ML20107G283

Provides Supplemental Info Re Structural Steel Welding at Facility.Welding Meets Requirements of Aws D1.1.Integrity Assured.Supporting Info Encl

ML20107G283
Person / Time
Site:	Wolf Creek
Issue date:	02/18/1985
From:	Koester G KANSAS GAS & ELECTRIC CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
KMLNRC-85-058, KMLNRC-85-58, NUDOCS 8502260370
Download: ML20107G283 (38)

Text

w KANSAS GAS AND ELECTRIC COMPANY THE ELECTFDC COMPANY OLENN L. MOESTER WSCE MIE5eOENT NUCLEAR February 18, 1985 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Comnissica Washington, D.C.

20555 KMLNRC 85-058 Re:

Docket No. SPN 50-482 Ref:

(1) Ietter KMLNRC 84-238, dated 12/31/84 from Gmoester, KG&E, to RCDeYoung, NRC (2) Ietter KMLNRC 85-037, dated 1/21/85 from Gmoester, KG&E, to RCDeYoung, NRC Subj: Supplemental Information on Structural Steel Welding

Dear Mr. Denton:

Questions raised concerning the structural steel welding at Wolf Creek Generating Station resulted in an extensive evaluation of the ANS welding program.

This included an evaluation of the relevant aspects of the various programs from the initiation of purchase orders for procurement of the structural steel and welding materials to final installation and acceptance.

Uposa conpletion of this evaluation, KG&E concluded that the structural steel welding at Nblf Creek Generating Station meets ANS Dl.1 requirements and, most inportantly, that the structural integrity-of the buildings has been assured.

This evaluation was h==nted in the report transmitted by References 1 and 2.

As a result of additional questions raised ooncerning the validity of visual reinspections through paint and its inpact on coupliance with the code, KGEE initiated additional actions to confirm the conclusions previously stated.-

These actions included contacting the-American Welding Society -(ANS) and' retaining three indepeixlent leading authorities in the field of structural steel welding to review the evaluation as documented g

in References 1 and 2.

-o n.

]

Detailed justification for the reinspection of welds that had been painted =haaq3ent to the initial inspectiorVacceptance was provided in section VI.E of the evaluation report.

In addition.

7 KGEE had Roger Reedy of Reedy Associates (Engineering Mars, J.

M Consultants), Doctors Slutter, Fisher,'and Yen of Imhigh so<

Oniversity (Fritz Engineering Laboratory) and Dr. Geoffrey Egan j

of APTBCH, Inc. to review KGEE's justification for reinspection gg through paint.

The results of their reviews are included as ina.4 Attachments A, B, C, and D to this letter.

All three of these same leading authorities independently came to-the. same conclusion as KGEE in that the important attributes of the welds

)I I

. 201 N. Market -Wictuta, Kansas -Met Address: RO. Box 2061 NcNts Kanses 67201 - Telephone: Area Code (316) 261-6451

. J

i h

KMLNRC 85-058 (2) j H. R. Denton can be reinspected through paint.

In addition to the issue of reinspection through paint, KGEE also had the same three leading authorities independently review the l

overall program associated with the welding verification effort documented in References 1 and 2.

Again all three concluded that j

the structural steel welding at E lf Creek meets or exceeds the structural requirements.

i In order to assure that the reinspection program documented in i

References 1 and 2 does not conflict with the AMS Code, KGEE and Daniel International Corporation (DIC) contacted the American Welding Society (ANS) to discuss the applicability of the ANS Code to reinspection efforts at Elf Creek. ~ Attachments E and F document the results of these discussions and confirm that the reinspections were not inconsistent with the AMS Code and in fact the Secretary of the ANS Structural' Welding Conunittee recognized the authority of the Architect / Engineer acting as the owner's i

representative to establish pertinent reinspection criteria.

In conclusion the structural steel welding at Nblf Creek meets the requirements of AMS Dl.1 and far more importantly the structural integrity has been assured.

Yours very truly, k-4WtY Glenn L'. Koester-Vice President - Itaclear GEK sjm Attach

xc PO'Connor, w/o BBundy,w/o sDenise, w/a y

w w

y-

~.

l Attachment A to KMLNRC 85-058 February 15, 1985 Glenn Koester Vice President-Nuclear Kansas Gas & Electric Company P.O. Box 208 Wichita., KS 67201

Dear Mr. Koester,

It is my opinion, based on the studies I have made on the Wolf Creek site, that the structural welding meets the visual acceptance criteria of AWS D1.1.

BACKGROUND One of the major reasons. for the controversy concerning adequacy of welding at the Wolf Creek site is directly related to the use of two different welding inspection philosophies in two different time frames at the site. In this regard, I an only referring to the visual inspection of the physical attributes each weld after completion.

About mid-1981, even though structural welding ' was 99-100%. com-plete,. a new inspection philosophy evolved for the re-inspection of completed welds.. This new philosophy, a "no tolerance" philosophy,

-by its very nature,. guaranteed that many welds which had previously been accepted, would be considered to ~ be " inadequate".

The "no tolerance" philosophy is contrary to what is taught by AWS (American.

D-Welding Society) to candidates for their Certified Welder Inspector (CWI) test.

(If this "no tolerance" philosophy.were applied to the.

inspection of steel bridges and buildings welded in accordance with the AWS DI.1 Structural Code, these structures would be found to -

have many " inadequate" welds.)

-The difference in inspection philosophies is as folloss:

~

1.

AWS philosophy -

Welds should be measured 1and evaluated using good -judgement.:

Weld sizes are designated to the nearest 1/16. inch. Deviations

~

of 1/32 inch or'less are irrelevant.. Weld-lengths are measured with a tolerance of about 1/4 inch. Tolerances:are allowed for all evaluations of attributes', including ' undercut.

Visually -

detected cracks are not allowed,. but it-is ~ recognized that not

+

all' " crack-like", linear 1 indications can be 1 found i by visual examination.- If.the.-Engineer. is concerned because: of. design.

' consideration 'about' minute J linear, indications - which : can. not -

-always-.be found by-visue1-examination,1 more crit _ cal i

examination methods, such - as magnetic particle L(MT) or. liquid -

penetrant (PT) will be specified.

~

~

+

.a

~.1 e

L

'C

2.

"No tolerance" philosophy-i All visual evaluations of welds will be made on strict (no judgement allowed) literal interpretation of acceptance criteria.

That is, any weld which is undersized, even by less than 1/64 inch is unacceptable.

The most critical interpretation is applied for each criteria.

Each acceptance "go-no go"

basis, with no tolerance.

This is on a

philosophy is contrary to AWS requirements and will i

automatically result in the rej e c t i or.

of AWS acceptable welds.

The advantage of this philosophy is that any weld accepted this way will always be acceptable, no matter who performs the inspection, and what the inspector's qualifications are.

When inspecting any item, judgement must be used.

For example, the inspector must choose the proper measuring tools for the condition to be examined, he must judge whether or not lighting is adequate, dete rmine areas most likely to cause concern, and must judge how and where to make measurements.

These judge-ments are caught in AWS Inspector Training courses.

I Engineers design structural welds to the nearest 1/16 inch.

E Therefore weld size measurements should be to the nearest 1/16 inch in accordance with " Rules for Rounding Off Numerical Values" 1

(ANSI Z25.1).

This standard provides that a weld 1/32 inch undersized would be rounded off to the next 1/16 inch and therefore accepted as adequate.

As discussed above, the "no tolerance" inspection philosophy which evolved at the Wolf Creek site in does i

not allow rounding-off, and any deviation in size, no matter how insignificant, is documented as inadequate.

The "no tolerance" philosophy was used on the site in order to

[

demonstrate that by "any criteria" the structural welds at Wolf

?

Creek are adequate.

y

[

INSPECTION OF PAINTED WELDS At the time the "no-tolerance" philosophy evolved almost all structural welds had been completed, inspected, accepted and c.

i painted.

Because of an inspection record control problem (some

$y

[

inspection records were lost or mis placed), it was decided that a large number of structural weld joints (each joint may contain a e

y number of welds) would be reviewed.

This type of review is

=

consistent with the requirements of 10CFR50 Appendix B which

[

provides that the applicaat take measure "to provide adequate r

confidence that a structure, syn. tem, or component will perform satisfactorily in service."

The question then becomes whether or not painted welds can reviewed to provide adequate confidence.

h This reinspection or review is a verification that inspections were performed and not a first time acceptance inspection, and not a requirement of AWS D1.1.

P k

E 5

~

4 Mr. Moss V. Davis' letter of February 13, 1985 to Mr. John G. Berra points out thet secondary inspections of welds are outside the scope of D1.1..The letter further states that secondary inspection of welds should be agreed upon by the owner or the Engineer and the contractor.

Obviously the techniques used for the secondary inspection techniques should not be more severe than the criginal inspection techniques.

It is known and understood in all welding Codes and Standards that magnetic particle inspections are far more severe than visual inspection.

(The ASME and AWS Codes make this an obvious conclusion by classification of inspection criteria.) The inspections required of the structural welding in question on site are all visual inspections.

VISUAL INSPECTION OF WELDS The weld attributes usually required to be visually inspected are:

o Weld location (including existence) o Length o

Size o

Undercut o

Cracks o

Cracers-o Fusion o

Concavity o

Convexity o

Overlap.

=

o Porosity o

Arc Strikes (with regard to cracks) o Slag and spatter:

Obviously, some weld attributes are more.- important than others.

The most important attributer. are those related to weld strength or loss of load carrying. capability.

In this category, I would place.

the following attributes as most important.

o Weld location (and existence)

~

o Length

-o Size o

Cracks o'

Craters.

- o Undercut o

Fusion o

1 Concavity The 'other attributes do'not generally affect weld strength 'and ~ are -

1therefore of-less consequence.

?

A s

y

}

s

. y;by,

.m7 r

r

With regard to painted welds, the only attributes which the paint may mask are some tight cracks, some tight undercut (a rare occurrence), fice porosity, some are strikes and some slag and spatter.

Arc strikes without cracks can be readily evaluated through paint and slag and spatter on accepted welds is immaterial.

AWS D1.1 address slag and spatter as issue only with regard to weld cleanliness in the chapter on Workmanship (paragraph 3.10).

Porosi Codes,,ty less than 1/16 inch is not even considered relevant by ASME and larger porosity can be evaluated through paint.

If it were ever considered uecessary or desirable. tight undercut and cracks could readily be evaluated by a magnetic particle examina-tion through the paint, but this is not a requirement of AWS Dl.l.

The MT examination will find cracks which are undetectable by the naked eye and is therefore a more. severe inspection.

l A demonstration was.nade a't the Wolf Creek site to assure that a magnetic particle (MT) examination would detect cracks through a painted weld surface.

Even with a heavy paint layer of 10-11 mils, all. cracks visually detected in the weld sample prior to painting were detected with MT after painting.

The. NRC inspection team reviewed more than 70_ random weld joints using both. visual and magnetic particle examination method 3 and found no welds which did not meet the AWS DI.1 acceptance criteria.

This sample size, assures with at least a 95/95 confidence level that the welds meet the AWS DI.1 acceptance criteria.

~

- In summary, I feel that based on my review of welds, documentation and reports, the reinspection programs used at'the Wolf Creek site 9-adequately demonstrate that the-structural ' welding meets the acceptance criteria of AWS D1.1 and provides adequate evidence that~

the welds - are structurally sound and meet the design parameters specified..

~

l r

. =

Ros F. Reedy, PE-

~Re stered Structu al Engineer n (Illinois)

Member AWS Member ASCE Fellow ASME e

I t

1 m

.b

'4.

s I

3'~--

.3k 2.w.

