g.
" cracked specimens occunni Imm the equal to 213, Imt . with a3, o pf, of ,
Cer, crete failure "j__ '""---
e ,
osmmenennent of loading. The initial only 0.2/; developed a strength almmt stilinesses were alnmst identical for e identical with that of a simpic pmb off . -
envelope
- e
/ , , _ ranging from 45 to 75 deg. When 6 was specimen having pf, equal to 0.2f'.) ,
3,,;,, 9 ,
' letween 0 and 45 deg., the initial stiff- Further investigations are necdal to g+o -g- '
Uncroched, Modified push-Off tests.
ness increased with both # and the val- . define completely the clicet on shear
'u - . [ o ne of pf,. When shearing faihnes oc. transfer strength of the ratio of a3,' to (psi)
/ ** #p _
curred, the ultimate slips were similar ' pf,, of direct tensile stresses acting .
1000 - # ,M to ilmse observed in initially unerackn] transverse to the shear planc, and of '
,e+ uncreched, specimens. Separations Irgan to devel. applying the shearing force after the
/ # Push -*tt '**'* op rapidly at three-quarters of the ulti. direct stress has been increased to its
,+ l i mate load, for # hetween 0 and 30 deg. maximum value.
+'# laitieur creched, -
N ', p.ea.ets voets f,c = 4000 psi For e equal to 45 deg., separations did
/ ""' d"elop ""til immediately pilor to .
/ f,- soksi tunapse, while for angics o of oO ana Hypotlieses for behautor i
I g g I 75 deg. only omtractions ocon rnl.
g 1500 2000 2500 3000 ,
kparations at ultimate were as large Shear tramfer behavior of initially tm-O SOO 9000 as 0.00 in. (1.52 mm). cracked concreic witti reinforcement Normal stress (ch + p f,) (psi) The ultimate shear strnigths of the 'mnnal to the shear plane. Esternal notlified pmh-off specimem which had loads are assumed to came a shear Fig. 6. Egcca on shcar transfer strength of direct stress acting framecrse to the shearing type failures am comparnt in stress o along the shear plane and di-shcar plane 8 fig. fl with results from the pmh-oK nrt stresses ex , and a3., parallel to tests of Series I,2 aml 3. In this figure and nonnal to tht shear plane, respec-the data from Series 9 and to are nor. tively. As loading begins the amnete is t malized to a concrete strength /' of unnacked; the transverse reinforce-l 1300 psi (288 kgf/cm?), the aver $ ige snent <hf is imstressed anti thnefore nmerete strength of the specimens in tioes not omtribute an addititmal direct Snics I and 2. Tlie values of applin] stress acrms the shear planc.
inumal sin ss ex , and of e, were mul. Several sfort diagonal temion uaits imens of Series 10 were initially crack- 6 of 30 deg. or less, failure occurral
- ed along the shear plane, while those with a continuous crack propagating tiplini by the ratio 4100/f'. The total will occur along the length of the shear of Series 9 were initially uneracked. thmugh the diagonal tension cracks, normal annpressive stresslicross the plane and inclined to it at an angle a Failures were characterized by a along the shear plane. Deformations tie- 6 shear planc is assunwd to lm equal to ulwn, under increasing shear, the prin-shearing action along the shear plane veloped rapidly after diagonal tension tru + pf,. Also shown in Fig. 6 is a cipal tensde sinss in the concrete be- '
when angic 8 was 45 deg. or less, and cracking, at a rate which increaseti con- failure envelope for e.mnetc with a comes equal to the tensde strength of by a cru hing failure across the plane timmusly with increasing load, but de- cylinder strength of 4100 psi. Tlic in. the concrete. The angle a will detwnd for 6 of 60 or 75 deg. 'the deformations creased as e increasett. W slips at trimic shape of diis faihue envelope upon the particular combination of r, of the initially uncracked specimens failure were in exnss of 0.03 in. (0.76 was obtained from hiasial tests of om. a v, and av, esisting at the time of i
were extremely small until diagonal mm) and the separations werc large trete reportnl by Kupfer, Ilitsdorf mut nacLing. In pmh-off tests witimmt addi-
'I"nal esternally applini direct stress tercion cracks developed across the enough to indicate yielding of the rein- Itmcho". The assumption that a v, may be addal to pf, when estimating ##" " I' "'"*"Y "I"*' O deg.
sher plane at about 80 to 70 percent of forcement when 6 was 30 deg. or less, " #"'
the ultimate strength. As in the push- For the specimens with # equal to 45 n. can he sn n to he nimervative for creawd a inns act m.'" n develops, as off specimens, these cracks formed at an deg., separat.ons did not develop rap- 8g vagnes of av ,. Fnethennore, umler symwn in Fig. 7(a). Diagonal stmts of angle of about 45 deg. to the shear idly until immc hately prior to failure, tertam omditums, the shear stinigth amuete are funned by the simrt, paral.
