ON

Beedle, R. J. ChristopherFisher, G. H. SterlingWallaert

288.14

LARGE BOLTED JOINTS

SUMMARY REPORT TO COMMITTEE 10

OF THE RESEARCH COUNCIL ON

~IVETED AND BOLTED

STRUCTURAL JOINTS

by

Project Staff

(Not for Publication)

This work has been carried out as part of ,the LargeBolted Joints Project sponsored financially by the Penn­sylvania Department of Highw8:Ys', the Department of Conunerce ­Bureau of Public Roads, and the Ame~fcan "-Inst,i,t1.1te of SteelConstruction~ Technical gUidance is provided b~ the Research'Council on Riveted and Bolted Structural Joints~

Project Staff: L8 So Beedle, R. J. ChristopherJo w~ Fisher, G. Ho Sterling,Jo J. Wallaert

December, 1963

Fritz Engineering Labo,r~tory Report No. 288014

LARGE 'BOLTED °JOINTS, PROJE'ci .288, LEHIGHtiNlVERSITY

SUMMARY OF WORK COMPLETED OR IN ,PROGRESS

December, 1963

Phase and Topic Remarks Tests PerformedTests to be

CompletedAvailable Material

On Hand Reports

#.',

288 .. 1288.2

288D4(IABSE)288 0 7

288 0 4(IABSE)288~7

55 - 7/8" x 5-1/4'-18A Lot BoltsNone

None

Tests toDetermine the"Breakawayft andKinetic Torque

Plate for 15 to20 joints atB. SD Co.115 - 8B Lot7Jan x 5-1/21

'

150 - HLotI I 7/Su X 9-1/2 t1

8 JointsE41 j E46, E7l,E74~ E741,EIOl, E131,E161One washer

Torque Measure­ments with aHand TorqueWrench on Boltsof Phase II

6 JointsE41a, E41b,E-41~ E41e,E41f-~~, E41g-H-

+ One wahser++ No washers

Authorization:Committee 9Minutes~

1/30/60Committee 10Minutes:1/30/62Dormant

Authorization:Committee 10Minutes4/19/60;1/19/61Completed

Authorization~

Committee 10Minutes4/19/60 ;1/19/61Completed

Compact Jointsof A440 Steeland A325 BoltsSeries E

Long Joints ofA440 .Steel andA325 BoltsVariable Width_Series E

III Inspection ofBoltsTightened by theTurn-of-NutMethodSeries E

I

C>

~

--.....)~~-

~

E'

~.

~ . . I I I IIii~~

rf

I~

~

288,,9-

271.21(ASeE)288,,5

4 Lots ofA354 Be Bolts13 Lots ofA490 Bolts

50 -·n Lot140 - H Lot50 - 8A Lot

100 -. 8B- ·Lot

None

F S-eriesBolts1-1/8" dia.

Direct andTorqued TensionTests of 7/8f1

and In dia.Bolts

Direct andTorqued TensionTests of170 - A325Bolts

Authorization:Commit~ee 10Minutes:1/30/62-Committee 10Minutes:11/7/62Active

IVa) Calibrationof A325Bolts

Series E, F

Authorization:Commj.~t:e€; 10Minutes:lf3Q/62_Committ-ee 10Minutes~. I '

'_~'_:-"-C-__~-"~'."",,"<~;:"-'::::::--_'.'k.~'_":'."';.,~.-." -'-'__-...._....~-J ~ 1~t"I;1~~__ i I--'-:~ '~_--+-I ~,

r-~) Calibration I

of A354 Beand A490

f ~ go 1- -Bolts~t ~ Series J, K

J...&tilhGJda DU;YJ!.~ J1UjU,'Jj,~ ~ rKU-J~~J,.- L,OO" L~tlJ.l;l1, lH.\Ll \l'~K;tjl:1"l

SllMMARY OF WORK COMPLETED OR IN PROGRESSDeeember, 1963

lPb,ase and Topic, f:

-~,

Remarks Tests PerformedTests to be

CompletedAvailable Material

On Hand~

Reports i

Authorization~

Committee 10Minlltes ~

11/7/62Active

.! Compression, Srlear:; 15~A440Jigs

12=C o Ao JigsTension Shear:

15<>eA440 Jigs

Tension~ Shear:! 12=C o A o

SteelJigs

,. Additional A440: and CeA o Steel

UN8

One lot of 1~1/8fi

dia .. bolts.,Plate material

One lot of Iffdiao boltsePlate material

Various lots of7/8" dia u bolts

None

6 Joints:F42a~ F42b,F42c5) F42d,F42e, F42£,

Long Joints tobe specified

4 Joints~

J'42a s J42b,J42c» J42d~

Long Joints tobe specified

None

50 tests of 7/811

x 5=1/2H and 7/8"x 9 -.11·2 f1 A490bolts in the S~W.

and solid plate

None

Aut.horization:Committee 10Minutes~

11/7/62Active

Authorization:Committee 10Minutes:11/7/62Active

II~

Joints of Con­stru,ctional,Alloy Steelconnected withA325 BoltsSeries F

~rVI

1

rl ~¥II Joints.of Con-t struct~onal

~ Alloy SteelConnected withA490 Bolts

t ,'_', .,__ Series J

r.V-~~Joints of A440 Authoriza.t.ion: i q, Joints: KK lot of 7/811

; Steel Connected Committee 10 N i K42a, K42b, diae boltsewith A490 Bolts Minutes: one J K42e-, K42d Additional A440 ','

I Series K 11/7/63 Long Joints to plate at B~Sc CooL Active be specified .1

1

IX Cooperative Authorization:Study with the Committee 15

1 Unive~sity of Minutes:! Illinois 2/14/63j Committee 10

RCRBSJ'

Meeting~

Active

..

PROJECT 288

Phases Now Completed

Series E

Series F

Serie-s J

Series K!