~,

b: ~

1J

Attachment B to KMLNRC 85-058 ISAPPLIEDTECHNOLOGY February 17, 1985 Mr.. John Bailey Kansas Gas and Electric Company Wolf Creek Generating Station Post Office Box 309 Burlington, Kansas 66839

Dear Mr. Bailey:

RE: Evaluation of Structural Steel Welding at Wolf Creek - CAR No. 19 At your request I have reviewed the approach developed by KG&E and implemented by Bechtel and DIC to evaluate welds on safety related structural steel at the Wolf Creek Generating Station. This review has concentrated on KG&E's final report on corrective action request (CAR) number 19 (1)* and documents (2) through (6).

~

My evaluation of the approach developed by KG&E was for convenience divided into the following areas:

1) Impact on FSAR Commitment

2) Impact on Structural Integrity w Some specific comments arising out of my review, and relating to these a,reas are summarized below:

Impact on the FSAR Commitment u

In view of the JSAR commitment by KG&E to work to the requirements of AWS D1.1-75 incorporating (2),; (3) and (5),. it is entirely appropriate for KG&E as owner to develop a reverification inspection program to provide assurance that the provisions of AWS DI.1 75 are met and to generate the documentation to support that position.

In addition, your review of related activities and their control has shown th~at this is not a generic problem but is confined to the structural steel work, welded to A9S DI.1 and covered by the Miscellaneous Structural Steel weld records. These related activitics include:

1)

Assurance that all welders and welding procedures were qualified to AWS D1.1.

s.

2)

Determination that_only acceptable filler metal (in this case E7018) was used.

'./[

v Support References are inc1hdedp t the end of this letter,y

,__ > b, y

795 SAN ANTONIO ROAD Ol'ALO ALTO O CALIFORNIA 94303 b (415) 858-2863 i

v a

0 w

g

[

wp - ;

w

J. A.i Bailey Page 2

2-17-85 3)

Evaluation of DIC inspection criteria.

'4)

Validation of inspections performed with paint on the weld.

5)

-Qualification and training for reinspection personnel.

All of these contribute to the conclusion that poor original documentation procedures -do not lead to poor welds. This was also confirmed by my

-examination of relevant welds in the Auxiliary Building and the Reactor

~ Building. fI'was able to examine both painted and unpainted welds and in all

~

cases ~the welds appear to be good with a generally uniform appearance, indicative of skilled crafts people.

With regard to the ability to reinspect welds after painting, I have already

. stated that this.is the proper approach for~KG&E to pursue for the following

. reasons:

cThe discontinuities that are.being examined for (i.e.; porosity, lack of fusion, etc.) are rather-gross imperfections and are readily detected by visual examination...A coating of a few mils thick would not obscure imperfections in the size ranges of 1/16 to.1/8 inch.

/Even these imperfection sizes are small compared to the. size-that

.would compromise structural integrity.

. Carbon manganese steel welded with'E7018 weld' rod is probably one of.

the easiest combinations to produce high quality welds. _ Carbon

< Manganese steels ~are:readily weldable and do not harden significantly~

.with welding thermallcyclesias.would alloy steels. ~ With proper rod fcontrol:(which is demonstrated in your review) the likelihood of weld-

. cracking is. low..This'is confirmed by the.results.of the'insgection.

of the uncoated steel in which few cracks and' lack of. fusion imper-o

.fections were discovered.~

^

The detection of size vaiian'ces '(either over or under) will not be y

limpacted by th'e, presence of paintLor; coatings.

• =wiMissing weld elements wouldLb'e rather obvious even where coatings =are:

.present.

1.a C II' understind from ' discussions with 1(G&E that(USNRC ~ Region ILmade' ai site. visit and ;

r performed ~~a sampling-inspection on more than 60 relevantijoints.7. This, iinspection= included examination by.UT and MT, before?and-after paint removal:and-s lthe?results'were positive. iThese'dataishould be requested:from Region 1fand; s

Lused;to. support your. position.

4 din'. view of the fact:that weare now using twenty: atwentyl hindsight and;are.

3 sensitized to the need:to perform detailed inspections the : defect rates aref -

=

relatively: low'in those categories of attributes that were Tcla'ssed 'as(defects :

(abouti3%.on 'a ' joint basis 3which would be euch less' onLa total-weld basis)b

~

1 4

g b

i(l

~

+

yj.

g,

, 2

^

V;. 3.;c iG

<!f u); il

^

e

-N

~

W

. +

^

q

,- h

'?,

~

t-

,i '

s. 7

~/

?$l

~

s.

+

)

i i

i

}

J. A. Bailey-

.Page 3

' 17-85 Normal reinspection detection rates come in at around 2% on a weld basis. We recently performed a review of previously accepted welds in Class I piping l

and established a reinspection call rate at about 1%.

i.

The focus of your-program on structurally significant details has enabled you to evaluate those situations that are most important. It is worth emphasizing i

that the extent of CAR No. 19 is limited to about 21% of these structural

-details. The other details are either shop welded or bolted.

I believe that with your re-examination program, the related activities referred to earlier and the confirmation that examination under paint is effective, you have met the extent of (4) and complied with your commitment in (7).

}_

Structural Integrity Since we have concluded that defective paper, work does not necessarily indicate a' defective weld, the real question is, "What is'the' impact on structural

. integrity of the imperfections discovered.in the reinspection?".

Bechtel has-evaluated those situations where the stresses'could exceed the

-design stress.because of-geometry in'dications.(missing welds, undersize, underrun) and in all cases the calculated stress are less than those that would be required to. fail a weld-(i.e. the weld. capacities are in~no way approached

~

C under the: design ~ loads).

I concur with Bechtel's approach,-but would point'out that it is conservative (i.e._ greater margins:will be available in'the actual--

joint than indicated by the Bechtel analysis)..

The first fa.ctor contributing lto.the conservatism is that for thelgoverning w

4 allowable stresses, the specified minimum properties are used whereas actual-properties'of as deposited welds.will'usually run 20-25% higher'than1th(

J J

specified~ minimums ~.. This means that based.'on: actual properties deviations from allowable' stresses at up'to-20-25% would not' violate l design-criteria ~ based on!

actual properties.:

~

~

The second factor relates to the consequencesiof exceeding theldesign allowable

, stress in fone weld,: or for that ;matteriall, welds, in a'connectionj thatf cont'ains ?

E 1several welds 'as imany of: theseijoints do. - ' There fare of L course none.

In':theS

~

y jointoneweld.maybeoverstressed,however,1the1structuralVintegritylof-thei*<

n F

jointiis'not' impaired at all. fit is important^.to re-emphasize?this-fact.

The integrity of a'structuralEdetail'is.not affected by the imperfections L.

r

'. detected-in the reinspection program..If:this was more generally recognized,-

kV

- (we would be, faced with far fewer; reverification exercises Lin nu' lear facilities. :

- t 1

e

.Afurtherfactithatfcontrib'utestothe5conservatisminthe7Bechte1[analksfis[

[

that where undersize has beenimeasuredito be? intermittent?iE the'actualfdetail,;

c t

Jinithe!analysisiit]hasibeen" attributed (tothe' complete 1 weld?lengthL

. T.

~ -

y hk,

r 4

L v-- >

~

s y>

E '

h~

~

~

r

'N-

.i I

\\

J. A. Bailey Page 4 2-17-85 A question may arise about the integrity of those welds that are:

1) uninspectable (because of access) and 2) could not be evaluated for alternate load paths There are 83 joints in this category and the approach chosen by Bechtel is to demonstrate that the expectation is that in only one joint would the design stress be exceeded. This is derived from the frequency of those structural joints that exceed the design stress. Remembering, as acped above, that small amounts of undersize are attributed to the complete weld it may be instructive to consider this on a weld basis.

Assuming an average number of welds per joint of 4 and the same liklihood of exceeding the design stress in a weld as in a joint, the followieg table provides the. probability that 1, 2, 3 and 4 welds would exceed the design stress:

Number of Welds In a'4 Weld Joint Probability 4

Detail That Exceed Design Stress A

. B*

1 3.17X10-2 8.7X10-3

~2 1.0X10-3

'7.6X10-5:

3 3.2'X 10-5 6.6X10-7 4

1.0X10-6 5.7X10-9 LThis column is based on a 0.87% rate-which excludes the polar crane radial stops.

. These numbers illustrate -the very.. remote liklihood of all welds fin a joint exceeding the designfallowable stress.at the same time and.further confirm that structural integrity ~is assured. On this basis, I would expect a timely closeout'of CAR 19 because there is no safety. impact and hence:it.is not reportable under'10 CFR 50.55(e).

In the foregoing,-I have tried to emphasize.the important' facts related to the.

closeout or: CAR;19. I think you would agree that there is-no safety' issue-and the ' documentation problem did not-spill.over to other related areas. iThere

~

are, -however, a few points ' that may be worthwhile making, particularly if you,

thave to present all.of the work that'h'as been done to date,.to the management 1 of KG&E.

First the question of cracks may-be raised. What isfthe liklihood'of having cracks in uninspectable areas?

The only cracks that have been observed were from construction ~ loading of beam seats and :not' attributable 'to welding _(1).

The : review of ~ weld procedures,.

4 2

}

I J. A. Bailey Page 5 2-17-85

" filler metal control, and welder records indicate that the welding was not out of control. Usually when something goes wrong with the welding process to cause cracking, the cracking is quite extensive and obvious at the toes of

-welds. Moreover, the A36 structural steel and A516 embed plates are easy-to-weld carbon manganese steels not prone to cracking. These steels are widely used in other industries in which the: rigorous quality assurance requirements of our commercial nuclear program are not adopted. These industries include bridges, multi-story buildings, offshore platforms and pressure vessels. Our record in these industries would confirm that integrity margins are.available in welded structural steels. On this basis I would

- conclude that there is no potential for structural degradation due to the presence of cracks.

' Further confirmation of this fact is provided by the good inherent toughness of these materials at the minimum operating temperature of the steel. This would preclude crack initiation and propagation from pre-existing cracks.

~ The thoroughness and detail of the reinspection program undertaken by KG&E

- ottests to the commitment that you have already made to safety at the Wolf.

Creek Nuclear Generating Station.

-In the rather short period that I have had to review' your approach to the resolution of CAR 19, I have probably not done justice to the extensive ~ work ~

already done.by KG&E, Bechtel, DIC and other consultants on this matter.

I hope, however,;that'I.have been able to grasp.the main points of this issue and if

~

L

-you would~like to discuss any of-the comments I'have made, please feel free to

' contact me.

Kind.Regards, Geo rey;. Eg'

'GRE/nw.

w h

M

?

Y t

y

'l s

1 u --

i t '

l -[,

~

r

i

~,.

REFERENCES i

1)

Kansas Gas and Electric Company Final Report Corrective Action Request No. 19 2)

Technical Specification for Erecting Miscellaneous Metal

.for the Standardized Nuclear Unit Power Plant System Bechtel Specification No. 10466-C132Q 3)

Technical Specification for Contract for Erection of Structural Steel for the Standardized Nuclear Power Plant System Bechtel Specification No. 10466-CR2Q 4)

AWS Structural Welding Code AWS DI.1-75 5)

Daniel Internations1 Corporation, Inspection of Welding Process Procedure No. QCP-VII-200 DATE REVISION 3-30-77 10-28.1.

2-01 2-18-78 3

11-08-78' 4

11-18-80.

6-1-21-81 7

3-12 8' 12-17-81 9

6-29-81 12 9-22-83 17 12-17-84 21

~

6).