planc. They were alamt 2 in. (5 cm) For the specimens with e of 30 deg. , can heln large as the intrimic streugde tel diagonal innimi cracts. When die long, and between I and 2 in. (2% to , I" the amerete. This mrurrnt when shear acts on the tniss, the struts teml to ,
5 cm) apart. In specimens with angle and having differing values of pf,, the i,y t'r t t..... ....a < s r ,,.r. t ...a m ., c.
n a
.* 2 tny particular circle and the r axis If a = 45 deg., then ' '
Shear Pione .
t will define the point (crf, r,,-), since e, = $ - r,y fla)
Applied
\ Applied sheor, V
" C - Compression in strut a, is mo. T17 thanictricaHy oppnite
. point on the circle mmt therefore he the, point (crf, r,y), where af and shear NV E. *
. rff are a pair of stresses o>rrespmding "' " Taf+ r, f pa)
- to failure of the omcrete.
N T '
T . 'N The state of stress in the element on r,, = -
2 (3a)
C V o V' - Shear the shear plane can also he expressed
/ _
Siful Externally \ (b) T+N as e,, e, and r,, with respect to the Since pairs of values of cr, and rff opplied force axes x and y, nonnal and parallel to the correspmding to failure of the concrete y shear plane, respectinly. These stresses can W oMainM as simwn in 4 8, it V C Y om he stated in terms of e, and rff is possible to calculate values of cr,,
--- -- g as follows: a, and r,, which correspond to faihire N T N n , of the concrete.
V a- cr, = crf sin: a - 2rf, sin a cos a (1) Now at failure, cr, is the direct stress -
$3i'/ c s
/\
Y#f , cr, = y, cos: a + 2rf,. sin a cos a (2) **'I"" *""55 ' h' 5h'*' P I "* *' * '*-
suit of the shear transfer reinforcement '
7,, = -af sin a cos a being stressed to yield, phis any ex-Diagonal /. + vf,-(cos: a - sins a) (3) ternally applied direct stress wy, act.
lension crocks (a) (c)
Fig. 'i. Shear transfer in initially uncracLed concrete e
Concrete failure envelope rotite and so stress the transverse rein. Consider an element of concrete forcement. Ilecause the diagonal struts lying in the shear plane, at the middlr Combinations of and Ts.
corresponding to lure. i are continuous with the concrete on of the thickness of a strut. With refer-Imth sides of the shear plane, there will ence to coordinates x' and (, the #f'T"'t he both compression and transverse stresses acting on the element will le ~~~ ~ ~ ~ '
g shear in the strut. The applied shear is as shown in Fig. 7(c). They onnprie therefore resisted by the components of a campression crf acting parallel to the f.",,,. ,
th'e' strut compression and shear forces direction of the diagonal tension cracLs, acting parallel to the shear plane,' as and shear stresses rff oriented as j~# !
shown'in Fig.7(h). simwn. llecause the faces of the strut The' reinforcement crossing the shear formed by the diagonal tension crads '
plane will eventually develop its yield are unhiaded free surfaces, cr, is zero.
strength i A.,f,, provided a failure of 'Ile pairs of vahics of cry and rff at ""' '7** /
the concrete does rmt occur first. Fail- failure of the concrete can he obtaincil ure will finally occur when the om- from the faihire envek>pe for the omi-crete struts fail under the o>mbined crete ming the geometrical omstne ai su,o of ..mperwuni ami shcar in the tion shown in Fig. 8. A succewinn 4 struts. wlule the reinforcement omtin-hiobr circles is drawn tangent to t!* and r'schich cause f if"'#
ues to develop its yield strength, failure envelope. The intericetion d Fid 8. Deriration of ofthmur, combinations of a"'e .
6 .
ITI fournal / 31 arch. April In72 n-3
' ' i ,
- - - l es - ep . e tei.g ol , s .
oni s - es nmel ehi g c lytn ai n nrhl ine nsi . f aKnvi e ennt el ci m a g c ieah eipt nnh ohid oi int : s m. n ioh L. m af u e u n. r s p el e e r m.
i mli lp a nsgei htn ni r l
a e s n a s h h hn w mm t
l i,t mn dh a a r e s et o . .tln.
mt i i s i we vn e s o c o s n gml pi lp c t
s e c t t
g nr ts II t 1 a a xI mrf i a o.