Series C

Seri-es H

Series I

Series S

Static tests of compact, long and wide A440 steel jointsfastened with A325 bolts o

Phases Now Active

St,atic tests of joints made of cons:tructional alloy -steelfastened wi-th 1-1/8" diao A325 bolts o

Static tests of joints wade of cortstructional alloy steelfastened with 1" dia· o A490 bolts o ----

Static tests of joints made of A440 steel fastened with7/8" dia o A490 bolts o

Phases Not Initiated

Static tests of shingle joints fastened with A325 boltsn't' ,

Static tests of high strength steel joints fastened withhigh strength riv:.tso

A study .0£ hydrid connections in which two or moredifferent grades of stee~mbers are fastened e

Tests of targe diameter boltse

Phases Not Yet Formulated

a) Effect of punched holesa

b) Tightness ani coefficient of friction as influenced by brci'om jointso

c) Fatigue of large joints o

Fritz LabReport

* Z88.l

'"J( 288.2

288.3

288.4

* 288.5

* 288.6

.-~..

oJ( 288.7

* 288.8

'J( 288. 9

-4-

PROJECT 288

SUMMARY OF REPORTS - TO DECEMBER 1963

Jo W. Fisher, S. E. Dlugosz, Po O. Ramseier"Summary Report to Committees 9 and 10"January 1962

J. Wo Fisher, S. E. Dlugosz, Po 00 Ramseier"~ummary Reports for RCRBSJ"March 1962

"Large Bolted Joints Project 288 - Manual"(Contains the "File System, Surrunary and Phases,Test Preparation and Procedure, Standard DataForms and Standard Project Forms" of Proj~ct 288)

~o. Ramseier, J. W. Fisher L.!f.Y"Static Tension Tests a 40 Steel Joints Connectedwith A325 Bolts"(Reports on tests of six pilot tests, five long andthree wide joints fabricated of A440 steel at the tension­shear ratio of 1/1.0. To be published, Publication of the­I.A.B.S.Eo, Vol. 23, 1963).

J. Lo Rumpf, J. W. Fisher"Calibration and Installation of A325 Bo1ts"December 1962(Revision of Report 271.11 plus additional studies onthe heavy head A325 bolt in conjunction with the testsof large joints o To be published, Proceedings, A.SoCoEoSt6, Vol. 89, 1963)

Project Staff"Sum.mary Report to Committees 9 and 10"November 1962

J. W. Fisher, L. S. Beedle"Criteria for Designing Bolted Joints (Bearing-Type)"February 1963

J. Wo Fisher, R. J. Christopher, J. Jo Wallaert"Summary Report for RCRBSJ"March, 1963

R. Jo Christopher, J. W. Fisher"Calibration of A354 Bolts"(Preliminary Report) March, 1963(This report contains the results ofdirect tension and torqued tensiontests on 7/8" and 1" diameter A354 bolts)

288.10

288.11

288.12

288.13

* 288.14

J. W. FishertiThe' ,Analysis of Bolted Plate Sp1ices 1l

(In preparation)

R. J. ChristopherI1Ca1ibration of Alloy Steel Bolts'-'(In preparation)

J. Jo WallaerttiThe Shear Strength of 1\.325 and Alloy SteelStructural Bolts"(In preparation)

J. Jo Wallaert"The History of Internal Tension in BoltsConnecting Large Joints"(In preparation)

Project Staff"Summary Report to Committee 10 of RCRBSJ"December, 1963

-5-

* ~ndicates distribution to subgroup, Pennsylvania Department ofHighways, B~reau of _Public Roads and certain other interestedpartieso

ANALYSIS OF BOLTED PLATE SPLICES

INTRODUCTION

A theoretical solution for the ,unequal distribution of load

among the mechanical fasteners of bolted.double-lap tension splices which

act in a non-linear manne.r is summarized h.ereafter" To accomplish this

solution, mathematical models have been developed which establish the

relationship between deformation and load throughout the elastic and

inelastic regions for the component parts of the connection e

ANALYTICAL MODELS

For the plate material the following stress-strain relation-

ship was developed for the inelastic region~

where cr; static yield stress

Cfu

= ultimate strength

g gage

p := pitch

e =€p = deformation

f:. ~ ~ ~ p~ w1lL (k U -~ ~cry s cr ~ CJult

Below the elastic limit, Hooke~s law holds e

The theoretical curves are compared with the test data in Figso

1 and 20 In Figo 1 the comparison is made for both A7 and A440 steelo

Figure 2 shows a comparison of the gage load versus deformation for A440

steelt The gage is varied from 3.32 to 5074 inG

The analytical expression used to express the load-deformation

re~ationship of a bolt in double shear was taken as~

where R = ultimate shear strengthult

~ = deformation of bolt and bearing deformation of theconnected material

(2)

coefficients which are functions of the type ofconnected material and type of bolt

Equation 2 is compared with the test data in FigG 3g

The work of Franc.is "-and,;Rumpf has shown that the following com-

patibility conditions and equilibrium condition must be satisfied:

~. + e7 .+11. 1,1

(3)

n

Li=l

R~1.

o (4)

Equations I and 2 are used with the equilibrium and compatibility

conditions to accomplish the joint solution.

COMPARISON OF THEORY AND TEST

The theoretical solution has been compared with test results of

eight full-size connections using 7/8-inch A325 bolts ,and -A7 steel plate

and seven full-size connections using 7/8-inch A325 bolts'and A440 steel

platee

The comparison between the theory and experimental results is

made in Figo 4 for A440 steel jointse Three different comparisons are

made. In one, the theoretical strength based on actual measured bolt

and plate properties is compared with the test data. The other two com-

parisons i-ndicate the influence that minimum strength materials have, on

the ultimate strengtho The maximum devi.ation between the theoretical

solution and the test results was 4%e

The solution has been used to make a number of hypothetical

studies in order to ,asce.rtai-n the relative importance of a number of para­

meters on the ,ultimate strength of the connections. Among the variables

studied were joint length, pitch, variation in fastener diameter, and

variation in the relative proportions of the bolt shear and net tensile

areas. These studies were made for both A7 and A440 steel plate connected

with A325 bolts.

Figure 5 shows the effect of fastener diameter on the ultimate

shear strength~ The comparison is made for A7 steel and the pitch was

maintained constant at 3~5 inches 0 Fastener diameter was found to have

no significant effect on the average shear strengthe

Figure 6 shows the effect of fastener pitch on the ultimate

Bhear strength. As can be seen the fastener pitch had no appreciable

effect on'~he shear strength other than its interaction with joint lengthe

The total join.t length, and -not the number of fasteners (gove.rned by

pitch), was the most important variable insofar as the average shear

strength was concerned e

Figure 7 summarizes the study of the 'variatio.n in the relative

proportionsof the bolt shear and the net tensile areas. The comparison

is shown for A7 steel plate connected by A325 bolts. This study shows

that the "balanc.ed .design" concept has n,o meaninge A joint can only

be in balance for a specified length which corresponds to a specific

ratio of the bolt she~r and the net tension area.

fiJdo{~

,~

Bo

ao~¥r ;;.

\ \--"f

I

o

~ ~ '~,"211. ~ ) d-z. OAA~?::' ~,S; \M..

