Civil Engineering Reference
In-Depth Information
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Dry unidirectional fibre sheets with the fibre running predominantly in
one planar (0 axis) direction
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Dry multidirectional fibre sheets or fabrics with fibres oriented in at
least two planar directions
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Dry fibre tows that are wound or otherwise mechanically applied to the
concrete surface. The dry fibre tows are impregnated with resin during
the winding operation.
16.2.2 Overview of pre-cured (pultruded and pre-preg) systems
Pre-cured FRP systems consist of a wide variety of composite shapes and
profiles, manufactured in the system supplier's factory and transported to
the job site. Typically, an adhesive is used to bond the pre-cured flat sheets,
rods or shapes to the concrete surface or inserted into slots cut into the wall.
The adhesive used to bond the pre-cured system to the concrete surface must
be specified by the system manufacturer. Adhesive selection is critical in that
the adhesive provides for the proper transfer of load between the surface
of the concrete and the cured reinforcement. Common types of pre-cured
systems are:
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Pre-cured unidirectional laminate sheets in the form of large flat plate
stock or as pultruded laminates coiled on a roll.
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Pre-cured multidirectional grids and mesh coiled on a roll or pre-cut in
sheet form. These grids are easily installed on the job site using tin-snips
or suitable cutters.
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Pre-cured shells in the form of shell segments are fitted around columns
or other structural elements and then bolted together and finally
grouted to form a composite section, to provide seismic confinement or
strengthening.
16.3 Strengthening techniques
There are three ways in which we generally can upgrade the structure, using
concrete, steel or fibre-reinforced plastics (FRPs).
Figure 16.3
illustrates not only the speed but also the weight savings made
by using composite materials. As can be seen from the example, the FRP
alternative is far quicker to install, using less labour or man-hours and cures
far quicker. An obvious saving using this method would be on traffic lane
rental or on railway possessions.
Typical costs of rail possessions or lane rentals in the UK in 2006 were:
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Rail - Gerard's Cross tunnel, c. £1m per day
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Road - £12 per vehicle per hour; M25, 30 August lorry fire, 40,000
vehicles, 2 hours: £1m