f aa e - a a r ,i mech r ed a e euh ish ph r r
t n t t
nmnmh a n pd i e ot s r
e p he e a hhd r f h a e l
a n
ih1 n nmluihntt f n gel e a i s'. r r wva r o f oWloh aiTi i. ein t l
a eh sL , h n s e ah e a
e t
o nu nt lo. s hut r
h L n f
t eisahl uFi ocn er c et oi n ,s eigkn s, .e sht ni s nb y c To r m s a ia t
cf p r (
af gomd f
s e w e c r go or .a s t gii ut i r n a e ebb to r r a
i n d nsect ul
. rhl on n( el til lic eh mtsh e . l n n r a nor nra ar en nf t c r a e u t
f oe ]
n ct s
!t Inma si log t
r o l a
eeo i
u a u eht a. ,u h pm r e ops n e e er s sra new a eiTpicppt i eia l e nog im en cai t
e ncd i a ud el o e. roh el c r at hi nit oechh mo h t
t sf n whh n ai s c l dn ef os l i f t
s Tta uK he wr a iaih nt ips oa nnt s cf s
t
'l h io 2l t
al a si i n5 a
. t e
c o , ei chmh e.
t hlo.ul s b t alel ehhlos i
on erer re eo
- i f .
[
sf b
tehs e pef s o o s l
s nl e t
oinsl miweb oc r a cent -
pi o n es eslpth a af s o d e iek ni ci se x gt a
s it mt i n a
s re if oi e n
sl is r-nat ei i m m nrk a r mt,yml u l
e e ic r umh n r
enll cl emit un r c p f rc c n r c r c nf a urees nosf e lui e r r l 5i r ws eh nht s pr ai i i mia chk iwf f
t pepa f i a a o o r o u e n eg t f s al h ta , v mimt c pee f ua n mtnoi as os n f g s ns m ee mx f
n ma 1 t l
r -
a t a
mgle'.g non pt gnh d a e et s f s l hh e s
ee a c or eieih n e et a
nt hil el n r y hf k et s tn
[
r tih c ec s h ir ni 0 oca or s n t r t oh e r a n pa i.
l e a nemmmsTit h
e wre .tc n g mol a'.hm t
e t l t l is n ut s lysTnr e nd n tc1 inf i t f o ndi f s dl e a es n a I r
e in i o nr c mie f n r e al a r, e. h s ioct n s h h La 52 lg <
e lu nn t
r o>immel a t a
e un a imns i
nl pal u a
l ot i a ri c m ak mia nl et oeo e c a r t e a mc r r pki ei ncf a r
e s n ve s- u oi s oh dt c ii s n mieh vae ts wh pw ak lmnls i rat n hf mr t
n r s a aMei gvt tei i r ah oa i a h r oinhl a aiTie ncat wopmi s iv ad t I
tuci r t s t I l S c nis paf t t e
n ee di lei
,f - - -
ef . r ,
f - sl nt r oto nf eialym9 .emins r g i ly s pa . i g a -
i opn mr e uede = oe o p ty ai h nh e i
,w.nn t
a i a iol n
emli n, nt
.f o s nch ieb a ao g. n ai r t mui dl a wh- og oel mt er .vfe Tl c o a o r
r o f' if p 0 ol a n a t
t t
e m g g n0 e egs pi oe l
i o c sbi f i e e pI e phtg a et f tai c tm e f /,' W id t v1 d s r tct t
olah p orpoma nt F e v mo sci t
r u n s i n u s n a a i at ali li no n o hd h r1 helalin t
t r i r 1 f
es r
nt in v me e h e(
M=k q L a nl e o a n u a es e g of o e #
el ic f nwnif f n ge co n MwonoKah l
t h n a a at r c e t I amIe tnli ognns, l
.bwa a ant ee htwohic r t eI e e n f it s a r s wis hsii s a isf P" d i t ol l h
ng l med i
o'v l u et g
l mgc o e l
ad i
ityt l it s c roo itmwi htmitpoh es s tut i
s sh esh nl l,eir ce h e r r r f r
hei ri ni e s en n e s
) r " p t t n eih i t i mn wht ret ei aila erd a vt s e m nd r i eh c o af po ml a t f joa o h n n3( ip aC" re,int is tu et m m n gd nge ., ni i e c n ri laf eisf apmah eh in noe mh ot as eh t r o mc f t t l
I t et ,
i e u sf n n s i orpf h c na ngde uga nl i tr s tw e r li ioia d e cf d gi- oma f r
,a ethb u K s te wf s e ivt p ear gs aot t
r totc ,ut ia r r
r e o t
Cl il ,h t a
ht e ot o ro in a a ia wah t
bt s a nK e mnpKt f n awc d e a s mw si i ha sde i l
i le o 5 ah f n y r
,e e l s l
u c o t f t di ht eI i n) uI c
- f a tc aeted r spr4 o s emiwd r o n nb n paf o nh o dhI t / nmMt ean nht I %
c o nf i eI ue w a e . a r ea a ef i lmpeh - I ioe sg a .u n eb p( n . hh v n (1lc"feh yl La pd d se c ut h t
si' e sl iidied r a n S (r c n* or1 ,. 0. inh nreUaoom e rI > Vs a a et t
bh i ic n t
a i epr p l gi s e
h os c alud e eo r t
a <
)- m t f nml cle ,.
