Civil Engineering Reference
In-Depth Information
Paul Russell
16.1 Introduction
FRP products (glass, carbon fibre and aramid) were first used to reinforce
concrete structures in the 1950s. During the next two decades, the quality
of the FRP materials improved considerably, the manufacturing methods
became more automated and material costs decreased. The use of these
materials for external reinforcement of concrete bridge structures started
in the 1980s, first as a substitute for steel plate bonding, which had been a
proven method for many years previously, and then as a substitute for steel
confinement shells for bridge columns.
The technology for external retrofitting was developed primarily in Japan
(wet lay-up sheet wrapping) and Europe (pre-cured laminate bonding).
Today there are more than 1000 concrete slab/steel girder bridges in Japan
that have been strengthened with wet lay-up 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 now
readily accepted in the construction industry. Owing to published design
guidelines similar to the Concrete Society TR55 (Concrete Society, 2004)
and 57 (Concrete Society, 2003) and CIRIA-C595 (CIRIA, 2004), engineers
now have the confidence to design strengthening schemes that are a benefit
to their clients and the users of the structures.
Reduced material cost, together with labour savings inherent with
their 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. Another advantage of the use of FRP materials is
that in many cases the structures can be returned to their owners a lot more
quickly than when using traditional materials such as steel and concrete.
Savings in lane rentals (highways) and line possessions (rail and track) are a
bonus to those people who use the structures, relieving traffic congestion or
delays on the rail infrastructure.
