Bolted Joints Slotted Holes

8/21/2019 Bolted Joints Slotted Holes

1/64

BEH vIOR

OF

BOLTED JOINTS WITH

OVERSIZE OR SLOTTED HOLES

by

Ronald

N Allan

John W

Fisher

This work was carried out as part

of

the Large Bolted Connect ions

Project sponsored f inancial ly by the Pennsylvania Department of

Highways the Department of Transportat ion Bureau

of

Public Roads

and

the Research Counci l on Riveted

and

Bolted S tr uc tu ra l J o in ts

Technical guidance s provided by

the

Research Counci l on Riveted

and

Bolted S tr uc tu ra l J o in ts

r tz

Engineering Laboratory

Department of Civi l Engineering

Lehigh University

Bethlehem Pennsylvania

August 1967

r tz Engineer ing Laboratory

Report

No 318 3


2/64

1

2

3

4

5

6

7

TABLE OF

CONTENTS

ABSTRACT

ACKNOWLEDGMENTS

INTRODUCTION

PREVIOUS

WORK

TESTING

PROGRAM

3 1 Description of Specimens

3 2 Plate Properties

3 3

Calibration of Bolts

3 4

Fabrication and Assembly of Joints

3 5 In strumen tation

of

Joints and

Bolts

3 6 Testing

Procedure

3 7 Loss in Tension Studies

TEST RESULTS N

ANALYSIS

4 1

Effect

of Hole

Size

on

Bolt Tension

and

Installat ion

4 2

Loss in

Tension

of

Bolts

with Time

4 3

Slip Behavior

4 4 Effect

of

Transverse Slotted Holes on the

Ultimate Str ength o f the

Joint

SUMM RY

TABLES AND FIGURES

REFERENCES

Page

i

3

6

6

9

9

2

4

6

9

9

3

24

8

30

3

58


3/64

ABSTRACT

Twenty one

bolted

joints

were

tested

to

determine

the

ef fec t of oversized

or s lot ted holes on the

s l ip behavior and

u l t i -

mate strength

of

bolted

joints Hole

sizes studied

had

standard

1/4

in and

5/16 in . clearances. S lo ts

paralle l and

t ra ns ve rs e t o

the l ine of load

were

studied. All joints were fabricated from A

s tee l plate

and

fastened

by

in . A3 5

bol ts . Also studied

was

the

need for washers f or o ve rs iz e holes and changes in

bol t

tension.

For

holes

with 1/4 in .

clearance

there was no decrease in

the

s l ip

coeff ic ient excessive loss in bol t tension or inadequate preload.

The s tud ie s ind ic at ed that a washer i s desirable under th e turned

element to

p revent s ev er e gall ing.

A

decrease

in

the

sl ip

co-

eff ic ient

was observed for the joints with 5/16 in . hole

clearance

and for

those with

slotted holes.

Slotted

holes perpendicu la r to

the

l ine

of

load

did

not

decrease

the ultimate

strength

of

the

jo in ts


4/64

CKNOWLEDGMENTS

The project has been sponsored f inancial ly by the

Penn-

sylvania Department of Highways the U.S. Department of ommerce -

Bureau

o f P ub lic

Roads

and the

Research

Council on Riveted and

Bolted St ruc tu r al J o in t s.

Technical

gUidance has been provided by

the

Council

th ro ug h an advisory committee under the chairmanship

of

Mr N G Hansen.

The authors

express their thanks

to

their

co workers

Geoffrey Kulak and James Lee for help

with

the tes t ing and to

Ken Harpel

and

his

laboratory

technicians. The manuscript was

typed by Daphne iversley

and

the photography and drawings done

under the supervision of Richard Sopko.


5/64

1. INTRODU TION

The

current

1966

Speci f icat ions

for

S tr uc tu ra l J oi nt s

using STM A325

or

A49

Bolts ,

as approved by the Research Council

on

Riveted

and Bolted

S tr uc tu ra l J oi nt s

recognizes

two types of

shear connect ions , des igna ted as fr ic t ion-type

and

bearing-type,

respect1ve

y.

In a f r ic t ion- type jo int movement of t he connect ed

parts

is

not

tolerated

because of

the

detr imental

effects on th e b eh av io r

of the s t ructure .

For

th is type of jo in t s l ip const i tutes fai lure

and

working

loads must

be

resisted by fr ict ion

between

the connected

parts

with

a

reasonable

factor of safety against s l ip

Where sl ip of the bolted jo in t is not objectionable, a

bearing-type

connection

can

be

used. For

th is

type of

jo int

the

working

loads

may be

resisted by bearing of the bol ts against

the

sides

of th e

holes.

In

such

a connect io n, th e she ari ng of th e bol ts

or

fa i lure

of

the

connected parts i s c r i t i ca l

and

allowable stresses

are

based on the u lt ima te s tr eng th of

t he connect ion.

The present specifications

specify

tha t

the

bolts

in a

bolted

connection

are to be used in

holes

not more than 1/16

inch

in

excess

of the bol t

diameter.

l

There

are no provisions

in the speci-

f icat ions for the use of larger or

slot ted

holes.


6/64

-2-

Most of

the

studies

on

bolted connections

have

used

t es t

joints having

hole s w ith

a

1/16

inch clearance. There

is

a

need to

evaluate the performance o f bolted connections

with

a greater amount

o f ove rs iz e

because frequently occurs because of

reaming

and

mis-matching. Slotted

holes

are

a lso o fte n necessary

when a new

s tee l

d 2 h d

structure

S connecte to an

eX1st1ng

structure. Bot overS1ze an

s lot ted

holes

are d es ira ble to permit

erect ion

adjustments.

The

purpose

of

this study is to

evaluate

th e

effect

oversize

and s lot ted holes have on

the

s l ip resistance and ultimate strength of

bolted joints . The results of

this

study should provide information

on whether

jo ints with ove rs iz e

or

slotted hol es f unct ion

sat isfac

to r i ly as friction-type or bearing-type

connections.

The

study

is

primarily concerned

with the effect

oversize

and s lot ted holes have on: 1 losses

in

bol t

tension

a ft er i ns ta l

lat ion,

2

th e

s l ip resistance of a jo in t 3

the abil i ty

to tig hte n

bolts using the

standard

ins ta l la t ion technique, 4 whether washers

are

needed

for oversize

holes

and 5 the changes in

bol t

tension

during tes t ing.

The effect

of

slotted

holes

placed

perpendicular

to

the

l ine of loading on ultimate strength was also observed.


7/64

-3-

2

PR V OUS

WORK

Various studies have

analyzed t he behav io r

of

high strength

bolts and

bolted

joints when the bolts

were

ins ta l led in holes larger

than

their diam eters. E arly

laboratory

and

f ield t es t s indicated

tha t

among

other things,

high strength

bol ts

could be ins ta l led in

holes up

to

1/16 in . larger than the i r d iameter wi thou t a noticeable

effect on the

performance of the bol ts or of the jOints.

3

Therefore,

the

Research

Council

on

Riveted and Bolted

Structural

Joints

per-

mitted a

bol t hole clearance

of

1/16 in .

in the i r

f i r s t

specifica-

t ion

issued in 1951.

4

Hoyer

reported in 959 that studies conducted in Germany

indicated

that

there

was no

influence on

the sl iding

load

for holes

up

to

1/8-in.

larger than

the bolt

5

Chesson

and Munse

studied the

effec ts

of t ightening

bolts

in holes

with

up to 1/8 in . clearance using

the

turn-of-nut method

with and without

washers

under

the

turned

element. They concluded

that

oversize

holes up

to

1/8 in .

greater

in diameter than the bolt

may

cause

some reduction in bol t tension when washers are omitted and

when

f inished

hex head bol ts and nuts

are

used,

but

the clamping force

wil l

s t i l l be

in excess

of the required tension for

A325 bolts See

Fig.

1


8/64

4

Studies

to determine th e loss in prelo ad o f high strength

bol ts

due

t o r el ax at io n

have

generally indicated

that

the

to t l

loss

is

about

1 of

the

in i t i l preload.

