PTI JOURNAL

Case Studies

FIELD APPLICATION OF CARBON FIBERCOMPOSITE CABLE POST-TENSIONING SYSTEM
By

BY KENICHI USHIJIMA, TSUYOSHI ENOMOTO,NORIAKI KOSE, AND YOSHIAKI YAMAMOTO

Authorized reprint from: December 2016 issue of the PTI JOURNAL
Copyrighted © 2016, Post-Tensioning InstituteAll rights reserved.

CASE STUDIESFIELD APPLICATION OF CARBON FIBERCOMPOSITE CABLE POST-TENSIONING SYSTEMBY KENICHI USHIJIMA, TSUYOSHI ENOMOTO,NORIAKI KOSE, AND YOSHIAKI YAMAMOTOINTRODUCTION

The first bridge using a carbon fiber composite cable(CFCC) post-tensioning (PT) system, the Bridge Street
Bridge, was built in 2001 in Michigan. Since then, CFCC
post-tensioning has been used for four projects in Michigan, one project in Maine, and one project in Louisiana.
In regions surrounded by harsh environments, corrosionof steel reinforcement and prestressing strands becomes amajor safety, durability, and rehabilitation concern.

Carbon fiber-reinforced polymer (CFRP) materials
are one of the alternative solutions because of theircorrosion-free nature, durability, high tensile strength,
and light weight. Precast prestressed concrete side-by-sidebox beams have been used in short and midspan bridges.
The development of longitudinal cracks in the deck slab
between the box beams was one of the major concerns
and corrosion-related problems. The longitudinal cracks
would allow water and deicing chemicals to penetrate into
the sides of the box beams and cause the corrosion of steel
reinforcement and concrete spalling. The deterioration of
the structures would require the owners costly repairs andrehabilitations followed by replacement of the bridges after
30 to 40 years. To resolve these problems, an unbonded
CFCC transverse PT system was designed and developedby the manufacturer. The unbonded CFCC is not susceptible to corrosion due to its corrosion-free nature andallows its force adjustment as well as the replacement of
the damaged beams in the future.

Fig. 1—Features and availability of CFFC.
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CASE STUDIESIn Michigan, four side-by-side box beam bridges wereconstructed using a CFCC transverse post-tensioning
system (2011, 2012, 2014, and 2015). In Maine, CFCC
strands were transversely post-tensioned for the voided
slabs on the Little Pond Bridge in Fryeburg (2012).
CFRP has been used not only for the replacementof the current bridges but also for strengthening existingbridges. In Louisiana, 17.2 mm (0.7 in.) diameter CFCC
strands were used as external cables for the I-10 New
Orleans East Girder repair (2014).
Because the use of CFRP as post-tensioning and pretensioning in highway bridge applications is expected toincrease in the future, the drafts of the CFRP design guide-line for Michigan Department of Transportation (MDOT)
and American Association of State Highway and Transportation Officials (AASHTO) have been under development
and will be available in the future. The design guideline
will allow the highway transportation agencies to consider
the use of CFRP among the options in the design of posttensioning the precast concrete bridge beams and girders
as well as the precast concrete decks. The manufacturer’s
CFCC factory in Michigan, the operation of which started
in September 2016, would improve the lead time fordelivery and eliminate the transportation cost by an ocean
or air shipment.

CHARACTERISTICS OF CFCC MATERIALSCFCC is a trademarked name of the product, which
has been developed by the manufacturer since 1988 (Fig. 1).
CFCC is a stranded CFRP and consists of Polyacrylonitrile(PAN)-based continuous carbon fibers with epoxy resins
as a binding material.
In addition to its corrosion-free nature, CFCC ischaracterized by its light weight and high strength. The
light weight enhances the workability and handling of thematerials.
Guaranteed breaking load of 15.2 mm (0.6 in.) diameter CFCC strand is similar to that of 15.2 mm (0.6 in.)diameter 270 ksi steel strand, Table 1. Relaxation of CFCC
is almost the same as low-relaxation steel strand; it is1.32 kN/mm2 (191.5 ksi). CFCC has twice the bondstrength of steel strand. CFCC does not exhibit any yieldphenomenon and its stress-strain relationship is linear to
failure. This unique performance influences the design
requirements of members with CFCC reinforcement.

