ML18046B070

Ack Receipt of 760506 Comments on Revision 2 of Reg Guide 1.35 Re Tendon Surveillance.Based on Expected Variations in Prestressing Matls,Site Dependent Factors & Method of Guide Implementation Acceptance of Statistics Not Yet Determined

ML18046B070
Person / Time
Site:	Palisades
Issue date:	07/27/1976
From:	Kehnemuyi M NRC OFFICE OF STANDARDS DEVELOPMENT
To:	Lex B BECHTEL GROUP, INC.
Shared Package
ML18046B069	List: ML18046B068 ML18046B070
References
RTR-REGGD-01.035, RTR-REGGD-1.035 NUDOCS 8111200634
Download: ML18046B070 (14)

Text

..

EXCERPT FRO!-~ SARB MimJTEs March 27, 1~{(4 Meeting

'l'endon Surveillance Report C. A. Hunt reported.on the Tendon Surveillance Report published by Bechtel Corporation. The principal results were discussed.

SARB exam-ined the report in light of the requirements contained in Section 4.5.4 of the Palisades Plant Technical Specifications.

Surveillance for Prestressin~ System "a.

The nine surveillance tendons shall be periodically inspected for symptoms of material deterioration or force reduction.

'l'he surveillance tendons consis*t of three horizontal tendons, one in each of three 120° sectors of the containm~nt; three vertical tendons located at approximatsly 120° apart; and three dome tendons located approximately 120 apart."

. H*SARB 'Finding - The testing satisfied this requirement.

"b. The inspection intervals, measured from the date of the initiai structural test, shall be as follows:

(1) One year.

(2) _Three years.

(3) Every five years thereafter."

• • SARB Finding - The testing met the letter of the inteT'\\ral*require~ent but, since the tests were not exactly comparable, the data generated must be considered new baseiine data.

"c. Each surveillance tendon *shall be inspected for the following:

(1) The number of broken wires.

(2) The surveillance tendon force at the end anchor.

(3). The corrosion and other physical conditions for the tendons, including bearing plates and end anchor assemblies.

The inspection procedures include removal, inspection and test-ing of specimens from not less than one nor more than five wires from each of the nine tendons.

The grease will be sampled and tested."

• • SARB Finding - The testing satisfied this requirement.

11d.

Comparisons shall be made between the quality control records and each of the surveillance inspection records for each of the silrveillance tendons. Acceptance criteria for paragraph (c) i.2_*

as follows:

c::>

(1) No eddi tional broken wires since last inspection.

en (2) 'l'hc force-time trend line for each tendon as extrapolated.rt shall not intersect eith~r the upper or lower boWlds of c_o the predicted design band.

(3) No unc>.-pectcd change. in corrosion conditions or grease O"J properties."

8pl11200634 811113 PDR ADOCK 05000255 PDR

2

• • SARB Finding - The testine showed.that acceptance criteria (1) and (3) had been met. It was doubtf'ul that acceptance criterion (2) was met. It was pointed out in the discussion that 1 t may be a meaningless criterion. A study on this point appeared to be necessary.

"e. If the criteria stated in paragraph (d) are not met, an inves-tigation shall be undertaken to determine and correct the cause for the changes and a report made to the AEC as specified in Section 6.6.

11

• • SARB Finding - It was not absolutely clear that all the criteria in (d) had been met.

SA.~B Conclusions

l. The c9ntainment tensioning is adequate and the facility can be used for. the purpose intended.

2, Sufficient information was not presented to veri:f'y the

.adeq~acy of the stress versus time trends.

SARB Recommendations

l. Tbe AEC should be notified of.the ~esults of the testing *

2. An acceptable test method, especially with regard to repeat-ability, should be developed to comply with the Technical 1

Specifications requirements.

3. Retesting should be done one year and three years from the latest test date, using.the acceptable test method in 2 above.

4. C. J. Maynard should be assigned to follow and coordinate the contacts to be made with Bechtel Corpora ti on on this issue, and report back to SARB on its disposition.

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f~PUCJ,JILITY: t-:oa::s 1, 2, 3 and 4.

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• re~e;.:iinir.g t~~t a r~presentativ~ Sj~D1e of at least 21 te~dons (o co;;:e, !i *.*~rtkal, l)nd 10 hcop) c::;1 hzve a lift off force of be~:.*:ee!'!

