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					Conference Session #B6                                                                                                Paper # 1115


     FIBER-REINFORCED POLYMERS USED IN BRIDGE CONSTRUCTION
                       Garrett Swarm (gss18@pitt.edu) and James Reist (jhr11@pitt.edu)

Abstract -Throughout the United States there are many                 dropped only two percent. Considering these statistics an
bridges that are either functionally or structurally deficient.       estimated $90 billion is needed to reverse this trend. FRP
Fiber-reinforced polymer (FRP) technology is a new                    technology offers a means to extend the life span of existing
emerging technology and its application in the construction           bridges, essentially slowing the need for repairs and thereby
industry is gaining support, including the utilization of FRP         reducing the total number of deficient bridges [2].
materials to build and strengthen existing bridges. FRPs are
very resistant to corrosive agents and harsh weather                                 MATERIAL DESCRIPTION
conditions. Incorporating FRP materials into bridge
construction can extend the life span of the bridge. FRPs             FRPs are a new technology that has been emerging over the
have a very high initial cost which has slowed the                    last decade. FRPs are a corrosive resistant composite
development process. However, as applications and                     material that can be used to strengthen or replace steel and
experience grow production costs will decrease. Despite the           concrete materials [3]. FRPs possess unique characteristics
high initial cost, many experts agree that combining FRP              that steel and concrete lack. These characteristics include
technology into bridge construction will help improve the             lightweight, high strength to weight ratio, high impact
efficiency of the bridge, extend its operational life and             strength, long term durability, resistance to corrosive agents,
reduce long-term costs. In the future FRP bridges will                and a low coefficient of thermal expansion. FRPs, if used in
become more cost-effective than bridges made with                     combination with traditional materials, can save money and
conventional materials.                                               make bridge repairs stronger and much more efficient [2].
                                                                      Currently, FRPs are more expensive than steel and concrete.
Key Words - CFRP, Externally bonded FRP plates, Fiber                 The lower overall costs associated with the use of FRP
Reinforced Polymer, GFRP, Innovative bridges, FRP                     materials are primarily a function of reduced installation,
                                                                      repair and maintenance costs along with the extended life
                WHAT IS THE PROBLEM                                   span of the structure constructed using FRPs. There are two
                                                                      types of the material, Glass Fiber Reinforced Polymers
Many bridges in the United States are structurally deficient.         (GFRP) and Carbon Fiber Reinforced Polymers (CFRP).
Generally, the deficiencies identified in most bridges are not        CFRP are the strongest type of FRP. Despite the fact that the
a result of poor construction techniques, but instead are a           two types have many similar benefits and qualities, they also
result of deterioration and operation beyond the bridge’s life        have characteristics that make them unique, such as
expectancy. Bridge statistics in North Carolina parallel              elasticity and tensile strength. GFRP has a modulus of
trends observed at a national level. Approximately thirty-one         elasticity and tensile strength of 6 million psi and 90 ksi,
percent of the 17,000 bridges evaluated across the state were         respectively, while CFRP is 19 million psi and 300 ksi,
determined to be either structurally or functionally deficient        respectively. Aside from the many positive qualities that
[1]. Structurally deficient refers to the bridge’s structure          FRP materials possess, they mostly began to be developed in
becoming weakened or faulty. This occurs most often as a              response to the need for a corrosive resistant material for
result of deterioration and continued operation beyond the            bridge construction [3]. A common cause of bridge failure is
bridges expected life span. If a bridge is said to be                 deterioration of concrete and steel components resulting
functionally deficient, it is referring to the bridge being           from exposure to chlorides and other corrosive substances.
incapable of performing a task for which it was designed.             Bridges that are exposed to road salts or are located in
For example, if a bridge was built to transport materials             coastal regions have significantly shortened life spans as a
across a body of water, but the bridge could not support the          result of these corrosive effects. Figure 1 depicts a
weight of a truck, it would be considered functionally                decreasing exposure to chlorides as the distance from the
deficient. Functional deficiencies are also commonly caused           coast is increased. The bridges most affected in coastal areas
as a result of the bridge being used past the life expectancy.        are in the range of zero to one kilometer from the coastline.
These types of bridges are often posted with a sign                   As the distance reaches three kilometers the effects of the
designating a reduced weight limit. The primary reason for            coastline are nearly eliminated. Figure 2 depicts the chlorine
the high percentage of deficiencies is simply because our             content present in the bridge over time. As shown in the
bridges are approaching the end of their expected life span at        figure, the effects from the chlorides resulting from de-icing
a rate faster than they are being repaired or replaced based          salts are much worse than the effects resulting from coastline
on current spending. In 1996, federal funding for bridge              proximity. Fick’s second law of diffusion explains how the
repairs and replacements was increased from $16.1 billion to          chlorine content in Figure 2 would be calculated as seen in
$20.4 billion in an attempt to reverse this trend. Four years         equation one.
later, in 2000, the percentage of deficient bridges had

