The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea

Basic Characteristics of High Strength One-Side Bolted Friction Joints
Hiroyuki SUZUKI*
Yuichi KAWABE**
Masaji FUJINAGA**
Kazuhiro NAKAJIMA**(Author)*Professor, Program in Architecture, Science and Engineering, Meisei University
2-1-1, Hodokubo, Hino City, Tokyo, 191-8506 Japan
Email:suzukihi@ar.meisei-u.ac.jp**Lobtex Fastening System.co.,Ltd.
1-5-11, Nihombashi Horitome-cho, Chuo Ward, Tokyo, 103-0012 Japan
Email:k-nakajima@lobtex.net
Abstract
High strength one-side bolts, which enable construction only from one side, are effective for repairing or strengthening
closed-section members or for connecting steel pipes as joints. In this study, experiments were conducted to verify thefatigue strength and other basic characteristics of high strength one-side bolted friction joints. As a result, it was
revealed that high strength one-side bolted friction joints have fatigue design curve to those of joints using conventional
high strength bolts. Also presented in this paper are case studies of application of high strength one-side bolted friction
joints to box steel pipe columns and of seismic retrofit of steel truss and arch bridges.
Keywords: Slip Coefficient, Fatigue, Relaxation, Friction Joint
1. Introduction
High strength one-side bolts (hereinafter referred to as the HOB), which enable construction only from one side, areeffective for repairing or strengthening closed-section members or for connecting box steel pipes. They enable theconnection of members requiring no field welding and therefore improve confidence in quality of connection, facilitate
construction, ensure safety and reduce the period of construction. The connection method is also friendly to theenvironment because steel members can be recycled or reused simply by removing bolts. An increasing number of steel
highway bridges have recently been repaired or strengthened with the increase of traffic volume and vehicle size,
deterioration of bridges and requirements for greater seismic resistance [1], [2]. HOB are frequently used also in seismic
retrofit of architectural structures as a connection method requiring no field welding because neither curing andultrasonic testing involved in field welding nor welder qualifications are required. As for the basic performance of HOB
used for friction joints and for the structural characteristics of connections, verifications have been made when the bolts
were applied 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 thesteel plate deck or highway bridge also carries a tramway or railway. The occurrence of fatigue cracks have, however,been reported recently at numerous positions of steel highway bridges [6] and future fatigue damage has been ofconcern. Then, the “Fatigue Design Guidance for Steel Highway 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
HOB friction joints. In this study, experiments were conducted to verify the slip coefficient, relaxation of axial force
HOB friction joints and fatigue strength, which represent the basic characteristics of HOB friction joints. As a result, it
was revealed that HOB have basic characteristics equal or higher to those of joints using standard high-strength bolts.
Tensile strength was also verified before and after fatigue experiments. Also presented in this paper are case studies ofapplication of HOB friction joints to box steel pipe columns, of seismic retrofit of strengthen concrete columns and of641

The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea
seismic retrofit and fatigue strength of steel highway bridges.
2. Outline of High Strength One-Side Bolt
2.1 Characteristics of HOB
The components of a HOB are shown in Figure 1. Six parts constitute a HOB: bulb sleeve that forms the bolt headbehind the member, shear washer and grip sleeve that support the bulb sleeve, bearing washer that secures the grip
range, core pin with a special trapezoidal screw and nut.
HOB are used in all kinds of steel structures for repairing bridges, seismically retrofitting or renovating buildings,
erecting buildings and constructing plants. Members can be fastened from one side using a dedicated electric shear
wrench regardless of the field environment or human skill.

Figure 1 Components of High Strength One-Side Bolt
2.2 Fastening mechanism
The process of fastening a HOB is outlined in Figure 2. A cross section of the fastened HOB is shown in Photograph 1.
The steps of fastening are described below.
(1) A HOB is inserted into the bottom hole and fastening 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 is started.
(4) The tail of the core pin is fractured, 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 is formed. Then, the designated axial force is introduced to the member due to the fracture of
the pin tail as for a torque-shear high-strength bolt. Thus, axial force is introduced at two stages in the fastening
mechanism for HOB.

Figure 2 Outline of fastening of high-strength one-side bolt
3. Slip experiments
3.1 Experimental procedure
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The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea
Specimens were developed simulating the connection of a box column (t = 22 mm, SN490B) (Figure 3).
The friction surface was subjected to either shot blasting or grit blasting. Surface roughness was set at 50 Pm Rz or
higher. Slip experiments were conducted also for standard specimens of high-strength bolted joints (M22-S10T) forcomparison with HOB joints. In the slip test, an Amsler type testing machine was used for tensile loading. The slip load
under which clear slip sound was created was considered to be the main slip load. Three slip experiments specimens
were developed.

