Bridge Maintenance, Safety, Management, Resilience and Sustainability – Biondini & Frangopol (Eds)© 2012 Taylor & Francis Group, London, ISBN 978-0-415-62124-3

Experimental study on High strength One-side bolted joints
K. Nakajima
Lobtex Fastening System.co.,Ltd.,1-5-11, Nihombashi Horidome-cho, Chuo Ward, Tokyo, Japan

H. Suzuki
Meisei University, 2-1-1, Hodokubo, Hino City, Tokyo, Japan

Y. Kawabe & K. Fujii
Lobtex Fastening System.co.,Ltd.,1-5-11, Nihombashi Horidome-cho, Chuo Ward, Tokyo, Japan

ABSTRACT: High strength one-side bolts, which enable construction only from one side, are effective forrepairing or strengthening closed-section members or for connecting steel pipes as joints. In this study,
experiments were conducted to verify the fatigue strength and other basic characteristics of high strength oneside bolted joints. As a result, it was revealed that high strength one-side bolted joints have fatigue design
curve to those of joints using conventional high strength bolts. Also presented in this paper are case studies ofapplication of high strength one-side bolted joints to strengthening of steel truss bridge and arch bridges.
1. INTRODUCTION

Bridges”[7] was published in 2002, which made theadoption of fatigue design mandatory also on steel
highway bridges. No fatigue strength has, however,been verified for OS-Bolted joints.
In this study, experiments were conducted toverify the slip coefficient, relaxation of axial force
OS-Bolted joints and fatigue strength, which
represent the basic characteristics of OS-Bolted
joints. Also presented in this paper are case studies
of application of OS-Bolted joints to seismic retrofit
and strengthening of steel highway bridges.

High strength one-side bolts (hereinafter referred toas the OS-Bolt) are bolt that construction is possible
from one side. Also, OS-Bolt are effective forrepairing or strengthening closed-section members.
They enable the connection of members requiring nofield welding. Then, quality reliability of connection
and construction property improve. Also, thosesecure safety and the period of construction isshortened. OS-Bolt has been frequently used for
repairing or strengthening steel bridges underconstruction constraints.
An increasing number of steel highway bridges
have recently been repaired or strengthened with theincrease of traffic volume and vehicle size,
deterioration of bridges and requirements for greater
seismic resistance [1], [2]. OS-Bolt are frequently
used a connection method requiring no field welding
because neither curing and ultrasonic testing
involved in field welding nor welder qualifications
are required.
As for the basic performance of OS-Bolted joints
used for the structural characteristics of connections,verifications have been made when the bolts wereapplied to architectural structures or steel highway
bridges [3]-[5] and their effectiveness have been
identified.
In the initiation design of steel highway bridges,
considering the effects of fatigue were determined
unnecessary unless the steel plate deck or highway
bridge also street railway. The occurrence of fatigue
cracks have, however, been reported recently at
numerous positions of steel highway bridges [6] andfuture fatigue damage has been of concern. Then,the “Fatigue Design Guidance for Steel Highway

2. OUTLINE OF HIGH STRENGTH ONE-SIDE
BOLT
2.1 Characteristics of OS-Bolt
The components of OS-Bolt are shown in Figure 1.

Figure 1. Components of High Strength One-Side Bolt

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Six parts constitute OS-Bolt: bulb sleeve that forms
the bolt head behind the member, shear washer andgrip sleeve that support the bulb sleeve, bearing
washer that secures the grip range, core pin with a
special trapezoidal screw and nut. OS-Bolt are usedin all kinds of steel structures for repairing bridges.
Members can be fastened from one side using a
dedicated electric shear wrench regardless of the
field environment or human skill. Strength
equivalent to F8T can be secured by high strength
bolt for friction joint.

The steps of fastening are described below.
(1) OS-Bolt is inserted into the bottom hole andfastening is started using a dedicated shear wrench.
(2) The bulb sleeve is deformed behind the member,forming a bulge (bolt head).
(3) The shear washer is sheared by the axial force
and the introduction of axial force to the member isstarted.
(4) The tail of the core pin is barked, and thereby
designated axial force is introduced. Then, fastening
is completed.
The axial force required for deforming the bulb
sleeve is temporarily released due to the shearing of
the shear washer at the same time as a bulge isformed. Then, the designated axial force isintroduced to the member due to the fracture of thepin tail as for a torque-shear high strength bolt.
Thus, axial force is introduced at two stages in thefastening mechanism for OS-Bolt.

2.2 Fastening mechanism
The process of fastening OS-Bolt is outlined in
Figure 2. The conditions before and after fastening
are shown in Photograph 1. A cross section offastened OS-Bolt is shown in Photograph 2.