~( S+ee\

o

• •

~?c:.c \MeV' ..., 0\ \

~~ S,Sto ~) d 1:. O,q4~

y~31S;:~

0,05 0.\b

511<. f\-nJ J z: om. o/~

Fi.g~ 1 Comparison of Th~ory with Test Data

/\ 4- 4.0 S +-e.eJ'P'2. ~IS'~

E \b\~ ~.s.14 ~

~ A ~I~0, \ <0, L.. O,~ Ol""- V

ELD~6tI\T'O~ ~kj '6.S;~ P\Tc.1-+ (1~C.H-ES ')

Fig. 2 Comparison of Computed Load-Deformation Characteristicswith Plates having various Gage Widths

~7

1'),0

,f' ,,," lIS. ' •(/) ,

f1i .. .'Q..- ql)~

o~

CG~u+ed""'\

w t "VcLC ~D~'

~-:r.V1 30\- t ~:.J()

ca0

() t \ 0, 'l. o,~

if'Q..~

)j , • ,'" ~1) • .,

\j)~

" -. •e ....

~G>o

\I) •~ ~oQ

OJ

i ~,0 0\ , o.~ 0,3

~CLrb.) ~D E'F-e)f2. MfirT \0~

Fig. 3 Load-Deformation Characteristics of A325 Bolts

rnJ~/mum S1Yentfh. hDJ/-SQO~ n e:f-J 'VIj JJ-44,O./ / ttkWI #.. .rru "Z. -; ~ k~ <..

~~

-~\(). I~ 8 _-. _~ -~~VJ 00

~'f\~ 40

~~

~20

• 1\ 4-4-0 Jo \-~t-s. C~s -== ~ '(\)7/'6~ A3'2,5 \oc>\+~ ) f"Z- 2,~ ~

~aSM <!:)", (Ack\ r\o~e'l·t\es (!)f "oo\t-s aw.&rlOvrt.,

~Inl~u.~ ~~~ bo\\-sQ.Ma ft~-\e- (~u-: ~-,k<;L)

Figo 4 Comparison of Predicted Ultimate Strength and Experimental Results~ 11

\

o 10 'iD ~o 4-0 ~o (,D

JOI~T L~6lT 14) I~L ~$

10 eo~

~

~C)V\~t-a.N\1- ~ \+c.~ -:z.. 3,s: ~c.ON\.<s\-~\- V'~\-\() <:)f ~~ '. ~~ ~ \ '_L \0

\'1V)"

~

~'~~

~

~ 80\'w

~ ~o~

~ 40

~~~ -LO

AI

...

~tee\ ?~o.te.7!B-''M f\~2~ bo \+-s\-~ ~2'2-5 \:>0 \\-s.\ Ifa"'\,,~ f\~'LS \oo\\--s

t:J \0 2.0 -:;0 4wD ~D o'D~ 0 t~T L~CqT~) INe..-ttt=""S

7D 8D

~

~'Fig o 5 Effect of Fastener Diameter on Ultimate Strength

A440 .::stee~ 7/2:>~ A~2.S bo\~s

~ N(!)\1)-

~

~,

~bO

~t 40

±\(lbJ~2D

ffi4

r~2.b'LS

f "% 6. \2S ~ efd)

•\Ny (3dl

r~"6,5~. ('\-!1)

o \0 ~() :>0 4D '.::>D (0 D

~ 0 {~T L E1\)q~ ~I\jc..tte:s

10 Sa

Figo 6 Effect of Fastener Pitch on the Ultimate Strength ~

~

\~ 8°\Jl~

if'~

~ ~o

\tD

~4D\t)

In~ ~o

~

1\I 5te~\ . I/~_~ ~ ~L~ l>o\-\--~,. J

1'~ ~lS .. \No..

~"::. '/ 1+n --:.. \: eo

Plct teo {tt\ \s ~Y '"+"", 'S> v-e~\o~ "::

B~~~

~~~l

'f. '\,00\ ~ I,~C

-- \'.1.\0\ ~ \.OD

\:071$

CJ \0 2.0 ~t> 40 St)

J~ ~~, L8\l(i~"b4) IN~-;

(01) 70 Bo

~Wl-(J~

~~M~

Figa 7 _Effective Variation in the Relative Proportions of theBolt Shear and Net Tension Areas ~

~

1-\ 44-0~4,\o

~\-ee\.~~\~~

100

~~Bo~\~

~~ 60~V)

~~ 4-0\04J~~

~20~

A'5. "~V\= \:00

o 10 :2D 30 40 SO ~o

JOI~T LEtV~TJ4.J J'~c...H-£S

Figc A Effect of Variation in the Bolt Shear andNet Tension Areas - A440 Steel; A490 Bolts

10 SC) ~

~

2.. 1

SHEAR STRENGTH OF SINGLE ALLOY STEEL BOLTS

OBJECTIVE OF THE STUDY

This study was concerned with the behavior of single A354BC

and A354BD (A490) bolts which were subjected to tension shear or com­

pression shear loading.. The effect of a number of variables on the ulti­

mate shear strength and deformation at ultimate load was studied o The

bolts used were manufactured from quenched and tempered carbon .alloy

steel in accordance with ASTM A354 - 58T.

DESCRIPTION OF BOLTS, TEST SPECIMENS AND TEST PROCEDURE

Table No. 1 gives a description of the six bolt lots that were

used in the studyo Three bolts per lot were tested in shear, with a

total of 36 tested in compression shear and 15 tested in tension shear ..

It should be noted that all the shear planes passed through the bolt

shank. For lots DC and FD, this necessitated milling approximately .13"

and .20", respectively, off of the underside of the bolt head so that the

shear plane did not pass through the thread runout o Two different steel

types were used in the test jigs, A440 steel and constructional alloy

steel (hereafter referred to as Q~ and T. steel)o

The tensile properties of the bolts can be found in Fritz

Laboratory Report 288 a 9 "Calibration of A3.54 Bolts, Preliminary Report"'o

The compression and tension shear test jigs are shown in

Figs. la and lb respectivelyo The jigs were assembled with the bolts

in bearing in order to minimize slip as much as possible.. The faying

surfaces were clean mill scaleo All bolts were torqued to an elongation

which corresponded to at least proof load ..

The bolted jigs were tested in a 300 kip Universal testing

machine. The test jigs containing the 7/8 in. diameter bolts were

first loaded to 30 kips and the jigs containing I in. diameter bolts were

loaded to 60 kips to insure removal of as much slip as possibleo This

load was subsequently removed and the actual testing then commenced ..

The jigs were loaded slowly and deformation readings were

taken every 10 kips until a deformation criterion controlled the load

readings.

TEST RESULTS

Tables 2 and 3 summarize the results of the shear tests con­

ducted on single alloy steel bolts for the compression and tension shear

tests, respectivelyo All values given are the average of the three tests

conducted. As of this writing, the tension shear tests using Qo and To

steel jigs have not been conducted o

A. Effect of Head Size

The effect of head size is shown in Figo 2 by comparing lots AC

and ce. The heavy head bolt showed no significant difference in behavior

from the regular head bolts, The mean ultimate strength attained by the

heavy head bolt was about 5 ksi higher than that attained by the regular

head bolt. There was no significant difference in the deformations at

ultimate load, irrespective of steel type. The variation between the

regular head bolt and the heavy head bolt was no greater than the varia­

tion between different lots of regular head bolts.