inar c boi Kn gE o "t r
ap .. o o g p 3 ), whwht c o
A a n O lgl d d inh r
t hoie t aTr mhl a u eyi msi i s r t l f
nl e
r c K. ca tnrpa al c f . on a eL' Ae o
,f nf e ict b remi f t n
e3 eienr cmt l
a ga ie r a he e lp1 n. ak im c o.
l iphs iish a
m e
ib+
s r
- a u n e et s si n c p
e a n mi'.wrepmo e e hc ]n !
icli nt h2h s tah ead p s M l,u r i t
a va " ' e h loi s a i pn empsnUsi ih s I el e l
e l ul ab t
" "e va e t
trn a t
e mimn r u
1 Tt et tnrgwhi pad s
od r n ilP ei n -n n r t I tshemh at a mlah r e o"'b o pte tin /
i
'Y cmht e ty re i
t o Ph pI s vc ai vt r s iwt r g g s 1 t t eI s n I t
o . rl . e - - r i.r E d ,n
- n r
an
- t metn .la n t r e h s neh nt noc co ad e nh oi F" o u
nrd e ol nt g a s a d sh h els mger m omgl e a ihlpm n i; s eh ,
o ne a,er ~ e ei a " a t
e al s
'5 _
f o ht mniaih rd rda eer af r a I pl e t c i* n
. ht d t
- - u
_ ,ly o p l sh e *M eI a -
4 l s
u ll t fnh e hi t inla sh e ro ss v res hifle r ci s e t pk guf aI a l o e
,lt mC e( y
= 5' eg a ig et tah vl u e t I r C b I n,
4 n e
ml r f gs e r a tsh esla c yl l nlp o tnd ra s s e o a as o a t ef tor eloic a ion r r t
=. t p ah a c l
n n I 0 ro, s o tesr s r r t ptf cih n i a I" lsc i o taveimr r r o a y h os t o
1 4 pf el s r a et a n e
= e o d a ol c K 8 f ms r r me z s r et o en eoc ga r a hl s a e ea en ods heat c ,m or i,I b ng W
I et a 0 u n t
a e I heti i
' d t
= 1 sd t
r e m s ime ut ht kl s ahl r p ,d s elt n t nt s e esht t t s e K e e ri a ce s h s ea c t e at h n eenhat a ec e a e e c tuy r
as ra b" se la- a etotepahgw'l t
i k ,t t s r r s t r u i r c e o mp 3 u n a uca lu s l
t h cs m I s
lc d
e Sr
, cn l 0
0 i
s s vts ia c nhe re eh e r r
nt h n S a cn iod i m
i a t 5 isp
) tg s et rsi os a nnt luri s ' no eI n I
t C lau ou 6 s o-es s
et e si h s n e s i ia a ei na r ut "gl a inm e "" e c
Aitshia inFhs t
oy r ts rctoTteht t
~ lc ( /
t c S a pot e s a dl i m
C t i la mp st ad ) Ket, r aelr a e in 0 0 e
, )
4 l
at, ee e, 5 = r
-ueem 7 TI I de r ( n nhh t (
,2t i P / ne wtr s s h wro 0 ek t i io ets g' u r taac 1
, p l
mi ,a,nw t
et nn
\ vi s i t a ,
. l r uc ce t e e h cn f
u s e c ,
s- r ree naiwh e( l t t ti l s a sf o l
au t a nh h = Ic e r l
n
+,
., c s t
/ 0 l y
c oihpy r
n oat l , mtsr wi o7ht erte c e fl , 6 f
0 oa n r A , . x
, t x
r a f
p r geh e a
/ 5 min i
t l a l .am K e e as 0 we p d+t,f h sd as rorh e f !* /* iui r r a
=
y t
t a rh of gs et e n sW h e =
5 p/ o mt esi wat
- - ~
/
/
a p
m e
hg a
+ hts r! snt ur e r rh t t
nee . " t t
" .d, I 4
= dl i et l
uf d s e l o no ne a i h o
l O O e = a t 0 0 C C -
akie s a na v 0. dn,d c mW 0
0 0
5 C .
ht I' d "I' i e iys
,h s a e
'f e 1 1 d tr i2 h e h l, ni c
' - 9 2 s
^' A, s s e f r
ef/Tbdmndlm O
m f t o ig - t e o i,-t 9 S c = r r c e )g. I o o wl P F a ,
r /r e a e d er e K .,n fomn r a I at g ., g h ad e en n Wa nh a se t
n e. r c
l l - 7 wu a s p$
i i Q
~
[
l
4- ,_. w e
, , , I I I
~st to its yield poht. At;uhl. pf,. Dire"t stresses parallel to the shear 3 - .