POST-TENSIONING ANCHORAGE SYSTEM

The anchorage system is a key for CFCC strands to
be used in the field applications. Conventional anchoring

Table 1: Material Properties
Material

CFCC Strand

Grade 270 Strand

15.2 mm (0.6 in.)15.2 mm (0.6 in.)Tensile Strength

2,337 MPa(339 ksi)

1,862 MPa
(270 ksi)

Cross Sectional Area

115.6 mm2(0.179 in.2)

140 mm2(0.217 in.2)

Guaranteed
Breaking Load

270 kN(60.7 kips)

260.6 kN
(58.59 kips)

DiameterFig. 2—Post-tensioning 40 mm (1.57 in.) diameter CFCC with
pre-installed anchoring devices on both ends.
20 December 2016 | PTI JOURNALCASE STUDIES
devices that are used for steel strands are not suitablefor CFCC strands in pre-tensioning and post-tensioning
as they damage the surface of CFCC strands and causepremature failure at the anchorage.
The anchorage devices for post tensioning are preinstalled on CFCC at the factory. Each CFCC strand iscut to the required length and is anchored at its ends withsockets and nuts using highly expansive grout material.
The CFCC strands with pre-installed anchoring devices onboth ends are shown in Fig. 2 and then packed and shippedto the field.

The operation of post-tensioning is shown in thefollowing post-tensioning procedure (Fig. 3).
1. Place the bearing plate into the concrete structure.
2. Install the CFCC with a socket into a duct.
3. Place the jack chair and the center hole hydraulicjack, install a nut, and connect a tensioning bar
and CFCC with a coupler.
4. Prestress CFCC using a hydraulic pump.
5. Fix the CFCC anchor with a locking nut.
6. Release the center hole hydraulic jack to transfer
the prestress to the concrete structure.

Fig. 3—Post-tensioning procedure.

Fig. 4—Hisho bridge side view and cross-sectional view. (Note: All dimensions in mm; 1 in. = 25.4 mm.)
PTI JOURNAL | December 2016 21

CASE STUDIESThe manufacturer is developing a new system that will
not require pre-installed anchoring devices and that will bedone in the field. It will consist of mechanical devices with
sleeves and wedges, similar to devices for prestressing steel,with different size and shape to avoid premature failure.

ACTUAL DEPLOYMENT OF CFCC POSTTENSIONING IN THE FIELD(1) Hisho Bridge (1993)

The Hisho Bridge (Fig. 4) is the first application of
CFRP in a cantilevered construction. CFCC strands were

Fig. 5—Hanshin Expressway underneath view and installation in a limited area.

Fig. 6—Bridge Street Bridge cables. (Note: All dimensions in mm; 1 in. = 25.4 mm.)
22 December 2016 | PTI JOURNALCASE STUDIES
used for internal (cantilever) and external (span) cablesin this post-tensioned structure. The number of internalcables is 100 (50 x 2), while the number of external cables
is 8 (4 x 2). Post-tensioning and anchoring systems for sixpiece multi-type CFCC with 12.5 mm (0.5 in.) diameter
were developed and applied, respectively, for internal andexternal cables. Internal CFCC cables were bonded bygrouting the prestressing ducts. External CFCC cables
remained unbonded.

(2) Hanshin Expressway, Japan (1999)

An 11-piece multi-type CFCC with 12.5 mm(0.5 in.) diameter was used for external cables of Hanshin
Expressway in Japan (Fig. 5). The length of the cables wasapproximately 20 m (65.62 ft) and installed over five spansto strengthen the existing bridge. The bridge was close toresidential areas. Due to its light weight, the workers could
pull and install CFCC strands in a limited area without
any problems.