Research

conducted in Germany

since

1954 has

shown

that high strength bol ts lose about 1

of

h

1

d d 6 7 Al h

1

d

e1r pre

oa

over a

two ye ar per10

so t e pre oa was un

8 9

affected

by

temperature

changes.

In South

Africa Denkhaus ob

served that the

loss

in

bol t

load using

a

washer

was

about f ter

1

day and 2 from

1

day to

1

year. Studies on

high tensi le bol ts

in

Japan

lO

showed

bol t relaxations of about

6

f ter 11

years for

bolts

tightened

to their y ie ld p oi nt .

Chesson

and

Munse

5

also

observed

the

effects of h oles w ith

up to

1/8

in .

clearance

on

the relaxation of A325

bolts. They

found

that there was no

signi f icant difference

in the amount of bol t ten

sion

los t

with

time

for

the

1/8 in . clearance

holes ei ther with or

without washers .

The loss in

bol t tension for l l tes ts

was

less

than 1

over

a period

of

from

1 to

5

days.

Tests conducted by the

Lamson

and Sessions

Company on a

load

analyzer showed a loss

in tension of less

than

1 over

a period

11

of days.

A

study to determine

the decrease of

the

preload in

high

strength bolts over a period of time was

conducted

in the Netherlands.

12

t

was

concluded that the

loss would be

about

5 over 2 years for

a

bol t with 2

washers

and about

1

over 2

years for a bolt with one

washer.


9/64

5

Studies to determine the changes in tension

in

the bol ts

f

1 d

1

d d d

Leh·

h

U

13a

o ~ n t

as

oa

was app

were

con

ucte

a t

n ~ v e r s ~ t y

Bolt tension

decreased

from

1 to

8

a t

major

s l ip

due to

the

Poisson

effect

Joints

with a 4 in . grip showed a decrease

in bo lt

tension

after major s l ip Nester

14

observed a decrease in bol t tension from

o to 8.6

a t

major s l ip

There is

no

record of

any research

done to

date

on the

effect

of

s lot ted

holes

on

the

performance

of

ei ther

high strength

bol ts o r bo lted jo ints


10/64

-6-

3.

TESTING

PROGRAM

3.1 Description of Specimens

All

twenty-one

t es t specimens

were

fabricated from l n

A36 s tee l plate supplied from the same heat. They had two l ines

of

1 in .

diameter

A325 bol ts connecting

four

plies of

plate

at a

pitch

of 5-1/4

in .

The faying surfaces were clean

mill s ca le .

Twelve

specimens wit h hole s

of varying

amounts of

oversize

and

three

specimens

with slotted holes

were

des igned a s fr ic t ion-

type jo in ts . The geome tri ca l la yout o f

the

oversize hole jo ints is

shown in Fig. 2.

The

twelve

joints with oversize holes were divided

according

to

hole

size

into

four

groups

of three

jo in ts .

The

ra t io

of

net

plate

area to to ta l bolt shear area the A A ra t io was 0.68.

n s

The

f i r s t group of three jo in ts

designated

OH

had a hole

diameter

of

1-1/16

in . providing the maximum allowable

hole

clearance

of 1/16 in .

These

three jo ints served as control specimens.

Because

the holes

were

normal

s ize

the bol ts

were

instal led

without

washers.

I n ano th er phase of this research

project

a number

of

bolted jo ints

were

tested to

determine the

influence

o f v ar ia tio n

of

the contact area upon the s l ip

resis tance.

These spec imens were

fab-

ricated from the same

plate as

the specimens

being

discussed. The


11/64

-7-

faying

surface

condition was ident ica l

for

both

groups of

jo in ts

The joints

of

the l a t t e r series had a single l ine of

four

7/8

in .

A325 bol ts and

the

contact

area

was

varied

by insert ing washers be

tween the

main and

lap pla tes . The hole

diameter

was

1/16

in . larger

than

the bol t

size.

The

three control specimens for

the

series

did

not have washers between

the plates. Thus the

phys ic al cond it ions

affecting the sl ip behavior were the same for these

control

specimens

as

they were for

the

th re e con tr ol jo in ts ORl

series

of the oversize

hole j oi nt s eri es

Therefore

a

direc t

comparison of the sl ip

co

eff ic ients

can

be

made.

The second

group

of

three

jo in ts designated OR2

had

a hole

diameter

of

1-1/4

in .

providing four times the

maximum

a ll owab le hol e

clearance. These jo in ts were also

bolted

up without washers.

The third

group

designated

OR3

also

had

a

hole d iame te r

of

1-1/4

in .

These were bolted up

with

washe rs under the nuts

in

order

to

determine whether

or

not washers should

be

required for holes of

th is

amount of

oversize.

The

fourth

group of jo in ts designated OR4 original ly

had

hole d iameter s

of 1-3/16 in . which provided three times the maximum

a llowable hole

clearance.

The

holes

in

these

three

jo in ts

were

en

larged to 1-5/16

in .

when the joints with

the 1-1/4

in . holes indi

cated no

signif icant

change

in s l ip behavior from th e c on tr ol specimens.


12/64

8

The nine jo ints with slot ted holes had

th e

slots placed

in the middle or main plates . Slotted h ole s lo ca te d in outside

pl ies would

normally

be

covered

with large

washers

which

would

cause

these pl ies

to act a s e nc lo se d plates similar

to th e t es t

jo in ts .

The s lots were

2 9/16 in . long and 1 1/16

in .

wide.

The

holes in the outside plates provided

the

maximum allowable hole

clearance of

1 1/16 in . The jo ints were assembled

without

washers.

Three jo ints SR1

contained s lo ts

placed

para l le l

to the

l ine

of load as

indicated

in Fig. 3.

These w ere

designed as f r ic

t ion type jo ints

and the

A /A ra t io was the same

as that

of the

n s

oversize

hole joints

so

that

th e

effect of slot ted holes placed in

the

direct ion

of s l ip on

the sl ip resistance could be observed.

Six

jo ints

were

designed

as

bearing type jo ints

and

had

s lots placed perpendicular to the

l ine

of load as shown in Fig. 4.

Three of

these jo in ts

designated

SR2, were

proportioned

with current

l y u sed a llowable st resses and fai lure

was expected to

occur

by tear

ing

of the

plate a t

the net section. Their net

section

area was

equal

to

the bolt shear

area. The

net section

efficiency was 60

The

remaining

three

jo in ts

designated SR3, had an

in

creased

net

section area so that fai lure

would

occur

by shearing

of

the

bolts . Earlie r experimental and

theoret ical

studies


13/64

9

ha d shown that

this

would occur i f net sect ion area was 6 greater

than

bol t

shear

area.

3.2

Pl at e P rope rt ie s

The A 6 s tee l plate used

for the

specimens was purposely

ordered

a t

minimum

s t rength.

The plates

furnished

from the same

heat were

rol led

2 8 1 /2 i nc he s wide and 4 feet long. A f o o ~ -

long

section

was

cut

from

the

middle

of

each

plate

Standard

ten-

s i le

coupons cut from

this

piece were

tested in a mechanical uni-

versal tes t ing

machine

equipped with an

automatic

load s t ra in

re -

corder . The tes t ing speed was

0.025

inches per minute unt i l

s t ra in

hardening began. The

s ta t ic

yield load was obtained by stopping

the machine times during yield and allowing

the

machine

to

equalize

each

time.

When the coupon

went

into

s t ra in

hardening

the

tes t ing

speed was

i nc re as ed to

0.3 inches

per

minute unt i l the coupon fai led

The load s t ra in curve for an 8 inch gage

length

was plot ted by

the

automatic rec ord er fo r

each

coupon.

Fifteen s ta nd ar d b ar tensi le

coupons were tes ted.

The

mean s ta t ic

yield s t ress

of

the

plates was

29.3

ksi with a standard

deviation

of 0.6

ks i

The mean

tensi le

strength was 61.0

ksi

and

i t s standard

devia t ion

was.D.7

ks i

3.3

Calibration

of

Bolts

One i nch d iame te r A 5

bol ts

were

used

to bolt up

a l l


14/64

10

jo in ts

Because some

joints were bolted

up with

washers and

some

without;

two different

bol t

lengths

were

required. Joints

without washers used 5 1/4 in . b olts; joints with washers used

5 3/4 in

bol ts

Representative samples of bol ts from each lo t were ca l i -

brated in both direct tension and

torque

tension

to

determine

their propert ies. Three bolts from each lo t were chosen

at random

for

each

cal ibrat ion.