University of Pittsburgh                                                                         Swanson School of Engineering
Eleventh Annual Freshman Conference                                                                               April 9, 2011
                                                                  1
                                                                                                     Garrett Swarm, James Reist


                 (dC/dt) = D(d2C/dx2)                               million tons. However, this increase in the market is for the
                         (Equation 1)                               entire composite industry so it isn’t a result completely from
                                                                    bridge materials. [2].
An explanation of equation one is as follows: C represents
the chloride ion concentration, t represents the number of                                COST ANALYSIS
years of exposure, x represents the distance from the surface       To accurately compare the cost of FRPs versus traditional
of the material, and D represents the diffusion coefficient         construction materials the materials should not be compared
[4].                                                                strictly on an initial cost basis. Due to the high initial cost of
       Chlorine Effects vs. Distance from Coastline                 FRPs, other less immediate costs need to be taken into
                                                                    consideration in order to make an accurate cost comparison.
                                                                    Specifically, FRPs are lightweight materials only about two-
                                                                    thirds the weight of steel. This lightweight characteristic can
                                                                    translate into lower transportation costs and shorter
                                                                    installation times decreasing overall construction costs [2].
                                                                    With respect to bridge construction, the strength and
                                                                    resistance to corrosive agents of FRPs increase the life span
                                                                    and also reduce the amount of maintenance and repairs
                                                                    required to keep a bridge in working condition. Both of these
                                                                    benefits decrease the long-term costs associated with the
                                                                    bridge [2]. Although FRPs have many positive long-term
                                                                    benefits, the high initial cost of the material cannot be
                                                                    ignored and can limit the extent to which these materials can
                                                                    be integrated into a project. FRPs are still a developing
                                                                    technology and similar to any new product that is mass
                                                                    produced; as the market continues to grow the production
                                                                    cost decrease over time. This analysis can be described by
                                                                    the learning curve approach. Figure 3, a learning curve,
                        Figure 1 [4]
                                                                    depicts a decreasing cost per unit as production experience
                                                                    increases. The learning curve can be described by the
                     Chlorine Content
                                                                    equation two.

                                                                                              y = a(ί -b)
                                                                                               (Equation 2)

                                                                    An explanation of equation two is as follows: ί represents
                                                                    the production count, y represents the labor hours required to
                                                                    reach ί, a represents the labor hours required to produce the
                                                                    first unit, and b represents the measure of the rate of
                                                                    reductions (0<b<1) [2].