Appearance of the bridge(3) Bridge Street Bridge, Southfield, MI (2001)

The Bridge Street Bridge consists of two parallel
bridges (Structures A and B) over the Rouge River in thecity of Southfield, MI (Fig. 6). Both bridges comprise
three spans skewed at 15 degrees over a 62 m (203.41 ft)
length. Structure A was constructed of standard AASHTO
precast concrete beams, reinforced with conventional steel
elements. Structure B was constructed of precast concrete
double-tee (DT) beams, reinforced with CFRP. The
Bridge Street Bridge was completed and opened for traffic
in 2001. Structure B is pre-tensioned and post-tensioned
with CFRP strands and tendons. Transverse unbonded
CFCC post-tensioning strands with 40 mm (1.57 in.)diameter and 21.8 mm (0.86 in.) diameter were installed
through each of seven diaphragms in each span. Loadcells were attached to the dead end of each CFCC strand
to monitor the force level during the construction and inservice. Four externally draped post-tensioning CFCC
tendons with 40 mm (1.57 in.) diameter were installed ineach DT beam. The draping of these tendons was achieved

Inside of the bridge

Fig. 7— Penobscot Narrow Bridge.
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CASE STUDIES
using a specially designed tendon slide plate and tendonalignment shoe.
Most of the bridges constructed with CFCC in Michigan have been monitored with various sensors by Dr.
Nabil Grace’s research team at the Lawrence Technological University in Michigan, with a research contract from
the Michigan Department of Transportation (MDOT).
No signs of degradation, loss of force, or slippage werereported.

(4) Penobscot Narrow Bridge, Maine (2007)

The Penobscot Narrow Bridge, Maine’s first cablestayed bridge, was constructed between May 2003 andDecember 2006 (Fig. 7). The bridge, with twin pylons anda 2120 ft (646 m) span, uses an innovative cradle system
to carry the stays from the bridge deck through a pylonand back to the bridge deck. In each pylon, 20 stays run

Passing CFCC strand through a duct

Post-tensioning of CFCC strand using the same equipment as
steel strands
End of post-tensioning strands

Pembroke bridge over Southfield Freeway
Fig. 8—Pembroke Bridge.
24 December 2016 | PTI JOURNAL

Passing CFCC strand through a duct
Fig. 9—M-50/US-127 Highway over Norfolk Southern Railroad.

CASE STUDIES
through individual cradle systems. The unique design
features of the cable support and anchorage systems usedin this bridge permit the removal, inspection, and replacement of each cable strand while the bridge is in service.
It also present engineers with the opportunity to test avariety of cable designs and materials for their longevity
and performance in order to better serve the entire bridge
industry. The engineers at Maine DOT recognized this,and in June 2007, two epoxy-coated steel strands were
removed from each stay at stay numbers 2, 10, and 17 of
the north pylon. Two CFCC strands with a diameter of
15.2 mm (0.6 in.) were installed in their places instead.
CFCC strands were anchored by the engineers of the
manufacturer and installed successfully in the field. A
structural monitoring equipment system is installed on
CFCC strands to collect data and evaluate their performance for future cable-stayed bridges.

(5) Pembroke Bridge over Southfield Highway,
Detroit, MI (2011)

the side-by-side box beams. This bridge has two spans witha total length of 32.51 m (106.66 ft). Each span has sixteen
686 mm (27 in.) deep x 1219 mm (48 in.) wide box beams.
Box beams were prestressed with 12 low-relaxation steel
strands. Each span has six transverse diaphragms at which
one 37-wire 40 mm (1.57 in.) diameter CFCC strand wasused for transverse post-tensioning to ensure the integrityof the adjacent box beams.
CFCC strand was passed through a 152 mm (6 in.)diameter duct and was tensioned with a force of 685 kN(154 kip) at each diaphragm, which corresponds to 57% of1200 kN (270 kip) guaranteed breaking load. To monitor
the force level during construction and in service, the loadcells were attached to the dead end of each CFCC. The
bridge opened the service in December 2011. The monitoring system with sensors and load cells started in January
2012, currently in operation and will be continued until
September 2020.