All

of

the

calibrated bol ts

sat isf ied

the

minimum

proof load and ult imate load requirements specified by the

ASTM Both

lots

of bolts had tensi le strengths that exceeded mini-

mum strength

by

13 to 15 In

both the

direct tension and torqued

tension cal ibrat ions

the

bol ts remained e las t ic well above

th e

required minimum tension. Since

the bol ts

were held a t

the

same

grip

when

tested as

existed in the joints

t he load e longa tion

curves used in

the

torqued tension cal ibra t ion tes ts were .used

to

determine the

tension in

the bolts instal led in

the

joints

3.4 Fabrication

and

Assembly

of Joints

The

t es t

jo ints

were fabricated

by a

local s tee l fabri -

cator.

The

individual plates were

flame cut

to rough size and

t hen m il led to the

specified

jo int dimensions. The

faying

surfaces

were

cleaned of

loose mill

scale and burrs .

The

four c orn er h ol es


15/64

of each

oversize hole

joint assembly were then sub dri l led

and

reamed f or a li gn ment . he fou r r emaining holes were

then

dr i l led

through a l l four

plies of

s tee l

to the

s pe ci fi ed s iz e

while the

plates

were

held in alignment

by

s tee l pins in

the

corner holes.

he s lot ted holes were f o ~ m by dr i l l ing two adjacent

holes in the plate and then

removing the

metal between

them.

Fil le r plates were welded to the lap plates on

one

end

of

each

jo int nd the m in

plates

were welded together at the

grip

end to ensure

uniformity of

wedge

g rip a ctio n during

t es t -

ing.

Cleaning assembly

and i ns trumen tat ion of the

joints

were performed at Fritz Engineering Laboratory. Before assembly

the

jo ints were

cleaned

with shop solvent to remove any

grease

or other

foreign

material . hey were then assembled and aligned.

he bolts were

instal led

either w ith or w ith out washers

depend-

ing on the individual t e s t · he turn of nut ins ta l la t ion

pro-

cedure

w s

used.

he

bol t

tensions were

determined

by

measuring

the changes in bol t

length

with the extensometer and

then

de-

t er mining the cor re sp on ding

bol t tension from

t he to rq ue d

tension

cal ibra t ion

curve.

In a l l

of

th e

jo ints except the

three

with

hole dia-

meters of 1 5/16 in the bol t tension

varied from

the

required


16/64

minimum tension

to

50

above t he r e9ui red

minimum tension. When

two

of

the

joints

with

the

1-5/16

in .

holes OH4

ser ies

were

bolted up with washers

under

the nuts only half of the bol ts

failed

to

achieve

proof

load f ter 2 turn

of nut. The

bol ts

were removed and l l

three

jo ints were

bolted

with washers placed

under

both the

heads

and the nuts.

3.5 Instrumentation of Joints and Bolts

All

of

the specimens were instrumented

to record the i r

performance

during

tes t ing

including

jo in t

s l ip elongation and

alignment.

Dials

reading

to

0.0001 in .

were attached to tabs

tack

welded

to

both

sides of

the

main plate

in

l ine with

the bottom

row.of

bolts .

The

pointers

of these

gages

rested

on

a

frame

tack

welded to the lap plates in l ine with the tabs. Thus s l ip move-

ment

between the

main and lap

plates

was measured on one

l ine

and

effects

due

to axial

strains were

minimized.

Joint elongation was measured between points one

gage length above the to p l ine of bolts and

points

one gage

length

below

the

bottom

l ine

of

bol ts .

These.

points

were

locat

ed

on the

center l ine of

the

joints

the

top points on both fa ce s

of the main plate and the

bottom

points on both lap plates . ne


17/64

13

half inch studs were tack welded to

th e plates

a t these points .

Elongations

were

read

from

0.0001

in .

dials

that

read the

re-

lat ive movement

of

the studs by means

of

a

sl iding

rod arrange

ment.

Elect r ica l resistance s t ra in gages were attached to the

sides of the main and la p

plates of a l l of

the joints

to

detect

any eccentr ici ty of loading caused by uneven gripping or curva-

ture

of the

joint

and

also to

determine

the onset of

yielding.

number

of the

bolts

were

ins trumented with

elect r ical

resistance fo il s tra in

gages

cemented to their shanks. Flat

areas 1 1/16

in .

long

and 1/16 in . d eep were milled into

th e

shank

under

the bolt

head

to

provide

a

mounting surface for the gages.

he

gages

were placed on opposite sides

of

the

shank

paral le l

to

the axis of the

bol t . he

g ag e w ire s p ass ed thr ou gh

two

holes

dr i l led

through

the bol t head.

t

was d isc ov ered during th e direc t tension cal ibrat ions

that the

shanks

for

the

bolts

remained

elas t ic into the range of

bol t tension achieved by the turn of nut method of

ins ta l la t ion

and

a l inear

load strain

relationship existed

as

shown in

Fig.

5.

Since the gaged port ion remained e las t i c i t

would

no t

be so affected by the high load and very l i t t l e creep would occur.

the other hand ine las t ic

deformation was

occurring

in

the

threads

so

that the overal l bol t elongation could not be expected


18/64

-14-

to yield

consistent

results

Each gaged

bolt

was

calibrated

in d ire ct

tension

in

order to re la te the

strain r eadings with

the

tension

in the bol t .

During

the cal ibrat ion,

the

bolts were

loaded

in

10

kip

incre

ments

to

50 kips and

then

in 5

kip

increments

to

65

kips.

The

ove ra ll b ol t elongations were also

checked

with the extensometer .

I t

was observed that

the

reduced

area

of shank

due

to

the m illed

surfaces did

not cause

any

measurable

difference

in

th e

l o ~

elongation relationship

of

the bolts

as

compared

to the

bolts

without gages. The load-strain

reading

relationship of the

gaged

bolts was l inear for

both

the loading

and

unloading cycles.

Four gaged bol ts were used in each of

six

of the

bolted

joints: OH1 1 and OHl 2 1-1/16

in . diam.);

OH2 l 1-1/4 in . dia

no

washers);

OH4 l

1-5/16

in .

diam.,

2

washers);

SHl-1

slots

paralle l to

l ine

of

load);

and SH3-l

slots

perpendicular

to

the

l ine of load). The bolts were arranged in a staggered pattern

as shown in Fig.

6.

3.6 Testing

Procedure

All of the

joints

were

tested

in

a

5,000 kip

universal

test ing machine us ing f la t wedge grips. Each jo in t was

held

by

the

top

grips

of

the

machine

while

dials were ~ l e d on

th e sp eci

men The

dials

and s tra in gages were a l l read at z ero load. The


19/64

15

bottom grips

were

then applied

and loading

s tar ted .

Load was

applied

in

25

kip

increments

un t i l

major

s l ip

occurred.

At

each

increment a l l

dials

and

strain

gages were read.

For the friction type jo in ts

the

s l ip behavior

was

ob -

served closely. Following major s l ip the dials

and

gages were

read

and load

was applied

in

kip

increments unt i l another s l ip

smaller

than the original

s l ip and designated

as

a minor s l ip

occurred.

This

loading

sequence

was

repeated

for

a l l

subsequent

minor

sl ips unt i l the

jo int

went

into

bearing at which

time

the

t es t was

stopped.

For th e b ea rin g joints the t es t was

carr ied

to ul t i -

mate and fa i lure .

The

i n i t i a l s l ip load

was

observed and the

jo int

was

then

loaded

in

5

kip

increments

unt i l

th e

load

approached

the predicted ul timate

strength.

The

p la te f ai lu re

specimens were then

loaded

to

fai lure

whjch occurred when th e

main

plate tore

apart a t the

top

l ine of s lots The b olt f ailu re

specimens were loaded unt i l the top

row

of b olts f aile d in shear.