Bo Effect of Grip

The effect of grip can be found by comparing lots ED and GD and

is shown in Figo 3.for A440 steel jigso Other steel types and loading

condition load-deformation curves are si.milar o The greatest difference

in ultimate load is 2.5 ksi; thus, there is no significant difference in

behavior between a 4~ ina grip and 8~ in. grip test specimeno The de­

formations at ultimate were approximately the same a

c. Effect of Loading

This effect is shown in Figo 4 where a typical load-deformation

curve compares the tension shear strength with compression shear strengtho

The test results show that the compression shear test gives a 4% to 11%

higher ultimate load as compared to the tension shear tests in A440 steel

jigs. It is expected that the same trend will be observed in the Qo and To

jig tests. This reduction in strength is due to lap plate prying action,

a phenomenon which tends to bend the lap plates of the tension jig outward 0

This induces an additional tensile component in the bolts which decreases

its strengtho

Also, for every case but one, the deformation at ultimate load

was reduced by 4% to 19%0 The FD lot deformation at ultimate load iu­

cre-ased by 2% over the compres-sion deformation o

Do Effect of Diameter

There seems to be no consistent trend in the variation of the

average ultimate shear stress with bolt diameter, as can be seen by com­

paring lots CC VSo DC and EF VSo FDo Figo 5 is a typical load-deforma­

tion curve showing the effect of this variableo Because of the larger

bearing deformations, the total deformations for 1 in o diameter bolts

were larger than those for 7/8 iU G bolts e

Ee Effect of Bolt Grade

The A354BD (A490) bolt has a higher carbon content than the

A354BC bolt and will therefore sustain a higher load, as is borne out

by the test data and shown in FigG 60 However, for the same reason,

the ductility of the A490 bolt is less than that of the A354BC bolt p

This fact is borne out by the average deformations at ultimate load,

which was greater for the A354BC bolts than for the A490 bolts o

Fe Effect of Steel Type

Fig. 7 is a typical load-deformation curve showing the effect

of this variableo There is no consistent trend in the variation of the

average ultimate strength with the type of steel used for the test jigG

However, because of the greater strength of the Q. and To steel, the

deformations at ultimate load were less than the deformations for A440

steel.

EFFECT OF END RESTRAINT IN TENSION JIGS

A series of three tension shear tests was run on 8B lot,

A325 bolts in A440 steel jigs with the lap plate prying action mini­

mized. It was found that the average load-deformation curve for this

test approached that of the compression shear test for the same lot of

bolts. Fige 8 clearly shows thiso

SHEAR-TENSILE STRESS RATIO

The average compression shear-tensile strength ratio <11(JJ for

the A354BC bolts is about the same as that for the A354BD bolts tested

in compression shear, namely 00708 and 0~7l8 respectivelyo The overall

mean,~s .007130 For the tension shear tests this ratio dropped to about

0.65.

It should be noted that the ratio is computed on the basis of

the tensile stresses obtained from testing 0.505 inch diameter coupons

cut from the A354 holts. Since the shear planes all pass through the

bolt shank, it seems unreasonable to include thread effects in the com­

putation of the shear-tensile strength ratioo Also, the bolt tensile

stresses, VB, are computed on the basis of a "stress area"" Thus, i.t

is more logical to compute the shear-tensile strength ratio on the basis

of standard 0.505" diameter coupons ..

SCATTER OF RESULTSi

For a number of tests, there was quite a large scatter band o

The maximum variation from the mean values for ultimate shear strength

was + 7.7 ksio and for the deformation at ultimate loa~ was + 00046

in~hes.

CONCLUSIONS

1 0 There is no significant effect on the ultimate shear strength

.or deformation by the head size or the grip length. (See Figso 2 and 3)0

2. The tensile shear strength is, on the average, 8% less than

the compression shear strength for A354 bolts connecting A440 steel.

Also, except for one case, the deformation at ultimate for tension shear

was less then that for compression shear o (See Figo 4)0

3. There is no consistent trend in the variation of ultimate

shear strength as influenced by bolt diameter" However, the deformations

for the 1" diameter bolt is greater than that for the 7/8" diameter bolte

(See Fig. 5).

40 The A490 bolt is stronger in shear than the A354BC bolt~

(See Fig. 6) 0

5. The type of connected steel affects the deformations at ulti­

mate load o The higher the yield point of the connecting material, the less

is the' bearing ,deformation o

68 When lap plate prying action is eliminated, the tension shear

strength approaches that of the compression shear strengtho

7" The compression shear-tensile strength ratio for A354 bolts

connecting A440 or Q~ and To steel is approximately 0 .. 71, based on the

tensile strength of 0 .. 505" dialT1ete.r coupons .. The tension she.ar-tensile

strength ratio is approximately 0 .. 658

BOLT LOTS USED IN SHEAR TESTS

GradeBoltLotMark

Diam o Hea-dLeng-thU·nderHead

ThreadLength

_ ___---.,. N u m b e r T est e d

Grip (A,44Q.:J A440 ~ - Q. & T.~. Tension Camp. Tension

~........~ ..... -~

7/8'jAC H 5~ 1-3/4 4-1/8 3 - 3 - i

IA354BC CC 7/8 R 5~ 2 4~ 3 3 3 3

DC 1 R 5~ 2t 4-1/8 3 3 3 3

ED 7/8 R 5~ 2 4~ 3 3 3 3

A354BD FD 1 R 5~ 2t 4-1/8- 3 3 3 3(A490) -

GD 7/8 R 9~ 2~ 8~ 3 3 3 3i

lZ {~ 1<6 i5

* All shear planes pass through the shank

Grip includes 1/8" washers ..

Table I.. Bolt Description

h~""6\,

COMPRESSION SHEAR

·r 1"Q.aB~Tensile

<k',Tensile rcA 'l:QBolt AV~ Shear Strength Avgo Deformation CouponLot Type Diao Grip A440 Q" & T" A440 Qo &T" Strength Strength (Jc VC

CC A354BC 7/8" 4_1/4'K"1f; 97,,3 ksi o 91 0 3 ksi o ,,2143 in" ,,1607 in" 134,,8 ksi" 133 00 ksi" 0731 0686

*DC -A354BC 1 4-.1/8 95 6 2 96 ~5 ,,2500 01688 137 00 131~6 <;723 0733

7/8 **ED A354BD 4~1/4 110~O 116 00 ., 1810 01482 168 0 3 16409 ~667 ,,704

'* ~

~?-FD A354BD 1 4=1/8 115 0 0 111 04 02293 01760 ( 163,,8 149 08 ~ 0767 0.744

7/8 **GD A354BD 8-1/4 112 c 3 116 08 01960 01500- 163.,3 160 0 9 0700 <> 7.25-

7/8 *AC ; A354BC 4-1/8 96 .. 6 96 03 02217 01583 14008 140,,4 0687 0685

* Grip includes o.n har-d-e-ned washer"

** Grip includes two hardend~d washers"

Table 2. Compression Shear Results

N

~ .