Figure 3 Slip experiments specimen
3.2 Experimental results
Tables 1 through 3 show the results of slip experiments. The slip coefficient for HOB joints (mean of the values forthree specimens) was 0.62 for bolts subjected to grit blasting and 0.57 for those subjected to shot blasting. The slip
coefficient for high-strength bolted joints was 0.60 (mean of the values for three specimens). All exceeded a slip
coefficient of 0.40.
Table 1 High strength one-side bolt (grit blasting)Specimen

Specimen

Specimen

No-1

No-2

No-3

P (kN)

710

759

707

ȝ

0.610

0.652

0.607

㩷

Table 2 High strength one-side bolt (shot blasting)Specimen

Specimen

Specimen

No-1

No-2

No-3

P (kN)

682

622

698

ȝ

0.586

0.534

0.600

㩷㩷

Table 3 High strength bolt (shot blasting)Specimen

Specimen

Specimen

No-1

No-2

No-3

P (kN)

575

550

531

ȝ

0.625

0.598

0.577

㩷㩷

4. Relaxation experiments of Axial force
4.1 Experimental procedure
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The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea
For obtaining the axial force of the HOB in the relaxation experiments, the train gauge of the axial force embedded in
the core pin was measured and the stress-strain relationship and the cross sectional area of the bolt were examined forconversion.
In the fatigue experiment specimen shown in Figure 4, two bolts were fastened first on the inside and then on theoutside of the joint. HOB were fastened to the specimen and the axial force was measured until 14 days passed.

Figure 4 Shape of specimen
4.2 Experimental results
The axial force of HOB and the time elapsed are shown in Figure 4. The bolt axial force dropped drastically in about
one day after the bolt was fastened, and was gradually reduced thereafter. After the lapse 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% ofthat at the time of fastening. The results show that the axial force relaxation of HOB was similar to the results ofrelaxation experiment for conventional high-strength bolts [8] and that no special consideration was required for thedesign axial force or the axial force to be introduced.

Axial Force (kN)220㪤㪈㪄㪚㪟㪈
210

㪤㪈㪄㪚㪟㪉

200
190
180
170
0

7
Time elapsed (in days)

14

Figure 5 Axial force relaxation
5. Fatigue experiment
5.1 Experimental procedureThree sets of specimens (M1, M2 and M3) were developed simulating the connection created by double friction (Figure4). The bolt-hole had a diameter of 26.0 mm. Shot blasting was applied on the friction surface of the base material andsplice. A strain gauge was installed 215 mm from the end of the base material, and the stress to be applied in the fatigue
experiment was measured in static loading tests. The “Fatigue Design Guidance for Steel Highway Bridges”[7]specifies class B for the strength of high-strength bolted friction 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 HOB friction joints and conventional high-strength bolted friction joints. In the fatigue
experiment, an electro-hydraulic servo testing machine of Meisei University (Photograph 1) was used for pulsating
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The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea
tensile fatigue experiment. Tension was applied cyclically at a rate of 6 Hz. Tests were repeated until the fracture of thebase material with the maximum number of cycles set at 10 million times. The mechanical properties of steel plates arelisted in Table 4. The materials of HOB and the mechanical properties of core pin are shown in Tables 5 and 6,
respectively.

Photograph 1 Fatigue experiment
Table 4 Mechanical properties of steel plates㩷㩷

Material

SpliceBase Material

Thickness

Tensile Strength

Yield Stress
2

Elongation

2

(mm)

(N/mm )

(N/mm )

㩿㩼㪀㩷

SS400

9

311

442

29

SM400A

12

333

458

30

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

Nut

Washer

SCM440

SCM440

SCM430㩷㩷Shear Washer

Grip Sleeve

Bulb Sleeve

SCM430

SCM430AISI1018

Table 6 Mechanical properties of core pin㩷㩷Strength2

Tensile Strength2

DrawingElongation

䋨N/mm 䋩㩷䋨N/mm 䋩㩷(%)(%)

Standard Value

Min 1006

1118-1216

Min 40

Min 14

Measuement

1111

1195

54

16

5.2 Fatigue experimental results
Figure 6 shows the results of fatigue experiments for HOB friction joints. The figure shows an S-N curve (strength class645

The 6th International Symposium on Steel Structures
November 3-5, 2011, Seoul, Korea
B) for conventional high-strength bolted friction joints presented in the “Fatigue Design Guidance for Steel Highway
Bridges”[7] .

