**A Successful Beginning for Fiber Reinforced Polymer (FRP) Composite
Materials in Bridge Applications**

(Published in the FHWA Proceedings, International Conference on
Corrosion and Rehabilitation of Reinforced Concrete Structures, December
7-11, 1998, Orlando, FL.)

[AUTHORS]{.underline}:

Benjamin Tang, P.E. and Walter Podolny, Jr., Ph. D., P.E.

[ABSTRACT]{.underline}:

Corrosion decay has been a continued challenge for bridge engineers, but
a new material technology that delivered the stealth aircraft can
eliminate corrosion from our bridges. The high strength, high fatigue
resistance, lightweight, and corrosion resistance of composites are
highly desirable characteristics for bridge applications. Of more than
80 bridge projects using fiber reinforced polymer (FRP) composite
materials in the world, the U.S. has a modest beginning with 31
projects, 27 of which were built within the last 4 years. This paper
will focus on some of the initial successful bridge applications in the
U.S. using FRP composites. The discussions will also include the
advantages, characteristics, concerns, and future needs to advance the
composite technology into the civil infrastructure. These new materials
are applicable to both construction of new structures and maintenance
and rehabilitation of existing bridges. This is an exciting time for
civil and structural engineers to be involved with the FRP composite
technology. The FRP technology for civil infrastructures has
demonstrated some initial success. The current focus for the FHWA is to
advance the FRP composite technology to rebuild the American
transportation infrastructure in new bridge construction as well as to
rehabilitate and maintain existing bridges. The rebuilding of the
Nation=s highway system presents a tremendous market opportunity well
into the 21st Century.

[KEYWORDS]{.underline}:

(corrosion, corrosion resistance, fiber reinforced polymer composites
(FRP), bridges, durability, high performance materials, composites
technology, FRP bridge decks, reinforcing elements, cable, tendon,
laminates, concrete pier repairs, retrofit)

**Background in Nurturing New Technology**

Corrosion decay has been a continued challenge for bridge engineers.
Bridges constructed of steel members or reinforcements must be properly
protected for their long- term durability. When the Intermodal Surface
Transportation Efficiency Act (ISTEA) of 1991 was signed into law, it
had not only recognized the corrosion problem faced by our Nation=s
bridges but also provided Federal funding in bridge painting and the
application of calcium magnesium acetate (a noncorrosive deicing
salt)^(1)^. For 1997, ISTEA provided \$2.5 billion for the Highway
Bridge Replacement and Rehabilitation Program; the majority of the funds
were expended to replace or rehabilitate bridges caused mainly by
corrosion deterioration. When the States= matched and unmatched
estimated funds are included, the amount doubled to a staggering \$5
billion.

For new bridge deck construction, epoxy coated rebar has been shown to
provide durable corrosion protection and to prevent premature spalling
or corrosion-induced cracking on more than 20,000 bridge decks in
America. When both the top and bottom mats of rebar are epoxy coated, a
concrete reinforced deck can be expected to have a 50-year life. High
performance concrete with added corrosion inhibitors will further extend
the design life. Stainless steel reinforcement shows a potential
corrosion-free service life of 75 or more years. For existing bridge
decks that are both reinforced with black reinforcing steel and
contaminated with chloride ions, cathodic protection systems are
routinely used as a rehabilitation technique to extend their service
life.

In spite of the high success achieved in alleviating corrosion-induced
deterioration in newly constructed and rehabilitated existing
salt-contaminated bridges, there is still a need to evaluate new
technologies for bridges of the 21st Century. It is believed that the
space age technology that delivered the stealth aircraft can eliminate
corrosion from our bridges. The proposed solution is simply to use high
performance, nonmetallic materials in our bridges. These new breeds of
nonmetallic materials developed in the last 70 years are called fiber
reinforced polymer (FRP) composites. The most common fibers are made of
glass, aramid, and carbon. The resin matrixes that bind the fibers
together to form composites are those of the polyester, vinyl ester, and
epoxy groups. These composite materials have been applied in almost
every type of consumer, industrial, marine and military defense products
worldwide. The Composites Institute reported that the U.S. has consumed
more than three billion pounds of FRP composite products each year in
nine industrial markets since 1994^(2)^.