Letter from C. M. Herbst.(Bechtel) to.G. L.iFouts (KG&E') date-2-15-85 regarding Structural Steel' Joint Sketches 7)

Final Safety. Analysis ~ Report-

~

SNUPPS Section 3.8.3.6.3.3.

b

\\

b y-

~ k'

+

e c

f i

V a'

4 Y

~

c

Attachment C to KMLNRC 85-058 LEHIGH UNIVERSITY Bethlehem, Pennsylvania 18015 Fritz Engineering Laboratory 8""*"a u February 14, 1985 1

Mr. John A. Bailey Wolf Creek Generating Station Kansas Gas and Electric Company P. O. Box 309 Burlington, Kansas 66839 Re: Visual Inspection of Painted Fillet Welds

Dear Mr. Bailey:

1 Dr. Fisher and I have reviewed the paper prepared by Bechtel Power Corporation regarding their position on the " Visual Inspection of Painted Fillet Welds".

Dr. Yen of our staff has also reviewed this and provided comments on the paper. We all agree that the important characteristics of the. welds ~ can be evaluated with the paint thickness of 14 mils (1) on the members.

)

The evaluation must be made on the basis that certain problems that could occur in' welding can be ruled out because they do not exist' or, are not important for the type of welds and materials involved.- We.

are concerned only about inspection items that might reduce-the strengthJ g--

J of. connections.. Tests made on welds from the Hope Creek Plan,t-(Fritz Engineering Laboratory Report 200.81.240;3) revealed that-evethvery large:

amounts of porosity in the welds reduced the strength' of connections by only -

~

a small am5. ant -Large porosity of the type present in" welds from the -

L

'. Hope; Creek Plant could be detected through paint. 1 Fine porosity of a'si$e l

that could not.be observed through: paint.is of no ;importance in evaluating '

.p

'the strength of these connections.

t We-feel confident. that the inspection results to date-demonstrate :

that the quality of welding on the buildings was more -than adequate tof provide' the strengt.h required' in the ' building' connections'. ;If there~are

, inspection items such!as fine porosity,Tminor undercutting or. cracking (in.

p'

welds. produced,by joint restraint.that can not be detected through paint,'

q.

.these' items are not apt;-to. reduce theistrength of" connections aufficiently W -

j

, p. z -

qs

~

P

~

?to be of concern. LThe redundancy in;thelcompletedistructure'is alsoK. vail-/

able. to. providei Alternate l load pathsLif-necessary in the eventithat a]

L

' connection of lower than expected strength exists.'

t LS ere

,=

i i

LRGS/df:

'Ro G.'

lutter ec': (Richard I,vy : wa g

G g

.e-tJohn W. Fisher k,. c r

g_

- to KMLNRC 85-058 s

e L E HIG H UNIVERSITY Bethlehem, Pennsylvania 18015

(]

Fritz Engineering t,aboratory

),

esan n i December 10, 1984

(

Mr. Richard Ivy Kansas Gas and Ele'dtric Company P.G. Box 208 Wichita, Kansas 67201 -

Dear Mr. Ivy:

Re: Structural Steel Welds at Wolf Creek Generating Station i

We have reviewed the problems associated with the structural welds in the structures at the Wolf Creek Generating Station.

Dr. Slutter was on the site on November 1 and 2,1984 to observe firsthand some of the weld deviations, the method of inspection, inspection records, and problems encountered in completion,

of the inspection program. The problems encountered at this site are not unlike structural welding problees that we have seen at other nuclear power plants.

The problems at Wolf Creek are perhaps more frustrating but less serious than similar. problems at other sites. The approach being used by Bechtel as summa-rized in " Weld Deviation. Evaluation Methodology" dated November 26, 1984 has also been reviewed.

(G)~

. The examination of the welds in this reinspection program is very thorough, N

as evidenced by the documentation on every connection. The thoroughness of the inspection has _ revealed some problems that. require evaluation from a structural analpis point of view and a much -larger number of instances where ' deviations-from AWS D 1.1 - 1975'are reported that do not constitute structural deficien-

.cies.

lt. appears = from the_ latest sucimary of inspection and evaluation received '

from Bechtel.(dated November 27, 1984) that no significantly deficient joints have been found.

We have the following comments on the various' categories of problems that have-been found in the reinspection:

a N

1.

Missing Welds Obviously the missing welds should be replaced if they are needed to resist design loads...Some'of these welds such as the. beam to beam seat welds may not be required 'and: replacement,should not.

be necessary. Where'they are inaccessibleland cannot.be replaced, an appropriate ana[ysis of the; other load paths should-be "

-provided.

L' y

i

/r

. f.,

I g[

i '

J.

_I4 i,p S-f U-d, u

Meseeren in Chrst Engineenne one Rosatog piogge jh&Tfbb~L~~

g w;a:

x-d '

Qpa.,1&&: %.asJ, & au "

v

~

^

~

i i

Mr. Richard Ivv__

1 December 10, 1984' ',,

Page 2 2.

Undersize, Unequal Leg, and Underlength Welds The approach that is being used to evaluate these types of condi-tions using the smallest weld dimension is very conservative.

Welds that are no more than 1/16 in. undersize will have adequate strength on the basis of the latest code recommendations.

The allowable stresses being used by Bechtel from the Seventh Edition AISC provide-a conservative basis for evaluation.

3.

Oversize and Overlength Welds These deviations are not generally a problem to be concerned

.about.

There are some instances where the additional amount of weld causes the connection to provide more restraint than in-tended.

The original design actually specified this~ additional welding. In these structures the additional weld metal should not cause problems. End rotation and the resulting connection deformation can result in cracking of the welds if the additional weld increases the bending stiffness of the connection and decreases ductility.

c i(

4 Cracked Welds 3etween Beam and Beam Seat These cracks resulted from rotation of the end of the beam as concrete slabs were poured and additional dead load was placed.

The cracking does not indicate a deficiency in the connection since the weld is not needed. The cracked welds that were detected were probably undersize because of the rolled edges of the members being joined.

5.

Return Welds That Are Overlength But Undersize The purpose of this weld is to produce a proper termination for the vertical we'.d.

It is not necessary that it meets AWS 1.1 -

1975 size requirements, since it is not needed structurally.

The added length can increase capacity in some instances.

The pri-mary objective of end returns is to minimize prying and distortion at the root of the primary weld.

6.

Lack of Fusion and Undercut These problems are very few in number and are being satisfactorily handled in the analysis.

~

^Y

...."- a

. so. - -~< e

• h N g.

.n n.

W

- - ~ ~ ~ ~

~ ~'*

r

~.

Mr., Richard Ivy Dec4mber 10, 1984,

~

Page 3 7.

Beam Seat Missing These may not be needed but an analysis of each one is being nade.

It is assumed that seats will be provided if needed.

8.

Fit-Co Cao with Undersize Veld This is a rare occurrence considering structures involved.

analysis of this is being made by Bechtel.

Proper 9.

Inaccessible Welds Since there are no significant structural deficiencies among the exposed welds inspected, it is reasonable to assume tnat the inac-cessible welds are similar.

The general problem of weld size should be considered in terms of the where the AISC allowable stresses are applicable. expected statistical va Fig. e showing the statistical variation of the 1/4 in., 3/8 in., and 1/2 in. Enclosed are F s

welds used to develop the AWS and AISC specification provisions.

These curves show the deviation in weld sizes that are to be expected with production welds.

The variation of weld capacity that resulted from the AWS-AISC fillet weld study in 19o8 was in part due to the variation in weld size that existed with the test sample.

exist with all welds.These were normal production welds, andisimilar deviations will strength based on nominal weld size. Figure 19.3 in Structural Steel Design shows the shear It is clear that part of the reason for the variation in capacity is based on the weld size vr..istion.

When a weld is found to be undersize by measurement, it is not significant unless it falls below the range indicated by the curves.

The AWS Specitication does not address the problem of deviations, and disposition of undersize welds be done using the' type of analysis that Bechtel'has proposed. The fact must that they are using actual weld sizes in calculations is conservative, the specifications used the lower bound of the test data which included weld since undersize.

Weld size deviations on the retarn welds does not require analysis. These welds are not intended-to increase the strength of the connection, although some additional strength does result f rom the addition of these welds.

i

.The main-function of return welds is to increase the ultimate strength.of the struc-ture by delaying end tearing of the weld and improving the ductility'of the connec:Lon.

These welds need not be held to exact dimensions but should be large enough to provide a satisfactory weld termination.

,s gle d.,

t.-.ed is, %

Em*.%,

, w.c.w wu. w. s,4m.

ye,m

..e e

+:.4

t Mr., Richard Ivy December 10, l W ~

~

Page 4 The analysis work being done by Bechtel is based on elastic design with reference to the" Seventh Edition of the AISC Sunual of Steel Construction.

This approach is conservative compared to the ultimate strength method avail-able in the Eighth Edition and the current approach used in LRFD design as given in Load and Resistance Factor Design Criteria for Connectors *,

One of the provisions of the earlier specification that is very conservative and not applicable to weld capacity is the allowable stress for base metal in shear given as F 0.4 F.

This limit state was arbitrarily adopted in 1969 and is

=

v y

related in any way to veld capacity. This is only now being corrected in not the AISC Specifications. The attached copy of Table J2.3 shows the proper limit state conditions that are used in the LRFD Specification.

Steps are now underway to change the allowable strass provisions for shear on the weld leg to 0.3 F in place of the value 0.4 F. Typical increases in allowable loads u

y for eccentric connections that one can expect to result from using the ultimate strength analysis outlined in the Eighth Edition of the AISC Manual can be seen by comparing the results given in Table III pn page 4-31.

With a weld length of 11.5 in., the C-shaped veld and the outstanding angle vertical welds are similar to the welded example shown on page 661 of the second edition of Structural Steel Design. The ultimate strength analysis of the clip angle to plate welds provides an 8% increase in load. The C-shaped welds of'the clip

~~

angles to beam web are permitted to carry 22" more load using the ultimate strength method. This can also be seen by ccmparing the standard angle connec-tion loads in the Seventh and Eighth Editions of the AISC lbnual.

The AISC provisions for the design of this type of connection are very conservative even when one uses the ultimate strength method.

The minimum factor.of safety for a connection designed by the ultimate strength method is given as 3.33 on page 4-74 of the Eighth Edition of the AISC Manual.

The usual factor of safety in weld design for single load vectors is 2.33.

The more conservative design for this type of connection recognizes that minor deviations such as found in the connections at Wolf Creek Generating Station.

will occur.

These deviations are not uncom=on, and this is recognized by the AISC provisions.

In particular, the veld size variations are typical where fillet welds are used.

The higher factor of safety in use for eccentric joints recognizes that other deviatiens are likely.

We do not believe that a structural problem exists with the Wolf Creek-welds once the obvious problem of missing welds has been corrected.

In the-November 27, 1984 su==ary, Bechtel reports only 17 joints requiring rework due to.overstress of 1620 joints evaluated. This is a very. low percentage in view of the conservative approach being used in the analysis. A leas conserva-tive approach might result in an even smaller number of joints requiring rework.

• Load and Resistance Factor Design Criteria for Connectors, by J. W. Fisher, T. V. Galambos, G. L. Kulak, and M. K. Ravindra, Journal of the Structural Division ASCE, Vol. 104, No. ST9, Septe=ber 1978.

-[

V i})' '

.,w.