                                                                                           Learning Curve

                        Figure 2 [4]

A widely accepted corrosion limit for chloride content is 0.5
kg/m3. If not maintained to prevent chloride exposure,
bridges like the Chatham County Bridge in North Carolina,
which had a chloride content of 2.1 kg/m3 in some areas,
become susceptible to an accelerated rate of structural
deterioration [1]. Utilizing FRP materials for bridge
maintenance not only repairs the bridge, but also increases
its life span based on the material’s resistance to corrosive
agents. Expanding sales in the FRP market suggests a
growing interest in this new technology. From 1970 to 2000,
the FRP composite market grew from 360,000 tons to 1.68                                       Figure 3 [2]
University of Pittsburgh                                                                        Swanson School of Engineering
Eleventh Annual Freshman Conference                                                                              April 9, 2011
                                                                2
                                                                                                    Garrett Swarm, James Reist


The two types of FRPs, previously referenced, GFRP and               stated earlier, GFRP has a modulus of 6 million psi and
CFRP are both expensive compared to steel. GFRP is                   CFRP has a modulus of 19 million psi. GFRPs modulus is
approximately four times the cost of steel. CFRP cost                very low which makes the material very elastic compared to
approximately twenty times the cost of steel [3]. Based on           steel. As a result, cracks that develop in the material will
the high initial cost of FRPs, and the estimated $90 billion         widen because of the material being more flexible. On the
already necessary to address existing bridge repairs, it is          other hand, GFRPs modulus is much more similar to steel
impractical to believe that FRPs will completely replace the         giving it a more firm structure. On an elasticity basis, a
use of traditional construction material in the near future.         logical and cost-effective way to integrate both types of
However, utilizing a combination of traditional materials            FRPs into bridge construction is to use GFRP as the main
and FRPs to rehabilitate existing bridges is a very plausible        material and apply CFRP in spots of high stress. This
solution to the national problem and a basis to start                combination will work well for rehabilitation; however, in
integrating FRPs into new bridge construction.                       the future if entire bridges are constructed entirely out of
     In 2002, the Chatham County Bridge in North Carolina            FRPs this combination will still prove to be cost-effective.
was inspected and determined to be in need of immediate              The tensile strength of FRPs compares to steel a bit
repairs. Bridge replacement was estimated at a cost of 2             differently. Steel has a tensile strength of 60 ksi. As stated
million dollars and would have disrupted traffic for years.          before, the tensile strength of GFRP is 90 ksi and CFRP is
Alternatively in 2003, the bridge was repaired to its original       300 ksi. For this material characteristic both types of FRP
strength in less than thirty days utilizing FRPs for only            are stronger than steel and CFRP is approximately five times
$120,000 [1]. Despite the high initial material cost this            as strong [3]. From these statistics, Vellore Gopalaratnam, a
example demonstrates the cost benefit that can be attained           professor at the University of Missouri, determined that the
utilizing FRPs. This example also demonstrates the quick             higher strength and higher flexibility of FRPs would make a
installation time of FRPs.                                           better material design then that of steel [3].
     Traditional bridges have an average initial construction             Plate end debonding is one method that uses FRP to
cost of approximately $430/m2. The initial production cost           repair structurally deficient bridges. During this
for FRP materials is estimated at approximately $750/m2.             rehabilitation, externally bonded plates are used to repair the
While the initial costs of FRP bridges are high, their life          outer parts of bridge decks and columns. Using FRP to
expectancy is also longer. Bridges constructed of traditional        repair existing bridges allows a smaller portion of the
materials such as steel and concrete have a life expectancy          material to be purchased while still receiving benefits from
of about forty years while FRP materials are predicted to            the FRP. Externally bonded plates have become popular
have a life span of approximately sixty years [2]. These facts       over the last decade. This new technique is a suitable
further support the premise that FRP materials have value in         solution that will lower the cost of repairing bridges and
the market and cannot be judged solely on an initial price           decrease the deficiency percentage. In addition, FRPs exhibit
basis. The real challenge of the innovative FRP technology           features that would make decreasing the deficiencies cost
is to be able to produce the material at a price that is cost        much less. However, without precise accuracy of
competitive with traditional materials [2]. Once price is no         measurements the FRP plates will fail. There are several
longer a factor, FRP materials will clearly be the material of       different ways the externally bonded plates can fail.
choice.                                                              Concrete cover separation occurs at a plates end when
                                                                     concrete is torn from the bridge while it is still attached to
         INTEGRATING FRP INTO BRIDGES                                the FRP plate. Critical diagonal crack (CDC) debonding
                                                                     becomes a problem when a diagonal crack occurs a small
The largest obstacle for FRP technology to overcome is its           distance from the plates ends which results in the plate end
high cost compared to traditional construction materials.            detaching. Plate end interface debonding occurs at a plates
FRPs possess many very desirable qualities, however, the             end when the concrete becomes unattached from the FRP
cost frequently limits the amount of material that can be            plate. This type of failure consists of vertical cracks and can
incorporated into a project. As applications and experience          prove to be fatal to the bridge if the debonding moves a far
grow production costs will decrease. GFRPs and CFRPs                 enough distance along the plate [5]. Figure four shows
elasticity and tensile strength compare to steel in different        examples of what the different failures resemble.
ways. Steel has a modulus of elasticity of 29 million psi. As