( 7.
mate ytrength therefore, the compres- plane will not affed either 'the friction- Specimens iniliolly crocked /
- sion force across the crack is equal to al resistance to slid,hg along the shear 14M Push-of f h PS O p/ -
the yield strength of the reinforcement planc, or the dowel c6cet. Ilence a o p / o p,,_,,, 3 4 , 3,ng ,, p j A,,/,. The frictional resistance to shcar change in this longitudinal direct stress g .,,,
f ~
0 #
along the crack is then equal to this from tension to compression does not -
forc3 roultiplied by the coefficient of affect the shear transfer strength to tids V j, 'O frictica for concrete. In addition to'the case. 3000 - g O po , _
frictional resistance to shcar, there is In a_ heavily _ reinforce,I der nlarle, also shear resistance due to the dowel oyne subject ,Je ~1awbt extrr- Vis
^
/o
/ k " Pfyf(300 Ve pg+ 0.5) action of the reinforn ment cmssing the nallylp.pliest normal comarcssimitess, 800 - e e- _
crack in the shear plane, and the re- it,,is nossihte for the theoreticalshcar (psi) O Ag v,= 800 psi sistance to shearing off of asperities .tcsis_t ancejlucJg. friction ,aud alowel.cf.-
pn>jecting from the faces of the crack. (n.ts to_hecome gIrater_.than.ihe.shcar-. ,,, _
oO
, p -Limit for f* = 2500 psi. (0.2()
It is hypothesized that the frfctional which would caus,c, failure _jn p.Ln,ini.ti_a,1-resistance to slidmg and the rem;orce- 1.g nnerwind snecimen havmg the sarDe -
4on _
ment dowel efKt are the principal J ysicalchar**ri"ie<
h In. sin}La_ case, SHEAR FRICTION , p = 1.4 '
contributors to shcar resistance. This theayack laahe shear plane " locks tip",
siew is supported by the fact that for an(the_ behavior and ultimate strength, o AfdF _
200 -
y, .
bd p , p P values of pl. greater than 200 psi (14 thou imune _tfic same as for an initial-Lgf/cm 2), the slope of the curve relat- lyuncracked_ spec.imen. When this oc. g , , , , ,
ing e, and pf, is equal to the cerifi. curs, the shear strength bemmes de- sM 8M pendent upon the mnerete strength, 2@ 4n 1000 12 % I4 m cient of friction between formed con.
crete smfaces measured by Caston and whereas before it was independent. p f, (psi)
Kriz"". Further, when the dowel action This change in behavior corresponds to was destmyed in two initially cracked the change in slope of the e,/pf, curve ,
Fig.10. Cemiparimn of shear tramfer afrength calculated using the push-off specimens (Series f ). the shear for 2500 gr.i (176 kgf/cm:) concrete ,
shcar friction prurisions of ACI 31&71 nith meamred aircngiln of strength dmpped almost to that which in Fig. 4. In Fig. 2 it can also be seen initiallu craded mah-o#i and pull-v# apccimen, that at the highest valocs of pf,, the muhl be pmvided by friction alone. In strengths of both initially cradal and ihne specimens the reinforcement be-came Linked at ultimate, and hence a initially uneracked specimens are the same.
onniwment of the reinforcement force In a mmlerately to heavily ,cinforced .
acted along the shear planc. it is thought that the excess strength of shear plane, diagonal tension crads may form at angle a to the shear planc, these specimens above the frictional but failure still occurs by sliding along resistance was due to this kinking ef.
the crack in the shear plane at an ulti- hypothnis for the behavior of initially other factors. For a crack in monolithic '
fect. male shear strength less than that of the craded concrete dnerikd ab=. b mg p is & m M N %,
The camerete strength does not ap- the shear-friction approach, it is as- vative calculatism of strength, the shear mrrnimndmg mitially imeracked speci-pear to alicct the shear transfer strength **- sumnl that for some unspecified rea- transfer strength is limited to 0.2 of an initially cracked under-reinforen! son a crack esists in the shear plane. 800 psi (56 kgf/cm 2 ) whichever the i[/* or specimen. This is consistent with the car rn tance is den anunied to Im. Tim shear-fricti<m opiation may shear strength being primarily devel. Slicar traits [cr itt desigri he developed entirely by the frictismal be written as oped by friction, since the coefficient of resistance to sliding of mie crack face over the other, when actal nimn by a A"In fricliim is independent of the concrete Sect. ion l..i. .a of the ACI linildi"X , ~ ~
NI' P = P 'P @}
strength. 't.he behavior hypothesis aho Code, ACI 318-71"'", allows design l I normal force npial to the vicht strength -
nplains why the shear transfer strength for shear tramfer to be based on the or tgm reinrorcement crou;mg the shcar but not more than 0.2/ or 800 uf imtially cradoy png-g am, pmyi- "shcar-frictiim" hypothesis proposal by plu . A fictitioudy high value of the In Fi* 10 il'" '1'#8' "*"'I"' "gth me[scient ,ir fricto n is mni to com- calculated according 'In Erg. M) is indi-off specimem are the same for the same Ili:Leland"* and Mastm. This is a sim- .