" ' ~

~

\\p)'

Mr. Richard Iv m.. -

December 10, 1984 Page 5 In any event we feel that Bechtel's approach in considering the inspection re-ports and their subsequent. analysis.is adequate and sufficient 1y' conservative

~

for. the type of structures and the type of connections involved.. The overall quality of the welds based on the inspection data and observations that we have made exceeds the requirements for structural welding for this type of construction.

We would be pleased to examine other Bechtel dispositions when they are available.

We agree with the proceiure being used..

Sincerely yo %

D1 m Wdy Joh W. Fisher

/

Prod,essor of Civil Engineering-f Co-Chairman,-Frit: Engineering Laboratory..

h)..W.=., : w;:/@/.

l

. './

't

\\

(

- \\.,

Roger. 'G.

Slutter

~

Professor of Civil Engineering Director..- Operations : Diviston -

~

JWF:RGSirag

' Enclosures J.'A. Bailey 7 cc:

a

(

+

y e

A.

p 7

.:.s' 3

)',

I(y u

.r,

~

w >,.; a

,i.s 4 5--na-

-"-?-~~.

' ~ " - '

e, n m, >y" te's N H W*

.j. -

e

Sect. 12.

Welds Tacle J2.3 Desian Strencth of welds Types of Weld and d Material ~ '

Resistance Nominal Recuired Weld l

a Stress Factor a strength strength F

or F lev e t -,, c gg w

Complete Penetration Groove Weld Tension normal to effective area

" Matching" weld be used Compression normal to Weld metal with a l

3j! effective area Base 0.90 F

fi strength level

{

p#arallel to axis of weld Tension or compression equal to or less than " matching" may be used i

p Shear on effective area Base 0.90

0. 60F Y.

Weld elect.

0.80 0.60F N

}

Partial Penetration Groove Welds

.tCompression normal to effective area Weld metal with a sC strength level equal.

Base' O.90 F

to or less than Tension or compression Y

i

. : parallel to axis of weld

" matching" weld s

i metal may be used !

I. Shear parallel to axis Base

• 0.75 0.60F of weld Weld elect.

0.75 0.60Fh Tension normal to Base

• 0.90 F

sf effective area weld Electrode 0.80 0.5,_ c 60 gg

}

Fillet Welds-2 Stress on effective area Base

• 0.75 0.60F Weld metal with a

~S N

Weld elect.

0.75 0.60F_

strength level equal

~

to or less than Tension or compression Base' O.90 F para!!el to axis of weld

" matching" weld

{

metal may be used Plug or Slot Welds Shear parallel to faying Base

• 0.75 0.60F Weld metal with a surfaces (on effective Weld elect.

0.75 0.60F area)

EM strength level equal to or less tnan

" matching" weld metal may be used

• For definition of effective area, see Section J2.

b For " matching" weld metal, see Table 4.1.1,_ AWS 01.1.

c Weld metal one strength level stronger.than " matching" will be permitted 3

s Fillet welds and partial penetration gro' ave welds joining component elements o members, such as flange to web connections, may be designed without regard to the tensile or compressive stress in these elements parallel to the axis of the welds.

"The design of connected material is governed by J4 --

.A

. ~-

M

r~

3 ;-

~

., ).~..,.,

/

l.'%

'b D

I e.+

.~*

,~g*.

~

~.

e.-

uO-

• • w N.

w

'

• q,=)

s e

tt $

at s

n.

~

B t.

e

-. q:.,~

-./

',i t

- ~.

--s-e.,

t.

7,,

A..

/

f.

... ~.

~.

c 4

/

s.%

~s 3 3 -

e o %

/

-Q R r~-

4~

0 s.

~

m 2.,

Qg y

..N +'.. m y.:.

)-

5 m

y o,.

9,, ~..-* ~ '

N t C. s. t -

.s.~.0 i

X*

3

. o a

cnx e -

.s y

.a.

g i c ::

s.- @.. -

.. - )s

h..Lja s

M

.t

• f

.w e

L e

.c d

~..

m,

..=/

a.*

2t

e ~4

$ 5 d.'.'.

.2p t f'

, f.. :

.a.

~

i L.

,,* ?. =. $*' ~'=

y.-tm.,.....,..,,...:.

i

.:, H..l y

,m

. w. p m

a \\ -

s vT:

i..

,.' y.7

.".*J g

'e.

i

• ~..'."

s

.r.

g

..W-g

~

,i..

/

6 C"., IX '. )

.'"\\***

~,

(

,,,- /pa, T--

7[-

,,,,- ~.-'.Oa' s

.4

• ...o.....*,.'

.:' J Q.

Q

,.-....-..,.t...y,....'

\\

6 7

'/. s.'U.". w...'.'

sJ fa.4ne'...*-.**...

4.',.-

g N

N s

s.,

.w.

s r.

~

s

s. ~:

E, ' -* ~

0. n. v.

,/- s p,. ' 4. ??.

. "..'.* h..'uf!.

s

~.

s.

4(..,

.f.

m t-

,' /

)

g

.---~; a. g.')

• ;t-T g.,,, o M,.f... q f. m

'. \\ %.

<,...s

.g g

s

. ~. u.. g f.

o

?.'. Q, ~. '

A e,

..s.. st' s IX p

'. 4 4,:

1'

.I t./s:.r..

r-.-

\\ t

~

2-r., _h.

t s,...-

.... > ~...s..

~ =.

• A.

\\\\s

. ;,. i f,,,

.S..

p.N.

~J w.

s.. -

s u._.. o.y i

m r

&s-4

.~.a,.

.. r

. 3

.r.

g =.. s

~

i e :

I.

t f r.

t e u,.., ' ' = * ~.

• f I f

a' t. i t i ! ! ! ! ! ! ' I i I ' ' '

<=

h 4e' E W aus.

$ bh

• .e eM NhD M 3... ~.,

s

-~~v*-

Onvi.m! niaNe.* ten: a c: = ie: : :: :

. '. e i m Id km" Aws -A-3c c,1:g:' ',, v :, T. > ;...:: e the

/- ~. ~..,.,., u.,.. i t2 te,. e.

~

...=.----~..'...c.~?..

4... - - ;.

.>,.,,. 9 n.,,y.,,.

. r s

, A.m u

m,i,.

, s.

.ub.

May 3I, 196 8 G-

-eh )

..a.

v i.

I^

ne <r=

.n U

,I f:

.., 3,3,.'F'

-d.

/s

.,. t

,, V nL i-w 7;

/TQN a

• Q.

,s.-

,'y ll i

.3.

m s

v u-e:>. f 3

. ~. //,

~'*

./

N

/,

y.

/

w

/

,. /

,i, r.

/,

n v--

.,L

_p,.,/ l, I /.N

N c

t.

_r

..i,,/..,

./

5 =y y t t.

.,/

s. ~

s.',is. /,,/ "/

.S : L.(

, N '.

u u I.

e Y'Y/,'/:'. 7/.'..,',. 'p{'. ' <,';;,'.

./. i

,- s

- /',,

aE

/

lN--

'* i,-

y /..

/j

/,/. ' '..':

./,i /, ;.

'./ /,.

<f

./

x.

-G. _.-:.

~.

/

w

,.,...,,.,,.,...r.r

.,r-M.,. :c.:.c ; -- ~ ~ -

.s

//-

N s

4.

4

-s.:.2 l' 1 '

\\

-:n~:.j 9

• u., ; -

.s v

n = /

• Tls 3_

5 : z. H is 4

-o. --

12-t

.v e m u. : T' s,,_ /

s. 61

--~'le o-m, f

% :n i z.

',, Q I:,:

/.i

g..a y.

t_ o m.

r^

v.;

I x

lp:) "O kT

.. s'../. <<,, ;,','V

.,/

,i.

,,y/,'.

^

v

/

ss -

/.s

/

//

.,i

, ;.. s.

/

, t., _

,/s <.*:/ - e.

jx r.e A

.a

.,,,i

, /// /../,/-

~g+

y /,s,,

/...

,'/

/

,L,

, t> -

e,,

/,

. ' / /..

.y.

..:/.

./,,,,.,.

'/

.y

- i.

i,,

~

n

/

.i.

.. /-

..i.

,/,<,,.

.<ji

. /r..

/

./

s,,.., ~.,

c_3,_-

/,

-v

n :.":.W.ss'.a,n.m. ts in :,n u.a in t.v ' n:a ' :,v'i.n' ;.1:' i: ' :.n

/. i,..,

7. & tm7._.:

s rat,'O(D.),1,,;..,.-

DJ sc:nr t

s. - -

+.

I y-f

?, n = V 2 9 7 - ).163 n

• 3 3 'o

'\\* *'l c A =. 0 2

= *

• I I

W-

- :.x.

.l. g y ;,;

n,. g

(

~-

t

• S' *I3I y

T

,, I a x. = O 2 u.I.

._ /

32-n=asa M

'$ w I ~ I.073 IV",

2 n

' 4 S =.13 '#

(tueie) 0 5 g.

y 4x =. 0 2, v

v; 'C i:,

/

+t

/

c,

9--

t2 y.

l},. m e

u*

c O /J i

Og L B- -

i

{ $

fa-

\\

~

_s i

+3 4-C z_

'.7 3 7.'i

.il. i n~ '. 31

.9 ), '. M ' 8. * ' i "J

8. L ? l'I * 'I ' l I'

• ;I

'^3 8'II I*I7 A#

I* S

1. ' 3 8'D

-)

f U,, a., : )

+

reto

\\

'--G c &.-e:

C2ere.spondem e irem Mr W C Cad.,-//, A,s: C.4. 4; or.'*.::e:yi//or h etc.- C.,

Pec.:2.."1i De: 22,49 f y

. CF 9 ?.5 l-islet,uelis che-keo',

-o m }' * !s VE from chn data

• a 6 2 2 (W.4 '4) f-sm nomina' (! 0) !a.:!7, e.ori:e (1.2Y

/:. 2 ', c.reres &s to 1 9G {/0 '-l fo) C/L*.*dd 2S,, eversite (f.?!)

es.+ d,

..,-m. es S s.

p: qz; y,,,.,, y, $

l9I (I5.~fa) up,fgr nomirsal Snieff,0) i ' l. Il ?.

f.D = X

!..*2 6 s h

$ *. /$ 9 i 2T 3

'* *<,. 3 ',* 1 xe x n,5 Nh D

/.2 5 = '7 a., 3 ""35

(/.2D 5) fro-Cf'a 3E C i*L'

&.$n

,k N&

i CG z

is.' 2 7.

3

/0.4 %

y

2. 4s --

beloy acmmt

,i

,,,,,,,_ gg, ;

s a b s.i e 2 5 3"

'I co gg Ag$c jgg

\\

d 'i d." S i 2 d' 0- 9 s

• s s

$b 2p

1. h,' -

q e.s 5,/

e.-

ya

,' \\'C,

i N

y E.w

.s ' -

s N

s h';h,

. f j "..

.n..n.a '.a.as '.95.tr pi i.n i.a. tn ',.n

,.:. e.:r. a e.n s.w i.9 e.w

,.4

$ e.

I^J a c tu al 3

gm

~

N desired )

-. -. _.-..,. ~-

-..... - ~

-~~ ' ' ~ ~ ~ ~ ~ ~ -

~ ^

p.e vs m.

r,

'i

~..

k.<

• 1425 SEPTEM8ER 1978 ST9 14087 SEPTEMBER 1978

7. Juhason. R. P., "stescasch on Stecl Concrete Cosnpossac scams." Journal of rAe ST9 Strues rad D.easwa ASCI:. Vol. 96. No, ST3. Proc. Paper 1822. Mar., 8970, pp.

441-419

., ass.a.. P..n.1 n..pc.G.ii. M C..