University of Pittsburgh                                                                        Swanson School of Engineering
Eleventh Annual Freshman Conference                                                                              April 9, 2011
                                                                 3
                                                                                                     Garrett Swarm, James Reist




                         Figure 4 [5]                                                        CASE STUDY

An interesting aspect that emerges from this type of                  In West Virginia, the West Virginia Department of
rehabilitation is that each failure occurred as a result of the       Transportation at West Virginia University and private
concrete failing. Concluding that the failures all occurred in        industry worked together to construct two short span bridges
concrete suggests that the FRPs are very strong.                      made completely of FRP material. The new FRP bridges
Hypothetically, a bridge made entirely of FRP material                were constructed to replace old timber bridges which were
should be very stable and long lasting.                               due for replacement. The FRP, which was selected to
     Bridges that are repaired with FRP materials will begin          construct the deck of the bridge, was lightweight,
to have increased life spans because of the resistance to             noncorrosive and had a high stiffness to weight ratio. The
corrosive agents [2]. Using FRP materials for rehabilitation          weight of the material allowed for relatively easy installation
is a continuous process of lowering the number of deficient           compared to traditional materials and because of its light
bridges across the country at a decreased price. However,             weight; the installation of the bridge required less heavy
this process is slow due to how innovative the FRP                    equipment. Lopez-Anido, a research assistant professor at
technology is. As of 1998, there were only eighty bridges in          West Virginia University, commented on the installation
the entire world that utilized FRP materials [2]. Many of             time of the FRP bridge stating, "It took five and a half hours
these deficient bridges have structural problems involving            to install the bridge from the time it was downloaded from
their supports. It is difficult to effectively solve the bridge       the truck until the deck modules were installed, bonded and
problem with traditional materials because there is no                bolted [6]." Short span bridges on average are about ten
resistance to corrosive agents. As a result of the lack of            meters long. Despite the small size, the bridge still cost
resistance, the life span is only extended until the corrosion        around $72,000 to construct entirely of FRP materials.
effects return. Utilizing FRP externally bonded plates repairs        Donald L. Williams, the Assistant District Engineer of
the bridge and also makes it resistant to corrosive agents            construction at West Virginia Department of Transportation,
extending the repair life span even further. In the future, if        Division of Highways, stated that the price of FRP materials
all bridges that are damaged by corrosion as a result of              are expected to drop as the technology catches on. Mr.
chlorine from road salts or in coastal regions of the country         Williams’ statement is supported by and consistent with the
are repaired with FRPs, bridges will last longer. As bridges          graphical representation of this statement in Figure 3 [6].
start to have increased life spans while having fewer repairs         The Mill Creek Bridge is another example of FRPs being
needed to be made to them during the course of their life             utilized for rehabilitation. The Mill Creek Bridge is located
spans resulting in reduced amounts of money needed for                near Charlotte, North Carolina in Union County. During the
upkeep of these bridges in the future. In addition, the money         repair of the bridge, the deck was replaced entirely with
that is saved can be utilized to repair other bridges in a            GFRP material. The deck of the bridge was tested and
similar manner.                                                       observed under several different situations. After these tests,
                                                                      Greg Perfetti, a state bridge design engineer, concluded that
                                                                      FRP decks “have proven to be a viable, lightweight,
                                                                      corrosion resistant alternative to conventional reinforced
University of Pittsburgh                                                                         Swanson School of Engineering
Eleventh Annual Freshman Conference                                                                               April 9, 2011
                                                                  4
                                                                                                       Garrett Swarm, James Reist