Stress Range (MPa)1000
M1䋺 10 million cycles
M2䋺 4.95 million cycles
M3䋺 5.00 million cycles

Stress Class B(155MPa) S-N Curve100
1.0E+5

1.0E+6

1.0E+7

1.0E+8

Number of Cycles N
Figure 6 Fatigue experiment results
The stress range for high-strength bolted friction joints was calculated using a formula specified in the “Fatigue Design
Guidance for Steel Highway Bridges” [7]. 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 times,
the fatigue limit. The results have revealed that HOB friction joints have fatigue strength to greater than that of standard
high-strength bolted joints [7].
5.3 Fracture of specimen
In specimen M1, the base material did not fracture until the number of cycles reached 10 million. Then, the test was
discontinued. The base material fractured from around the bolt-hole along the width of the plate after approximately
4.95 million cycles in specimen M2 and after approximately 5.00 million cycles in M3.
6. Tensile tests
In order to verify the strength of the HOB after the fatigue experiment, specimens M2 and M3 were dismantled andtensile tests were conducted for bolts. The results of tensile tests for HOB at the time of shipment and after the fatigue
test are shown in Table 7.
Table 7 Results of tensile test before and after fatigue test㩷㩷
Before Fatigue(N=10)㩷
After Fatigue(N=8)㩷Maximum

Minimum

Average

(kN)㩷

(kN)

(kN)㩷

270.9

269.2

269.9

270.8

269.2

270.0

After the tensile test, HOB all fractured at the screw of the bolt. It is therefore evident that the bulge (bolt head) that was
deformed had sufficient strength. Tensile strength remained unchanged after the fatigue test. It was verified that nostrength reduction occurred in HOB after cyclic loading was applied approximately five million times.

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November 3-5, 2011, Seoul, Korea
7. Case studies of application of HOB
HOB have been frequently used for repairing or strengthening steel highway bridges under construction constraints. In
recent years, HOB have been adopted in an increasing number of cases for seismic retrofit of relatively large bridges
such as arch and truss bridges. The example is the seismic retrofit of the corner of an arch rib [1], [4] (Photograph 2)
and Photograph 3.

Photograph 2 Strengthening a steel arch bridge

Photograph 3

Strengthening a steel arch bridge

Recent works also present case studies of adoption of HOB for strengthen against fatigue cracking at intersection of the
U-shaped and transverse ribs of a steel slab [9]. An example of connecting a reinforcing member on the bottom surface
of a U-shaped rib of a steel slab using HOB is shown in Photograph 4, and strengthen a steel pipe piar Photograph 5.

Photograph 4 Strengthening a steel slab U rib

Photograph 5 Strengthening a steel pipe piar

8. Conclusions
Tests were conducted to verify the slip factor, relaxation of axial force and fatigue strength, which represent the basic
characteristics of high-strength one-side bolted friction joints. Tensile strength after fatigue experimenting was also
verified. The findings are described below.
(1) Slip tests were conducted for faying surface that was subjected either to shot blasting or grit blasting. As a result, aslip factor of 0.45 or higher was obtained. Performance grater to that of standard high-strength bolted friction joints canbe obtained by properly cleaning the friction surface.
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November 3-5, 2011, Seoul, Korea(2) Relaxation of axial force was approximately 5%. The relaxation of axial force of HOB is similar to that for standard
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 fivemillion, more than 2.5 times two million, the fatigue limit. HOB friction joints have fatigue design curve toconventional high-strength bolted joints(4) It was verified in tensile tests before and after fatigue testing that no strength reduction occurred in HOB after cyclicloading was applied approximately five million times.
9. Acknowledgment
This bolt are a patent of Huck International,lnc in USA. In addition, Fuserashi co., LTD produces it in Japan.
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 in testing in this study. The authors arealso thankful to the staff concerned of Fuserashi Co., Ltd. for providing high-strength one-side bolts and supporting intensile 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 symposium on the seismic designof bridges and other structures 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.: Report on 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 Design, construction and maintenance guidelines forhigh-strength bolted friction joints (draft), December 2006 (in Japanese).
9) Hirano, T., Takada, Y., Matsui, S. and Sakano, M.: Report on moving wheel loading tests focused on thefatigue-induced cracking at the intersection of U-shaped and transverse ribs of a steel slab, Proceedings of the 61st
Annual Conference of Japan Society of Civil Engineers, pp. 1125-1126, September 2006 (in Japanese).

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