An Experimental Study of the Behaviour of Sleeved Bolt Connections in Precast Concrete Frames

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Magazine o Concrete Research, 1995 47 No. 171 June, 119-127

An experimental study of the behaviour of

sleeved bolt connections in precast concreteframes

S . A . M . Mohamed* and C . K . Jolly

U N I V E R S I T YF S O U T H A M P T O N

Sleeved bolt beam-to-column connections have been used

in the precas t concrete industryo r many years. Theyhave

advantages over other jointing methods in component

produ ction, qua lity contro l, transportation and assem bly.

However, there is at present limited information

concerning their detailed structural behaviour under shear

loading. The study reported in this paper was undertakento elucidate the behaviourf such oints under symmetrical

vertical loading. Two series of full-scale tests were

pelformed on sample columns for which the column

geometry and bolt arrangements conformed withsuccessful commercial practice. The first series of tests

was used to investigate the influence of bolt density on

the ultimate load, ailure mode andstifSness o such

connections. The second test series showed the influence

o varying co ncrete strength and the effectiveness of the

confining reinforcement. Full details of these test

programm es are given. The finite element modelling

technique was used to develop three-dimensional models

which were calibrated gainst the test observa tions. These

models subsequently provided complete stress and

deformation distributions within the joi nt components at

intervals up to the ultimate load, and are the subject of

another paper.

Introduction

Thesefrecastoncretemembers by the

construction industry has increased rapidly throughout the

world over the past wo decades. Advantages such as

speed of erection, better quality, dimensional precision

and,aboveall,reduction of costs have made precast

concrete superior to its site-cast counterpart. The

satisfactory performance of arecast structure as a whole,

* University of Southampton, Southampton S09 5NH, UK.

Paper accepted 6 July 1994.

and its economy, depend to a great extent on the proper

selection and design of itsconnections. In skeletal frame

construction, beam-to-column connections are the most

critical part of the structural concept because they must

be capable of transmitting axial forces, shear forces and

bending moments safely and without xcessive deforma-

tion. It is essential to consider their design very carefully

under all stages of the construction process, from

conceptual studies through to construction.

The joints must e capable of easy fabrication,

transportation without damage, rapid and positive locationwhenpositioned by crane; of absorbing construction

tolerances, andyetmust provide a robustand igid

connection when fully assembled. In spite of the wide

variety of beam-to-column connections in use, their

practical design is not overed in detail by current design

codes. Few references, such as thatcompiled by the

Institution of Structural Engineers,' deal with design of

connections.

Sleeved bolt connections are among the most

extensively used. They are popular because

a ) their manufacture is simple and can be varied withoutcausing significant damage to formwork

b ) there are no vulnerable cast-in protrusions to be

damaged during handling and delivery

c ) pre-assembly at ground level of the steel brackets onto

the columns facilitates rapid and positive location of

members during frame assembly, hile retaining the

ability to accommodate tolerances until the frame is

complete

d ) they require little supervision compared with other

types of connection, so they are suitable for site

conditions

e ) they provide connections with high rigidity due to theuse of high-tensile bolts

f, in their,finished form they have no visible protrusion

below the beam lower soffit, whichs sually

119



Sleeved bolt connections in precast concrete frames

Bolt sleeve Grout hole

Fig. 1.

Steel bracket

Precast column

Typical deta ils of a sleeved bolt beam-to-column connection

essential for the architectural and functional

requirement.

Site assembly of the connection

The details of a sleeved bolt connection are shown in

Fig. 1. The steps of assembling the connection are,

briefly, as follows. A group of high-tensile, grade 8 . 8

steel bolts, threaded at both nds, are passed through mild

steel sleeves embedded through the breadthf a reinforced

concrete column. The bolts are also passed through

matching holes drilled in two stiffened steel brackets. A

vertical bolt runs between the upper and lower brackets.

Pairs of brackets on opposite sides of the column are held

in position by the hexagonal nuts on each bolt’s end.