**FRP Composites in Civil Structures Are Gaining Momentum**

While the defense industry has taken this technology to new heights in
the development of the stealth aircraft, civil engineers are beginning
to gain confidence and experience in applying this technology to civil
structures. In October 1996, the Federal Highway Administration
organized and sponsored a scanning tour on advanced composites in
bridges to three select European countries and Japan. The purpose of the
tour was to assess the state-of-the-art in the use of composites in
bridge construction. The technical findings from the scanning team are
basically categorized into new bridge construction, strengthening of
existing bridges, and seismic retrofitting of bridge piers. The scanning
report states that the U.S. composite materials bridge technology has
developed concurrently with those of the world and is neither behind nor
significantly ahead of the countries visited^(3)^.

According to a data base recently compiled by the Composites Institute,
there are more than 80 bridge projects worldwide using FRP composites
materials^(4)^. The U.S. has a modest beginning with 30 projects, 26 of
which were built within the last 4 years. The remaining discussion in
this paper will focus on some of the initial successful bridge
applications in the U.S. using FRP composites. The discussion will also
include the advantages, characteristics, concerns, and future needs to
advance the composite technology into the civil infrastructure. These
new materials are applicable to both construction of new structures and
maintenance and rehabilitation of existing bridges. In new bridge
construction, the FRP composite materials may be used in the entire
structure (pedestrian and vehicular), or they could be used as
structural members or components.

**FRP Composite Materials for Bridge Applications**

The first pedestrian FRP bridge was built by the Israelis in 1975. Since
then, others have been constructed in Asia, Europe, and North America.
Many innovative pedestrian bridges have been constructed throughout the
United States using pultruded composite structural shapes which are
similar to standard structural steel shapes. Because of the light-
weight materials and ease in fabrication and installation, many of these
pedestrian bridges were able to be constructed in inaccessible and
environmentally restrictive areas without having to employ heavy
equipment^(5)^. Some of these bridges were flown to the sites in one
piece by helicopters; others were disassembled and transported by mules
and assembled on site. The advancement in this application has resulted
in the production of second generation pultruded shapes of hybrid glass
and carbon FRP composites that will increase the stiffness modulus at
very little additional cost. The recognition of providing high quality
fibers at the most effective regions in a structural member=s cross
section is a key innovation to the effective use of these high
performance materials.

With the knowledge gained from working with pedestrian bridges, many
researchers took the next step toward designing FRP composite vehicular
bridges. Many deck systems were developed and tested beginning in the
early 1990\'s. The first U.S. all-composite vehicular, public bridge was
placed in service on December 4, 1996 in Russell, Kansas. It was a wet
lay-up manufacturing method, a technology transfer from the defense
industry. The FRP deck panels were shop-fabricated with composite
honeycomb cells sandwiched between two face sheets. It took the Russell
County work crew one day to install the bridge superstructure. Since
then other demonstration projects using different geometrical variations
of fiberglass composite deck systems have been constructed in States
such as West Virginia, Delaware, Ohio, Idaho, Virginia, Maryland, and
New York.

FRP composites have a high tensile strength; however, in almost all of
the demonstration bridge projects constructed to date, the design has
been driven by the stiffness requirement rather than strength. There is
still much room for improvement and advancement of the composite deck
systems in order to capitalize on its material strength. The key to
successful application of the deck superstructure system is to optimize
its geometric cross section and to establish well-defined load paths.

Because most of these deck systems are sealed and enclosed, they are
inaccessible for field inspection. To ensure the composites= integrity,
sophisticated nondestructive evaluation/testing (NDE/NDT) devices and
fiber optic sensors have been incorporated into some of the composite
deck systems to monitor the in-service condition of and the presence of
moisture in the bridge deck. With time the effectiveness of the
monitoring systems and the long-term service performance of composites
can be ascertained.