After the joints were

removed

from the tes t ing machine

each

one

was

dismantled.

The

fracture surfaces of the

plate

failure

specimens and

faying

surfaces

were

inspected.

A sawed

sect ion

of one of

the b olt f ailu re specimens

was

taken to in -

spect the

condition

of the bolts and the

s lot ted holes.


20/64

16

3.7

Loss in Tension

Studies

Immediately

fter the nu t on

high strength

bol t

is

t ightened loss in

bol t

tension

occurs. This

is

thought

to be

resul t of creep

or plast ic

yield in t he th re ad ed port ions and

e l s t ic

recovery caused by pl s t ic flow in the s tee l plates

under

the

head

nd nut. om research

has been

done on holes with the

s ta nd ar d h nl e c le ar an ce o f 1/16

in .

Only few relaxation

t es t s

have been conducted on larger holes.

t

w s

desirable to e va lu ate

the

effect

on relaxation

of holes tha t

were

substant ia l ly

oversize.

he largest hole

size studied w s 5 16

in .

oversize

2 1 2 times the mount in

previous studies

of holes 1 8 in .

oversize.

he effect of the

enclosed slot ted holes on loss of bolt

tension

w s

also

eval-

uated.

Since t he load e longa tion relationship of the bolt

shanks

w s l inear within the range of bol t tension used the

bol ts with the str in gages

cemented to thei r s hank s s ho ul d give

an accurate

indication of the bolt tension a t any time. hus

meaningful

relationship of the bol t

tension

varia t ion with

time

could be established. he six bolted joints containing the gaged

bol ts

provided good representat ive sample of l l

of the

joints

in

the study.

he

six joints were

placed

horizontally and were

not

disturbed

for the

duration

of the study. Strain

gage

readings


21/64

17

were taken

a t the

moment each bol t was

ins ta l led

Subsequent

readings

were

taken

a t

one

minute

five

minutes

one

hour

one

week two weeks and one month after

ins ta l la t ion

The

strain

gage indicator

remained

connected

to the

s tra in

gaged

bol ts

through a

switch box for the duration of the

study. In addi-

t ion

to

the strain gage

readings

extensometer

readings

were

taken

a t the

same

intervals on a l l

bol ts of each jo in t This

provided

an opportunity to correlate the s tra in readings on the

bol t

shanks

with the bol t elongation

readings.

t

the

completion

of the stu dy the six joints were

tested

using

the

standard

procedure.

During

each t e s t s tra in

readings were

taken

so

tha t the

changes

in bolt

tension during

tes t ing

could

be

observed.

In order

to

check

the

accuracy

of

the

bol t

gage

readings

over an

extended

period of

time

gaged bol ts

of the

same lo t were

instal led in

a

load ce l l as

shown

in

Fig.

7.

The

load ce l l

was

made

of hardened tool

s tee l and had a hole

1 1/16 in . in diameter

through i t s

center

through which

the

bol t

was

inser ted .

Four

strain

gages

were

cemented to the outside of the load ce l l two

placed horizontally and

two

placed ver t ica l ly

They

were con-

nected to

a

strain gage indicator in

a Wheatstone bridge arrange

ment.

One half

inch thick A

s tee l plates were

placed

over

each en d of the load

ce l l

so that the behavior of the plates


22/64

18

under the head and nut

would

be

similar

to the behavior

of

the

plates in the actual jo in ts

Three

sets

of these

plates were

used one

se t

for each of the three

hole

diameters used

in the

oversize

hole specimens.

The

tot l grip of

the

assembly

was

inches.

Thus the

condit ions

tha t

affected the

relaxation be-

havior of

a bolt in the

t es t

joints were closely approximated.

The bolt to be studied was ins tal led while the load ce l l

assembly

was

firmly held

in

a

vise.

The

bolt

gages

and

the

load

ce l l

gages

were connected to sep arate str in

gage

indicators

set to indicate a load of 6 kips. The

nut

was t ightened by a

hand wrench

unt i l the

desired

load was reached. Readings were

taken for both the bol t

tension

and load ce l l

deformation

t

intervals

of one minute

5

minutes

one hour and

each

day

for

a week.

Overall

bol t elongation

readings

were also taken

with

the extensometer.


23/64

-19-

4.

TEST RESULTS

AND

ANALYSIS

4.1

Effect of Hole Size on Bolt Tension and Ins ta l la t ion

I t is of in te res t to examine the effect of

varying

hole

diameters

on the ease of ins ta l la t ion degree of scouring,

and clamping force of bol ts

ins ta l led

by th e

turn-of-nut

pro

cedure.

The bol ts

in the

OHl joints 1-1/16 in . hole diameter

were ins ta l led without washers in accordan ie w ith th e present

specifications for

bolted jo in ts which permit ins ta l la t ion

without

washers

when using the

turn-of-nut method. There

was

no diff icul ty

in

achieving a

bol t

tension

above the required

preload in these

jo ints

The tension achieved in

the

4

bolts

of the control jo ints ranged

between

5

and

49

of

the

requi red pre load ,

as shown

in

Fig.

8.

The average

bol t

elongations

and

tensions

for

each jo in t are

l is ted in

Table 1.

The mill

scale on

the

plate area under

the

turned

element

around

the 1-1/16 in . holes was

s l igh t ly

galled as shown in

Fig.

a

A s l igh t

depression occurred

under

the

bol t

head,

as shown in Fig. 9b. This

nominal

amount of damage indicates

tha t

washers

are not

required

under

the

head or

the

turned

element for

holes tha t

contain

the

nominal

amount of

clearance.


24/64

-20-

The bol ts

in

the 3

joints

of the

OR

series i l /4

in .

hole diameter were insta l led without washers while the bolts

for

the OR series also

1-1/4

in . hol e d iame te r were

installed

with

washers under the turned e lemen ts .

There

was no diff iculty achiev

ing bol t

tensions

above the minimum required tension in a l l six

jo in ts . The

average bolt

elongations and tensions

for

th e two

series are summarized in Table 1.

The

range

of

bol t tensions

achieved for each series is shown in Fig. 8.

As can be

seen in Fig.

8, the

average

bol t

tensions

for

the

two groups containing 1-1/4

in .

holes were about equal 118

of proof load

but

were noticeably lower than th e average tension

in

the control groups 130 of proof

load .

Plate depressions

occurring

under

bolt heads during t ightening

Fig. lOa

were

greater

than

those that had occurred in the control joints .

This

meant

that t he e longa tions

of

th e

bolts in

th e

1-1/4

in . holes

were sm aller than those in

the control

joints af te r 1/2 turn-of

nut and

hence the

bol t

tensions were

reduced.

Severe

galling

of both the

plate

and th e nu t had

oc

curred

during

ins ta l la t ion in

the

OR ser ies .

The damage to

the

plate

is shown in Fig. lOb. For comparison, th e s ur fa ce

con ditio n of the plate where washers were used under th e nuts

in

the

OR

series is shown in

Fig. 11. Only

a s,light

depression

occurred under the

washer. I t can

be

seen from Fig.

8 that th e


25/64

21

of washers in the 1 1/4

in .

holes did

not

affect the average clamp-

ing force

of

the bol ts . However the scat ter in bolt

tens.ion

for

the

bol ts

without

washers

was nearly twice

as

large as the

scat ter

in the bolt te ns io n fo r the

bol ts

that were instal led

with washers.

The 1 3/16 in . holes in the OH4 s eri es jo in ts

were

dr i l led

from the original to

1 5/16 in .

af te r the

studies

on the s l ip

be-

havior

of the

OH2

and

OH3

series. The

bol ts

in two of

the three

OH4

s erie s jo in ts were

ins ta l led with

washers placed

under the

nuts

be-

cause

of

the

severe gall ing

that occurred

in the OH2

series

when the

bolts were ins ta l led

without

washers. When the bolts in these two

specimens were t ightened by t he s ta nd ar d turn of nut procedure

hal f

of

the

6

bol ts failed

to

achieve the i r

required minimum ten-

sion. The

bolts

were removed from the

jo in ts

In spection of the

two jo ints revealed

tha t

the

bol t

heads

had

recessed

severely into

the

plate

around the

holes

far more than

in the OH2 and OH3

ser ies

as

shown

in Fig. 12 . In this instance the

elongations of the

bolts

were

reduced suff ic ient ly

so

that

the

bol t preload

was

less than

the required

minimum

All three OH4 joints were then rebolted with washers

in -

stal led under both

the

heads

and

nuts. This time there was no

diff icul ty in achieving bol t

tensions

above proof

load

as

indica ted

in Fig.