./ /~

/~J\

l ~?-~~~~ W~ ~fWcuJ;:o(~7

TENSION SHEAR

LotBoltType Diao Grip

4119 0 Shear" Srreng+hA440 Qc &-To

A Dei: -t' rr 07,Tensilev9· Qrrna JQ~ VB, Tensile CouponA440 Qo & To Strength Strength

~ACf'e

Z'Que

CC A354BC 7/8 4-1/4 86 03 ksi o * 01781 in" '* 134.,8 ksi" 133 .. 0 ksi 0649

DC .A354BC 1 4-.1/8 88 .. 2 .. 2123 13700 131 06 0670

E.D A354BD 7/8 4~1/4 103 .. 3 01736 168 03 164 0 9 0626II

-- ...~ ... ~

FD A354BD 1 4..,1/8 10003 .2338 16308 149 0 8 0671

GD A354BC 7/8 8-:1/4 102.1 ,,1700 163.3 160 0 8 0636

** 7/8AC _A354BC 4-1/8 140 0 8 140 04

* T-ests with Qo &.T. jigs not complete.

** Tests found to be unnecessary ..

Table 3-__ Tension Shear Results

f'.,)

&

p

F/g- fa

y- 7esl Bo/I

", ..,/00

~~,

80'\flV1

~ 60~<J)

\. 40~(lJ

0 PO

Q0

fig.}6

":\\

-=' - ~ AC Lo+) l-Ieoll.Y. JleQcI. CC. Lor) RegL/lar /lead

0... ~T. Sfee ICompres'5lon Shear

,05 ./0 ./5 ,20 .Z5'De.f'o rmClnonJ Inches

;:;9~ 2 E.ffecf 0 f l-/eQd Sire

----=z~£D J...ol- 4~" grlp-~-GD LeI 8~" gripA440 S+ee/CompressIon 5heor

,05 • 10 ./5 ~20 .zS'Deformaf/on) inches

/20

, t /00,\i\~

vJ 80-

~ 60

05~ 4D

~ ZO

"0

Fig_ 3 Effeer of GrJ;:;

E {fecI 0 f' Loac/;0g.

.05 -10 .J5 .2" ,25 .,:'0

f)efOrmCl flo II J inches

Hj, 4- EFFect of loC/cling

120

100... ....

"-

.JQ 80-"~ r;,o "~\J) 40.~(\J ZO~

0-0

£ffec..1 ofDitlmefer

~ --~ ~~

~-~~~ ""-,

~~ED Lof J r-vS" dio.. 110-=-=' ~~F[) 1-.0+ J I" d la. 115

Aif..40 Sfee/Compress/on £*,g~lS

IJ05 ,to ,,15 ,,20 .25OePormo!iCJJ?J Il?che.s

h'g, 5 Effect- of OIO!7lt:;:k:,r

?

---cc Lo! 13C Grode--£ D Lof BD GracieA440 Ske/Compress/on ~~ Jt5

-05 910 .15 ~Zo .25De+ormQf'i'onJ inches

h9- 6 £ ffee:!- of Boll Grade;

.....

~

, £0 Lof A440 5-ree./==-~-IE'D LO~ Q~ ~7: Sr8e/COI'i?f/ressIDP 3heq,-

,05 ~JO ,,115 .20OelOrmClhol7/ locl?e5

Hg; 7 £f'fecf of -Skel ~I'e

£ [feci of Ead Pesl-CtV'nr813 Lol; 4.325 80/1.s

C 0m;=:ressiol? Shear-==::t> - -7ension S?eQ'j Prfjl~~ - ~-,er;5joV) 5het:11/ A/o ,o~/n!J

9

.05 _10 .J5 .eo ~2!5

{)eft>rm~f/ol?) /YJeks

,,03- c3 £;:fec! t:>~Encilksl-rl11llpT-

LEHIGH PRELIMINARY REPORT - COOPERATIVE STUDY OF A490 BOLTS

INTRODUCTION

At the February 14, 1963 meeting of Committee 15 of the Res~arch

Council on Riveted and Bolted Structural Joints it was reco~ended that

Lehigh and Illinois Universities conduct tests on bolts from the same

lot to determine if testing procedures consistute a variableo Each

Un"iversity was to test bolts in direct and torqued tension using their

own' standard calibration procedures 0

The results of twenty direct tension and thirty torqued tension

tests are given in this reporto These tests constitute the work done at

Lehigh on this studyo

TEST PROCEDURE

a) General

Two lots of 7/8" diameter, heavy hexagon head, A490 bolts were

tested. Bolts in the AB lot were 9-1/2" long with 1-1/2" of cut thread;

bolts from Lot LI were 5-1/2" long with 1-1/2" of rolled thread o In, all

tests A194 Grade 2H nuts (heavy hexagon), with a hardened washer were

used. Two grip lengths were investigated, namely 4 inches and 8 inches 0

Each nominal grip had two lengths of thread under the nut, 1/8" or 9/16" ..

b) Torqued Tension Tests

For all torqued tension tests the holt-nut threading was

checked by running a nut up the holt thread to runout o If this could

not be accomplishe~ "finger tightening" only, this bolt-nut combina-

tion ~as rejected. ~~ot of bolts was checked for fit with NclA go

and no-go ring gages and each nut was checked with NC~ go and no-go plug

gageso The torqued tension tests were conducted on the Model M Skidmore­

Wilhelm calibrating device and in a block of solid A440 steelo

In the Skidmore-Wilhelm -device the bolt was hand tightened to

a "snug" load of 10 kips, in two five kip increments from "finger tight",

with load, elongation and "turn-of-the-nut" being measured at each load

interval 0 The nut was then rotated in 450 (1/8 turn) increments with a

pneumatic impact wrench until failure. Load and elongation measurements

w-ere takenate-ach increment of turn ..

In the solid steel plate a " snug" elongation, equal to the

mean elongation determined at ten kips in the Skidmore-Wilhelm device,

was applied. Nut rotation-elongation readings were taken for each 1/8

turn-of-the-nut.

For all torqued tension tests a CP612 pneumatic impact wrench, with

a new 7/8" socket supplied by the University of Illinois, was used ll

c) Direct Tension Tests

As a preliminary test the bolts were loaded to the specified

proof-load and then unloaded to check the ASTM requirement of minimum

permissible set (0.0005 in.). No bolts were rejected by this test t The

direct tension tests were conducted in a 300 kip Baldwin hydraulic test­

ing machine at a speed of 0.01 11 per minute.