The modular panel construction of bridge deck systems enable quick
project delivery. A bridge built of composite materials can be
constructed and put in service in a relatively short time and at a
competitive cost. Its lightweight materials and ease of construction
provide tremendous labor and traffic control cost savings to offset a
higher first cost. An FRP deck could reduce the weight of conventional
construction by 70 to 80 percent. This technology has demonstrated that
a bridge structure can be replaced and put into service in a matter of
hours rather than days or months. When a driver can cross a bridge on
his way to work the next morning without realizing that it has been
replaced the night before, it is innovative technology put to good use.

The FRP composites offer the potential to eliminate the problem of
excessive dead load of long span bridges. Structural components for
hybrid bridge construction such as FRP reinforcing elements, cable and
tendon systems, and laminates have been successfully demonstrated in
highway bridges. The reinforcing elements are fabricated into 1-D rods,
2-D grids or gratings, and 3-D fabric or cage systems. The University of
West Virginia has designed and built the first U.S. all FRP composites
reinforced concrete deck for vehicular traffic. Prestressing tendons are
another one-dimensional elements that has been successfully
demonstrated. Professor Grace of the Lawrence Technological University,
Southfield, Michigan, has demonstrated that the carbon fiber composite
prestressing tendons can be cost effective when combined with
conventional materials and can also be designed to perform in a ductile
manner^(6)^. Cable and tendon systems are subject to fatigue, and under
sustained loads will creep. Creep rupture is a major concern for glass
fibers. Proper selection of fibers and adequate design criteria must be
established to ensure the proper use of these products and are essential
to the advancement of FRP=s in prestressing applications. Laminates are
pultruded with unidirectional fibers to form thin and narrow plates. The
University of Maine determined that by adding about 2 percent FRP
laminate into timber glulam beams, the strength is increased by more
than 70 percent^(7)^.

There is much work to be done in developing well-designed anchorages,
connection details, and bonded joints in compsites for long-term
durability. Bridge engineers are reluctant to rely solely on epoxy
adhesive bonding technology to connect or join structural components.
Electrical transmission towers out West have been built with connections
that were snapped and locked together without the use of any fasteners.
It is a tough challenge, but when adequate testing and performance data
are available, bridge engineers will change their paradigm.

After the 1989 Loma Prieta earthquake, the California Department of
Transportation mounted an extensive testing and development program to
retrofit bridge piers using FRP composites. Having confirmed its
performance in the laboratory, fiber wrap, filament winding, and
pre-cured cylindrical half-shell systems were quickly developed, tested,
and accepted as alternates to steel jackets for seismic retrofit of
bridge piers in high seismic areas. Since then, thousands of concrete
bridge piers that were designed with inadequate ductility, lap splices,
and shear capacity have been successfully retrofitted using FRP
composite wrap systems. The University of California at San Diego has
determined that when a wrap system is properly designed and installed,
the ductile capacity can be significantly increased to allow twice the
deformation levels without any reduction in its capacity as compared to
the as-built bridge piers^(8)^.

These fiber wrap systems are also being used to repair deteriorated
concrete piers, pier caps, and damaged beams. Under a small-scale
research study, the FHWA repaired a damaged prestressed concrete girder
with carbon fiber sheets. The repaired girder was tested to a higher
capacity than that of the original girder. State highway departments
such as those in Georgia, Florida, South Carolina, and Utah have
successfully applied FRP composite materials to the repair of damaged or
deteriorated beams in highway bridges. With this application, the
condition of the deterioration in the concrete behind the composite
materials remains uncertain. A good repair program should include an
evaluation of the preexisting condition and structural integrity of the
concrete to establish a baseline reference. After a structural member
has been repaired, the in-service condition of the concrete substrate as
well as the performance of the composites should be continuously
monitored.