3. SLIP TESTS
Figure 2. Outline of fastening system

3.1 Experimental procedure
BeforeBlub Sleeve

After

Deform of Blub Sleeve

Specimens were designed for friction joints (Plate:
22mm, SN490B, OS-Bolt:ĳ27) in Figure 3. The
friction surface was subjected to either shot blastingor grid blasting. Surface roughness was set at 50 ȝm
Rz or higher. Slip tests were conducted also forstandard specimens of high strength bolted joints(M22-S10T) for comparison with OS-Bolt joints.
In the slip test, an Amsler type testing machine
was used for tensile loading. The slip load underwhich clear slip sound was created was considered
to be the main slip load. Three slip tests specimens
were developed. For the conventional bolt axial
force for calculating the coefficient of slip, the meanof axial force measurements for five bolts in thesame lot as that contained the one used in the slip
test was used. (OS bolt: 291 kN, high strength bolt:
230 kN.)

Photograph 1. Before and after of fastening

Figure 3. Slip experiments specimen

Photograph 2. Cross section1331

3.2 Experimental results
Tables 1 through 3 show results of slip tests. The
slip coefficient (ȝ) for OS-Bolt joints (mean values
for three specimens) was 0.62 for bolts subjected togrid blasting and 0.57 for those subjected to shot
blasting. The slip coefficient (ȝ) for high strength
bolted joints was 0.60 (mean values for three
specimens). All exceeded a slip coefficient (ȝ) of
0.40 in Japan Road Association.
Table 1. High strength one-side bolt (grid blasting)㻌
Slip loads(kN)ȝSpecimen
No-1
710
0.610

Specimen
No-2
759
0.652

Figure 4. Test specimen

Specimen
No-3
707
0.607

4.2 Experimental results
The axial force of OS-Bolt and the time elapsed areshown in Figure 5. The bolt axial force dropped
drastically in about one day after the bolt was
fastened, and was gradually reduced thereafter. Afterthe elapse of about one week, the axial force became
stable at a certain level. At a point when 14 days
passed, the reduction of axial force was about 4.5%of that at the time of fastening.

Table 2. High strength one-side bolt (shot blasting)Slip loads(kN)Specimen
No-1
682

Specimen
No-2
622

Specimen
No-3
698

ȝ

0.586

0.534

0.600

㻌

Table 3. High strength bolt (shot blasting)Specimen
No-2
550

Specimen
No-3
531

ȝ

0.625

0.598

0.577

220
㻹㻝㻙㻯㻴㻝

210
Axial Force(kN)

Slip loads(kN)Specimen
No-1
575

㻌

4. RELAXATION TESTS㻹㻝㻙㻯㻴㻞

200
190

4.1 Experimental procedure180

For obtaining the axial force of the OS-Bolt in therelaxation tests, the strain gauge of the axial force
embedded in the core pin was measured. The stressstrain relationship and the cross sectional area of thebolt were examined for conversion. The gauges
installed are shown in Photograph 3. In the test
specimen shown in Figure 4, two bolts were fastened
first on the inside and then on the outside of thejoint. OS-Bolt were fastened to the specimen and theaxial force was measured until 14 days passed.

170
0

7

14

Time(days)

Figure 5. Axial force relaxation

4.3 Effect of bolt length
The Axial force was measured for one year for fourtypes of OS-Bolt in order to verify the effects ofaxial force relaxation and long time relaxation where
the length of OS-Bolt varied.
Figure 6 shows the long time measurements ofaxial force relaxation. A strain gauge was attachedto the bolt head in a constant temperature andhumidity testing machine at a room temperature of
20°C to measure changes in longitudinal strain of
the bolt with time. The rate of axial force relaxation
after one year was 2.1 to 4.9% of the axial force
introduced right after the bolt was fastened.
The results show that the axial force relaxation of
OS-Bolt was similar to the results of relaxation test
for conventional high strength bolts [8] and that no

Photograph 3. Gauge position1332

special consideration was required for the design
axial force or the axial force to be introduced.

The “Fatigue Design Guidance for Steel Highway
Bridges”[7] specifies class B for the strength of highstrength bolted joints and a base stress range of 155
MPa. In the tests, however, stress grade was raised
to class A and the stress range was set to be 190
MPa because comparison was made in fatigue
strength between OS-Bolted joints and conventional
high strength bolted joints.
In the fatigue test, an electro hydraulic servo test
machine in Photograph 4 was used for pulsating
tensile fatigue test. Tension was applied cyclically at
a rate of 6 Hz. The Tests were repeated until thefracture of the base plate with the maximum numberof cycles set at 10 million times. The mechanicalproperties of steel plates are listed in Table 4. The
materials of OS-Bolt (ĳ24) and the mechanicalproperties of core pin are shown in Tables 5 and 6,
respectively.