Ap, catma of Simpic Pi.si.e nico,, to Consinuous Cornsmisc Iscams." ProceeJmgr of ske lnssssurson of Cara Engsneers. Vast JOURNAL 0F THE

2. voi

.l. ua.. im.,,. im i9'-

9. O!!sansJ. J G. Stutact. R G and tr.ber, J. W.," Shear Strength of StuJ Connectors STRUCTURAL DIVISION i

e i

in Laght.cashi and Nesmal Wcight Concacte." Amerscan lassisuse efastel Censsrutraon l

l Easmeersas Jenin.J. V' ! 5. No 2. Apr.,1971 pp 55 44.

0 30 Ravindsa. M. K, and Galambos. T. V " Load and Resistance Factor Design for Seccl." Journal of the Strucsural thnswn. ASCE. Vol.104. No. ST9 Puoc. Paper LOAI) AND RESISTANCE FacrOR DESIGN 140uo. Sept. 891s. pp 8441 1457.

CulTERIA FOR CONNECTORS

• II. Slutter. R. G., anJ imscuit. G. C. Je. *'l le sural Streasth of Sicel-Concrete Cosnposite Beams." Journal of sAe Ssrucserol Dunswn. ASCE. Vol. 98. No. ST2 Proc. Paper 4294. Apr.,1965 pp 78 99.

By Juha W. I.isher.' heodore V. Calambos.' Felloves. ASCE I1. Spect(icassenfor nae Desogn. Fabncarson and Erecsson ofStructuralSteelfor BuslJmgr.

g,,rg,,, g, g uy,g,s and f5fayassadra K* Ravindra

• American lastetute of Sicci Constructium.1978 hiembers. ASCE

13. "Sicel S wouses for asus!Jangs-limit States Design." CS.4 SsanJard Sid 11974 Canadian Standards Association. Readale. Ontano. Canada. Dec. 1974.

!=inoouenoss Design criteria based on the Load and Resistance Factor Design (1.RI D) approach must include a treatment of connections. This report wdl focus on Jewelopment of the critcria accessary for the principal fastening elements (wclJs.

high-sticagth bolts, and ordinary bolts) and will include illustrations of the application of these elements in comrnon types of joints. Comparison will be rnade with results achieved using working stress design.

As Jeveloped in Ref. II, the LRFD method can be synthesiscJ as 4 R. h Y. Q..

. (1)

The left-hand siJe of Eq. I is the resistance of the member or sinutture (R, is the nominal resistance and 4 is a " resistance factor") whde the right-hand siJe gives the cIfects of the load on the member or situcture. ConsiJcitug.

for exaraple, only dead loaJ and live load. Eq. I would be written illI

+ R. 2 Yo Go + Ya e,-

.(2) in which 0, and G,, are the mean Jead and live load effects, respet tively; I*

and y, and yt are the corresponding load factors. The principal purpose of

[-

this paper is to develop capressions for the parameters & and R in Eq f.

Noac.-Discussion open untilIchruary 1.1979 Sepasste discussions should be submiucJ i

for the indivnJual papers sa this sysnpusium. To calend the causing date onc month.

a writica request must be filcJ =ath the Edder of Technical Pubhcations. ASCE. ' Ibis paper is part of the copyrightcJ Journal of the Structural thvision. PsucecJangs of the American Sodcty of Civil lingiacess. Vol.104, No. ST9 Sepacmber,1978 Manuscraps mas submasted for review for possible pubhcasson on May 11. 1978.

'To be presented at the October 16-20. 4975 bclJ at Chicago, !!!

ASCE Annual Convention & lispossanoa, i

5{

' Prof. of Civ. Esgrg. Fnta Easts. Lab., Lchish Univ., Bethlehem. Pa.

'Psof.. aaJ Chsna.. Osv. lingra Dept. Washineson is w 0 ~~ 8 8 --

t

~.

+n f

1428 ' b

(< v)

(%

W SEPTEM8E*11978 u

Syg sig LOAD.ftESISTANCE FACTOR De development will be based on the use of first-order probabilistic methods.

29 The fundamentaircquirements for a wcIl-designed connection can be considered WelJs.-The wcld types used for structuralpurposes are primarily the groove to be:

welJ and the fdlet weld. In the case of groove welds, the forces actmg are usually tensile or compressive. Tests have shown that complete penetration

1. Adequate Strength-It is generally considered good practice that groove welds of the same thickness as the connected part are capable of developing connections be somewhat stronger than the parts being joined. Thus, if failurethe fuu capacity of that part. Since it is normal to use wcld metal that is the should octur, it will take place in Ibc members rather than in the connections at least as strong as the base metal, this means that the properties of the base

j thereby ensuring that ample warning (e g., large deflections) will precede failur metal will govern the design. Thus, when complete penetration groove welds

2. Adequate Ductility-Care must be taken in proportion:ng the elements are used, design csn be based on the properties and behavior of the member e.

of the connection to ensure that ducide behavior will result. Of course, su(h in which the connection is being made.

e

[

undesirable phenornena as buckling of plate elements, brittle fract rre, lamellar The ultimate strength of fillet welds subjected to shear (the usual case) is tearsag, and cacessive local distortion must be avoided. Provision of adequate dependent upon the strength of the weld metal and the direction of the,slpplied ductihty wdl mean that the structure containing the connection wiu have capacity load. He wcid may be parallel to the direction of the load (a " longitudinal" for distortion before failure and wiu allow for the redistribution of loads. The 611et weld), transverse to the direction of the load (a " transverse" fillet weld).

provision of adequate ductility is a requirement generally less wc!! defined or or at any angle in-between. Regardless of the orientation, the welds fail in understood than that of adequate strength.

shear, although the plane of rupture varies. All caperimental studies have shown

3. Economy-As for all structural componenta,it is desirable that connectionsthat longitudinal rdlet welds provide lower strength but higher ductility than s

be economical of material and be as simple as possible in fabrication.

transverse filles welds (1,2,7). Since in comples joints it is not always possible to define the direction of loading on the weld and since the longitudinal fillet in working stress design, specifications (13) customarily specify allowable welds provide the lower bound to weld strength, they will be used b{re to stresses and give rules regarding buckling problems and the like. Ahhough not provide the basis for design recommendations. Tbc results can then be appued necessarily obvious, most allowable stresses for fastening elements and most in general to lillet welds without reference to abe directioe of loading.

rules for proportioning connections are, in fact, based on ultimate strength Early tests on low carbon stects connected by manual arc longitudinal fillet considerations. "Traddional" design of connections is much closer to the LRFD welJs showed that the ultimate shear strength on the minimum throat area approach than most users of these specifications perhaps realize, was 6N85% of the sensile strength of the deposited material (4,6,12). These caily studies also showed that shear yielding was not critical in Idlet wclds Causmanon or Com.acios Desaa Raoumamente because the m aterial strain. hardened without large overall deforma tions occursing.

Thus, the y.icid point of fillet welds is not considered a significant paramet' r.

e He load factors, m and the resistance factor. 4, in Eq. I depend upon More recent tests on a wide range of steels connected with " matching" a "safcty inJem," p, that is obtained by cat bra: ion to caisting standard designs electrodes have provided data on strength and its variability (2,3,8,9). (For many (ll). Rus, it is intended that successful past practice will be the starting point of these tests, data were not obtained on the tensile strength of the deposited for LRFD. For beams and columns, it has been found that a value of p =

wcid metal; only the shear strengths were obtained.) Dh>dgets gives sesults for 3.0 provides a good estirnate of the rehability inherent in current design. This 127 samples of wcld metal for which the minimum specified tensde strength tatue has been taken also as the basis for LRFD criteria for all other types is 62 ksi (unpublished). The mean sensile strength value, (r,). was 66 0 ksi, of c"ructural membert la view of the desirabihty that connections have a higher the standard deviation, o,. was 2.56 ksi, and the coefficient of variation, V,,,

degree of rehabdity than the members theyjoin, the safetyinden p for connectionswas 0 039. For a sample of 138 specimens of E70 electrode wc!J metal (minimura q t.

should be somewhat larger than this value of 3.0.

specified teusde strength 72 ksi), Blodgett detern.ined (r.). = 74 9 ksi, o.,

)

he cahbration procedure uscJ bere is the same as that followed for beams

= 2.61 ksi, and V., = 0 036. Unpublished studies by Nash and IIoltz for the and columns (II). It wdl be carried out for various combinations of dead and same cr,tegory gave (r.) = 86 8 ksi, a., = 9 88 ksi, and V,, = 0 247 with live load and wdl cover wclds, high. strength bolts, and ordmary bolts.

a sample size of 40. BloJgett also obtained data from tests on wclJ metal i

De safety indes p is delincJ (II) as made with E80. E90, anJ Ell 0 electrodes. Table i summarizes all of abe data from Blodgcit's report. It is worth noting that Blodgets also obtained results g

in ~

for E70 electrode wcIJ n.etal that were higher than those listed and comparable O.

to the values found by Nash and floitz. For a sample of I28 specimens made Il a p g'......

,,,. (3) using E7024 and E7028 ciectrodes (minianum specified sensile strength 72 ksi).

Bhmigets obtained values (r.), = 85.4 ksi, o, = 4.77 ksi, and V

= 0 056.

is which A. and Q,, are the mean values of the resistance and the lond effect; Until more data are available, it seems reasonable to use the lower bound s

and V, and V,are che correspondans coefficients of variation. Detailed dermilions resuhs listed in Table I as the basis of the formulation herein. The value of of these quantities can be obtained fross Ref. II.

the ratio of the actual tensile strength of weld metal to its minimum specified tensile stret gth wdl be taken as I.05 with a coctricient of variation of 0 04.

t

?

- - - - - - - - - - - - - - - - - - - ~

Th O

h 1830

~

SEPTEMBE 11978 sig JTS LOAD 4IESISTANCE FACTOR his will be considered to apply to all electrode classifications being considescJ.

al i.e., E60 through Ello-The coefficient of variation of the resistance, V,, required for the solution Fis. I shows a distribution of the ratio of Gilet wcld shear strength to weld of Eq. 3 is defined as (II) c!ccarode tensde strength for a sample of 133 specimens. Me welJ shear strength, E,a "

8' * '*

'b v., is that for the appropriate matching cIcctrode using the values descnbed herein. These data provide the following results: (r.), = 0.84, o., = 0.W. and in which the coefficients of variation on the right. hand side of the equation V., = 0.10.

represent the uncertainties in material strength, fabricstion, and a " professional" Intor, respectively.

TAhtE 1.-F4Het WelJ Strength The variation in the professional assumptions seflect the accuracy with which the forces acting on the fasteners are estimated. He exact determination of Minimum these forces is highly comples and they are usually assigncJ according to a distribution that fulfills the static equihbrium requirements only. Ilowevef, for specdication a ductile structure, the principles of the lower bound theorem of plastici(y are Tensile tensite Mean Coefficient sesess valid. Rus, as no error is made in statics and wcIJ material is provided to seness.in tensde Standard ol

/specdica.

resist the forces assigned, the joint will be safe. There is, therefore, no variabibly Electrode hips per semple stresa.

deviation.

variation.

tion ten-of the professicnal assumptions: the assigned, statically correct forces will be group square inch aue (v l.,

o, V,

sde stress resistcJ. Accordingly, the term V,in Eq. 5 is set at zero.

o (t)

(7)

(3)

(4)

(5)

(El (7)

E6010, L6041, Variation in fabrication reflects the variation of the wcld length and I,hroat thickness from those assumed in the design. At the present time, there are E6027 62 127 66 0 2 56 0 019 1 06 not enough data available to obtain V, quantitatively. A value V, = 015 will E70:4. E7018 12 838 14 9 2 67 0 016 1 04 be assumed for fillet welds. This implies that there is a 50% probability that E80t8 X 80 116 87 9 4 34 0 049 I to the actual shear arca will be within 110% of the ares assumed. This is beheved E90 8.X 90 16 t00 2 4 32 0 04)

I 18 to be a conservative assumption.

bs_ _ jt0-l}6

_, ~

g, __,, -

0 06 72 4 68 M

The coefficient of variation of the material strength from the statistical data avadalste for fiUet wcld strength is ys y*a

.. nn y3

,, =

+

= (0.10)' + (0.04)' = 0.0116

' (6)

QO fuss u

Also necded for the calibration is the wcld size required by the 1978 American

?