The columns are then raised, positioned and plumbed.

The top bracket and verticalbolt are temporarily removed

by the erector. At this stage, each bracket can serve as

a seat cleat for the incoming beamend. The beams usually

have recessed ends to confine the bracket within their

cross-section. Replacement of the top bracket and vertical

bolt provides stability and torsional restraint to the beam

end. Later, the steel bolts and brackets are surrounded

with expanding grout to provide corrosion and fire

protection.

The research programm e

This paper provides basic research data regarding the

behaviour of sleeved bolt connections under symmetrical

120

vertical shear loading. There are several potential failure

mechanisms.he connection is assembled using

components of several different materials. Material

properties such as concrete strength and yield strengths

of the various steel components (i.e. bolt, sleeve, links

andrackets)anreatlyffect the connection

performance. Geometrical variables such s number, size,

spacing and arrangement of bolts within each joint also

affect the joint’s ultimate capacity.

The precast concrete beams are relatively stiff and can

therefore normally be assumed to apply only a vertical

bearing force on the seat cleat. This bearing force can

cause failures within the notched endof the beams, which

are described fully in an earlier paper.*

The lower bracket is normally designed to resist the

entire bearing force. The brackets themselvesre normally

designed to act rigidly, and are consequently unlikely to

fail under service stresses. The bearing force produces

a large shear load, which s the major action obe

transferred into the column.

Uppermost bolts through the lower bracket must also

be checked to ensure that they can provide a restoring

moment to counter the moment produced by the small

eccentricity from the column face of the bearing force on

the seat cleat. When the connection is under pure shear

loading, the load is transferred from the seat cleat to the

column through the bolts. Bearing of the bolts on thesleeves then transmits the load to the concrete.

Thus, two principal modes of failure are likely tooccur

at the column face at ultimate load, as follows.

Magazine of Concrete Research, 1995 7 No. 171



Mohamed and Jolly

Tensi le forcesin steel l inks

Fig. 2 . Confining force develop ed in the inks near a jo int

a ) The bolt may fail by being sheared off completely:

this is most likely at the root of a thread when the

threaded portion of the bolt extends into the shear

plane.

6 ) Under the application of a concentrated load, the

concrete in the region below theoint level is confined

laterally by the column link einforcement against the

bursting stresses that develop. Another contribution

to this confinement is provided by the bracket’s back

plate, which is compressed against the column face

in this region. None the less, the concrete beneath

the sleeve may crush sufficiently for the sleeve to

deform vertically downwards at the column face.

Bearing of the bolt in the sleeve invert causes lateral

stresses to develop in the concrete as shown in Fig.

2. Horizontal components of these stresses create a

lateral tensile stress in this region. Consequently,

concrete cracks start to develop. At higher loads, the

steel links beneath the sleeve may yield due to these

transverse stresses, and the already cracked concrete

will then fail.

Thus, two full-scale est programmes were undertaken.

Test series A was performed to examine the influence of

bolt density on overall joint behaviour, e.g. failure mode,

ultimate strength and stiffness. Test series B was carried

out to assess the effect of concrete strength and its

confinement on he load-carrying capacityof single-bolted

joints.

Numericalhree-dimensional models were then

developed using the finite element package ANSYS3 to

obtain additional information that could not be observed

or measured experimentally, e.g. stress distribution in themost highly stressed zones at both working and ultimate

loads. The experimental study of theseailure mechanisms

in the column is the subject of this paper.


t

Fig. 3. Series A test column geometryandsleeve ocationsdimensions in mm

The tests

All tests were carried out on reinforced columns of

300mm square cross-section. Formwork and sleeve

setting-out dimensions are shown in Fig. 3.

White Portland cement was used in both mixes as it

facilitates crack detection. The concrete had a moderately

high workability, with slump values in the range of

65-76mm.A consistent 40mm concrete cover was

maintained to the longitudinal column reinforcing bars.