Relaxation(%)

100
98
96
94

OS-Bolt24-20
OS-Bolt24-40
OS-Bolt24-50
OS-Bolt24-85

92

1year

10months

8months

6months

4months

2months

1day

5min

0min

90

Time

Figure 6. Axial force relaxation
Table 4. Mechanical properties of steel plates

5. FATIGUE TESTS

㻌㻌

5.1 Experimental procedure

Material
Thickness(mm)Yield Stress(MPa)Tensile Strength(MPa)Elongation(%)

Three sets of specimens (M1, M2 and M3) were
designed for friction joints by double friction in
Figure 4. The bolt-hole had a diameter of 26.0 mm.
Shot blasting was applied on the friction surface ofthe base plate and splice plate. A strain gauge wasinstalled 215 mm from the end of the base plate, andthe stress to be applied in the fatigue test wasmeasured in static loading tests.

Splice Plate
SS400
9
311
442
29

Base Plate
SM400A
12
333
458
30

Table 5. Materials of High Strength One-Side Bolt
Core Pin

Nut

Washer

SCM440

SCM440

SCM430

Shear
WasherGrip Sleeve

Bulb Sleeve

SCM430

SCM430AISI1018

Table 6. Mechanical properties of core pin㻌Strength䠄MPa䠅
Tensile Strength䠄MPa䠅
Drawing(%)
Elongation(%)

Standard Value
Min 1006

Measurement
1111

1118-1216

1195

Min 40
Min 1454
16

5.2 Experimental results
Figure 7 shows the results of fatigue tests for OSBolted joints. The line shows an S-N curve (strengthclass B) for conventional high strength bolted joints
presented in the “Fatigue Design Guidance for SteelHighway Bridges”[7]. The stress range for highstrength bolted joints was calculated using a formulaspecified in the “Fatigue Design Guidance for SteelHighway Bridges” [7].

Photograph 4. Fatigue experiment

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The result was 190 MPa at strength class A,
approximately 1.8 times 155 MPa at strength class
B. The number of cycles for a stress range of 190
MPa was more than 2.5 times two million cycles, thefatigue limit. The results have revealed that OSBolted joints have fatigue strength to the same level
as conventional high-strength bolted joints [7].

1000Stress Range (MPa)M1䠖10million cycles
M2䠖4.95million cycles
M3䠖5million cycles
Stress Class B(155MPa䠅100
1.0E+5

1.0E+6

1.0E+7

1.0E+8

Number of Cycles N
Figure 7. Fatigue test results

Photograph 6. Fracture of base material (M3)

5.3 Fracture of specimen
In specimen M1, the base plate did not fracture until
the number of cycles reached 10 million. Then, thetest was discontinued. The base plate fractured fromaround the bolt-hole along the width of the plateafter approximately 4.95 million cycles in specimen
M2 and after approximately 5.00 million cycles in
M3. The state right after the fracture is shown in
Photographs 5 and 6 for M2 and M3, respectively.

Photographs 7 and 8 show the fracture of the baseplate on the bulge and nut sides after the dismantlingof M2 and M3. The fracture of the base plate
progressed from the end of the bolt-hole. Fretting
was observed on the surface due to cyclic loading.
Fatigue-induced cracks that occurred on the surface
around the bolt-hole subjected to fretting may havecaused the base plate to fracture.

M2 Nut Side

Fretting

M3 Nut Side

Photograph 5. Fracture of base material (M2)
Fretting

Photograph 7. Fracture of base material (Nut side)1334

FrettingM2 Bulge Side
Photograph 10. After tensile test(M3)
Fretting
Table.7 Results of tensile test before and after fatigue test
Maximum(kN)

Minimum(kN)

Average(kN)

Before Fatigue

270.9

269.2

269.9

After Fatigue

270.8

269.2

270.0

㻌

M3 Bulge Side

Photograph 8. Fracture of base material (Bulge side)

7. CASE STUDIES OF OS-BOLT
6. TENSILE TESTS

OS-Bolt has been frequently used for repairing or
strengthening steel bridges under construction
constraints. In recent years, OS-Bolt has been
adopted in an increasing number of cases for seismic
retrofit of relatively large bridges such as archbridge and truss bridge. The example isstrengthening steel bridge of arch rib in Photograph
11 and 12, 13 and strengthening steel truss bridge in
Photograph 14.

In order to verify the strength of the OS-Bolt (ĳ24)
after the fatigue test, specimens M2 and M3 weredismantled and tensile tests were conducted forbolts. The results of tensile tests for OS-Bolt at thetime of shipment and after the fatigue test are shownin Table 7. Photographs 9 and 10 show how the bolts
fractured.
After the tensile test, OS-Bolt all fractured at thescrew of the bolt. It is therefore evident that thebulge (bolt head) that was deformed had sufficientstrength. Tensile strength remained unchanged after
the fatigue test. It was verified that no strength
reduction occurred in OS-Bolt after cyclic loading
was applied approximately five million times.