**Challenges and Technical Issues**

There are challenges with all new materials technology. Those challenges
mentioned above should not be viewed as barriers, but as opportunities
to study and improve the materials to ensure that the product will be
durable and reliable. The main concern with FRP composites is long-term
durability because the materials do not have sufficient historical
performance data in bridge applications. There is a concern among bridge
engineers for the long-term integrity of bonded joints and components
under cyclic fatigue loading. There are concerns with improper curing of
the resins and moisture absorption and/or ultraviolet light exposure of
composites that may affect the strength and stiffness of the structural
system. Certain resin systems are found ineffective in the presence of
moisture. In the case of a glass fiber composite, moisture absorption
may affect the resin and allow the alkali to degrade the fibers.

The high strength, high fatigue resistance, lightweight, and corrosion
resistance of composites are highly desirable characteristics for bridge
applications. Currently, these new materials are a direct technology
transfer from the aerospace industry, and they are far more advanced
than those required by civil applications. Most of the advanced
composite materials that are cured at high temperature produce high
quality components and possess excellent characteristics. In bridge
applications, resins as the binders for the fiber and adhesives for
joints and connections that can adequately cure at ambient temperature
and still offer comparable quality and characteristics are more
desirable and practical. More research is needed to develop the most
effective and durable resin formulations. More efficient manufacturing
and effective production methods for large volume panels and higher
modulus materials are needed to make it more cost effective for
composites to compete in the civil infrastructure. At the present time,
the direct use of fiber composites from the aerospace industry is not
cost effective as compared to conventional materials in bridge
applications.

**New Structural Concepts Using FRP Composites**

More than 25 years ago, a paper^(9)^ was published in Finland that
addressed the feasibility of elevated tubular tunnel highways utilizing
advanced materials such as high-strength steel, high-strength concrete,
and plastics, materials that are currently available or being developed.
A tubular bridge constructed of composite materials would protect the
environment from traffic and the traffic from the environment. Safety
would be increased because the roadway surfaces would be kept dry and
free of fog and ice at all times. Maintenance would be reduced because
snowplowing and deicing chemicals would not be required.

The tubular monocoque bridge girder would have greater stiffness as a
result of its large moment of inertia. Its elliptical cross section
would be reasonably aerodynamically advantageous. Traffic within the
enclosed tube would be unaffected by wind gust on the vehicles. A
tubular highway could be constructed of successive suspension spans of
1,000 to 1,500 meters (3,000 to 5,000 feet).

Another advancing tubular highway concept in recent years is that of the
submerged floating tunnel, or Aunderwater bridge.@ A number of proposals
have been made for environmentally sensitive projects applying this
concept in Norway, Italy, Japan, and Switzerland. The concept is simply
a tubular superstructure that is sufficiently submerged under water to
provide adequate clearance for marine vessels to pass over it. Support
for the superstructure would be provided by underwater piers at
appropriate spacing, or alternatively, the superstructure could be
anchored to the bottom of the lake or sea by cables.

**Exciting Times for Civil and Structural Engineers**

This is an exciting time for civil and structural engineers to be
involved with the FRP composite technology. Although most engineers are
not trained to work with fiber and resin composite materials, they can
quite easily pick up the knowledge. Education and training should be
provided to the critical mass of practicing engineers. Research studies
and results of the composite technology and its durability should be
published in civil and structural engineering journals. Technical papers
should be presented in conferences and workshops where civil and
structural engineers participate. Until recently, most of the papers
have been published in the materials science and testing, manufacturing
and trade journals, which are not read by bridge designers. Information
and knowledge must be openly shared with civil engineers, bridge
designers, and owners. Professional organizations should be dedicated
and/or established to direct the technical advancement of the composite
technology if it is to have a future.

There is still more work needed in material science development and
production. Design and construction specifications are important
protocol for engineers, and they need to be developed. Bridge owners
must know how to inspect, maintain, and repair FRP composite bridges and
these procedures must be established.

We need to involve more knowledgeable and experienced engineers to help
develop standards, design guidelines, and specifications. When we have
an approved design standard specifications for FRP composites, the FHWA
anticipates that the FRP composite technology will launch the U.S. into
a new era in bridge construction and rehabilitation.