Steel tubes 300 mm long with an internal diameter of

27 a 0 mm and a 3 0mm wall thickness were used as

sleeves. This internal diameter was chosen to suit the

24 .0 mm nominal dia. bolts used in all the tests. Each

bolt had a total length of 390 mm. This length, which

included 35 mm threaded on each end, was chosen to

avoid direct contact between the threads and the sleeve’s

inner surface, and to allow for tightening of nuts against

the brackets’ backplates.

Brackets were made from grade 43 steel plates welded

together. Steel webs were designed to carry safely the

anticipated applied shear load. The plates were connected

with continuous fillet welds.

Test series A

In test series A, the number of bolts per joint was the

121



Sleeved bolt connections in precas t concrete frame s

principal experimental parameter. The series was divided

into four tests. Each test involved a joint with a different

number of bolts ranging from one central bolt to four bolts

in horizontal pairs. Vertical and horizontal spacings

between sleeves’ centrelines within each joint were

140 mm and 65 mm respectively. Tests in this series are

identified by a number corresponding to the number of

bolts attaching the seat cleat to the column.

The column used toprovide all specimens in test series

A was reinforced longitudinally with four 25 mm

deformed high-yield steel bars. 8mm dia. steel links, at

50 mm centres, were used along the column height. A

concrete mix was designed with he following proportions

by weight: 1.0: 1. 48:0 .85: 1. 70 :0 .375 (cement-fine

aggregate- 10 mm aggregate-20 mm aggregate-water).

Specimens were damp cured at 20°C for 15 days in a

curing tank.

Test series B

Three tests were carried out on single-bolted joints to

examine the effect of varying the concrete strength and

degree of confinement on the joint’s ultimate load and

failure mode. The joints tested were similar to test 1 in

series A . However, the concrete compressive strength was

reduced by almost half. The degrees of confinement were

low, medium and high and the tests are referred to as L,

M and H respectively.

Columns used in test series B were reinforced with four

16 mm bright mild steel bars. To reduce the strength of

the steel links below the joint’s level, the first two links

in this region were spaced at 50 mm and 175 mm from

the bolt sleeve.A 150mm vertical spacingwas maintained

for the remaining 8 mm steel links in the 1. 0 m high

column. The designed concrete mix adopted for these tests

hadheollowingroportions by weight:

1.59 :0.89 : 1.79: 0.485 (sequence as above). These

columns were air-cured.

To minimize the concrete confinement in test L two

12mm high and3 -0mm thick steel plates were introduced

across the upper andower edges of the brackets’ flat back

plates, between the back plates and the column faces.

These plates actedas packing at both top and bottom edges

of the bracket to createan almost uniform gap into which

the concrete from the face could spa11 under load.

Furthermore, the steel links located immediately beneath

the joint level were reduced in cross-sectional area so that

they yielded at a tensile force equivalent to the link steel

minimum design stress of 250.0 N/mm2.

In test M the brackets were machined flat so that they

were initially in direct contact over their whole area with

the concrete. The steel links’ reduced cross-section

provided the only reduction of confinement.

In test H the back plates of the brackets were left with

their thermally induced curvature from the welding

process, and this provided the maximum confinementpossible to the column face immediately below he sleeve.

Also, the full cross-sectional area of steel links was

retained in this case.

122

Fig. 4 . Equilibrium of orces on a oaded bracket

Additionally, static friction tests were carried out on

the loose brackets against the precast concrete column

faces. For these, a column was laid on its side, and the

brackets in turnwere placed on the horizontal surfaceith

vertical loads applied to them covering the derived range

of interface loads for the in-service brackets. The

horizontal force required to initiate movement was then

measured for each case. The static coefficient of friction

values enabled corrections to the shear load on the bolts,

thus allowing for the effectf friction between the brackets

and precast concrete columns.