concrete decks, and the ease with which it can be placed                                      CONCLUSION
fulfills the need for structural options that minimize the
impact on the motoring public [1].” Greg Perfetti’s                    FRP materials are an innovative new technology that has
observations moved FRP technology one step closer to                   been developing over the last decade as a viable solution to
creating a large scale operational bridge entirely out of FRP          lower the percentage of deficient bridges in the nation and to
materials.                                                             control costs. Compared to steel, FRPs have a high initial
                                                                       cost however, they also possess unique characteristics that
               FUTURE OF FRP BRIDGES                                   steel and concrete lack. Two of the most beneficial
                                                                       characteristics of the FRP material include their superior
As discussed earlier in the paper, FRP materials are a new             strength and their resistance to corrosive agents such as
technology. As with nearly all new technologies it takes time          chlorides. These two characteristics in particular can be
before they catch on and potential users fully appreciate their        utilized to extend the operational life span of bridges. It is
application and integration into the general market. Over the          these unique characteristics that allow FRPs to remain cost
past ten years FRP materials have been used more frequently            competitive with traditional materials in the market place.
to repair damaged bridges across the country. One of the               As FRP materials become more developed and production
reasons that FRPs are taking so long to catch on as a viable           costs decrease, it will become much easier to justify the use
means to repair or replace bridges is the high cost to produce         of these materials in future projects. Smaller scale bridges
the materials. According to Roberto Lopez-Anido, a research            have been constructed completely out of FRP materials and
assistant professor at West Virginia University, "If we could          have proven to be very strong. Ideally, full utilization of
achieve mass production, it would bring down the cost and              FRP materials would make the strongest, longest lasting
we could have many other states interested in this system as           bridges, however, until the production cost are reduced this
well[6]”. As more users start to accept FRP materials and              remains impractical for large scale construction. Until
realize how positive the benefits are regardless of the initial        production costs are reduced the utilization of a combination
cost, the price will begin to moderate. As costs moderate the          of FRP and traditional materials appears to be a practical
material will eventually settle into a price range where it will       solution to reduce the overall percentage of deficient bridges
become realistic and economical to utilize FRP materials to            in the nation.
construct entire bridges. This applies primarily to building
bridge decks. There are several bridges made completely of
                                                                                            SUSTAINABILITY
FRP material in existence today. At this time, these
experimental bridges cover only short spans ranging from
approximately 5 to 15 meters in length. Creating these                 Sustainable can be defined as the ability to maintain a
smaller scale bridges allow engineers to study qualities and           certain rate or level of something over a period of time.
characteristics that only FRP material bridges possess.                Sustainability is a different root of this word, but it means
     In the future an ideal model for a completely FRP                 the same thing. FRPs when used in construction of bridges
bridge would be to construct the complete structure out of             are a sustainable material in several different ways.
CFRP materials, which are the strongest types of FRP on the                 When dealing with the sustainability of FRP materials
market today. Currently, this is impractical because of the            in bridges, there are two main areas that can be looked into.
high cost associated with the material. For a FRP bridge               First is the financial sustainability of the bridge. This
built in the near future, before prices drop, the most                 includes all of the costs over the bridges expected lifespan
economical model would probably include the use of both                including: material costs, constructions costs, maintenance
CFRP and GFRP materials. In general the bridge would be                costs and installation costs. Over the course of a FRP
built with the GFRP, while areas that will come under the              reinforced bridges life span, the bulk of the cost is during the
most strain will be strengthened with the stronger Carbon              construction of the new bridge, or the rehabilitation of the
FRP.                                                                   damages bridge. After this large initial cost the bridge
     It is likely that bridges made entirely of FRP will be            becomes very financially sustainable because FRP
used in the future because of the significantly shorter                reinforced bridges are very resistant to chlorides, which
installation time compared to traditional bridges. For                 deteriorate traditional bridge materials.        The financial
example, if a natural disaster destroys a bridge, it would take        sustainability of FRP bridges is one of their great aspects
several months or years to replace this bridge. Instead,               because FRP bridges cost much less to maintain after their
replacing the structure with an FRP bridge could prove to be           construction [2].
convenient because it would require significantly less time                 The second area of sustainability that needs to be looked
to have the new FRP bridge installed than to construct a               at is environmental sustainability. The FRPs used in the
traditional.                                                           construction of bridges are not dangerous to the
                                                                       environment. However the way that they are the most
                                                                       environmentally sustainable is that they take so little time
                                                                       and machinery to install. When constructing a traditional
                                                                       concrete bridge in a rural area, much of the surrounding area
University of Pittsburgh                                                                           Swanson School of Engineering
Eleventh Annual Freshman Conference                                                                                    April 9, 2011
                                                                   5
                                                                                    Garrett Swarm, James Reist