**Opportunities for Rebuilding the American Transportation
Infrastructure**

The FHWA, for the past 20 years, has researched and confirmed the use of
FRP composite technology as a potential bridge building material. The
FRP technology for civil infrastructures has demonstrated some initial
success. The current focus for the FHWA is to advance the FRP composite
technology to rebuild the American transportation infrastructure in new
bridge construction as well as the rehabilitation and maintenance of the
existing bridge inventory. The rebuilding of the Nation=s highway system
presents a tremendous market opportunity well into the 21st Century.

**References:**

1\. AThe Status of the Nation=s Highway Bridges: Highway Bridge
Replacement and Rehabilitation Program and National Bridge Inventory,@
Thirteenth Report to the U. S. Congress, Federal Highway Administration,
Washington, D.C., May 1997.

2\. Lindsay, Karen F., AState-of-the-Industry: 1995-1996,@ Composites
Design and Application Journal, pp. 12-16, SPI Composites Institute, New
York, February 1996.

3\. AAdvanced Composites in Bridges in Europe and Japan,@ Report of FHWA
Study Tour, December 1997, p. 135, Federal Highway Administration,
Washington, D.C.

4\. AA Look at the World=s FRP Composites Bridges,@ A publication of the
Market Development Alliance, SPI Composites Institute, New York, 1998.

5\. Eric Johansen, et. al., ADesign and Construction of Two Pedestrian
Bridges in Haleakala National Park, Maui, Hawaii,@ Proceedings,
Fiberglass-Composite Bridges Seminar, 13th Annual Bridge Conference and
Exhibition, Pittsburgh, PA, June 3, 1996.

6\. Grace, N. & Sayed, G., ADuctility of Prestressed Concrete Bridges
Using Internal/External CFRP Strands,@ presented at the Scotland
Conference on Composites, Scotland, July 1997.

7\. Dagher, H., et al., ACenter for Advanced Engineered Wood Composites
in Construction: Research and Demonstration Projects,@ Proceedings,
International Composite Expo \>98 Conference, Nashville, TN, January
1998.

8\. Sieble, F.; et. al., ASeismic Retrofitting of Squat Circular Bridge
Piers with Carbon Fiber Jackets,@ Report No. ACTT-94/04, November 1994,
pp. 12-20, University of California at San Diego.

9\. Simonsén, B., J. Sulkiewicz, & J. Virola; ASillanrakennuksen
Tulevaissuudennäkymiä \[Future Aspects of Bridge Construction\],@
Rakennustekniikka. Helsinski, 1972.

**Biographies**:

Benjamin Tang received a B.S.C.E. from the University of Maryland and a
M.S. in Structural Engineering from the University of Illinois at
Urbana. He is a registered professional engineer in Maryland. He has
been with FHWA since 1977 and serves in the Bridge Division, Office of
Engineering, as the technical expert and review authority for all
structural matters in the Federal-aid bridge program. His work
experience includes many long span bridge projects such as cable-stayed,
tied arch, steel truss, segmental concrete structures, and movable
bridges. Currently, he is actively pursuing the use of high performance
materials technology for bridge applications.

Walter Podolny, Jr. has been with the Bridge Dvision, Office of
Engineering, FHWA, for the past 27 years. He is a registered
professional engineer in four States and a Fellow of the American
Society of Civil Engineers and the American Concrete Institute. Dr.
Podolny is the author or co-author of over 75 technical papers, reports,
and articles; including the books, AConstruction and Design of
Cable-Stayed Bridges@ and AConstruction and Design of Prestressed
Concrete Segmental Bridges.@ Both books are published by John Wiley &
Sons and have been translated into Japanese and the latter into Chinese.

He has served as an advisor to the Kuwait Ministry of Public Works, as a
member of the Governor=s Board of Inquiry on the 1989 Loma Prieta
Earthquake, and as Chairman of an International three-man design review
panel for the Yangpu Bridge in Shangai, China. He has also provided
technical assistance to the Mayor of Guatemala on the Incienso Bridge
and is the receipient of the Secretary of Transportation=s Silver Medal
for Meritorious Achievement.