When the equilibrium of vertical forces for a loaded

steel bracket is such as that shown in Fig. 4, the applied

vertical load P must equal the sum of the shear forces

carried by the bolts R b plus the frictional force acting

at the column face R f . Top bolts are subjected to a tensile

force T to provide a reaction to the moment resulting from

the eccentricity of applied load from the column face.

Load eccentricity is small in these tests compared with

the backplate height. Consequently, within the range of

geometries investigated, the estimated ratio of the tensile

stress to the shear stress per bolt was not large enough

to cause a significant shear strength reduction. Hence the

effect of the tensile force on the joint ultimate shear

strength has been ignored.

Friction occurs in the lower, compressive contact area

between the backplate of the bracket and the column face.

To obtain the actual shear forces carried by the bolts, anestimated value of the corresponding frictional force

developed in this contactrea was deducted.By satisfying

the moment equilibrium conditions for a loaded bracket,




Mohamed and Jolly

a value for the developed compressive force C was

obtained. Then, using the measured friction coefficient

between steel and the precast concrete, a value for the

frictional force could be estimated t each load ncrement.

The load values reported in this paper are per bolt end

cross-section, after the deduction of the corresponding

frictional force. This is to allow direct comparisonbetween results obtained for bolts in different joint tests.

Separate tests were carried out to determine the

compressive and indirect tensile strengths of the concrete,

and the yield strength of the reinforcement used.

Experimental procedure

The column base was arefully centralized in a 1500kN

maximum capacity testing machine. The machine top

platen was denied any free rotation after the application

of the first load increment. This ensured that the applied

load was shared equally between the twobrackets despiteany initial asymmetry.

All tests required deflections to be monitored at the same

positions relative to he brackets. Thus a single frame was

assembled around the joint to hold the measuring equip-

ment in the required positions (see Fig. 5). The frame

was made rom two 6 mm thick U-shaped steel plates fixed

independently to the column top by 12 mm bolts. Each

bolt was threaded into a hole drilled and tapped in the

ends of the main column bars. An 8 mm hole was drilled

and tapped in the U-plates outside the column section.

Four steel rods of 12 mm diameter and 500 mm length

were threaded and connected into these holes. These rodswere also connected at a level below the joint by a closed

steel frame, formed from four 6 mm plates around the

column. This provided a rigid and stable mounting frame

for transducers.

Linear variable displacement transducers were used to

determine the movement of the bolts, the brackets and

the concrete around the test joints. Transducers were

calibrated independently using a micrometer. A Solartron

Orion data logger recorded the deformation data at each

load increment. The following measurements were taken

in each test

a) the downward vertical deflection of the bracket’s

back plate; these measurements were taken as

representative of the bolt’s vertical deflection

b) the bolt’s longitudinal deflection, i.e. its axial

extension

c ) the variation of the concrete’s sideways expansion at

a series of points along both sides of the bracket;

transducers were mounted around the joint, using

purpose-made aluminium channels bolted to a steel

angle; the angle ran horizontally between two of the

vertical steel mounting frame rods, to which it was

fixed.

Loads were applied to the joint brackets through two mild

steel plates300 mm high by 250 mm wide by 40mm thick,

as shown in Fig. 6 . The top surfaces of the plates were


160

6 mm thick steel U-plates

Bolts

12 mm dia. steel rod

concrete column

I I I

6 mm thick tiemm thick tie

Fig. 5. Transducermounting framedetails dimensions in

mm)

not less than 50mm higher than the column top to avoid

applying anydirect load on the column. he test procedure

was to apply load increments until the joints were not

capable of supporting any further load. When the

monitored deflections indicatedhe onset of non-linearity,

the load increments were reduced from 50kN to 25 kN.

The progress of any visible crack formation wasmonitored by visual inspection of the joint between load

increments.

Test results

The test results are summarized here. More detailed

results are given in Ref. 4.