(mird;::L*~) ?.nd (r~xir.,~::i) po:mds.

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i:;rcceed cor:sici~rir.j the sin-;.:le deficic:1c.:,* as unique und accc~:

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!*'.~'re th~n or.e ce"fei:tive t.:>.'ldo:i out of t.'1~ origi:-:3J se:-?L:!

p~~ulaticn is evidenc~ of ~b~nr~al d2Jr~caticn of the contJin-

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1.::i1~ss tr.ere is cvicer.cc of ?.bo.J:r~ai r'.::>~r.:ic~~~:":~

of the cont.:-ir:cent structur~ d11ring th~ first t.1r~e t~sts of~~<'

tt>ncons, the nnber of rcr.dcns checked for 1 ift off fore~ <.!ue:U:!J' su:.is~quent t*~:>ts r.:.:? b~ reduc~d lo.:i r:>;ireser.tative s<:~:i;>le o~">

at least 9 t.:r.~ons ( 3 dor.:e, 3 vertical.:ind 3 hoop).

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~l~0r~r. !.n initial report of any i!!.>norral C:egr:JcJtion of tic

• c?1t:::ir.-*:;:;t ~::*:1::.;r:?_:.l?::?:~~d.dJrin:i t~.e i".~ove ~eqJired. :2sts a~d insp::!C-lthin~ s:'.~11 t:e -::.~ 1;1t:i1~ ~() c!,:y:. after t(-:~~e~1on of tn~ s..:r'/~1llar:ce 1r!:c'.:li":--~*1ts ~*f :.*:1s ~'.'l::c~f1:~t1~~ l\\r.d J.s;::c1~1 ~~~ort shall I:;~ su~

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Thi~ limftJtinn ensur~s th!t t~e structural integrity of the contain-r.i!nt vess~l \\till L~ nin:afr;~d ccc*:'larJble to th~ orioinal desir;n st.11rdards fcir t~t> Jiff! cf U-e fj,::Jit::.

Str:;ctiJral int::!rjrity h r~r;uircd to ensure li1:tt !..:Oe \\"!'5Scl Iii 11 1-;i i:~S ~-~"d t:;e :-;<1;dr.:lJ"1 pres$ure of (*~0) rs i9 in 'the

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-e~s:;n~1ent of con~Jinr.ent tcnccn 1 ift o:'f force, The s11rv~*illt1nc.:-

r*:.-~uir~~~!'lts f.:;r c!t?1:in5tratinq th':! conta.inrr:ent's Hr-..;c~.:;r,!l ht~s:-i:y u'-' ~n c:-""'.;->li':r.ce 11iU1 the r~co:-;.;.~:;d<1tions of r~uulJtJry :ui~e 1.35 *rns~r?iCP S;r~e11;~nce of Ungro~ted Tendons in Prcstrrss~d Co~crete Cc~tJi~~~nt S:ructurcs".

t;~e vb11.1l :;rid r:etJ!Lr*JicJl C'X~'1i::aticn of ter.dcns, iir.chor?.~es end 1 foer,

• ~r'td t!"Je T.:,-pe,; lealoge tes::s are ~:lffich:it to de::1ons::rate this c.:pabil ity.

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e REF.J Bechtel Povver Corporation Engincr~rs-Con:;tr1Jc!ors Fifty Bc:nlc Street S~n Frcinci~;co, C;i!ifornia Mail Acldre>ss: P.O. l1oi< 39G5, San Francisco, CA 94119 M<Jy 6, 1976 Hr. Ro1icrt n. Hi:1oguc Director Office of St~ndards Developcent Nuclc~r Rczulatory Comnissicn

• Pld.llips Bui1dinr, 79 20 liorfol k /1venuc Bethescl.'.1., MD 20014

Subject:

Reguiatory Guide No. 1.35, January 1976, Revision 2

'In-Service Inspection of Ungrouted Tendons in Prcstress~d Concrete Containment~' -

Co~ncnts

Dear Mr. Minogue:

We sub~it the followin~ inforoation on in-service inspection of un~routed tendons in prestressed con~r~tc cont~inment structures.

Your Regulatory Guide 1.35, Jam!ary 19.16, Revi:;ion 2, st11tP.s det;iilcd survc:.ilJ.;:.nce requircmr=nts..

