ComPile® Technology and Services
The highway system represents a significant level of national investment. Since
the early 1950's, the federal government has invested over $1 trillion in highways.
Sate highway agencies are now faced with a major challenge of keeping this investment
in working condition. Premature deterioration and structural deficiency are the
two major problems that plague the infrastructure. These problems are intensified
with excessive loading caused by natural hazards such as earthquakes. Corrosion
protection measures such as epoxy coating of reinforcing steel have not been successful
over long periods of time in severe environments. At the national level, over 40%
of bridges are classified as structurally deficient or functionally obsolete. Even
newer bridges have shown a growing rate of premature decay.
A major effort is now underway to rebuild the nation's infrastructure. The Federal
Highway Administration (FHWA) estimates that over $212 billion will be needed to
eliminate the current deficiencies in bridges and to maintain the current repair
levels. Hence, it is vital to the U.S. economy that cost-effective structural systems
and materials be explored in order to extend service life, and to improve performance
of infrastructure facilities.
In recent years, FRP composites have emerged as a potential solution to problems
associated with the infrastructure. Resistance to electro-chemical corrosion, electro-magnetic
insulating properties, high strength-to-weight ratio, and versatility of fabrication
has made FRP materials attractive to civil engineers. FRP is less susceptible to
environmental deterioration than steel. In example, FRP does not deteriorate in
the presence of road salts that shorten the life of conventional structures. Therefore,
maintenance costs are expected to be significantly lower than conventional structures
| FRP laminates have strength-to-weight ratios up to 50 times that of concrete and
18 times that of steel. The lightweight mass of FRP makes the construction easy,
fast and with minimal manpower and equipment. The low dead weight further allows
a reduction in structural cross-section or an increase in the live load capacity
of the structure. The versatility of fabrication manifests itself in the ability
of optimizing the geometry, strength, stiffness and durability characteristics of
an FRP structural system for a particular application. |
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The most effective use of FRP materials is in the form of composite or hybrid construction
with concrete, in which FRP is the load-carrying partner and protective measure
for concrete. The main advantage of ComPile is in the optimal use of materials based
on their cost, mechanical properties and resistance to corrosive environments. It
also results in members with ductile characteristics, high strength and stiffness.
The tube has a constructional role as the stay-in-place pour form for concrete,
a structural role as the sole reinforcement for the concrete core, and an environmental
role as a protective jacket against moisture intrusion. Restrictive requirements
on concrete piles in salt or brackish water have made ComPile?a potential alternative
to concrete piles by eliminating formwork, reinforcing cage and the additional corrosion
protective cover.
| Experiments have shown that concrete-filled FRP tubes can outperform reinforced
concrete (RC) and prestressed concrete (PC) columns. A 7" square section with a
ribbed angle-ply E-glass FRP tube was comparable to an equivalent RC column with
at least 5% conventional steel reinforcement. Also, a 13.7" diameter section with
off-the-shelf E-glass FRP tube and only 0.55" wall thickness proved as strong as
a 23" diameter concrete column with twenty 1/2" diameter prestressing strands of
Grade 270 ksi steel. |
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| A total of sixteen 9-ft long specimens were tested under various combinations of
axial and lateral loads in order to prove effectiveness of the system. The research
resulted in a thorough understanding of confinement behavior, slenderness issues
and shear capacity of the system. |
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| Long-term behavior of the system has shown lower creep and shrinkage of the concrete
core in comparison with ordinary concrete. The research has also developed a design
program for concrete-filled tubes under combination of axial and lateral loads.
Nondestructive inspection tools with acoustic emission and ultrasonic pulse velocity
techniques have also been developed for the system. |
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As part of a study for the Florida Department of Transportation, a number of concrete-filled
FRP tubes were driven. Field tests showed the composite piles to be a feasible alternative
for bridge substructures. No damage was observed at the top of the filled tube,
nor in the tube-concrete interface. The work was presented at the 80th annual meeting
of the Transportation Research Board in Washington, D.C. on January 10, 2001.
SDR provides engineering design, fabrication, and installation of ComPile technology
at your site. For more information, contact: SDR.
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