Institute of Secci Construction (AISC) Specification (11) Using Part 2 of the

[

Specification, the design criterion for a load cornbination of dead and live load is so 2

m_

l.7 A. x 0.3 r,,, = I.7 c (D, & L,,)

.(7) t

~

in which A., = the cross-sectional arca through the throat of the weld D,

= the code value of dead load; L,, = code hve-load value as reduced for I

arca; maJ c is an influence coefficient transfoaming load intensity to member

'I o -4,[g gp g

]',

force. [ Note that the load factor (1.7) appears on both sides of liq. 7; the

}

r.i w.u sa = si.

u.

result obtaincJ here usi,ig Part 2 of the Specification are identical to that which w.u 6.J. M. E si. 7a l

would have been obtaincJ using Part I, allowable stress design, of that same specification l tlc mean resistance of a fiuct welJ JesigncJ according to the FIG.1.-Relationship of Wold Sheer $srength to Electrode Tenaue Sirength l

1978 AISC Specification is therefore c (D, t L,,)(r.).

The shear strength to tensile strength ratio and its coefficient of variation R. = A,(r. ). =

i

~

~

wdl be used to evaluate the safety inden, p. 'Ibc mears shear strengils of fiUct 0' 3 F'

welds can be espressed as i

and the corresponding coefficient of variation is V, = M + v = V0 0ll6 + 0.0225 = 0.185 193 i

(v.). =

r., = 0 s4 x 1. 05 r,,,,,,,,,,,,,,, (43 k

L*

la d888 l=

.I Substitution of R.(Eq. 8), V,(Eq. 9), G.,. and V (Ref. II)into the capression a

y

.t.

..-m 1432 SEPTEMBER 1978 Sig 9

LOAD RESISTANCE FACTOR 3

.or the safety indes p (Eq. 3) can now be performed for a variety of deas.

.d and live-load intensitics and for various values of the tributary esca. Table sts va ucs of p kr &c bask M beload value d L, = M pd and for TABLE 2.-Safety indes gi for High Strength Bolte and Fiftet Wolde dead load intensitics of 50 psf, 75 psi, and 100 psf and for tributary areas ranging from 200 sq ft-l.000 sq ft. A plot of p versus inbutary area is shown

- =.=

Deed in Fig. 2 for D, = 50 psf. Esamining the tabulated values, it is apparent that i

f 8 *d',

p for the whole domain of variables does not change much, the range being I

Safety inden. gi from p = 4.20 to p = 4.91. lThe safety indca has also been examined for higher live-load intensities (75 psf and 100 psf). The minimum value for L, P+8 A in A325 A490 A325 A490 A325 A490 for L, = 100 psf it is p = 5.77.l

U psf is p

a square square F.itet bolts botts bolts bohs bolts bolts y

lil b-Strength Bolts.- A relatively large amount of data concerning the strength i

t foot feet w= eld s tension tons.on shear shess friction friction (t)

(2) 01 (4)

(5)

(6)

(7)

(8)

(9) characteristics of high-strength bolts are available. The results are scattered throughout a large number of references but these have been well sumrqjrised 50 200 4 20 4 s1 4 74 5 86 5 23 1 46 3 32 in a publication sponsored by the Research Council on Bolted and Rivcted 400 4 44 5 28 5 Il 6 36 5 77 I 58 1 44 Souctural Joints and this will be the principal reference cited in this section 575 4 33 5 19 5 23 6 30 5 70 1 46 1 12 800 4 56 5 58 5 72 6 69 6 15 1 63 1 48 (5).

l.Ouo 4 70 5 33 6 03 6 95 6 43 8.78 3 33 Direct Tension.-The mean resistance of a high-strength bolt in direct tension 75 200 4 53 5 50 5 62 6 61 6 05 8.59 8 46 is

~*

400 4 73 5 96 6 24 7.10 6 61 1.70 1 56 g

g R* = l h l

A* F*

'(10) 720 4 50 5 71 6 00 6 88 6 39 I 47 I 33 1.000 4 67 6 02 6 41 7.19 6 75 1.58' l.45

( F, 4 100 200 4 13 5 99 6 29 7,13 6 66 1 68 1.55 400 4 91 6 41 6 89 7 57 7.17 1.78 8.64 in which o, = the ultimate tensile strength of the bolts; F, = the specified 600 4 82 6 34 6 86 7 52 7 13 I 68 1 55 miaimurn tensile strength; and A, = the tensile stress area of the bolt. The 750 4 48 6 IS 6 65 7 35 6 94 1 56 I 42 following data are available (5): (a.,/F,), = 1.20 for A325 bolts and I.07 for 4.000 4 80 6 38 6 96 7.57 7 21 1 64 I si A490 bolts; V.,/F, = 0 07 for A325 bolts and 0 02 for A490 bolts.

• Lave loaJ is 50 psf foe all cases.

It will be assumed that V, = 0 (as for fillet welds) and that V, = 0 05 l

(reflecting the good control characteristics of bolt manufacturing). In addition, I

the arca of. the bolt A,, corresponding to the nominal diameter will be 'escJ.

' ' ~

nis is about 75% of the tensile stress arca for bolt sires commonly used in e am e

-oo s structusal work. Using these data, for A325 boles:

e ame w

R. = 0 90 A, F,;

V, = 0.09 (lIa) e for A4'A3 boles:

R., = 0.80 J, F ; Va = 0 65 (lib)

The term A can be obt.ined from the 1978 AISC Specification where 1.7(A,F,)

s f,

[

= 1.7 c (D, + L,,) or

^*

c

.3 A, = - ( D, i L,, )

(12) f.

1

$Z in which F, = the allowable tensile stress as given in the Specification ne resistance terms of Eq. Il can now be wnsten as, for A325 bolts:

F R., = 0 90 "- c (D, + L,,)

=

=

o O

s00 e000 f,

(!3)

I Isatmterv Asee (Ag ). St F*

for A490 bolts:

R., = 0 80 c (D, + L,,)

Flo. 2.-S.sety Indea for variou. connecaera l

In general terms, Eq.13 can be expressed as b,

MB

A/~')

b r,s h

SEPit MBE0 8918 ST9. * * ~ ~ '

.v 1434 579 LOAD 11ESISTANCE FACTOR 135 te A. = i

, t A, F, f,

fF 3

A, - {

,, i} / a, iIl l

c(D,* L.,)

(14)

<a.i.,\\f.>.<F.-

c (D, + L,, ).

(19)

T r F. >. A. F.

The safety indes p (Eq 3) can now be determined for high strength bolts g

acting in tension The values of Q,, and V, are defincJ in Ref. II, while R.

As noted for the case of high-strength bolts in tension, the specified minimum is given by Eq. Il or 14 and V by Eq. II. The specified minimum tensile tensile strength will be taken as 120 ksi for A325 bolts and 150 ksi for A490 j

g bolts. Tbc permissable shear stresses accordmg to the 1976 Research Councd I

i strength. F., for A325 tmlas up to I in. in diameter is 120 ksi and 150 ksi

- on Riveted and llotted Structural Joints Specification and the 1978 AISC for A490 bolts up to 11/2 in. in diameter. The allowable te.isite stress, F,,

j S ecification are 30 ksi and 21 ksi for A325 bolts (no threads in a shear plane P

is 44 ksi for A325 l>olts and 54 ksi for A490 bolts.

Table 2 lists the values of fl dete: mined for this case and they are also shown and threads intercepting a shear planc, respectively), with the corresponding q

A figures of 40 ksi and 28 ksi for A490 bolts. The ratios of these shear stresses 4

in Fig. 2 for the particular case of D, = L, = 50 psf. Far A325 bolts, the are approximately the same as the ratio between the gross bolt area and onc

~;

safety indes varies fron 4.8I to,42 and for A490 bots it ranges from 4.74 taken through the root of the threaded portion of a bolt. Thus, the safely inden, i

3 to 6.95.

p, for the two cases will be peasly the same.

'.J Shear.-The mean resistance of a high-strength bolt acting under a force tendmg to shear it through a right cross section is The values of p for high-strength bolts loaded in shear are givenlin Table

'3 2 and are shown in Fig. 2 for the case of D, = L, = 50 psf. Over the range 7

IT.

I ".

enarnined, p varies from 5.86 to 7.58 for A325 bohs and from 5.23 to 7.21 I

A. =

A, F,m.

. (15) for A490 bolts. It is worth noting that the safety indes for high. strength bolts j

loaded in shear is significantly higher than that for fillet welds.

in which v, = the shear strength; e, = the tensile strength of the bolt; F, Fricslon.-Iligh-strength bolts may be used in joints where it is desirable 3

= the specified minimuni tensile strength of the bolt material; m = the number that slip not occur under the working loads. The contribution provided by one of shear plancs in the joint; anJ A, = the cross-sectional area of the bolt.

boh to the total slip resistance is

~j q

De statistical data availabic for the ratio of bolt shear strength to bolt tensile

& = m(4 ). (T,).

strength are (5): (v /a.). - 0 625 and V,,/a, = 0 053. These are applicable (20)

{

for both A325 and A490 bohs. The data to be used for the ratio of bolt tensile in which m - the number of slip planes; A, is a shp coefficient reflecting the

'l strength to specified minimum tensile strength are the same as given previously type and condition of the faying surface; and T, = the clamping force provided j

for bolts in sension and are different for the two grades of fasteners. Thus.

by the bolt. A good deal of information is known about the shp coeffscient a

for A325 bolts:

and the clamping force and their distributions (5).

The sncan value of the clamping force and its distribution depend upon the P., = 0 625 x I 2 A.F,m = 0.75 A, F* m; V, = 0.10 (16a) strength of the Mt og upon the meM used fu bstaHanon (caWated wrench and for A490 twhs:

or turn-of-nut). In cather method, the clamping force is to be a minimum of

=

0.70 times the specificJ minimum tensile strength of the bolt material, F,,6mes

. the tensile area of the bolt, A,. Using the data for bolts instahed by the turn-os-nut U, = 0 625 x I 07 x A.F,m = 0 67 A.F,m; V, = 0 07 (16b) method (5):

In a fashion similar to the development of Eq.12, the bolt shear area requircJ 1.20 by the 1978 AISC Specification can be developed as (T,)., = 1.20 x 0 70 F x A, = 0.98 A, F,,.

(21) c I

A=

F,m (D,+ L,,)

(17) in which 1.20/l.03 is the ratio of the mean tensile sisength of all A325 bohs 3

to the meso tensile sirength of the particular lot of t,ults used in these tests in which F - the allowable shear stress given in the Specification. The resistance b " h '"* P '. ' II

'E"' "I **' "" ""**P" 8 '"

terms of Eq.16 can now be written ns. for A325 l olas:

I which as obtained by using 0 08 as the variation in the ratio of the is actual clamping force to that specifi:d (1.20). 0 07 as the vanation in the ratio F

D., = 0.75 *- c(D, + L., )

1.20/l.03, and 0 05 as the assumed variation due to fabricatiori uncertainties.