value of the reinforcement parameter phficato, n for design purimes of the pensate for negIcet of dowel artiim and catnl by unhmken lines and is osm-70 . .. . . . . . _ , 71
9 sE
_ d .
u )) -
- - n a n ). c- teos 3, 3S P a isis 0
p p
s p
u o a ls ht te >i n . . (
(7( 6 2 3 v e r e :m a d p a t i
,9-3 4,' e @ 0 o [ o ) l a in eq3iewc)
O @, '- 0 o it r
7 G
(
l l
e sE1 0pw s nt e, /f (G li u a g 3
- , 2= o 24i4 s s
f a n o1 g . q v ),
'u[ 'c 2
= 0 '/ / f3i5it / h q ots ia.
e s
t a3 ah3 3 e r y0,k E
)
eae y n
'c ="=.=ws o E
g ht t l
ad t
og4f o h+
r e
w h
n nmev n gs e l
@f a# J .g )
V u
/"=.=b te r
o s sp i n e e hi tah r met a n+d y nt 1 .def(p, ):
, 7 N u o 'm si t si c eo rvt l f r y , al i i 7 t m
". ( c. d> c ieht e s ssh t
p3b8 rf c a n is
- - - . - s t n
) t e.o nsp d eg( (2 a1ic3 poesf o/
i S
- io o*^+xy p o d o b l ac u
r ndt l
nn ml lif a s oil s pI r eg H s cd s e ruc) uk es p pCsl t
T a o d / l e aL e c pIoms xd ,
a9 A
- u 0 e , at s mar rerfeaal s
nu2 aAiv9 7f r(
t n
- E c 2 lc
. , *.* q ) N e R
O
. =
)
io n ir c l st ef e c e
wly+) va5 oo s eo t t
rf i I
8 ..
p\ ;i f. 6 t ( 0t c o 0 - br so ht lymi a khf t
,2mrdinmg o e) s p
i hn (7
.,- m 4 f y oh hi gal l
a r gpcf ai i( l 0
~ Z
.' i n 4. i r p ct g t o e s r f /e3 erT d 3 i o1 f t i q40 I
R gv3c h o Nia=
i
( f o ne n w i ph i fL r s oi3t K
t - t E1
.e r hr t F u t o o = t g s I
= *'a, 'c q} e ;
o nd - er ) e ),/ir -
O E h s ) ee ph at f e
7 b xf
(
g d e rei n a s lei
. s S - S a r r t u ofoa n ee l eLih pma ep r T e .,
g (
o s s r a t
r r r t l a I i ns omt 2 ae e m I
S E
- ** g a[ 0 +
hem e et lpmra mgh+I s ,
.f( pilpe ph c a o c 9 7
T i,I g 0 y se mee a e( sp a t ar s 1 L
- al. g 2 f
(
p h
eht ishh .t s h ic + , ta dn0llyss o ) r f oi l i
r p
E Pi aoa fi th t h e ri t f p a02 an cr of ev( e7 A-B a.8. oe ch ol a f o (
ht ; net r a ivit I h
I R t 0 n o
t mi k ni E s/
a t
i gI a <t c s 7) 0 x O o g aa l
1 i(
pn mmO a pri u n 3. hegme o0t .
r a
C i
inpnI a wta n +
l r
o s o a p e ,u i isi t
c nsh s ?
t I t
l a o r a let c sd -X a a n /
@o m t
a gn lk c p tsh s na
- ~ - - - g, C
o ni"a r s 0 r et t o i,s e s I' 8
l a
0 0
o 0 0
0 0
0 o . te eRn0 2 er en xe a e "
r sk s n r
u 0 la d i" a h me ub )ets 2
- 2 1 E 8 6 4 2 1 inWw = t t
e s
.t r I o
n ;e ""
' ,i . f y, . g I" o e,. h t ll F
i ^ lpyII" n ,ti
> ane t la v I
C a wisnh n e P ,sa r
' P is gt - - n , es) t n n inx oiohhtgcl y t 2
t n
h islp er pepn f r t miuio n s e n nn a uit fi r o ef n/a
,si
)d t h de u ph nhdt gnif l l r ri 7 n t
- iip - s n m Te n ee sk a hf i r t
- - ( t o .a g nf - k t e t t s a r te G w qf t 4
.o o )
, I 0
0 Eo -
eisi h ge s
e7mh rl i
t t
ee1 7 r we cAu n l g pi a 4 gd pwcent m(I . o ln a
I gl l h i h im= f 1
nu u
+o '3 sea f e /h eht ois) i;
\
l f
,0 0 i
mp ,
5 t
b h )0 g tysi r sh2 pt n g mt i w
, ewf o0 n ah a s t 8 t s 0 de of uy p f p na I 2 k a g02 5. k Ib n nodr ta0 5t e I
. o o 1 t o n l r f t n 0 ( ) ah o mi+( 4t gs
+ 0 5 2
8 h t is l
um l t i ,i a a cd h d a2 r
L n .
