Civil Engineering Reference
In-Depth Information
The adhesive was developed originally for the contract carried out in
Qatar for QAFCO where the parameters for the adhesive were that it had to
have a
T
g
of > 65°C. The obvious advantages of using carbon fibre laminates
instead of steel plates were that no holes had to be drilled into the concrete
substrate to keep the plates in position. The other advantage was the time
element, as well as a reduced labour requirement on the job site.
16.9 Tay Bridge, Dundee
The Tay Bridge is again a very good example of where MBrace Kevlar has
been used to strengthen the columns both for confinement and for shear
to the north approach road. The columns in this case were wrapped with
Kevlar.
The columns are 6 m high, and the criterion was that the columns had to
be able to carry 40 tonne vehicles. The designers, Babtie, decided on using a
thicker aramid sheet to save time on the contract. MBrace Kevlar AK90 was
chosen for this.
The shape of the columns dictated the method of application. As the
columns were oval shaped as well as tapering, the material was applied in
two halves with an overlap of 200 mm.
16.10 St Michael's road bridge, NW England
St Michael's Bridge is a good example of how the speed of application was
a major influence in its use. Earlier in this chapter we looked at the cost of
possessions on the West Coast main line. St Michael's Bridge is not on this
main line, but is still on the main route from Manchester to Liverpool. This
is the first overbridge to be strengthened in possession for Network Rail.
Details of the bridge are as follows:
•
RC train carrying (underline) bridge
•
Original bridge metallic beams and cast iron jack arches - mid-19th
century
•
Deck replaced 1959
•
4 pre-cast RC concrete deck units carry the track
•
2 pre-cast RC parapet units
•
Deck under strength in flexure due to increased live load.
The criteria was that the bridge had to carry 140 mph Virgin trains, so
the engineer and client looked at the various options available to them.
The options were to use steel plates for equivalent strengthening, with the
following requirements:
•
270 MPa tensile strength, 210 GPa modulus
•
8-10 mm minimum thick plates