Jlm.;cvcr, in

- Section D, 11 lrnplc:n1~nt.::!ti.on", it su.itcs that tlic applicant m<iy dcvcJ.op an acccpt;.iblc altern.:1tivc i::c:Lhod.

We rcquc:st your rPvi<'.h' of the folJ.m:i.n~ matcri2l on a generic-basis for al] ft!ture cor-ta:in;:;c'.:*:t:;.

In tlw follcY,.;ing '-! c1tt.::*iqtcc1 t.o co1::Tf.1-Y i.*j th the intent of Rcg1;~;:tory Gujde: l.35 C1;-Jd, in ;H;d:i.t:i.l'rl,

\\*.3 r..;;ve co;i.sidc:rc,d the k'10\\*.']0:.:dzc \\,*cha\\'~ r,ainod in r~st tendon inspections.

Att<;ched for: your in.for:;i.1t.:i.on is a St1;:-.:r.2ry of TcnJon Surveillance D.'.1.ta for B~chtcl c'le:;.;iu;..:.:d cont:iim,:cnts in whici! we su;:;-,J.icd te:chnic.:.11 ~uic:;ncc during in-service in~: pt: ct io;-i.

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TENDO~ LIFT-OFF FORCE ACCEPTA~CE CRITERIA The containments arc orir,:i.n:.illy d~s:ii:;nc'd for an averar;e pre~;trcss force from :ill tcncl.::,ns in a p;:irticular rc1_;ion and our past e:xpcri~ncc h.::i:; shoi:n.

varintion in lift-off for a group of tf'rnlons.

Lift-off readings rnust be Corrected lO rc>f]cct t)H~ concJitiCln Of '111 L.VCT:lp,C!

tc~ndon, therefore, \\..*C havL' norr:;:;l).z,*.1 the lift-off r<!~ll!inr:!.; to c.:orrect for init:i.al cl;1sLic lo~~;cs an<l *.1l!;o the.:

init:i~1l :ictu:il [l'IHlon

~mcho:r.::ig(* v.1lue,

~inc-c ;i~l t.cn-uons c;mnot be.:md101ed at tht~ exact ~;Jrne V.'.ll11c.

After norm:1l)~:in~ \\.Jt:

li~vc dctcrmlneu th.it the v;ir:iaLion ":in lift-off con*bc uhout :!:(2 tu 5~0.

This v&iri.:ition j~; due Lo rr.c:isurcmcnt error und other unkno1.*ns.

D'~c to this v:tri.1tion ;1:; tht?

cunL~im::e:1t nc.irs end of life, about hnlf the m~Ll~1irc*111t*nL,;

will be :ibovc tl:c required v.1lue nnd thc other h.:ilf will be bcloi...*, whic:li i:.

&rn ;iccept:ihlc l"<*11ditjun. providccl that rhe

ivcr."lf.l~ of th~ somplc is :ibuvl' or ~qu:1l to l)1,. n*quj rL*<l V;Jlut*.

'fliis !;itunrion j!:> illu:..;Lr.:iL1:d in t:l11.:

fol lu*.'int; fik1* 1.- ~1.

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Spccific mc.cisuremcnts

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X Expected pre:-t:ress x

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10 20 I

40 Tim*:= nftcr: initial tensioni~g (years)

Inste:::;d of r_c~quirh1g t:l1nt: all v;1lu(~S must be above the m:i.r.irr.L::.i rc*quired v;1lur-~, l.'e con.s:!dcr Lile follo\\-.*inz il rJorr.: rc.-ilistic acccpt.:I<c0. crircri<i.

(1)

AlJ. J ifr-off v.-.lt~c;, n:usl be corn:~c tc:c1 fur initi.:iJ. inst.JlJ.:11i.on conditio'.1!'.' (:::ctu.-:-..l c.nc!i:::JT"~!f,C fo:*cc.:.ncl elastic losses dui:i;1i_: initi:-,J posl-tcnsio:1ir::; Dml.J:1y otlicr sii~r:ific.-111c £.!ffects) so th2t. tlic:-

v.:ilt:c is intljcaU.ve of the a\\*~r.-:;_;L~ level of prestrcss.

• (2)

The avcr~sE of nJ.1 corrected lift-offs shnJ.l be cqu3l to or above the minin:urn required prcstress.