is destroyed and the natural ecosystem is disrupted because
of all the heavy machinery need to transport and install the
traditional materials. When dealing with FRPs much less
heave machinery s needed to transport and install the
materials. As a result of less machinery being needed for
installation, bridges can be built and rehabilitated in harder
to access areas. Since FRPs are much faster to install the
natural ecosystem and environment are disturbed less than
with traditional concrete bridges [6]. This makes FRP
environmentally sustainable, because they disrupt the natural
habitat less than the construction and repair without the use
of FRPs in traditional bridges.
     Overall FRPs are financially and environmentally
sustainable because they will cost less in the future to
maintain and don’t destroy the environment in the present
when being installed. In the future these qualities will
become increasingly important, as costs rise and more of
earth’s natural nonrenewable resources are depleted.


             ACKNOWLEDGEMENT SECTION
The authors greatly appreciate the help received from our
chair and co-chair members, Dr. Budny, Heather McCoy,
and the library assistants.

                      REFERENCES SECTION
[1] Rochelle, Rodger D. "Coposites Add Longevity to Bridges." Public
Roads (2003): 28-31. Print

[2] Nystrom, Halvard E., Steve E. Watkins, Antonio Nanni, and Susan
Murray. "Financial Viability of Fiber-Reinforced Polymer (FRP) Bridges."
Journal of Management in Engineering 19.1 (2003): 2. Print.

[3] Hansen, Brett. "Researchers Combine FRP Reinforcements in Bridge
Decks." Civil Engineering June 2005: 32. Print.

[4] Stewart, Mark G., and David V. Rosowsky. "Time-dependent Reliability
of Deteriorating Reinforced Concrete Bridge Decks." Structural Safety 20.1
(1998): 91-109. Print.

[5] Yao, J., and J. Teng. "Plate End Debonding in FRP-plated RC Beams—
I: Experiments." Engineering Structures 29.10 (2007): 2457-471. Print.

[6] "First fiber-reinforced polymer bridges." Civil Engineering
(08857024) 67, no. 8 (August 1997): 10.Academic Search Premier,
EBSCOhost (accessed January 28, 2011).

[7] Cheng, Lijuan, Lei Zhao, Vistasp M. Karbhari, Gilbert A. Hegemier,
and Frieder Seible. "Assessment of a Steel-Free Fiber Reinforced Polymer-
Composite     Modular      Bridge     System." Journal    of    Structural
Engineering 131.3 (2005): 498. Print.




University of Pittsburgh                                                         Swanson School of Engineering
Eleventh Annual Freshman Conference                                                               April 9, 2011
                                                                             6

				
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