I-For A490 bolts instaticJ by abe turn.of nut method, the expression equivalent

ggg, in meaning to Eq 21 is (5) or for A490 bolts:

R. - 0.67 c (D, + L,,)

(T,). = 1.26 x 0.7d F. x A, = 0.86 A, F.

(221 1.10 Is general terms Eq. la can be capressed in the form l

with a coefficient of variation equal to 010.

i I

s e._,

.\\

p s

1436[

Sig [

SEPTEMBER 1978 sig LOADMstSTANCE FACTO'1 437 The.., eoefGcient obtained from o sample of 312 specimers of A7, A36, cases, fillet welds and hief.-strength boks. Although it would be more econ ical A440, and FE 37 and Fe 52 (European) steels is 0.336 with a coefGcient of in terms of material used, two values of p would increase the design complexity.

vasiation of 0 07 (5). Similar data are available for a number of other cases.

For the serviceability state p = 1.5 will be used. Based on the cases examined.

For example, gnt-blasted A514 steel has a slip coefficient of 0.331 with a this represents a reasonable value, coefGcient of variation of 0 04.

tlc value of the shp resistance expressed by Eq 20 can now be further Oriena.usanom or Hamasianca Facion i

quantiGed. Considering bolts installed by the turn-of-nut method and stects such j

as A36 with clean mill scale, for A.125 bolts:

The resistance factor 4 (Eq.1), can be expressed as (11)

. P, =i O 3 3 m d, F,; V = 0 24 (23a)

R"' e x p (-a p V. )

(27)

'j and for A490 bohs: r, = 0.29 m A, F.;

V, = 0.24 (236) 4 R,

The 1978 AISC SpeciGcation presents the requirements foi friction-type in which R., = the mean resistance; R, = the nominal resistance as capressed connedions in terms of an allowable shear stress (even though the bolts are by the design criteria; and a is a numerical factor equal to 0.55 (II). Ilg terms not actually auing in shear).

p and V, have been defined previously. 'Ihc sections following will establish F. A, m u c (D + L")

the values of the resistance factor for the various fastener conditions. '.

(24)

Fillte WelJs.-The nominal resistance of a fillet weld m shear as cust' marily o

Solving for m and using a value of 0.75 for the ratio of tensile stress area taken as 0 6 times the specified minimum tensile strength of the deposited weld to gross boh arca, A,/A,, the strength terms in Eq. 23 become, for A325 metal. This is based on an assumption that the fillet weld is in pum shear boks:

and that the distortion energy theory describes the condition of plastic flow.

F.

(Itc"casca"numberis I/Oor0.577.)CallingIhe throat area of the wcIJ.*,,the A

P, = a 25 c (D, + L, )

nominal resistance is then (23I 7

(28)

R, = 0.6 F,,, A.

or for A490 bolts:

P, = 0. 22 *- c (D, + L,, )

F,

.hhc mean resistance of the wcld is la general terms. Eq. 25 can be written as

1. * ^ I' I * * *

' y*

As described in the development of the safety inden for fillet welds, p =

f, " (A.) (T.),,

c(D,& L ),

(26) 4 5. (r.)., - 0.88 F,,,, and V, = 0.19. Substitution of these values and the A,- F, empressions given by Eqs. 28 and 29 into the capression for the ecsistance The specified minimum tensile strengths. F., are again 120 ksi, for A325 factor (Eq. 27) gives a value 4 = 0.93.

bolts and 150 ksi for A490 bolts. The values given by the AISC Specification

, liig* Strengtis IMts: Tead a.-Re nominal resistance of a high-strength boh i

for F, are 17.5 ksi for A325 bolts and 22 ksi for A490 bolt.. The natues of in sensi n is (5) the safety indca.. for joints of A36 (or similar) steel with clean mill scale g*. 3, f,,,

(30) f:ying surfaces and using either A325 or A490 bolts installed by the turn-of-nut snethod are tabulated in Table 2. A plot of values for the case of D~ = L and the mean resistance. as given earlier, is R., = 1.20 A,F, for A325 bolts

~I

= 50 psf is shown in Fig. 2. Over the range caamined, the safety index varie and R., = 1.07 A,F, for A490 bolts. For these two fasteners, it was found from I.46 to I.78 for A325 bolts and inom 1.32 to I.64 for A490 bolts.

that V, = 0.09 for A325 bolts and V, = 0 05 for A490 bolts. Again using As capected, the values of the safety indem are low for t>olted, friction-type p = 4.5, it can be determined from Eq. 27 that 4 = 0.97 for A325 bolts in comacctions as compared to the other cases considercJ. This is because the sension and 4 = 0.94 for A490 bolts in tension.

consequences of fadure of a friction-type bohed connection are less severe liigh-Streagth IMis: St. ear.-Re nominal resistance of a high-strength boh than abe failure of high-strength bolts in shear or tension or of filles wclJs in shear is (5) is shear. A separate value of the safety indes should be established for each of the serviceabihty lunas states (bolts in friction-type connections) and strength R* = 0.625 A. F*.....

(33) limit states (boks in tension or shear and Gilet welds).

and the mean resistance, as developed in Eq.16. is R., = 0.75 A.F,m for The value of p = 4.5 =d! be selected for the strength hmit state. This reflects A325 bolts and R., = 0 67 A.F,m for A490 bolts. The values of V, were quite accurately the values obtained for fillet welds, cacept for some cases found to be 0.10 for A325 bolts and 0 07 for A490 bolts. Using a value of l

of high live-to deaJ-Ioad ratios, and will be conservative for high-strength p = 4.5, the resistance factor (Eq. 27) is 4 = 0.94 for A325 bolts and 4 =

boks. It would be in order to select two different values of p for these two 0 89 for A490 bolts.

A

l h

1438 SEPT E MBE01978 ST9 ST9 LOAD RESISTANCE FACTO 2 8439

'c liigh-Strength Boles: Conibised Shear and Tensios.-For a fastener subjected For beams, columns, and other main structural components (p =

,,the to t.oth tension and shear, the following relationship has been recommended use of y, = 1.1, y, = 1.1. and y, = 1.4 has been recommended for use in (SI:

the LRFD format (11). Whnic y, = y, = I.I would still be appropriate for 8

S + (0 6 T)* - 4 (0 6 A. F. )'

(32) both categories of fasteners, a value of y, = 1.2 should probably be chosen for fasteness an friction type connections and y, = 1.6 should be used for all in whwh S is the factorcJ shear force; T is the factored tensile force; and other fasteners. Ilowever, rather than using different load factors for these A

septesents either the bolt area through the shank or through the root of s

the threaJs, depending upon the actuallocation of the failure surface.

cases, the effect of the different p factors can be imposed on the value of 4 to be used. For the category described in Table 3 as " Connections-All The resistance factor,4, can be establ:Shed from Others," this means that R

IR,,, i f v. i

=I l (

l 1.09 (1.09 c,,D

+ l.39 c, L )

R.

( R. /., ( F. /.

. (33) 4 R,1.13 (I.I4 c D., + 1.59 c,.L ) a 1.1 (1.1 c, D., + 1.4 c, D, )...

(40)

V1"" 4V.'

Tbc ratio on the Icft. hand side of this inequality varies only from 0.86 to and 8**=

4 V,' e V}

.,,... (34) 0.90 as the live load to dead-load effect (c,L.,/c,,D.,) goes from 2 to 0.25.

The corresponding variation for the category " Connections-Friction" is from in which K.,/ R,is tbe ratio of the emperimentalstrength to the nominal strength 1.18 to I.12 over the same range. Since the variation is not large in either accordmg to the interaction cquation (Eq. 32 with 4 = 1.0). He statistical case. it is recommended that the resistance factor,4, be modified for connections data for the ratio are (R..,/R,)., = 1.05 anJ V,,,, /R, = 0.10. Using those as follows: 4 - 0.88 4 when p = 4.5 and 4 = 1.15 4 when p = 1.5.

data and the previously developed information, V, = 0 V, = 0.05, (v /F ).,

t

= 1.20 or 1.07 for A325 or A490 bolts, and (V,,, /F,) = 0.07 or 0.02 for A325 TABLE 3.-Lead Factors for Various Safety Inden Vatuna or A490 bolts,4 can be determined using Eq. 27 as 0.91 for A325 bolts and 0.85 for A490 bolts.

lingh-Strength Bolts: Frictica.-The nominal frictional resistance provided by Load Factors the clamping action of one high-se,rength bolt is h',

[3 h'3 8

. d*"

R. = m A,( A, x 0.7 f.)...

(35) p = 3 0 (men bers) 09 1 09 8 39 i

and the mean resistances and coefficients of variation are as given by Eq.

E

• U I'**"" " **~'"E"I 3"

I

23. The value of V, mas found to % 0.24 for both fasteners. Using these p - 4 5 (canceuonran otten)

In m

iW data and abe value p = 1.5, the resistance factor is found frorn Eq 27 to be 4 = 1.I5 for A325 bolts and 4 = 1.01 for A490 bolts. In both cases, it has been assumcJ that the bolts are installed by the turn-of. nut method and The modified resistance factors for abe various cases considered are therefore, for fillet welJs: 4 = 0.88 x 0.93 = 0 82. For high-strength bolts:

that the faying surfaces are in the clean mill scale condition.

Modilled Reslatance Facewe.-Re use of two different values of the safety

1. Tension: A325 4 - 0.88 x 0.97 = 0 85 and A490 4 = 0 88 x 0 94 -

iaJes (p = 3 for members and p = 4.5 or 1.5 for fasteners) introduces some 0.83.

~{

operational difficulties that must be resolved. Writarig Eq. 2 in terms of the dead-and hve-load intensities, D., and L_:

2. Shear: A325 4 r, 0 88 x 0 94 = 0 83 and A490 4 = 0 88 x 0 89 = 0 78.

3. Tension and shear; A325 4 = 0 88 x 0.91 = 0 80 and A490 4 = 0 88 C R. 21a (r,1, D., + c,1, L.)

.. (36) x 0 d5 = 0.75.

j is widch 3, = the load factor representina uncertainties in the analysis. Froin

4. Friction joints: A325 4 = 1.15 x 1.15 = 1.32 and A490 4 = 1.15 x Ecf.II:

1.01 = 1.16.

y, = cap (a p V,).

(37)

Clearly, it is desirabic to reduce the number of values to be u ed for the resistance factor to a minimum. It is recommended that 4 = 0 EO be used 7 = I + e p V Vi + V',

(38) for all cases involvin,; abe strength limit state, i c., fi!!ct welds, and high strength y, = I + a p V V' + V,,

..................... (39) t, oles in tension, shear, or combined tension and shear and that 4 = 1.15 be uscJ for the serviceability limit state, i c., shp-resistant joints using high-strength Uds the values Vi = 0 04. V, = 0 04, V, = 0.20, V, = 0.13, and V, =

bolts. The value selected for the strenath limit state is somewhat unconservative 0.05 (Ref. 5), the load factors y can be established for the three values of for A490 high-strength bolts in shear and for A490 bolts in combancJ tension

p. These are tabulated in Tabic 3.

and shear. It should be recalled, however, that the value of the safety index i

G 144U (s SEPTEMBER 1978 ST9 ST9 LCAD.CESISTANCE FACTOR 3448 in = is as conservativt for all c:ses involving high-strength bolts Tlic value 4 = 1.15 seiceted for the serviceability limit state is conservative, reflecting information necessary for the development is also presented. The worm shows the fact that bolts will not always be installed by the turn-of-nut method that current design values for different connectors provide substantially different levels of reliability.