8.

The range of

tensions

a ch ie ve d f or bolts

ins ta l led

with

washers under

both

the.head and the nut was from 11

to

144 of


26/64

22

proof load with

an

average

tension

of

125 of

minimum

tension.

This

compares

with

the range

of

bol t

tensions

achieved

in

the

bol ts in

the control

joints

The resul ts

of these studies can be extended to

determine

the

maximum a llowable hole c le ar an ce f or

other

sizes of A 5 bol ts

for the

given grip

length in A36 steel plate . The diff icul ty in

achieving

proof load tension

was a resul t

of the

bol t

depressing

in -

to

the

pla te

around

the

hole. In

the holes with

the

5/16

in .

clear-

ance

the

bol t

heads r ecessed severe ly

into

the

plate because

the

bear ing pressure

between

the f la ts

of the

heads and th e plate was

in i t ia l ly

to o high. This was no t

the

case for th e bol ts that were

in sta lle d i n

the

holes with 1/4 in .

clearance. t can be assumed

tha t

the bear ing pressure developed under the f la t areas of the

bol t

heads

with 1/4 in . clearance

holes

was the maximum a llowable bea ring

pressure.

t was 72 ksi when

the

bol t preload was 2 in excess

of

the

required tension.

The maximum

hole clearance

for

any size

bol t

may then

be computed

on

the basis

tha t

the area of

plate

re-

maining under

the f la t of the head must be suff ic ient to

permit a

maximum

bearing

pressure

of

7 ksi when the

bol t is

ins tal led

The resul t s

of these

computations

are

summarized in Table

2 All of

the

hole d iameter s have

been rounded

off

to

the

nearest

sixteenth of

an

inch. The maximum a llowable hole

clearance

for

bol ts

equal

to

or

less than one inch in diameter is 3/16 in . Fo r

bol ts with d iameter s greater than

one

inch a 5/16 in .

hole clearance

is

permissible.


27/64

-23-

4 2

Loss

in Tension o f

Bolts

with Time

The

loss

in ten sio n

on e

minute a ft er i n st a ll a ti o n

agreed

w ith the

one-minute l os se s r ep o rt ed in

previous

inves t iga t ion S

where the

loss

in t ens ion fo r heavy-headed bo l t s and nuts ranged

be

tween

and

4

of the i n i t i a l

clamping

fo rce

Nearly a l l

of

the loss occurred within the f i r s t few hours

a ft er i ns ta ll at io n Also none of the var i a t ions

of

hole diameter

o r the

presence of s lo t s

had any s ig n if ic a nt e f fe c t

on

the p e rcen t

loss in ten sio n of

the

bo l t s dur ing the

study period of

one month.

The extensometer readings

indica ted t h a t the ungaged b o l t s behaved

the

same

as

th e gaged

bo l t s

The load c e l l

s tu die s are

compared

with

the bo l t

gage

readings

in

Table

4.

Since v i r tua l ly a l l of the losses in th e bo l t s

ins t a l l ed

in

the j o in t s occurred within week a f t e r i n s t a l l a t i on

the load c e l l

s tud ie s were

a lso conducted fo r

one

week.. The

re su l t s

showed good agr eemen t b etween the b o l t s t r a in measurements and th e

load

c e l l The maximum er ro r was

2-1/2

of

the i n i t i a l clamping

force


28/64

-24-

4.3

Slip Behavior

The

s l ip

resistance

of

a

bolted

joint

is

a function of i t s

s l ip

coeff ic ient and the bol t preload. The

s l ip

coeff ic ient ha s been

defined

as:

15

K = PINT. where K

is

the

sl ip coeff ic ient

P

the

s s s s

s l ip load N the number

of

s l ip

planes

and T

the

to ta l i n i t i a l clamp

ing force.

The

to ta l

clamping

force

was

taken

as

the

sum

of

a ll

of the

bol t tensions measured approximately one minute after

ins ta l la t ion

The s l ip coefficients for

each of the

joints are

summarized

in

Table

1.

Typical load-slip and load- joint

elongation

re la t ionships

are

shown

in

Figs. 14 and 15 .

The

load-slip response

of

the oversize and slot ted

hole

jo ints

was

l inear

unt i l

the

load approached

the re gion

of

major

s l ip

The

dia l

gages that recorded s l ip moved

very s low ly in

this region.

Occasionally there

would

be a sl ight

noise and

the

sl ip dials would

indicate a

sudden

movement of about 0.0001

in . This

was

probably

caused by the extension of the sl ip

zone

into the joint h n the

load

approached the major

sl ip

load

the dia l

movement began

to

ac-

celerate and when

major

s l ip

occurred

there was a

loud

noise accom

panied

by a

sudden

movement about 0.04 in of

both

the sl ip and

elongation

dials which caused

a

drop

in the

tes t ing

machine

load.

The in i t i a l

sl ip

was never equal to the hole clearance of the joint

Subsequent loading of the

bolted

joint produced small additional


29/64

25

s l i p s un t i l the

j o i n t

was in bear ing These smal l s l i p s

seldom

oc

curred

a t

higher

loads than

the

major

s l ip

load

The

number

of

smal le r s l i p s increased as the hole diameter increased The

i n i

t i a l s l ip did

not br ing

the j o in t

in to bear ing because of

the

de

crease in lo ad c au se d by

the

s l i p In an a ctu al s tr uc tu re th e load

might

remain

cons tan t and the j o i n t would s l ip i n to bear ing a t th e

i n i t i a l s l i p

The

three

j o in t s

of the OHl

se r i es

which

had

the

nominal

hole c learance

of

1/16

in

served as

con t ro l

specimens The average

s l ip coe f f i c i en t fo r these three j o in t s was 0 29 T his v alu e i s com

14

parable

to

the average s l ip

coe f f i c i en t

of 0 34 obtained by Nester

from a

se r ies of bol ted connect ions made

from

th e same hea t o f s t ee l

16

Tes t s conducted a t

the

Univers i ty o f s h ~ n g t o n on

A 6

s t e e l bol ted

j o in t s yie lded

comparable

r e su l t s

Inves t igat ion of the faying

sur faces

of

the j o i n t s ind ica ted

tha t

damage to the

m il l sca le

sur face

was

confined mostly

to

the

a r ea s

immediately ad jacen t to

the

hole s This i s in

accordance with

the

theory tha t

the

areas immediately adjacent to

the ho les

of

a

bol ted

j o i n t

a re the a reas of

h ig he st c on ta ct

pressure and

t he r e fo r e

provide

most

of the s l ip r es i s t ance Figure

16

shows

the m ill sca le surface

damage near the bo l t

holes

The OH

and

OR j o in t s with the 1 /4 in hole c learance

pro

vided s l ip

r es i s tance comparable

to the

OHl t e s t s

The average

s l ip


30/64

-26-

coeff ic ient for both

the

OH

and

OH

series

was 0.28. Inspection

of the

faying

surfaces indicated that

most

of

th e s urfa ce

damage

occurred around the holes See Fig. 16 . This also

showed

that the

pressure distr ibut ion in these

joints

was

similar

to the pressure

distr ibut ion in the control joints

damage was more

severe for

the

1/4 in .

hole clearance joints

because

the distance

of sl ip

was

four times as great.

The

three

joints

of the

OH4

series

which

had

hole

clear

ances of

5/16

in . showed lower sl ip resis tance. The average sl ip

coeff ic ient for

these joints was 0.24. Inspection

of the faying

surfaces

af te r tes t ing also

showed

that most of the

surface damage

occurred

around the holes. The damage for

these

jo ints was

the

most

severe

of th e oversize-hole joints

because

the greatest amount of

s l ip occurred.