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(3)

Lift-off r:li.-111 be obr.-:incd* on ac!jaccnt tendons for <my tendon which is bcJ.ow 90:~ of the r.ii11imum rcq uired pres tress.

The l\\l'~ u) ;i l ~ry Cui <11~ ;i pp '1 re. n t ly r0. qui.res t h;-1 t th c tendon:. be cl c~ tr: n~;j 0111.:d durinb Lb?

~;urve)l]:Jncc.: to chc<.k wire or :.;tr::i11d:,contin1d ty.

Since the Rctul;aory Guide only n:c1uirc:; wire or str~nc.1 rc1i1ov<ll from one tc.:nc.lon f.rom each Group duri11r.; c.,ch lnspection, then only a sinGle wire or st:raml tendon \\.*.'ill be dcLcn!..;i.oncd from c;:ich ~roup :1t c:;1ch in!;pcction for purpo:;,~s of str.anc.l or wire rc:.nov.,l,,ncl continuity ch~cking.

Our past jn:;pcctit,11;,

hnve on1y dct.?ctcd."lhout O.lZ lo~;s of wire contjnuity out of.3.

m;)lc~

;

i:~c of 13,JOO \\..'ire~!>.

Then~forc, thi::re ;1ppc:Jn; to he in!ii£nific;:rnt j11-*!>l'rvicL"

\\.lire br1:;1Lq~\\.! ;lnd !iincc tl11.: hr1?;il;,;q:::e would occur l';.1rly in.life (:.i:1cc !.a.n.*s!;

decrca!ic:; \\.lllh lin1v). it i:; our co11cJu~:ion th;1t continuity 1ir~1*1l 11ur.

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clwcla*cl on :ill lt.'1Hlt1n~* clu1* in;: i11spect ion.

For u~nclun!i which ;11 i: "!',,,,_

tcn:;imH'll, it i!: only nl'l'L'~;:;;1ry to obt:1in lift-off r~arli.n1~:..; !J:inu" 1.*)unl::irion uiea!iur<:ml!nt:; do not add ;Ill)' lll'C:L'S!;:iry inforu.Lition.

[3ec191 rovH;r Corpora!ior1 Hr. RolJcrt TI. Mi nO[;llP.

r:ucl c:.-ir P.(*r.uJ ntory Co;::,r;is;;ion 10)' 6. 1976

}' c"l[;C 3 III.

Another altcrnat:i.vc th::-1t \\.l'c cr,*n~;':i.rlC!r ;:ccr.pt2.'blc is the use of load tr.Ca.Suring clcvic_C!~; !;UCh a;, Jo~d CC!lls, and, in this ca:;c, the SL!I:1ple is prr:detc:rrnincd.

INTERI'F.ET/,TIC:; OF SPECIFIC REGULJ;TORY GUIDE REQUIRD*IT:NTS We interpret P.q;uJatory Position Section 6(3), "pl*occdure to 1mcovcr possible voids in gre2sc :i.n the trur.;pet *** " to.meLJn that the volum(~ of grease removed prior to detensioning and reinstalled after rctensionin~

be estiT!lated to assu:.-e that the rcDOved volume is rcpli3.ced.

Section J3 Di::;cus;,ion states 11 *** To the fullc;;t e::-:tcnt prnctic;i.l it shouJd also cover the due ts th;:it co;~t::in ti1e tcrldor.s."

We propo:::;r: to implr~r:ient this requ:i,rc::.:::r:t by pc:.rfo-::-1.::.:i.. :1s <!

visu:~J. inspr:-c:tio*r: of tho."

cont;-~in!!,*2nt structm:-e to dcter:..:.d ne

• c::cr~~si V(!

gn:0.~~c* (ten ti on d l!.C t filJ !.!~) ] c;akZJL;e fron tbc tcncon ducts and lo reco;:,::;;c:nc.l con:ect:ive actio.n if required.

} 1Jc::.sc noti.*:'y us rcGcrcHn[; t11e ncccp~~;;~b:i.J.ity of the pro;:>c-sed tendo:;:i lift-off force CJ.ccepto.nc2 crit~:d.u and ouJ~ inter;;:::-ct:ation of specific l~C~j~.iln.tcry G1!:5c..l2 require-ments.