Photograph 11. Strengthening a steel arch bridge
Photograph 9. After tensile test(M2)1335

An example of connecting a strengthening member
on a U-shaped rib of a steel slab using OS-Bolt isshown in Photograph 15.

Photograph 12. Strengthening a steel arch bridge
Photograph 15. Strengthening a U-Rib of steel slab

Research and development has been made in recent
years concerning a method for replacing bolts buried[9] in concrete members with OS-Bolt. It enable
construction from one side, and the method has been
put to practical use. The replacement of highstrength bolts F11T using OS-Bolt is shown in
Photograph 16.

Photograph 13. Strengthening a steel truss bridge

Photograph 16. Replacement of OS-Bolt

8. CONCLUSIONS
Experiments were conducted to verify the slip
factor, relaxation of axial force and fatigue strength,
which represent the basic characteristics of OSBolted joints. Tensile strength after fatigue test wasalso verified. The findings are described below.

Photograph 14. Strengthening a steel truss bridge(1) Slip tests were conducted for friction surface thatwas subjected either to shot blasting or grid blasting.

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As a result, a slip factor of 0.40 or higher was
obtained. Performance the same level to that ofconventional high-strength bolted joints can beobtained by properly cleaning the friction surface.

based on the seismic strength method, pp. 207-212,
February 2006 (in Japanese).
[5] Tanaka, T., Tabuchi, M., Furumi, K., Murayama,
M. and Matsubara, Y.: A study on the connection
between a box steel pipe column with increased
thickness and a beam, Proceedings of annual
conference on steel structures, Vol. 3, pp. 355-362,
November 1995 (in Japanese).
[6] Takada, Y., Hirano, T. and Sakano, M.: Reporton fatigue-induced damage to steel slabs on the
Hanshin Expressway, Proceedings of the 61st
Annual Conference of Japan Society of Civil
Engineers, pp. 1067-1068, September 2006 (inJapanese).
[7] Japan Road Association: Fatigue Design
Guidance for Steel Highway Bridges, March 2002
(in Japanese).
[8] Japan Society of Civil Engineers: Steel structure
series 15 Recommendations on Design, Construction
and Maintenance for Friction Type of High strength
bolted Connections, December 2006 (in Japanese).
[9] Ohyama, T., Ohte, K., Nakajima, K., Suzuki, H.
and Tadokoro, M.: Report on the replacement ofbolts subjected to delayed failure with high-strength
one-side bolts, Proceedings of the 66th Annual
Conference of Japan Society of Civil Engineers, pp.
511-512, September 2011 (in Japanese).

(2) Relaxation of axial force was approximately 5%.
The relaxation of axial force of OS-Bolt is similar tothat for conventional high strength bolts. No special
consideration is required for the design axial force or
the axial force to be introduced.
(3) The number of loading cycles for a stress range
1.8 times the stress range for high strength bolted
joints was five million, more than 2.5 times two
million, the fatigue limit. OS-Bolted joints havefatigue design curve to conventional high strength
bolted joints.
(4) It was verified in tensile tests before and after
fatigue tests that no strength reduction occurred in
OS-Bolt after cyclic loading was applied
approximately five million times.
9. ACKNOWLEDGMENT
This bolt is a patent of Huck International,lnc inUSA. In addition, Fuserashi co., LTD produces it inJapan.
The authors would like to express their gratitude to
the members of the steel structure laboratory,
Program in Architecture, Science and Engineering,
Meisei University who provided support inexperiments in this study. The authors are also
thankful to the staff concerned of Fuserashi Co., Ltd.
for providing high-strength one-side bolts andsupporting in tensile tests.
10. REFERENCES[1] Yoshizu, H. and Fujii, K.: Design for reinforcing
steel deck Langer bridges, Civil Engineering, Vol.
59 No. 7, pp 55-62, July 2004 (in Japanese).
[2] Hashimoto, Y, Kameyama, S. and Hiromura, O:
Reinforcement of splice at steel deck U-shaped rib
butt welding, Takigami Technical Report, Vol. 23,
pp. 87-96, November 2005 (in Japanese).
[3] Ohno, T., Natori, T. and Matsumoto, Y.: Friction
bonding method using torque control type one-side
construction high-strength bolts, Yokogawa Bridge
Group technical report, No. 26, pp. 236-240, January
1997 (in Japanese).
[4] Matsumura, M., Kitada, T., Yoshizu, H., Kijitani,
M. and Muramoto, K.: An experimental study on
corner reinforcement for rectangular steel columns
using one-side bolts, Proceedings of 9th symposiumon the seismic design of bridges and other structures

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