Test series A

The observed structural behaviour of a typical series

A joint test can be described as follows. Bedding of the

bolt onto the sleeve invert during the first load increments

gave rise torelatively large vertical deflections. The bolt

also tended to part from the column at one end and was

drawn in to the column face at the other end. On further

123



Sleeved bolt connections in precast concrete frames

Steel tie rod

Steel lo ad in g plate-

Steel bracket

Concrete column-

Bottom platen

--l-

1Fig. 6. Genera l arrangement of the stub column in the test machine

loading, the bolt became well seated against the sleeveinvert, giving rise to an almost constant stiffness for most

of the load range.By the time significant bending moment

had developed due o the small load eccentricity from the

column face, the rotation of the backplate was visible and

resulted in a further gradual increase of axial bolt

deflection. Just before failure, the vertical deflection rate

increased rapidly, with shear deformation of he bolts

visible in the gap created between the column face and

the bracket backplate.

There were no visible cracks around the joints at any

stage in test series A , and correspondingly noappreciable

lateral concrete movement was recorded at any of themonitored levels. Most of the bolts showed a significant

shear deformation at their loaded ends. Examination of

the bolt shanks againsta flat surface also indicated limited

plastic bending about their longitudinal axes. Neither the

bolt sections nor the threads were significantly distorted

by the bearing stresses.

Inspection of the steel components at the end of each

test showed that the upper curved surface of the holes

through the brackets had deformed due to bearing f the

bolts. Yielding of thebracket material had developed the

contact zone into an identifiable trapezoidal area, greatest

next to the column. The topof each hole had consequentlybecome oval in shape. Imprints of the bolt threads were

formed in this trapezoidal area.

Similar evidenceof yield wasapparent within the ends

124

of the sleeves cast into the columns. By compressing thesleeve against the oncrete beneath it at each end, the bolt

had crushed he concrete in this area, and some ocal

spalling occurred as the steel brackets were removed.

However, mostofhe rushedmaterialwasirmly

compacted, andbecamedislodgedonlywhen apped

gently. Friction marks were found at the interface between

the lower parts of the backplates and the corresponding

column faces, and on the areas of compacted, crushed

concrete below each bolt. Fig. 7 shows a photograph of

these marks, which provide qualitative visual evidence

ofhigh pressure and frictional resistance to vertical

deflection of the bracket.The result ofhaving a high concretecompressive

strength and substantial steel link concentration around

the joints in test series A was that shear in the bolts was

the dominant mode of failure. Since all bolts used in the

tests havenominallydentical properties, theoad-

deflection data obtained for the single bolt in test 1 are

compared in Fig. 8 with corresponding data for each bolt

in joints containing numerous bolts.

In test 1 the bolt failed by shearing off at one end, at

an ultimate load of 210 e kN. The failure shear plane

passed hrough he reduced section at the root of he

threads. The other endof hisboltwasalsoseverelydistorted in shear.

Tests 2 and 3 were stopped and the joints deemed to

have failed when they could no longer support the applied




load. The ultimate load per bolt in both these joints was

found tobe 177-0 N . Severe shear istortion in he bolts

was clearly visible after the tests.

As the shear plane assed through the threaded portion

of the bolt in tests 1 to 3 , the bolt stress at failure was

calculated using the reduced diameter. he threaded cross-

sectional area is 0 7 times that of the bolt shank for a

standard 24 mm bolt. Based on the reduced area and the

failure loads quoted, the bolt shear stress was calculated

to be 663 1 N/mm2 and 558 -0 /mm2 at failure of joint

1 and of joints 2 and 3 respectively.

Test 4 used brackets that were not fabricated

commercially. A weld fracture in the bracket caused

failure. Thispremature failure occurredat a oad of

120 kN per bolt end, which corresponds to a shear stress

of 379 N/mm2.Thisncident emonstratedhe

importanceof using factory-weldedcomponentsof a

consistent standard to avoid different modes of failure

within joints formed in this way.A repeat of this test using

a commercially fabricated bracket was undertaken

subsequently, and failed at a load of136 kN per bolt end.