t 0 p cp I
O O ;
- )
7 0 er
+ o is p
I o (
0 1
l a
cde m n e op a mp/ 0 inI nnhh rvf pi s dtc c acla nal t a ei lum F o f
(
m o ht l
l e ,0 0 .i et s upl d
n G 0 6 s 0 s i 1 i imref o p e.p. p o pso n r
e o 0 e t im i
t 2 ) ga 3 e k =
0 g nr e c g o( sl a .a eal n l r t r n n )6 (ini gs pe uunhin il 0 if c it O I s n I
o a \ a O t l a
8 o r ; ei qy s
io r r
c iiss ie s u u 'w t.s DeEb euF p n g n.
r cl I
hi pp p p q 2 b c + r a o oe E + ei oo o Wi0 O l
yooo 0 0 , f s -
= f t a - s gonf . nnf o d
,I 0 f a pta nmh d na nl oayt ni t.CP l t o5 8 f ni s I la 42 S45 l
g v, (
p 6 p
(
a r
i ol e i
it . = = = t h l r l l niet a e y r. d isbairl im c.i. no- ten. eh t
n**{ *f $'f. m r gf e l 8 u 0 a i
- - - - imI 0 eI enmh e s e et e t
o s t s h rh mn e7 hc kid rI I 1 s n m o { ,. A 4 f
4 s n t e . i. o r inp n.
s s s p i b 8 er im f e - a , .
g f 0 a or p f. . 9 n f df f t d n1 h c vc eo i.
- ee s u f
o f 0 s d a3t ic - o eo
- i-o9 0 m ed r e c 1
oe weryq I
l e h h 4 2 ie ud uet s I f t . 6 p us lump l c u r r sk a cteI .C eclr so s a t
mc S P P pm a ear At a nI et r . mu
- - - _ - - - m a e mcsnef e r
mc o e.tsl te r o'. e.
r u. ..n t
o ey eh oi a o o o 0 0 0 Cm hllaid m tsf nr a s ti s.
ms eh eoa e e.
L 0 0 o o o 0 o 0 0 o g s 4 2 .e t ce l
, I.
h 4
8 2
1 l 1h 1 t it hi n poiri vt et i ph sht s ., . g s
it gr t
v,
)
is
.h gt iw ef i r pv s
e a n a ta o . . : uo.
e eh f
(
p ii Fe t f
o mv rh r pet s s t
upt s
n
?tr hs l ma en r e ca ce s r eu .p h
g al l papgt cf lurh oehi nv t r ..lu 9
~1
,n .
~. . ,
' 2. Higher' shear transfer strengths ' 7. %e shear trsusier strength of ini- 4. Chatterjee, P. K., "Siwar Transfer *\
. zero or compressive. %e results 're-
. tially cracked concrete with nmeierate in Heinformi Concretc," NISCE ported by Kriz rnd Hathst885 for corbels than: the upper limit of 800 psi (56 . ;
subsceted to shear and to tension forces . kgf/cm2 ) speci6ed in ACI 318-71 can tmounts of reinforcenwr.t is developed Tlwsis, University of Wash'ingt<m, ,
,in the direction of the reinforcement - be developed if appropriate reinforce.
. pumarily by frictiimal resistance to slid- Seattic, June 1971.
ing between the faces of the crack and 5. Vangsirinmgniang, K., "Isifcet of imlicate that there are a wide variety ment is provided and the' concrete ,
by sk>wel action of the reinforcement n Normal Compressive Stumes on of comlitions for which Eq. (7) is also strength is adequate. Such reinforce.
v316d for values of as ,.which are ten- ment may be proportioned using Eq. cmssing the crack. Wlu n large amounts ,
f - Shear Tramfer in Heinforent Om-d rnnforcement, or sullicient external- cretc," MSCE %csis, University of sile. In' Fig.12 Eqs. (6) aml (7) are (7). ,
ly applied mmpression stresses normal Washington, Scatile, July 1971.
compared with data from Krii and ;
to the shear plane are provided, then 6. Zia, P., " Torsional, Strength of Pre-
- Haths' corbel tests in plotting Fig.12, Concerning fimdasnental behav.sor. ~ the crack in the shear plane
- locks up" stressed Concrete Members," Jour-
. p,was taken as Ae nominal shear stress
- et yield of the' tension reinforcement,
.l. A pre-existmg crack ahmg the and s'near transfer strength is develop 4 ,ml of the American Omcrcic In-or at ultimate strength of the corbel shear plaae will Imth reduce the ulti. as in initially imcracked concrete. stitute, Vol. 57, No.10, April 1961, mate shear transfer strength aml in- po.1337-1359.