~hould our pro~osed nccept2nc~ criteria and intcrprctat.ions*he not fully ac1.: Cjl toh:i. e t 0 y ('>ll. pl c:::~:e a cl*: i.s c us :15 t:o wLi.ch p.:: r ts nrc ;;c ccp t:;~l;.l c.

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7 ery tr~uly.your;;;;:;*

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Burt on L. Lex Manager of En~inePrinG BLL/m;rp I smo

• Attch. (1) t

ATT,\\I. ll:-1 !"~ ~T e*

4/0G/7C su:-:r:.... OF TEl!DDt~ Slll'.Vl.J LL/..!iCE DAT!*.

The follo*.::in~~ ::a11~:1nry of tendon s1frvrilJance d:it.:i ;:irr. bri"cd on tendon survcjll:!nce.c; performed bl!t.\\.Jcc~1 197) ;1rl(l 1976.

Durin~: th0t time, Hccht0l provic)l~d tccb1ic;1l r,uicl;rncc for tenclon sur*.:c'ilL.!11cc~ wor.1: t'n I'ali:;::i.dc~; NucJ.e:ir Power Pl<u;t; Point Hc.:;ch Nuclenr Po..._*cr 11l;mt, lli*:i.Ls l Linc1. 2; Turl:Py 11oint Nuclear l'ow~r Pl;rnt, Units 3.:ind

'; and Ark~nsas Nuc]c~E One, Unit 1.

SURVEILVJ*:CE l'l~OCEDlJRE 1.1

1. 2

1. 3 l.4 1.5

• 1.6

1. 7 Inspection 'of An.cl~or Asse?r:blies Visu2l and Laboratory Exami~ntion of Sheathin~ Filler Measuring Lift-Off Force DC!tensioning Tendo11:; and Ch<:cking Wire Contil1uity Wire Removal, Exami~ation and Te~ting Rctensioning of Tecdo~s Evaluation of Test and lnspectj_on Results

2.

SUINEILL.f,NCE S/iHI'LE SIZE Description Quantity_

(1) l~uEJ:J c-r of tc~1dons de::cns:i.oncd dur:i.ng 1-ycar survciJ J;mce 79 (2)

'Nu::".her of tcr.C.n.ris cct c*n.s:i oncd du::inr_; 3-:icar survcill<!ncr:.

56 (3). Nmr:hcr of tendons dctcnsioncd during 5-ycar surveillance*

21 (L1) lJ ll !~1.' f: T of lift-off d~tcrmination~ during 1-ycar s u ;.*v r.: J_ l l ti 1; c c (5)

J\\11:'*.:..,~*r cif l:i ft-off c.lcrcr::1L1n!::ions dur:ing 3-yc.:ir survcil.1 ;rncc.

(6) l::u:::l:~r of l:i.ft--off dctPn-:in::itior:.s durin6 5-yc<:.r (7)

(B)

(9)

(10)

(11)

(12) su :rvcilJ.nnc c Volu;::c of shc:ith:':n~: fi1lcr v:!.:.11.'.1lly cxnmincd (!j[!llons)

Nu:?*.bcr of J.;1bor.:;tory rcstcJ shctith:in[: filler samples Nur.:ber of... :ires indi.vidu:Jlly checked for co:1::inuity Nuclier of buttonhu~ds checked for size an~ splits Nu~hcr of tcndun cnd-nnchor~~es inspcct~d tfombcr of continuous wires rcrnovcd for examination and tcstine

3.

SURVEILLAr~CE l~ESULTS 3.1 Tendon Lift-Off Force 3.1. l One-Year:

79 tendons dctcnsioncd

_l~ ndt! j Li on al. tendons 1 i ft-of [

011 ly 148 104 37 3,800 178 13,300 26;600 312 123 93 tcmlon:> sllrvc*y*:d L!;-:\\L'.L:d*. J cr::-iectcd lift-off force by ;m avcracc of 2.~7Z A-1

> J. l.2 5 6 [ (.' 11 rJ 0 I I : ; ti l' t* r' !1 :. j * *.

• I 10.JdcliLiCJnnl tc*lll~.*.