Pembroke Bridge over Southfield Highway M-39 in
Detroit, MI (Fig. 8), was the first bridge using a CFCC
transverse post-tensioning system in the construction of

Post-tensioning of CFCC strand

Passing CFCC strand through duct

Side view of the bridge with the ends

Fig. 10—Little Pond Bridge.
PTI JOURNAL | December 2016 25

CASE STUDIES(6) M-50 Bridge, Jackson, MI (2012)

The M-50/US-127 Highway over Norfolk Southern
Railroad (Fig. 9) is the second side-by-side box beam
bridge using a CFCC transverse post-tensioning system.
This bridge has three spans, and each span is composed of
12 box beams with a depth of 533 mm (21 in.) and a widthof 1220 mm (48 in.). The exterior spans have a length of
9.14 m (30 ft) and the interior span has a length of 22.4 m(73.5 ft). There are six transverse post-tensioning cables
with a single 40 mm (1.57 in.) CFCC at exterior spans

Passing CFCC strand through a duct

Post-tensioning of CFCC strand

and eight transverse post-tensioning cables with a single
40 mm (1.57 in.) CFCC at the interior span. The initialtransverse post-tensioning force was 667 kN (150 kip) per
diaphragm. This bridge also has a monitoring system andthe data will be recorded until 2020.

(7) Little Pond Bridge, Fryeburg, ME (2012)

In the state of Maine, the corrosion of reinforcing
steel in concrete has been a constant problem and requires
expensive maintenance. This problem was raised due
to Maine’s coastal environment, harsh winters, and theuse of deicing chemicals on the roads and bridges. The
Maine DOT decided to use CFCC for the transverse posttensioning of the precast voided slabs on the Little Pond
Bridge, in the town of Fryeburg, ME (Fig. 10). After thebid was made, the project team decided to use five CFCC
tendons with a diameter of 40 mm (1.57 in.). In posttensioning CFCC tendons, the fabricator and contractor
can use the same equipment that they normally employ totension the conventional steel tendons. The polyethylene
sheathing was used to protect the CFCC strands.

(8) I-94 Bridges over Lapeer, Port Huron, MI (2014)

Michigan DOT has constructed two side-by-side box
beam bridges that carry the east- and west-bound I-94
Highway over Lapeer Road in Port Huron, MI (Fig. 11).
This is the first field application in which a CFCC transverse post-tensioning system was used in interstate
highway bridges. The east-bound bridge was completed
in 2014 and the west-bound bridge was completed 2015.
Each bridge has three spans with an exterior span lengthof 10.67 m (35 ft) and an interior span length of 28.65 m(94 ft), resulting in the total length of 50 m (164 ft). The
east-bound bridge is 17.6 m (57.7 ft) wide and is composedof 14 beams. The west bound is 18.8 m (61.7 ft) wide andis composed of 15 beams. The box beams in both bridges
have a depth of 840 mm (33 in.) and a width of 1220 mm(48 in.). The east-bound bridge is post-tensioned by 20
CFCC with 40 mm (1.57 in.) diameter with the force of
623 kN (140 kip) per diaphragm. The west-bound bridge
is post-tensioned by 20 CFCC with 40 mm diameter withthe force of 667 kN (150 kip) per diaphragm.

(9) I-10 New Orleans East Girder Repairs, Louisiana(2014)Side view of the Bridge with the ends of CFCC strands
Fig. 11— I-94 Bridges over Lapeer, Port Huron, MI.
26 December 2016 | PTI JOURNAL

Louisiana Department of Transportation andDevelopment (LaDOTD) identified the concrete girders
at Interstate 10 west- and east-bound bridges (Fig. 12) as

CASE STUDIES

Post-tensioning cable with load cellFig. 12—I-10 New Orleans East Girder Repairs, Louisiana.

Side view of the bridge and post-tensioning cable

Fig. 13— In hot spring areas, due to the strong acid-related environment, steel materials are unusable.