TEST RESULTS AND CONCLUSIONS

Table 1 and Figures 1 through 6 summarize the test results li

Figures 4 and 5 show the broad scatter associated with the torqued tension

tests of the LI lot bolts.

AB Lot

(1) The length of thread in grip had a pronounced effect on the

number of turns to failure, with the long~r grip requiring more rotation.

(2) The ultimate strength of the bolts tested in direct tension

was 10 to 13 percent greater than that obtained in torqued tension o

(4) Proof load was not reached at 1/2 turn-of-the-n.ut froIT't

"snug" with either 1/8" or 9/16" thread in the grip when tested in the

calibrating deviceo

L1 Lot

(1) An average of 1-1/4, ~urns-of-the-nutwere required to fail

specimens with 1/8 11 thread in grip, and an average of 1-9/16 turns were

required for those with 9/16" th'read in gr~p.

(2) The ultimate strength of the bolts tested in direct tension

"-showed ,a 20 - 23 p,ercent increase over tho-se t-e-sted in tor~ued tension G

(3) An increase in grip length (i..eG more thread in grip)

resulted in a decrease in the ultimate strength in both torqued and

direct tension tests~ (See Figures 3 and 4)0

(4) In specimens tested in the Skidmore-Wilhalm device proof

load was reached at 1/2 turn-of-the-nut from "snug" only for 3 of the

ten bolts tested. The average load value at 1/2 turn was below proof

load in' both cases (i41e. 1/8" and 9/16" t-hread in grip)o

(5) Figure 5 indicates that the specimens torqued in solid

steel did reach proof load at 1/2-turn from "snug"; and also they indi­

cate that fewer turns-~-the-nut are required in solid steel than in the

Skidmore-Wilhelm device to achieve the same elongation- (and therefore,

load) .

TABLE l!

Me~tt' Load a·t ~rn from '. kips',' .n snug" ~ ,

Mean Elongo atptu~~ ine

Mean E1ongo atoof Loaq in~

LOT L1

L

9/16

5

5804

3~OO

00310

34

ell

0018

5000

LOT A;a'i

9~

1~50

55045

6.903I

~D.=I~RE~C~T~T;,.=;E~N~S,~IO~'N~.,....';;C~A::.=L~I~BRA~T~·I~O~N"'--_IlID\!IIID!II:I .--.,.. "J!,

L II L L 'Ell L !

8'; 8 .tl 8~5"8 8-5/C14·L/S 4;1/8, 4-9/16 4- W16

1/8 l/sl \/10 9/16 1/8 1/8 ,I 9/1) 9116

5 615 .5 5 5 1 4 5

73,2 73,6 169 ,8 70,8 7600 75.8 1 72 ,1 72.1

L59.· L75 L33 L69 054 0050 1 0,90 017

00779 ,,074~ ,0794.0846 ,0508 ,0471 ',0610 ,0647

65 66 62 61 67 6S I 61 59. I012 018 013]:- 0245

eQ282 0027 :0030 00292 80154 ~:014510016.5 e0171

106 ·106 ! 101 102 110 109 104 104

TORQUEDTENSIQN" GA.LI~RATION in S'ki.dmore-W.ilhelm'-~,.• ,,--,--.--=-,,-..,..~, . , :1.', . '.~" ·_,·..,....-~r ..-"'~~--.-·""'''~'~~ ;-~~."""-""·O';",.--'-·,·_, ~--..r~~~~ It;

L I I L I L' I . I

1/8 1/8:' I~l I"~ 10 .'.9/16 1/8' 1'/-8" Q /1 6. "I ..... I d ~

5 . 5 i· 5 5, ~ 3 3

65,46S; 4i160,O 61.8 61.1 630316002

2,80· 3, 40 I 0080 2, 18 2" 80 3 40 12 n 80

00525 '00553 00616 e0698 oQ~QO,0252 00360

52 I - 50 4@ I.O~, ,114 ,075 IoO;,~8. ~0281 ,033 .031 .016 0016 I,OiS

4808 4900 4780 41 0 1 5304 5~05 53I

oS91 086 087' 080' .84 I .84

1, 42 11.64 LS? L25 1.38 11.64 1,56

\ I

ino

in~

kip&~

ki~p,s;"

k~ps

kips

kips

kips

kips

(t?r,que'd 'T:¢p:s~U1to ).~

(D~reet :reus vi t :)~~

Ave (> Tutns to lure

Standard ·Devian·

Mean EIQuge att~ Load

Mean Rupture r"·" '. ~'J • • 'I ~

~~an, 'E10ng~ af RUI,ture in o

'. "'~ . ' I·, '

Mea~ ~~ong~ atoof' Load in o

~~rTfl~: ~n GripNo (> ·of ·'SpecimeTe~.t;ed

.;.. ,'

Mean 1J1 t 0 Load., ~. ,

Nb;m.i:,Il.Cl,l' Gr~iV··Thread',f in. ,Gpip

No ,o,~ Specim~Te~t~Q."Mean 'Ul~o Load

Sta,n~tard Devictn

M~a,%' ~long<) att e Load.:·,t,., .

Mean Rupfure L

Bol~t Length

Thr"ead, Length

'$;p'~:,c 0 Proo·f Lo

~~e~o Mino Ul~oad

N6te.'~ L = I.Jeh\t.

.,.] ~ Iloi s~

TABLE 1

LOT AB LOT LI

Bolt Length

Thread Length

Spec. Proof Load

Spec. Min. Vit. Load

9~

in. 1~50

kips 55.45

kips 69.3

DIRECT TENSION CALIBRATION

5~

Mean Elong. at V1t. Load in.

Mean Rupture Load kips

Mean Elong. at Rupture in.

Mean Elong. at Proof Loa4 in.

% Spec. Min. V1t. Load

L

4

9/16

5

72.1

017

00647

59

0245

.0171

104

B

4

1/8

I

4·-

1/8

LIB L L

8 : 8 8 8 '4

1/8 1/8 1/8 9/16 1/8

555

73.2 7008 76.0

1.59 1 0 69.54

.0779 .0846 .0508

65 61 67

.12 .18 .137

.0282 .0292 .0154

106 102 110

TENSION CALIBRATION - in Skidmore-Wilhelm

kips

kips

Nominal Grip

Thread in Grip

No. of S~ecimens Tested

Mean Vlt. Load

Standard Deviation

in.Thread in Grip

No. of Specimens Tested

Mean Vlt. Load kips

Standard Deviation kips

Mean Elong. at Vit. Load in.

Mean Rupture Load kips

Mean Elong, after Rupture in.