The bolt shear stress in this case was calculated to be

430 N/mm2.

Test series B

In test series B bolt shear failures similar to those

500

400

3 300

aY

DE

S 200

TQ

1oc

0

Mohamed and Jolly

Fig. 7. Friction marks on he spalled concrete below ested

sleeves

reported for series A were obtained for tests H and M

again with novisible concrete cracking. However, in test

L a horizontalcrack appeared on both faces of the column

at 88 of the ultimate load for test A . These cracks were

just above the steel link located immediately below the

I

2 4 6 8 10 2

Deflection: mm

Fig. 8. Load-de fec t ion curves for the four tests in series A

Magazine of Concrete Research, 1995 47 No. 171 125



Sleeved bolt connections in precas t concrete frames

joint level. During the following load increment, both

cracks lengthened and propagated at a shallow angle to

their initial direction, and joined together across the

column sides. This was followed by the appearance of

a crack up the column’s vertical centreline, propagating

from both ends of the sleeve. These vertical cracks

extended almost to the base and top of the column as

failure approached. Sudden large deformations showing

lateral expansion were recorded along the column sides

as soon as this cracking occurred.The above result

emphasized the effect of the concrete confinement at the

column face by pressure from the brackets.This confining

pressure provided a significant enhancement of the

concrete compressive strength, which delayed cracking

and crushing in the.critica1 zone, and thereby inhibited

this mode of failure in tests H and M. When the bracket

was removed, there was again crushing and spalling of

the concrete, extending to a depth of 90- 100mm below

the sleeve invert on both column faces.

Other test results

Supplementary tests on control specimens of the

material used for test 1 in series A were carried out on

the same day as the column tests, and gaveaverage values

of 61 .90N/mm2 and 4.05 N/mrn2 or hedirect

compressive and indirect tensile strengths respectively.

Similar control tests for series B gave an average concrete

compressive strength of 3 0 - 5 N/mm2, and indirect

tensile strength of 3 00 N/mm2, on the day of testing.

Four tensile tests on the high-yield steel bars used as links

in the column produced anverage strength of

450.0 N/rnm2.

The static friction test results gave friction coefficients

that were independent of the load, yet varied according

to the contact conditions. The original black steel bracket

used in tests A and H gave a friction coefficient of 0-66.

However, the machined steel face on the back of he

bracket used in test M gave a reduced value of 0.52. The

bracket on painted steel packing, which formedhe contact

in test L registered a coefficient of just 0.2.

Conclusions

Joint shear stiffness is characterized by the slope of the

experimental load-deflection curve. Curves shown in

Fig. 8 illustrate the difference in stiffness for the four

joints tested. Each curve was obtained by taking an

average of the top bolt deflections for that joint. There

is a clear trend for an increase in shear stiffness as the

number of bolts in the joint is increased.

Joint moment stiffness is characterizedby the moment-

rotation curve. A moment M is created at the concrete

face due to the eccentricity of the load from the column.

This moment, which tends to extend the top bolts, is

responsible for the plate rotation9

alues of andwere computed, and are plotted in Fig. 9. These curves

show that the number of bolts per joint also has an effect

on the joint’s rotational rigidity. Once again, joint 1 has

126

the lowest rotational rigidity while oint 4 has the highest.

The almost flat region in the joint 1 curve indicates a

continuous bracket rotation during shear and tension

yielding of the bolt immediately prior to failure.

For the two-bolts joint, the resulting ultimate oad

capacity was found to be about times that of the single-

bolt joint. The three-bolts joint provided anultimate

strength almost2 6 imes thatof the single-bolt oint. Thecorresponding figure for a four-bolts joint is 2-8 .

With high-strength concrete, the joint failure mode was

governed by the bolts yielding in shear. If weaker concrete

is used, as was the case for test series B there isan

increased likelihood that local crushing beneath the sleeves

will permit the sleeves to distort into an ovoid cross-

section with a smaller invert radius. This increases the

lateral forces, and vertical cracks in the concrete are more

likely to develop beneath the joint as seen in test L.