if the yiekl of the tension reinforcement -
slid ist occur. hi accordance with Krii crease the slip at all lesels of load.J -
Ackflolc/cdgtticitts 7, A'nderson, A. H., "Comtmsite De-and Haths' findings and as required by 2. Changes in strength, size, and signs in Precast aml Cast-in-Place
. Section 11.14 of ACI 318-71, the re- spacing of reinforcement affect the This study was carrini out in the Struc- Concrete " Progressire Architec.
inforcenwnt ratio p was taken as (A, + shear transfer strength only insofar as tural Hescarch Laloratory of the Uni- ture, Vol. 41, No. 9. September '
. A.)/hd when shear only acted on the they change the value of the reinforce- versity of Washington, Scattle, It was 1960, pp.172 179.
corbel and as A,/lul when Imth shear ment parameter pf, for f, :E66 ksi made Imssilde by the support of dmmrs 8. Kupfer, II., Ililsdorf, 'II. K. and V, and tension N. acted on a corbel (4640 kgf/cm 2). to the Structural Omerete Hescarch Husch, II., " Behavior of Conciete In this latter case, ax, = N,,/Inf. It 3.. In initially cracked concrete, the Fund at the University of Washington, Under Biasial Stresses," Journal of can he seen that, pmviding the limita- camerete strength sets an upper limit and by the Hethlehem Steel Corpora- the American Concrcle lentitute, ,
tin who donatal reinforcing hars. Vol. 66, No. 8, Aug.1969, pp. 656--
tions placed on them are observed, vahic for pf, below which the relation, both Eqs. (6) and (7) yickl conserva- ship between o,, and pf, is imlepen- 666. .
tive estimates of the ultimate strength dent d mucrete strength. Above this l Rc[crences 9. Caston, J. H. and Krii, I II., "Om-of entbels. (%c corbel tests etmsidcied - value of pf,, the shear transfer strength I uretions in Precast Omerete Sime-included specimens for which the ratio increases at a much reduccal rate for I 1. Hirkeland, P. W. and HirLcLmd, tures-Scarf Joints," Journal of the i of the tensile stress ay, to the shear lower strength concrete and is equal to H. W., "Onmeetisms in Precast Prestressed Concrete Institute, Vol.
stress e,, varied from 0 to 1.25, and that of similarly reinforced, initially un. Concrete Omstnietion," fournal of 9 No. 3. June 1961, pp. 37 59.
for which the ratio of moment acting cracked cimerete. the Annnican Concrete institute, 10. "lluikling Cmic Hequirements for on the corbel to the shear times the Vol. 63. No. 3,11 arch 1966, pp. Heinforud Concrete FACI 318
- 4. Du.ect tenm.n skesses paraHel to
- 315-368.
efIective depth at the . cohimn face &c shm plane nduce &c Am hans- 71)," American Omerete Imtiente'
- 2. Alast, H. F., "Amiliary Heinforce- Detroit, Alich.,1971 j (s/d) varied from 0.11 to 0.62. %e I
- maximum value of (pf,- N.,/lul) was ,,l ""} ment in Concrete Connections," 11."PCI Design llandimok," Pre-j Proceedings, ASCE, Vol. 94, ST6, stressed C merete Institute, Chica.
l t
514 psi (36 kgf/cm t), and the masi.
mum value of pf, considered was 700 .In f[ June 1968, pp.1485-1501. go,1]L,1971, r p yanc. 3. Ilofheck, J. A., Ibrahim, I. O. aml 12. Kriz, L. H. and Haths, C. II., " Con-i psi (49.kgf/cm8).
5.An extemally applied compres- hiattock, A. II., " Shear Transfer in nections in Precast Omcrete Stnic-sive stress acting transversely to the Heinforced Concrete," Journal of tures-Strength of Corbels," Jour.
'h'*' P'*"' " *dd'" ' 'I'*'*"' 'h* ^merican Camerete imtitute, nal of the rrestressed Concrete in-Corsclltssorns lations of the ultunate shear transfer Vol. 66, No. 2, Feb.1969, pp.119 stitute Vol 10, No.1, Feb.1965' strength of both initially cracked and 128. pp.16-61.
i Concerning design. uneracked concrete.
- 1. Within their range of applicabil- 6. %c shear transfer strength of ini-i ity, the sheasfriction pmvisions of ACI tially r.ncracked concrete is developed Discusahm of this pcper is inrited.
318-71 yicid a mnservative estimate of . by a truss action after diagonal tension Please forreard your discussion to PCI IIcadquarters hy Jedy 1 the shcar tramict strength of reinforced cracking. Failure acents when the in- to permit publication in the July-August 1972 issue of the PCI JOUllNAL.
I .,
cnnerete whether or not'a crack exists clined concrete stmts fait under a com-
- in the shear plane. hination of shear and axial force.
~ i 2 Tf PCI fournal ! .11arrh-%rd 192 N.
-