The three fr ic t ion joints of the SHl group had slot ted holes

in the

enclosed

plates

placed paral le l to the l ine of load.

These

joints also

showed

lower s l ip coeff ic ient .

The

average sl ip coeff ic ient

for the series

was 0.20.

The

sl ip behavior of

three of the

bearing

joints SH2-i,

SH

and

SH3-l

was different

from

that

of

the

res t

The

behavior

of

these three

joints

prior

to major

sl ip

was

basical ly

the same

as

the

other joints

slow

dia l

movements with an bccasional sudden move-

ment of 0.0001 inch.

When

major s l ip

occurred

there was no loud


31/64

-27-

noise or drop

of

load. Instead,

the

dials began

to

move

very rapidly

while

the

load continued to increase.

The

to ta l amount of rapid

dial

movement was enough

0.30-0.50

in

to

be considered a

major

s l ip

Following

this the joints

underwent

a few minor s l ips unt i l the bolts

went into bearing. The s l ip coeff icients of the

six b earin g jo in ts of

groups SH

and SH

are also

summarized

in Table 1.

The average s l ip

coefficients for

the

SH

and

SH

series

were 0.23

and

0.21,

respec

t ively.

The

average s l ip coeff ic ients of a l l

of the

j oi nt se ri es

are

compared

in Fig. 17 . I t is apparent that

th e

average sl ip co

ef f ic ien t

for the

OH

and OH series was

about

the same as

the aver

age

s l ip

coeff ic ient of the OHI

jo in ts

There was a decrease in the

s l ip coefficient

for the OH4

jo in ts

This indicates that

for

in

bolts

there

is

no decrease in

the

sl ip

coeff ic ient for holes with

up

to 1/4 in . clearance.

The

s l ip

coeff icient

for a l l

of

the s lotted

holes

were also lower than the average s l ip

coeff icient

of the control

joints

A

possible

hypothesis

to

ex pla in th e reduced

sl ip resistance

of

th e

OH4 joints 5/16 in . clearance and the s lotted

hole

jo in ts is

based on the theory that the greates t

con ta ct p r es su r e

between two

plates bo lt ed togethe r

occurs

immediately adjacent

to

the hole.

High

f r ic t iona l forces that are p ropo rt iona l t o the contact

pressure

the

interlocking

of the

stir

face i r regular i t ies in

these r ~

con

s t i tu te a

major port ion of the resistance

of

the bolted jo in t

to

s l ip


32/64

28

Removal

of

a large port ion of this area as

in

the case

of

the OH4

jo ints

with

5/16

in .

hole

clearance

and

the

slot ted

holes

causes

very high

contact p ressu res

immediately adjacent

to

th e

hole

which

tends to

f l t ten

the surface i r regul r i t ies This r ed uces the

sl ip

resistance of the joint This reduced

resistance

to sl ip should

be

taken into

considerat ion

in

the

design of fr ic t ion type joints

con

ta ining

l ar ge o ve rs iz e

or slot ted

holes.

4.4 Effect of

Transverse

Slotted

Holes on

the

Ultimate

Strength

of

the

Joint

The three

joints

of the SH2 series

were

designed to

f i l

by tearing of the plates .

The

resul t s of these t es t s are summarized

in

Table Sa. The

load joint

elongation and load specimen

elongation

re la t ionship

of

jo in t

SH2 3 is summarized in Fig. 18 .

In l l cases th e inter ior s lo tt ed p la te

failed

a t the

f i r s t

row of slots Fig. 9 shows t he d eforma tion

in

the slot ted

holes of jo in t

SH2 2

at f i lure

The ultimate

load for l l three

specimens was

r o u ~ y

11 of

the

predicted

load

based on the coupon tes ts

This

is

in

agreement

with the resul ts of

e r l ier studies conducted on bolted

5

jo ints

w ith s tand ar d round holes.

The three

joints

of the SH3 series ¥ere

proportioned

so

that

fai lure

would

occur by s he ari ng o f the bol ts . The geometry of the


33/64

29

joints was

based

on the assumption that minimum strength bol ts were

to

be used

for the t es t s However

the shear strength of the

bol ts

exceeded the plate capacity and joint SH3 l failed

by a

tear ing of

the

plate.

A new lo t of bolts

specified

to be

of

minimum strength

was ordered. The bolts were tested

in

shear

j igs

with

both s lotted

and round

holes.

The average shear strength of the bolts in the

slot ted

hole

shear

j igs

was

84.3

ksi

while the shear

strength in

the

round hole

was 81.3 ksi . This was

caused

by a

ballooning

of th e

plate as the bol t shearing caused deformation on the f la t

port ion

of the s lot as shown in Fig.

20.

T hi s cau sed a shif t ing of

the

shear

p la ne w ith

a resul tant

increase in the shear area of

the

bolt

shank.

The

t es t s

of

jo in ts

with these

bol ts

are

summarized

in

Table

5b .

The deformation of a

bol t

and

the

plates of jo in t SH3

are shown in Fig. 21.

In

both

cases fai lure

occurred

when the head

end

of one

of the two

top bol ts sheared

off .

The

average bol t

shear

s tress a t ultimate

was

about

lower in both joints than

was

predicted

from

the

s lotted

hole shear

j ig t es t s The sawed

sect ion

of jo in t SH3 shown in Fig. shows

the

deformation

of the bolts and of t he e nclo se d plate

t ca n

thus

be concluded that

slot ted holes in

the

enclosed

plates of

a

bolted joint

do

not reduce the ult imate strength of

ei ther

the

plates or the

bolts

in shear.


34/64

30

SU RY

On the basis of this

study

the following conclus ions

have

been

reached:

1. One in.A325 b ol ts i ns ta ll ed by the

turn of nut

method

in holes

with

1/4 in .

clearance

ach ieved ave rage p re10 ad s

2

above

the

required bolt tension. Washers

under

the

turned

element

are

recommended to p revent s ev er e gall ing.

Bolts in sta lle d in h ole s w ith

5/16

in . clearance re-

quired.washers

under

both the head and the turned element

to

achieve

pre

loads

in

excess of the required bol t tension.

2. Oversize

or

slotted holes do no t great ly affect

the

losses

in

bol t

tension

with time following

ins t l l t ion Virtual ly

l l of the losses

occurred

within one week fter

ins t l l t ion

he loss in

tension

w s

about

8 of the in i t i l preload.

3. he s l ip

behavior of

joints

with

oversize

or slotted

holes

w s sim ilar to

the s l ip b eh av ior o f joints

with

holes of nom-

inal size. There w s

series

of small s l ips b efo re the jo int

went into bearing. he number of small slips

increased

as the

d istan ce o f s l ip

increased.


35/64

31

4 he

average s l ip

coeff ic ient

for the joints

with

1/4

in

hole

clearance

w s

about

the

s me

as

the

s l ip

coefficient

for the control

joints he

joints

with

5/16 in clearance

holes

showed 7

decrease

in

th e

s l ip

coeff ic ient

he

s l ip coeff ic ient

for

s lot ted

hole

jo in ts

showed

22

to 33 decrease when

compared to normal

t e s t

specimens

5 Changes

in

bol t

tension

during

tes t ing

were

no t great ly

affected

by oversize

holes

or

s lo ts in

the

enclosed pl tes

All changes in

bol t tension

at major s l ip

were

w ith in the

previously observed range for change in

tension

at s l ip

6 Slotted

holes placed perpendicular

to

the l ine of load in

the

enclosed plates of

bolted

jo in t did

not re du ce

the

tensi le strength of

the plates or the shear

strength of

the bol ts


36/64

T LES N FIGURES

3


37/64

Test

Results

TABLE 1

Slip

Behavior

of All

Joints

-33-

Joint

Hole

Average

ni t i l

ni t i l

Slip

Diam

Bolt Bolt

Slip Coefficient

Elongation

Tension

Load

OH1 1 1-1/16 .0213

551.6 314.5

0.285

OHl 2

1-1/16

.0227

558.0

327.5

0.293

OHl 3

1-1/16

.0227

570.4

322.5

0.283

Average

0.287

OH2 1

1-1/4

.0178

522.8

274.5 0.263

OH2 2

1-1/4 .0119

422.0 242.5

0.290

OH2 3

1-1/4 .0132

474.5

295.0

0.312

Average

0.282

OH3

1-1/4 0143 495.2

286.5

0.290

OH3 2

1-1/4 .0139 482.5

267.0 0.277

OH3 3

1-1/4 .0135

473.5

260.0

0.274

Average

0.280

OH4 1

1-5/16

.0151

502.6

265.0

0.264

OH4 2

1-5/16

.0173 531.2

253.5

0.238

OH4 3

1-5/16

.0174 533.1 236.0

0.222

Average

0.245

SH1 1

Slotted

.0154

504.0

185.5

0.184

SHl 2

Parallel

.0162 524.1

199.0 0.190

SHl 3 to

l ine .0191 549.5 237.0 0.215

of

load)