• lift-off only

(,(j t c111IP n:; :; 1ir vc'yr*d

~ xc ec.*c! 1 *d t.*):p ;_:ct eel 1 :i ft-off f o rec by ~n nvcrnuc of 5.ns~

3.1.3 FivL-Yc.::ir:

22 ti~ndons dC'tcn:.;jr;ned The :.;vcr:*;.;<:'. lift-off fen-cc v.::i5 0.13% below t.hc expr:ct-r.d lift-off force, hul \\..'~11 nbovc tlie rec}uired min:ir*:um effc*cr.ivr. dcsi.zn

3. 2 Tendon Wint Ins pee tinn 3.2.l 3.2.2 3.2.3 3.2.4 Continuity -

.1% discontinuous Buttonh~ads -

1.4% off-size or split*

Corro5ion -

minor Physicnl pr.opert:ies -

unchan~cd 3.3 End Anci1ora~e Inspection No fl~ws or cracks; sornc minor corrosion.

3.4 She~th5ng Filler E:;.:.::i,;nnat::.on So~~ small air porkets.

3.4.1 3.4.2 178 s2rnples -

r.1iniP.Jum of chloriccs, nitrates, and sulfidc::s.

'*. J.

'].,..,

.c.:*-

-./::] ~--~: ::.

4. 2 Tend on!; 1-i:: vc not d I! tc.. :*i u:-.:1 r* r: c~.

1-i. 3

\\*?ire Lr c;;l::'f'.2 h::.'.*~ r:o:: cccuJ-rr*cI. >'d 4.4 Phy.:~i.r.:11 pro~*!c:TticD of te!:dn11

\\.

1 :i.rc~ zre rr-rn1~ini.r.r, ~zscnti;!J.Jy co:..stt?.~~t.

4.5 Sl1 1-:.:"itlt:i.:1~ f..'.1Jcr has ri::>t.

u:1r~c:rr.onc drtcrior<jlion.

1,.6 Corros*ion r:-.~c 01-

\\*1irc~s

.~;:!cl co::~pc.*ncr.ts h~s been in.sitnifir:~~nt.

4.7 No sr.1-c:~;~;

cor~-o~;ion o:- l1yc'.r:c,r;e:n c;_;*!ffittlo*:,c~nt b<:s been ob~;crved.

4.11 Tcl!,i0ns.::r:d end 21Jcl:on:it.t:s !1~1vc sl:own no siLns of proercssive dctc*rioration.

t..

Minor splits w~rc ncccpr~~lc durin~ initial installation.

"fh<' ev.idc*nce incUc:1tcs th:it the di.!.:contin11ow; ui rC!i per Sec. 3. 2.1 (O. li.) arc Lhc r1~~;ult of 'l..':irc b1*t.!;1\\;:i~;c \\:hich occu1-rt*d <.Jurin;; the installation of Lill~ post-

'*'!l~ioning !>)'!.tl'm.

The 0.1~~ lo!>:; of prc~*Lrt:!;S (ciiscnntinuou!> \\Jirc!;) is \\o.1cll bl'lm..

• tlic 2.v:;;

Jo~:!:: of prcstrcss nlJm,*L"cl b)' ACI-71, Section 18.19.3.

A-2

l.11.. 1 I t: IJ.:*I H f l :...

CLEM? nrGULAlO!lY CQr.'oMlf;SION e Wl*SHllJGTOfJ, D. C.

.>O!J!;~

Mr. Burton*L. Lex Manager of Engineering Bechtel Power_ Cor"poru. ti on P.O. Box 39G5 San Francisco, California 94119 JUL 2 7 1976 4

Subject:

Yolir Cor.:rnents on Revision 2 of Regulatory Guide 1.35, dated May 6, 1976

Dear Mr. Lex:

We have re 1riewe,d your comments and suggestions and the follm-ling are clarific~tions of the guide relating to your comments:

I.

This comment ru.ises various questions regarding the

. prestressing OReration and methods of keeping track of the initial prestressing force, sequence of prcstressing of tendons and their effects on 1 ass of pre*stress due to elastic shortening, method of computing the time

• dependent 1 asses and determining the predicted fo1*ccs.

It is the intent of the guide that the applicants construct a tolerance band bounded by two concurrent prestressing force curves against time, i.e. one using anticipated small amount of time-dependent losses (upper bound) ahd 0112 usin~

large amount of time-dependent losses (lower bound) for each tendon using the actua 1 i nit i a 1 pres tressing f 01~ce measured by accurately calibr~ted pfessure gages (or load cells) a.pd checked by elongation.