Fig. 14—Ground Anchor System.
PTI JOURNAL | December 2016 27

CASE STUDIES
being in need of repairs due to the corrosion of steel strands.
They selected the two worst bridges, one of which was I-10
Littlewoods, and decided to strengthen the current structures by external cables. One span is east-bound of I-10
Littlewoods, which has six girders that had been strengthened by CFCC with 17.2 mm (0.7 in.) diameter. Eachgirder has two CFCC external cables. The load cells were
installed to monitor the performance of the girders.

(10) Ground Anchor System

Conventional ground anchor systems have been
designed and used for slope stabilization and/or landslide
prevention, but have been degraded under the highly
corrosive environments, such as hot spring areas inJapan (Fig. 13).

The Ground Anchor System using the following newmaterials has been developed in 1993 (Fig. 14).
1. Carbon-fiber composite cable tendons
2. Fiber-reinforced foamed urethane (FFU) passive
plates3. (Epoxy resin) grout
To demonstrate the life of the newly developed groundanchor system, a 5-year long-term exposure test had been
performed from 2001 to 2006 (Fig. 15). Five years monitoring in the field had been done at a hot spring area withpH value in the 3 to 4 range and temperatures ranging from60 to 100°C (140 to 212°F). Conventional steel strands
and cement grout were deteriorated severely. However,
CFCC strands showed neither degradation in strength nor
visible defects. Fiber-reinforced foamed urethane passive

CFCC: No Deterioration

Exposure test and deterioration of sampled specimens at year 3
Steel strand: Crumbled by rustFig. 15—Exposure test of newly developed ground anchor system using CFCC.

Easy handling at the narrow space
Fig. 16—Installation of new ground anchor system using CFCC.
28 December 2016 | PTI JOURNAL

No water pollutionCASE STUDIES
plates maintained stable properties. The resin grout kept
its required compressive strength for design.
The new ground anchor system has been used in Japan
with the installation of over 80 projects (Fig. 16). The
benefits of the new Ground Anchor System are as follows:
1. No need for double protection due to the corrosion-free characteristic of CFCC.
2. 
No maintenance required for CFCC groundanchor system.
3. Eco-friendly and no water pollution as no greaseis used.
4. Workability in a limited area due to its light weight.
5. No need for heavy equipment such as a large-scalecrane.
As previously stated, the new ground anchor system
can be used for slope stabilization and/or landslide
prevention in strong acid-related environments. It can bealso used to strengthen the structures for seawalls in coastarea, ports/harbors, and dams.
Test setup

CFCC strands with pre-installed anchoring devices
Fig. 17—Research test configuration.

RESEARCH PROJECTThe University of Nevada, Reno, has done the research
project, the title of which is “Precast Square Column withUHPC in Plastic Hinge Zone and CFRP Tendons with
Pocket Connection to Footing.” Two CFCC tendons withdiameters of 34 mm (1.34 in.) were used to investigate
the effectiveness of CFRP tendons in minimizing residual
displacement (re-centering the column) under strong
earthquakes (Fig. 17). The initial post-tensioning force
was 289 kN (65 kips) per tendon corresponding to 24%of the guaranteed capacity. The maximum tensile stressof the tendons reached 64% of the guaranteed capacity of1200 kN (270 kips) during the test. The CFCC tendons
performed well as intended and eliminated the residual
drift during different levels of earthquake

Kenichi Ushijima: Plant manager, the new manufacturing
facility, Tokyo Rope USA Inc.
Tsuyoshi Enomoto: PhD, Vice President and Sales Engineer, Tokyo Rope USA Inc.
Noriaki Kose: Manager, CFCC Division, Tokyo Rope
Manufacturing Co. Ltd.
Yoshiaki Yamamoto: President and CEO, Tokyo Rope
USA Inc. and Deputy General Manager, CFCC Division,
Tokyo Rope Manufacturing Co. Ltd.
PTI JOURNAL | December 2016 29