Average

0.196

SH2 1

Slotted

.0223

573.9

248

0.237

SH2 2

Perpen-

.0230

574.5

220

0 192

SH2 3

dicu1ar

.0161

525.7 262.5

0.250

to

l ine

of

load)

Average

0.226

SH3 1

Slotted

.0223

568.5

225

0.200

SH3 2

Perpen-

.0232

475.4

210

0.221

SH3 3

dicular

.0250 480.2 214 0.223

to

l ine

Average

of

load)

0.215


38/64

TABLE 2

Allowable

Hole Clearance for Different Hole Sizes

Bolt Proof

Min

Flat

Max

Hole Area

=

Max

Hole

Amount

Bearing

Size

Load

Area

Area /

e

Flat Area Min.

Area

Diam

Clearance

Pressure

1/2

12

.200 .601

0.401

11/16

3/16 62.6

5/8

19

.315 887

0.570 13/16

3/16 62.0

3/ 4

28

.465

1.227

0.761 15/16

3/16

62.5

7/8

39 .647

1.623

0.973

1 1/16

3/16

62.9

1

51 .846 2.074

1.224

1 1/4

1/4

72.0

1 1/8

56

.930

2.580 1.646

1 7/16 5/16

70.3

1 1/4

71

1.180 3.142 1.962

1 9/16

5/16

69.5

1 3/8

85

1.410 3.758 2.340 1 11/16

11

5/16

67.0

1 1/2 103

1.

71

4.430

2.713 1 13/16

5/16

66.9

The

area of

a

ci rcle with

a

d iameter equal to t he w id th across th e

f l ts

I

W

-

I


39/64

l;ABLE

3

Loss in Tension of Bolts I nst alle d in Joints

35

Joint

Average

Loss

in Bolt Tension

1 Min.

5 Mins.

1

Hr

1

Day

1

Week

4 Weeks

OH1 1

1.21

1.69

3.10

4 121

4 2Si

5 52

OHl 2

1.33

1

7 io 2 16i

66io

3 Si

5 3 i

OH2 1

1

6 io

2 43i

3.00 4.22

4.6S

6 lSi

OH4 1

3.1S

3 34i

3.347.

3 34i 3 34

i

3.34

SHl 2

4.4S

4.90

5.07

5.45 5.5S7.

6.94

SH2 3

3 34

i

4 3i

4.52

4.52

4.527.

5.72


40/64

T LE

4

R esults o f

th e

Load

Cell Studies on Single Bolts

-36-

Hole

ni t i l

Loss

in

Tension,

Kips

Clearance

Bolt

in.

Tension,

Min 5 Min

Hr.

Day Week

Kips

Bolt

Cell

Bolt Cell

Bolt

Cell Bolt

Cell

Bolt Cell

1/16 in . Std

60.0

1.0

0.6

1.3

1.4

1.3

1.9

1.3

2.5

1.3

2.6

1/4 in .

59.5

0.8

0.4

1.3 0.9

1.6

1.3

2.0

1.4

2.3

1.4

5/16

in .

60.7

0.7

0.2

1.1

0.4

1.5 0.6

1.5

0.8

1.5 0.9


41/64

T LE

5

Test Results

Bearing

Joints

a

Plate Failure Tests

37

Joint

Net

Plate

Ultimate

Ultimate

Coupon

Area

Load Tensile

Stress

Ultimate

Tensile Stress

in

2

Kips

Ksi

SH2 l

12 46 820

65 9

61 6

SH2 2

12 42

854

68 6

62 5

SH2 3

12 42

852

68 5

62 0

10

SH3 l

17 37

1104

63 6

61 6

b

Bolt

Failure

Tests

Joint

Net Bolt

Ultimate

Apparent

Shear J ig

Shear

Area

Load Avg

Ultimate

Ultimate

Shear

:>tress

Shear Stress

in

2

Kips

Ksi

Ksi

SH3 2

12 56

1000

79 6

83 8

SH3 3

12 56

1006

80 0

83 8


42/64

4

Required

Bolt

Tensfon

3

ONE

MINUTE

BOLT

LOAD

KIPS

1

38

Washer

Under Nut

o

No

Washer

Ot L.. O

L.. O _

13

16

13

16

3

II I

HOLE DIAMETERS

Reg semi fin. hex head

3

11

bolts

and heavy nuts

FIG 1 Effect of Hole Size

mn

Bolt

Tension Induced

by

Turn of Nut


43/64

I

W

I

-t

-+

4

' ;='

I

-

f 4

I

I

I

2

..

I

l

w

4

39

w

4 =

-

4

:

l

:

I

1

I

I

I

I :

•

I

I

:

I

I

I

I

......

-

i I :

I

l l

:

I

I

I

I

----

I A325 Bolts

I A 36

SERIES

NO

HOLE

WIDTH

TESTED

DIA.

W

II

OHI 3

6 40

OH2

3

6 78

OH3

3

I

6 78

OH4

3

1 5 ~ 6

6 65

FIG. 2. Oversize/Hole rest Specimens


44/64

40

I

I:

I

I....

....

-

I

0

I

v

•

I

-

-

I J .... J

I

A 6 It

A 5

Bolts

3 @ 5

4 =1 -3

3

/4

I

I :

I :

l I

II I

I

I

jo..

I I

I

l : I

: I

:

: I

I

I

I

I ~

Detail of Slot

Series SH I

FIG 3 Test Specimens

- Slotted Holes r lle l to the

Line of

Load


45/64

4 1

w

W

2

t

W

4

3

a

5

4

II = 1

1

3

3

4 II

-I

l :

i

I

: I I

:

I I I

: I

:

i

i

I

i

I I I

A 5 Bolts

SERIES

NO WIDTH

An As

TESTED

W

II

SH 3

11 42

1 00

SH

3 13 68

1 36

FIG 4 Test Specimens Slotted

Holes

Perpendicular

to

the Line of Load


46/64

42

III A325 Bolt

11

6

BOLT

TENSION,

KIPS

2

1 2 0

ELONGATION IN

0.001 0.002 3

STRAIN GAGE READING lN/IN

FIG. 5

Calibration of

Gaged

Bolts

e 9

1

Go ad

Bolt

FIG. 6 Location of Gaged

Bolts in Joint


47/64

IG

olt in oad

ell

4


48/64

44

8

6

Required

Preload·

Maximum Bolt Tension

Mean Bolt Tension

Minimum Bolt Tension

4

BOLT

TENSION

KIPS

OH4

SHI SH SH3

5 16

Parallel Transverse

Slots

Slots

None

one one

in 3 joints

OH3OH2

OHI

- - - - ' - - - - ' -_ . . . . I . . . - - - -L. . ._ . - - . . . . I . . . - - - - - 'L. . . . - . - - - - ' - - - - - ' ' ' - - - - -L. . . - - -L_. . . . I . . . - - - I -

Series

Hole

Clearance

Washers None one ne Two

Each

bar

represents

bolts

FIG The Range of

Bolt

Tensions

for

a l l Jo in ts Tested


49/64

-45-

IG

a

Galling of

Plate

Under Turned Element Joint OHl-2

IG 9 b

Depression

Under

Bolt

Head

Joint OHl-2

1/16-in.