Asurro Connecroa Paoattua Acanowtsooutura g

ShirRestatance Connectioma: Check for Strength.-When it is considered neces.

sary that connected parts not slipinto bearing under service loads, the connectionThe work that resulted in this paper was sponsored by the American Iron will be designed as a friction-type joint using the criteria already developed and SteelInstitute (AISI)-Commitices of Structural Steel Producers and Steel for that case It must be recognized, however, that such a design does not y

Itate producers as AISI project 163 " Load Factor Design of Steel Buildings."

)

automatically ensure that the criteria established for a bearing type connection 'the members of the Advisory Task Force. I. M. Viest (Chairman), W. C.

t willalso be met Therefore. if the serviceability limit state (slip)is being examined llansell (Engineering Supervisor). L. S. Beedle. C. A. Cornell, E. II. Gaylor.

l the strength limit state (both shear strength and beanos capacity) must alJ. A. Gilligan. I. M. Ilooper W. A. Milek. Jr.. C. W. pmkham. and,Ps. Winter.

be checked.

have been most helpful with their encouragement and advice.

so 4

Ordinary Bolts.-Il has been customary in the past to apply the sarne design rules to ordinary bolts (American Society for Testing and Materials (ASTM)

Arranoix.-Ratsaraces A307) as those specified for high-strenath bolts (ASTM A325 and A490) Very hitle data about the strength of ordinary bolts are available and it is therefore I. Butter. L. 3.. and Kulak. G. L., " Strength of Fauet WeIJs as a Function of ihrection recommended that the same procedure be followed,i.e.. the LRFD procedures

• I L88J " W'lJms Jawaal. WelJans Research Council. Vol 36, No. 5< May,1971 y' {gl,, g 2 ls s

developed for high-strength bolts be considered vahd also for ordinary bolts.

Sr,uc,,.f p,vnion. ASCE. Vol. 98. No. STS, Proc. Papes 8874. May, Of course. ordinary bolts should not be prescribed for friction-type connections j,,, f y,5, Pal. S., and Kulak. G. L., "Eccentncauy I onded WelJcJ Connections."

since the level of their clamping force is both uncertain as to magnitude and 8972. pp. 989 4005.

probably highly variable.

3. Dawe 3. L., and Kutak. G. L.. " Welded Conaccuans under comt>incJ Shear and Moment." Jowaat af she Servctural psvistoa. ASCE, Vol. 800. No. S H. Proc. Paper Bolts-Bearing Capacity of Connected Material.-The bearing capacity of the( [,,,

l*f 57rvey connected matenalimmediately adjacent to a bolt is a design problem usually siating Pubbshc4 Infonnasion. Appendia D." Repost associated with the fastener. $ltietIy speaking, it should be assigned to the of Weld Panel of the Stect Structures Research Commince. Department of Scscace member but it wt!! continue here to be related to the fastener.

and Industrial Research. Lond.fr. England.1933.

He nominal resistance in bearing has been established as I5)

5. Fisher. 3. W.. and Sasuik 3. II. A.. Gs,IJs sa Destga Criserda for BolstJ gaJ AlvaJ

• I '"

C. = c F, s 3 : J F*....

6. l'acem'an. F. R.. "The Strength 'o'f Arc.WelJed Joints.' frect<Jease. Insutuuon of

• * (.g g CivJ Engiacers. London. England. Vol. 231.1930, pp. 322-325.

in which F = the specified minimum tensile strength of the plate material.

7. Ihggins. T. R., anJ Preece. II. R., "Peoposed Staesses for l'JJet WcIJs in Budding 4 = the bola diameter; e = the end dist6nce of the bolt; and = the 8overninEConstruction." Wefddag hewaal. Vol 47. No.10. Oct. aus, p 429 S.

g

8. II Itz. N. M. and Kutan, G. L., "litab Strength Bolas and WcIJs an 1.onJ Sharing p ate thickness (the th.aner of the two thicknesses in a lap joint or the least of the sum of the thicknesses of tne two outer plies or the thickness of the Systems." Studies an Structural Engiacering. No. 8. Nova Scous Technical Codesc.

llahtaa. Canada. Sept.1970.

enclosed ply in a butt joint). Eq 41 is applicable as long as e/d is not less

9. Khanna. C. K., " Strength of Long iJte WclJs." thesis presentcJ to Nova Scotia than 1.5.

Technical Coucsc. at llatitaa. canada. in 1969. an partial futfitiscat of the rcquuenients He following statistical data relate to Eq 41 (5):

for the Jearce of Master of Engiacenas.

Number of tests = 27; to' p*,,*,P',J' ** Mg,r Coun[ctions." Ass <nich Ayers Na 33. Department R

K and Galambos T. V.

"Tentauve Load and Resistance Factor ratio of mean test to predicted values = 0 99; and coefficient of variation =

C.ll. With respect to f,. the following data are available (ll):

Washu ston Univessity. St. Louis, Mo., May,1975.

3.

Ratio of mean to specified ultimate tensile strength = 1.10 and coefficient of variation = 011.

ll. Ravindsa. M. K., and Gatambos. T. V.. "t oad and Resistance Factor Dcatga for i

Fross these data. V. = 0.16. Using Eq 27 and the value p = 4.5. 4 = 0.w Siccl." Jawad' */ 84' 58'""'"I D88'*". ASCl! Vol 104. No. S19. Proc Pa per X g.IO cap (-0.55 x 4.5 x 0.16) = 0.73.

tes. Sept,197s. pp.13374 3H.

12 " Report of sarmai.ral Stect WelJang Comniittee.,, Amencan Welding liureau,1931.

Moddying list $ to account foT the use of the higher safety index. 4 - 0.g8

13. "Specaricaison for the Design. Fabrication, and Erectico of Structural Sicci for x 0.73 = 0 (4.

suildings." Amencan lastitute of Stect Construction. New York. N.Y. 1978.

14. "Specificaison for Structural Jointa (Jaing ASTM A325 or A490 Belts." Research Suesasang ano Concsusoes Council on Raveted and BolicJ Structural Joints of the Engiacesing FounJauon.1976.

This paper develops the nominal resistance scrm and resistance factor for each of abe commonly used connectors in structural steel. The statistical 3

t

y t

I.

4 A rt.19.3]

RESULTS OF TESTS OF WELDS 643 PThe incre$ sed'use of high-strength steels and the need to refer to them

{

speciscation provisions resulted in further studies on nilet welded connec.

• },

(

tions."

• j Since fillet welds may be made with e!cctrodes whose mechanical

{

properties are not equal to those of the base metal, the study evaluated the l

influence of type of electrode, size of fillet weld, type of steel, and type of i

weld.

l All test specimens were designed to fail in the welds, even though the mechanical properties of the weld metal exceeded those of the base metal.

9 j

The study indicated that when longitudinal fillet welds were made with electrodes that " matched" the connected steel, the weld strength varied from 60 to 85 per cent of the electrode tensile strength as illustrated in Fig 19.3.

The study indicated that the failure plane generally was at an angle l

l 0 to t

0 80 j.

l

,Y

.t'

-k.

I 7

(;

i t

.t 0 6o s 1%

Pear crea rm

{

Tenso,e strentn er e ctroce

{

0 40 L l}

i i

s w e. een,vr.ss in P

_=

0 00 L c.i i

y O '-

h[

Base rretat A36 AA41 A514 hi E'ectrece E50 E70 E70 Ett0 y;

Fig.19.3 Shear strength of longitudinal fillet welds with matched base j

metal.

p less than 45' to the plane of a leg. Thus, use of the minimum throat thick-ness is conservative.

Since weld metal may be deposited on base metal with different mechanical 11 properties, combinations of strong base metal with weaker wcld metals and vice.sersa were also evaluated."'

The results are summarized in Fig.19.4 I

i This revealed that the effect of dilution upon weld strength was not great.

Where plate bendingis not a problem tests of welds subjected to combined bending and shear hase indicated a varying factor of safety against weld failure.

The results of tests on sertical weld groups are plotted in Fig.19.5.

i As the ratio of eccentricity to weld length (c/L) varies from 0.06 to 2.4, the tI j

)

l

\\

k

}

i

.~~-

e y'T gwgvw-*w-twwgr+-w,-+vv

-wwwe-t suu'-'e'%yww*"w--w

---wywww em'ei-w-'-

w

+ - - * -

-t=

ur

--we'*

w

-'we w-e-

-ww w~w

• • -*w-*'tw wN

-t--"

Attachment E to KMLNRC 85-058 DANIEL INTERNATIONAL CORPORATION DANIEL SUILDING GREENVILLE. SOUTH CAROLINA 296o2 4803D 298-2500 Feb rua ry 13, 1985 a

Il Dr. Hoss V. Davis American Welding Society 550 N. W. LeJeune Road j

Miami, FL 33126 l

Subject:

Secondary inspection in Accordance with AWS DI.1-75 and Subsequent issues

=_

Dear Sir:

Daniel International recognizes that AWS D1.1-75 and subsequent re-visions require that " welded joints shall not be painted until after

^

the work has been completed and accepted" (3 10.1).

Further, it is our understanding that 61.1 is appIIcable to inspections performed during the fabrication and erection process and does not' address sub-sequent, secondary inspections over' the life of the structure. There-fore, when it is desired to perform secondary inspections of structures, it is necessary to develop inspection procedures, and results evalua-

, tion criteria specific to that structure.

In IIght of the above, we submit the following Inquiries:

1.

Does AWS DI.1 address secondary inspections over the life of the structure?

2.

If AWS 01.1 does not address such secondary inspections, what parties are recommended to develop parameters for such inspections?

t_-

na hn G. Berra Ice President - Operations i

Y s

Attachment F to KMLNRC 85-058 (jj AMERICAN WELDING SOCIETY Founded in 1919 to Advance the Science and Technology of Welding Februa ry 13, 1985 Mr. John G. Berra Vice President - Operations DANIEL INTERNATIONAL CORPORATION Daniel Building Greenville, SC 29602

Subject:

Secondary inspections in Accordance with AWS D1.1-75 and Subsequent issues

Reference:

Daniel International Corporation Inquiry Dated February 13, 1985

Dear Mr. Berra:

This is in response to your inquiry concerning secondary inspections in accordance with AWS D1.1-75 and subsequent issues.

INQUIRY 1: Does AWS 01.1 address secondary inspections over the life of the structure?

INQUIRY 2:

If AWS DI.1 does not address such secondary in-spections, what parties are recommended to develop parameters for such inspections.

l REPLY 1:

No.

Inspection (secondary inspection) of welded l

Joints that have been accepted after fabrication or erection, or both, is not covered by AWS 01.1.

[

REPLY 2:

Inspection (secondary inspection) of accepted welds i

subsequent to the~ fabrication and erecti'on is not covered by Code provisions and such inspections and criteria for acceptance would have to be as agreed upon by the owner or.the Engineer (the owner's representative) and the contractor.

i We trust this answers your questions regarding this matter. Should you have any further questions, please do not hesitate to contact me.

Sincerely yours, h

Moss V. Davis, Secretary AWS Structural Welding Committee MVD:Jw File: 01-30.1 D1e/SCS 9

550 N.W. LeJeune Road.

Miami, Florida 33126 Telephone (305) 443-WELD (P.O. Box 351040 Miami, Florida 33135)

Telex: AMWELD SOC. No. 51-9245

.~

.