Depending upon the sequence of prestressing, the ~nticipated elastic shortening loss can be allowed for*as a'non-time-dependent loss.

If other tendons in a sub9roup are expected to have

.the same time dependent characteristics (giving due

-consideration to the effect of age of concrete at prestressing), with variation only in the actual initial prestrcssing force and in the loss due to elastic shortening, the sLime tol erJnce band rnuy be used \\*:i th some means of tracking the variation.

When a tendon i~.randomly selected during an

i:"~:1C(_.i...ion from these tendons, its lift-off value should he chPcke~ to see if it is withtn the predicted tolerance band ib~ that tendon.

-~~~

i 1

I i

Mr: Burton L. Lex e *. JU. 7 197G II.

The practice indicated in your letter is not acceptable as it rni>:cs up the init"ially detcrminzible parameters (i.e. initial anchorage force, loss due to elastic shortening) with the parameters which can not be determined so accurately and are timc-dep~ndent.

Such a pructi ce reduces the effectiveness of the in~pcction progrnm.

However, the criteria that you have sugge~tcd mny be modified as follows:

(l)

(2)

(3)

All curves of predicted tol~rance bands should be cor1~cted for initial installation conditions such as actual anchorage force and loss due to elastic slwrteni ng.

All lift-off values should be within the corrected tolerance bends of respective tendons.

Lift-off shall be Ob '-::i1*n~-' 0*1

-r1J*-~c-.._ "'-~-- 1 o~s.r~1* *--**"---..Jon 11*:r._,_ o.r.f 1..c.

t::~I l

au UI-

-111..

1..t:llU Ji I u 011.)'

l..t::llU I L.-

I value which is outside tlie limits predicted for the time ~f the test.

The average of the lift-off values from all ten~ons in a particular region shu 11 be equa 1 to or above the minimum required prestrcss.

We recognize the cost and inconvenience invo10ed in detens ion i ng the te;1dons to verify the win:'. or s trt:tnd disi;ontinuity.

Since; the conclusion of insiqnificant inservicc \\\\'ire bn:a:~cige is based bn \\*1h'1t still must be considered as 1 ir.1itec.l exp~1iencr., wire: or st1~and discont"inu-ity should st-ill be checked by detcnsior.ing the \\':hole tendon during each 1 i ft-off test.

If means other tlw.n d;;tensi oni ng are available to chc:ck discontinuity, \\'le \\'muld be interested in reviewing them.

Only a single wire or strand frcim one tendon of each type need be removed for testing and examination over the entire length.

~

As pointed out in your cor.iment, the randomness of the sampling will be lost if load cells are substituted for the

• lift-off testing.

Therefore, the use of load cells mt1y only be practical for the one tendon from each group which may be kept unchaJ!gcd after the initial selection.

,r.

Mr. Burton JUL 2 ? 13?6 III. The intent of this recom~~ndntion was to make sure that the l

variations in tcmperuture during the.inspection interval has not creuted voids in the: tendon duct thus exposing the tendon to tl1c possible influence of the outside environment.

To verify the full covc:rt;9e of anchoru9e components, the procedure indicutcd in your letter is adequate.

However, after deten~ioning it will be prudent also to ch~ck thllt the tendon duct is filled with grejse from bearing plate to bearing plute.

The procedu1*e of perfonri"i ng the vi sun 1 exnmi nu ti on of the containment structure for the purpose of determining the grease*leakage fro~ the tendon duct is acceptable.

Because of the expected variations in the materials of prestrcssing systems, construction procedures, site dcpcnd2nt factors, and method of implementing the guide rcccn~cndations, we have not yet determined to \\*that extent \\'le shcul d accept the statistics bas!::~d on lurr:;:ied data froITi various groups of tl:!ndons and vnrious containm::nts.

HOV.'i.'\\'Cr, 1*i2 apprr:'ciate your having sent your surr.rn2ry of tendon surveillar:ce data.

cc: Public Document Room Sincerely, 1;;f ?r<tJ / ~, /. -~

///. l/5n--rz..(::'.r 71.A---1)l /

M. Kehnemuyi, Assistant Director for General Engineering Standards Division of Engineering Standards Office of Standards Development t

1.* *

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