Clearance


50/64

46

FIG 10 a Depression

Under

Bolt

Head

Joint

OH2

FIG b

Severe Galling of

Plate Under

Turned Element

Joint

OH2

1/4-in. Clearance, No

Washer


51/64

IG

7

Plate

Area Under

Turned Element

Where a Washer

s

Used Join t OH3

1/4-in. Clearance


52/64

48

FIG

epression Under

olt Head

Join t

OH4


53/64

49

6

6

BOLT

TENSION

KIPS

I

Min

Min I

Hr

LOG

TIME

I

Day

I

Wk Wk 4Wk

FIG

Time Tension

Relationship

of Bolt

XB 9

in Joint

OHl


54/64

JOINT

LOAD,

KIPS

300

200

100

r r

Slip

50

d

300

0 02 0 04

0 06

JOINT SLIP IN

0 08

0 10

JOINT

LOAD,

KIPS

200

100

J

r

•

26

1

•

J

,

o

0 02 0 04 0 06

JOINT ELONGATION IN

0 08

0 10

Join t

Slip

and

Elongation

of

Joint OH4 3


55/64

25

2

_[Ini t io I

Slip

LOAD

r

r

[

IPS

15

5

1

2 3

4

5

6

7

SLIP

IN H S

I

V

FIG

Load Slip Diagram of Joint

SH1 l

t

I


56/64

-52-

FIG.

Faying

Surface Damage of

O

Join t

1/4- in . Clearance


57/64

53 ·

o Results of

Tests

Nester

• Results of OHI Series Tests

• Results of

Oversize and

Slotted

Hole Tests

4

3

2

~ e r a g e of 6 Joints

K V e r ag e

of O Joints

0.1

Il _

Oversize Holes

Slotted Holes

Series

Hole

Clearance

OHI

I/

16

OH2 OH3

OH SHI

516 Parallel

Slots

SH SH3

Perpendicular

Slots

FIG

Comparison

of

Average

S l ip oe ff ic ie n ts


58/64

54

700

600

500

JOINT

LOAD

400

KIPS

6 ~ 4

300

Joint SH2-3

200

100

0 1 0 2 0.3

0.4

700

600

500

JOINT

400

LOAD

KIPS

300

200

Joint SH2-3

100

46

Q

o

0 1 0 2 0.3

ELONGATION IN

0.4

FIG

18

Load Jo in t Elonga tion

and Load Specimen

Elongation

of Joint SH2 3


59/64

FIG

e fo rmat ion o f Slotted oles

55


60/64

t

....

/ / ~

-

I

r T

/

1

ound ole

5 6

t

h

1

7 / /

/ / / 7

.

Slotted ole

FIG

20 Comparison of Bolt and Plate Deformations

FIG

21 Deformed Plates

Bolt

in Sawed

Section of

Joint SH3 2


61/64

7

FIG

Sawed ection

of

oint SH3


62/64

-58-

7. REFERENCES

1. Research Council

on Riveted and Bolted Structural

Joints of

th e Engineering

Foundation.

SPECIFICATIONS FOR STRUCTURAL JOINTS USING ASTM A325

OR

A490

BOLTS, September, 1966

2.

OUT

OF

PLUMB

TILT STRAIGHTENS

BANK

Engineering News

Record,

Vol. 178,

No.9 ,

March

2,

1967,

pp. 33-35

3. Wilson, W M., and Thomas, F. P.

FATIGUE TESTS ON RIVETED JOINTS , Bulletin

No.

302,

University of I l l inois Engineering Experiment Station,

1938

4. Hoyer, W.

UBER GLEITFESTE

SCHRAUBENVERBINDUNGEN

3 . BERICHT)

HOCHFESTE SCHRAUBEN MIT VERSCHIEDENEM

LOCHSPIEL

ON

SLIDE

PROOF

BOLTED CONNECTIONS 3RD.

REPORT) HIGH-STRENGTH

BOLTS WITH

DIFFERENT

HOLE CLEARANCE), WISSENCHAFFLICHE

ZEITSCHRIFT

DER HOCHSCHULE

FUR

B UWESEN

COTTBUS,

3,

1959-1960 , Heft 1,

pp.

49-53

5.

Chesson, E., Jr and Munse, W.

H.

STUDIES ON

THE BEHAVIOR

OF HIGH-STRENGTH

BOLTS

ND

BOLTED

JOINTS, Bulletin No. 469, Vol. 62, No. 26, Univers ity of

Ill inois

Engineering Experiment Station, University of

I l l inois,

Urbana,

I l l inois,

October, 1964

6. Steinhardt, 0 and Mohler, K.

VERSUCHE

ZUR NWENDUNG VORGE

SPANNTER SCHRAUBEN

1M

STAHLBAU,

I

TElL TESTS ON THE APPLICATION OF HIGH-STRENGTH BOLTS

IN

STEEL CONSTURCTION,)

Part

1,

Berichte

des Deutschen

Ausschusses

for Shahlbau, Stahlbau-Verlags, GmbH, Cologne, 1954 Heft

r 18.

7. Aurnhammer, G.

HV-VERBINDUNGEN. UBERLEGUNGEN, BETRACHTUNGEN,

VERSUCHE

HIGH-STRENGTH

BOLTED

JOINTS, THOUGHTS, OBSERVATIONS, TESTS).

Preliminary Publication,

Seventh Congress,

IABSE,

Rio de

Janeiro, 1964,

pp.

415-430


63/64

-59-

8. Steinhardt,. O.

THE GERM N CONTRIBUTION TO RESEARCH JUBILLEE SYMPOSIUM

ON HIGH STRENGTH BOLTS

The

Insti tution

of

Structural

Engineers, London

June,

1959 pp. 2-9

9.

Denkhaus

H.

G.

STRENGTH

OF

WASHERS The National Mechanical Engineering

Research Insti tute,

CSIR

Contract No.

CN378

Council

for

Scientific and Industrial Research, Pretoria, South Africa,

February, 1961

10.

Tajima,

J.

EFFECT OF RELAXATION N CREEP ON

THE

SLIP LO OF

THE

HIGH-

STRENGTH BOLTED JOINTS Structural

Design Office, Japanese

National Railways,

Tokyo

June,

1964

11. Waltermire, W. G.

EVALUATING FASTENER N JOINT PERFORMANCE WITH A LO ANALYZER

Assembly and

Fastener

Engineering,

January

1962

pp . 33-35

12.

Stevin Laboratory

DECREASE

OF

THE PRE LOAD IN HIGH STRENGTH BOLTS IN

THE

COURSE

OF

TIME Provisional Results ,

Department

of Civil Engineering,

Delft, The

Netherlands,

1965 C.E.A.C.M. X-65-l3

13.

Wallaert,

J. J Sterl ing,

G.

H.,

and

Fisher,

J. W.

WH T HAPPENS TO BOLT TENSION

IN

LARGE

JOINTS?

Fasteners,

Vol. 20

No.3 ,

1965 pp. 8-10

14. Nester, E. E.

INFLUENCE OF

VARIATION

OF THE CONTACT AREA UPON THE SLIP RE-

SISTANCE

OF A BOLTED JOINT M. S. Thesis, Fritz Engineering

Laboratory Report No. 318.1, July, 1966

15. Foreman R. T., and Rumpf

J.

L.

STATIC TENSION TESTS OF

COMPACT

BOLTED JOINTS Journ al o f

th e Structural Division, ASCE Vol. 86, No. ST6 Proc.

Paper

2523

June,

1960

16. Chiang, K. C., and Vasarhelyi,

D.

D.

THE

COEFFICIENT

OF

FRICTION IN

BOLTED JOINTS

M E

WITH

VARIOUS

STEELS

N WITH MULTIPLE CONTACT

SURFACES

University of

Washington,

Seatt le, 1964


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17.

Upton K

A.

n Cullimore M G

THE DISTRIBUTION OF

PRESSURE

BETWEEN W FLAT PLATES· BOLTED

TOGETHER

International

Journal

of

Mechanical

Sciences

Vol.

6 No.1

Feb. 1964 pp. 13 27

Bolted Joints Slotted Holes

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