Mean Elong. at Proof Load in o

Mean Load at ~ turn from kipsII snug" . '

LIB L I. B

1/8 ~/8 1/8 9/16 1/8 1/8 1/8

555

65~4 61.8 61.1

2.80 2.18 2.80

00525 .0698 00260

52 50 40

.08 .114 0075

0028 .031 .016

4808 41.1 5304

L

9/16

5

58e4

3.00

.0310

34

ell

e018

5000

(Torqued Tension U1t.):(Direct Tension V1t.)

Ave. Turns to Failure

.90

1-3/8

.87 080

1-7/8 1-1/4 1-9/16

Note: LI =B

LehighIllinoisBoth

AB Lot Bolts, 7/S tf Dia. x 9-1/2" Longo Cut Threads

k__ Proof Load, 55 .. 45

-J

1

.. 18,,17016,,15~14

Specified Ultimate Load, 69c3k

,,13012,,11010

l/~' Thread in Grip

9/16" Thread in Grip

.. 09

.-x------

\/7,''-- :F¥racture of Bolt

.08

13,2 W

.,07.,06,,05.. 04.03002.01

7

9

10

r-rjcoo

I"":"

Elongation (inches) .

DIRECT TENSION CALIBRATION AB=LOT BOLTS

FIG.. 1

100

.. 90

80

AB Lot Bolts, 7/8" Dia~ x 9-1/2l1 Long.,Cut Thread'"

~ 15014., 13011 - 012., 10~09

l/S" Thread in Grip

9/16" .Thread in Grip

Fracture of- Bolt

~08

~--

--

007

I~»--~-

I

006

""

.,05004003

---1(-x -1:-,~1/2 Turn of Nut from "Snug"

002DOl

7

50.""-'"

CIJ~

-M

~ 40"0

C'd0H

3

20

10

0_

0

Elongation (inches)

~ kAA (Uil~b O~~~~~~

TORQUED-TENSION CALIBRATION.. AB-LOT BOLTS

FIG$ 2

W

0'\

'\./__ Indicates Fracture/,

it '.

£...1 Lor BOLTs. Yg D,,... x 5~ LfHlt:r.

X---

x

118 ft Thread in Grip

9/16 f1 Thread in Grip

-- -- ~inG Specified Ultimate Load 6903k

e----

k- - - - - - Proof Load, 55.45

o

20 .<

30

10

80

70

...-....to 600..

.r-l.~

"""-/

ro 50en0

....:l

40

Elongation, (inches)

o .,02 .. 04 '006 008 010 012 ,,14 .,16 ,,18 ., 20 022 ,,24 ,,26 028 .,30 w

'"DIRECT ~ENSION CALIBRATION - 'LI-LOT.BOLTS

FIG e 3

Elongatio~ (inches)

Lot-LI _Bolts, 7/8" Diao x 5-1/2" Leng-th

x 1/3f1 Thread in Grip

wo

co

016015,,14

-+-

<> 13012011

\ .-1-

*

<> 10

-1-+

,,09c08,,07~06

9/16" Thread in Grip

c05c>04

.----

.x .... •x •-~

•II

-- -

1/2 Turn of:~•

------~

f ut,. )(•

rom Snug

c>03.. 02cOl

'"0coo~

...-...CI)

~..,..{

~~

TORQUED TENSION CALIBRATION ON LI-LOT BOLTS

FIG. 4

Elongation, (inches)

ELON~TION~NUT ROTATION CHARACTERISTICS OF LI-LOT BOLTSTORQUED IN SKIDMORE -WILHELM AND IN SOLID STEEL

l~I-Lot Bolts, 718 ft Dia o x 5-1/2H Long,Rol1edThreads,

1/8 i1 Thread in Grip

014

)(

FIGc 5

o

90

80

70

60

~

t/":)

~

0 -ri~~ .......~,.

"'0m0

r-=I

30

20

1 w010 \..0

012 013ell010009

/"

• 'h. ~"R x~*' #

'17-

008

K

~.

,,007

__-- La ad CU.I."ve

• •

.~

006

••

• 1#

Torqued in Skidmore-WilhefmTorqued in Steel PlatesAverage Load Curve Determinedin Skidmore-Wilh.elm p

,,~

005

•• k-l-roof~oad,--55~

\o.~~ 'IC. )( ''';>'',..

/'

"."It:/'

)It.. X)f/" ~

~---

..--~o--=--

004,,03002,,010'o

12/8

~1/8

10/8

9/8

bJ);j

d 8/3tIJ

S0$-I

4--1 7/8d0

-r-1+J

2 6/80~

.I-J

~ 5/8

4/8

3/8

2/8

1/8

~ wkoH~~(~f

LV

f---lo

ang

-I

•

9/1611 Thread in Grip

Comparison of Load-Turn Data

AB Lot Bolts, 7/3" Dia ..

)l-- l/S" Thread in Grip

for Different Lengths of Thread in Grip

X--,. 1/811 Thread in Grip

__ 9/16" Thread in Grip

..

LI-Lot Bolts, 7/81t Dia. XE-l/ain Length

Comparison of Load-Turn Data

for Different Lengths, Thread in Grip

o.~

70

60 _PR~OF l~-' ,_....- --

I I50

~

(/,)

40p...",....4~'-"

"-

30'"0C'Ij

0H

20

10

60

50

...-.. 40CI)

~~

~""-"'"

30'0a$0~

20

10

-?'g-'Vb -¥e

Average No. of Turns from I1Snug" of 10 kips

FIG q 6

FURTHER TENSILE TESTS OF A354 BOLTS

1. REVIEW

This report is a continuation of the preliminary report, "Cali­

bration of A354 Bolts", Fritz Engineering Laboratory Report No. 28809(1)0

As a review, this preliminary report included the results of the direct

and torqued tension tests of A354 bolts, grades Be and BD. Some of the

more important conclusions reached i.n this report were ~

1. The ultim,ate strength of the bolts when tested in direct

tension was from 6 to 27 percent higher than that obtained

during the torqued tension tests o This effect has also been

noted in previous tests of A325 and A354 bolts at Lehigh and

the University of Illinois.

2. The average preload induced by torquing the bolts ~ turn

(1800

) of nut from a " snug" load of 8 kips was just above

proof load for most lots of bolts with grip lengths up to

4~ inches~ For the longer grips of 7-5/8 to 8-1/8 inches,

the load at ~ turn of nut was always below proof load.

3. Thread lubri.cation had, at most, a slight beneficial

effect on the behavior of torqued bolts.

4. Failure of bolts torqued with an impact wrench occurred

after 1 to 1-7/8 revolutions, depending on bolt size and

grade, and on the length of thread in the grip. These

correspond to rotational factors of safety from 2.0 to 3.75 if

one half turn of nut is specified for installationo

Figure 1 shows typical load-deformation relationships for the

A354 bolt, and also illustrates graphically the first three conclusions

stated above.

