Introduction
FRP products were
first used to reinforce concrete structures in the 1950s. During the next
two decades, the quality of the FRP materials improved considerably,
manufacturing methods became more automated and material costs decreased.
The use of these materials for external reinforcement of concrete bridge
structure’s started in the 1980s, first as a substitute to steel plate
bonding and then as a substitute for steel confinement shells for bridge
columns.
The technology for
external retrofitting was developed primarily in Japan (sheet wrapping)
and Europe (laminate bonding). Today there are more than 1000 concrete
slab/steel girder bridges in Japan that have been strengthened with sheet
bonding to the slabs. Also, many thousands of bridge columns have been
seismically upgraded with the same materials. Ongoing development of
cost-effective production techniques for FRP composites has progressed to
the level that they are ready for the construction industry. Reduced
material cost, coupled with labor savings inherent with its low weight and
comparably simpler installation, relatively unlimited material length
availability, and immunity to corrosion, make FRP materials an attractive
solution for post strengthening, repair, seismic retrofit, and
infrastructure security.
The principles
behind externally bonding FRP plates or wraps to concrete structures are
very similar to the principles used in application of bonded steel plates.
In general, the member’s flexural, shear, or axial strength is increased
or better mobilized by the external application of high tensile strength
material.
Reasons for applying
FRP systems as an external reinforcement for bridge structures:
-
Capacity upgrade
due to a change in use of a structure
-
Passive
confinement to improve seismic resistance
-
Crack control
-
Strengthening
around new openings in slabs
FRP composite systems
have been applied to many structural elements including beams, columns,
slabs and walls as well as many special applications such as chimneys,
pipes and tanks. More recently this technology has been applied to
infrastructure security applications relating to hardening and blast
mitigation of structures.
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Add Shear and
Flexural Capacity in Reinforced Concrete Beams for strengthening and
seismic upgrade. |
Add
Confinement and flexure to Reinforced Concrete Columns for seismic
upgrade and strengthening |
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Add Flexural Capacity to Reinforced Concrete Slabs in the Positive &
Negative Moment Areas. |
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In lightly
reinforced and unreinforced masonry (URM), such as concrete masonry
units and brick, FRP material systems have demonstrated multiple
benefits by adding shear and flexural capacity, ductility for
seismic upgrade, and in some cases, blast resistance for the
hardening of buildings for industrial applications. |
FRP composite systems can be categorized based on how they are delivered
to the site and installed. External FRP composites systems come in a
variety of forms under the general categories of
1)
wet lay-up systems, and
2)
precured systems. The FRP composite system and its form should be selected
based on the acceptable transfer of structural loads, load capacity, and
ease and simplicity of installation.
Go to next section:
Features Benefits
and
Codes & Specs.
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