In these tests, most of the bolts showed a significant

shear deformation at their loaded ends prior to failure.

The bolts were made of sufficiently hard material to have

retained their circular cross-section. However, the steel

sleeves yielded substantially at their ends to form ovoid

cross-sections.

Further work

There is a need for a more detailed study of bolt and

sleeve distortions, to allow for construction tolerances.

The single-bolt oint showed a lower stiffness at ll stages

of loading than other joints. The addition of a bolt to a

joint increased its stiffness, but by a decreasing amount

for each successive bolt. This is clear when curves of

joints 3 and 4 are compared in Fig. 8, where the stiffness

of the latter is only slightly higher. The curve for joint

4 showed a slight gain in stiffness during the application

of load. The probable reason for this stiffness change is

that the bolt tolerances will have delayed the full number

of bolts from being in contact with their mounting sleeves

during the early stages of loading. This behaviour also

explains the low initial vertical component of force per

unit vertical deflection until either the bolt or the sleeve

has distorted sufficiently for its vertical diameter to

coincide with the sleeve invert.

A more comprehensive study is also needed of the

variation of strength when the geometry of the bolt holes

is varied. An increase in joint strength can obviously be

achieved by increasing the number of bolts per joint.

However, two factors reduce the benefit gained from the

additional bolts. First, the second and subsequent bolts

do not bear initially on the invert of their sleeves due to

the bolt hole tolerances, and additional lateral forces are

produced. This reduction in benefit appears to e

approximately 30 of the second bolt load capacity and

10 of subsequent bolt capacities. Second, there is a

further reduction of the additional load capacity of about33 if additional bolts are directly beneath each other.

This reduction is caused by the overlap of the stress

contours for the upper bolt with those for the lower bolt.

Magazine of Concrete Research, 1995 41, No. 171



Mohamed and Jolly

Rotation: mrad

Fig. 9. Mom ent-rotation curves fo r the tests in series A and B

The reductions quoted apply to he specific configurations

tested, which are identical to those used by one particular

design consultancy.

There is potential for developing a more cost-efficient

joint if the steel link density is reduced. Steel links in the

joint region inhibit the formation of vertical cracks and

are therefore subjected to tensile stresses which may be

high enough to cause yield. Vertical cracking and failure

of the concrete column ensues. A substantial reduction

of link area was necessary to permit this type of failure

in the joints tested. Thicker sleeve walls and strongersleeve material are variations for further study to inhibit

the development of lateral forces in the column.

In addition to the experiments described in this paper,

finite element modelsare being developed that canredict

the different joints' behaviour up o failure. They represent

a potential meansof comparing the strengths of joints with

different geometries without resorting to large numbers

of expensive and time-consuming tests. Further details of

these modelling echniques, which the authors believe are

also applicable to resin-bonded and expanding anchor

bolts, will be given in a subsequent paper.

References

1. INSTITUTIONF S T R U C T U R A LE N G I N E E R S .anual o structural

joints in precast concrete. London 1978.

2 . JO L L Y . K. and PARSAA. Application of finite element design

to precast concrete beams. Proc. nd Int Conf on Computer Aided

Analysis and Designof Concrete Struciures.Pineridge Press New

York, 1990 pp. 61-76.

3 . ANSYS ngineering analysis system theoretical manual version

4.2. Swanson Analysis Systems Pennsylvania PA 1985.

4. MOHAMED . A. M . Behaviour of sleevedboltconnections in

precastconcretebuilding frames. PhD hesis University of

Southampton 1992.

Discussion contributions on this paper hould reach the editor by

29 December 1995

Magazine of Concrete Research, 1995 47 No. 171 127

Documents

An Experimental Study of the Behaviour of Sleeved Bolt Connections in Precast Concrete Frames