Since this report was written, several special tests have been

conducted to determine other tensile properties of the A354 bolt. These

tests included~

Ie Direct tension tests of bolts previously installed

by torquingo

2ft Repeated installation of bolts by torquingo

3ft Torqued tension tests of polts installed in

solid plateso

4. Torqued tension tests of bolts torqued continuously

rather than in small increments.

Following are the results of these tests~

2. TEST RESULTS

2.1 Effects of Installation

Direct tension tests of ~olts previously installed by torquing

are conducted to determine the reduction, if any, in direct tension

strength of a bolt previously installed with an impact wrench. Figure

2 shows typical results of these combined torqued tension and direct

tension tests. The bolts were first torqued to 5/8 of a turn after

which additional load was applied in direct tension. Also shown in this

figure are the load elongation relationships for the direct tension and

for the torqued tension tests of the same lot of bolts. It can be seen

that when direct tension is applied to the torqu~d bolt, it has an ulti­

mate strength approximately equal to that of the bolt tested in direct

tension alone.

Four representative lots of bolts were tested in this manner

and the ultimate strength far each lot was within 3 percent of the

ultimate strength for direct tension tests of the same lot.

2.2 Repeated Installat~6n

As implied, the purpose of these tests is to determine the

feasibility of reusing previously installed bolts o Shown in Fig6 3 is

the load-elongation relationship for a bolt repeatedly torqued to 3/4 turn

of nut from snug 6 In Figo 4, the behavior of a bolt from the same lot

torqued to ~ turn is shown 0 From these figures it can be seen that the

reaction of these bolts to reuse was very critical e For cycles of 3/4

turn of nut, only two cycles 'were completed before failure and for cycles

of ~ turn of nut, only three cycles were completed Q This behavior was

much more severe than that shown in earlier tests of A325 bolts, and was

typical of all four lots tested, including both Be and BD grades &

It should also be mentioned that, after the first installation,

required torquing time increased substantial1yo

2.3 Bolts Torqued in Solid Plat~

These tests were conducted as a result of the belief that the

deformation under load of a 11ydraulie load cell such as the bolt c.ali.brator

used for the torqued tension tests of A354 bolts might be greater than

that of the steel plates in a bolted joint, thus 'affecting the relationship

between nut rotation and load o If this is the case, the laboratory tests

conducted so far do not truly indicate the bolt load to be expected at

some given number of turns 0

For this reason, several lots of bolts were torqued with a solid

material being gripped, and the resulting relationships between elongation

and nut rotation were plottedo From these curves, the elongation for a given

nut rotation can be measured, and then this elongation, when plotted on a load­

deformation curve for the same lot of bolts, will indicate the true bolt

load induced by the given nu.t rotation ..

This manipulation is made possible by the assumption that the

load-deformation relationship for a given bolt is a property of the bolt

itself, and is independent of the bearing material used to resist the

applied load. While this assu'mption is probably not completely true, all

indications at this time are that it is very closely approximated for these

tests.

The results of this type of test are shown in Fig& 5 for one lot

of A354BD bolts torqued, using four-one inch plies of A440 steel in lieu of

the bolt calibrator. The heavy line without test points is the load­

deformation relationship arrived at from tests in the bolt calibrator e The

deformation vs. nut rotation relationships are shown, with the solid test

points indicati.ng the relationship for the bolt calibrator, and the open

points for the steel plateso It can be seen that there is a marked in­

crease in deformation at a given nut rotation for the steel plates& This

is due to the smaller deformation of the plates under load, causing the

deformation to be taken up in the bolt itself e At one half turn of nut,

an increase in load of 9 kips was indicated for this lot of bolts e

Another effect to be noted is th.e reduced nut rotation until failure. for

the steel plate, indicating a smaller factor of safety against failure

for installationo

Later tests in another study indicated that, if the gripped

material were one solid block, the deformation-nut rotation relationship

would approach the dashed curve shown in this fi.gure. The deviations

from this curve are seen to occur at the initiation of torquing, leading

to the belief that these deviations are caused by slack or gaps in the

gripped material that close under moderate load e

While these tests indicate a greater load to be expected from

~ turn of nut, it Wlst be cautioned that they were conducted under fairly

ideal conditions and that, for an actual joint, the behavior may, in

fact, be worse than that shown by the bolt calibrator. These tests do

show however, one possible cause of early bolt failures reported in the

field when the turn of nu.t method of in.stal1ation is used o

2.4 Continuously Torqued Bolts

These tests were conducted to simulate actual field installation

methods and the results were compared to the torqued load-deformation

relationship obtained using 1/8 turn of nut increments 0 Several lots of

bolts were tested in this manner to either ~ or 3/4 turn of ilUt o Figure 6

shows the correlation between the two methods e The continuously torqued

bolts are indicated by the solid test points superimposed on the load­

deformation relationship for incrementally torqued bolts of the same lot o

For the four lots tested, the loads achieved by continuous torquing

ranged from 90 to 105 percent of those achieved by incrementally torqued

bolts, well within the expected variation&

3. CONCLUSIONS

Ie No reduction in direct tensile strengths were exhibited in

these tests by A354 bolts previously installed by torquing~

20 Repeated installation of an A354 bolt is not advised, for

the following reasons~

a) Only a few cycles can be applied before failureo

b) Reduction in clamping force is exhibited after

the first instal1ationo

c) Re""instal1atio'n i.mmediately becomes difficult and

time. consu'ming &

30 For ideal cases, the clamping force of an A354 bolt of a

given nut rotation may be higher than indicated by present calibration

methods. However, this is accompanied by the disadvantage of a smaller

rotation be,fore failure& This effect is also presum,e.d to be present for

other types of boltso

4. The behaV'ior of a continuously torqued A354 bolt is

practically identical to that of an i'oc.reIne.ntally torqued bolt 0

405

?

,p

/~/

;ii, i/C(D iiiI

go

o

•

A

• Oiv--ec.+ TeV\~I,oV\

o

o T=~lJ,~d ,enS\oIA ) . Q~ recejv~d

i::. To~'Ueci TI!V\~iol1l Th..r;>Qcb lub-ico.+ed ll..v~(ip~r?))

ED Lor'¥'giI DlaW\a+e~

'34" ThI"Bdd if} 6rtp

.-

.oso .0(5 .JOO J;l.S .150 ~ 17S ,~oo

+'"0

r:LCNG~T\ON J tV\~~e-s. 4~u G t0'\

~ 'r\p

Flgo 1 Typical Tensile Behavior of A354 Bolts ~~s4 50

~ TU,."

Load

t4in~ UIf:

20 I-~0

AO

I6-

£

l,0:2.S0

40

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