A
potential technique utilizing advanced polymer composites to rehabilitate a
steel railway bridge open to traffic
during the adhesive curing period is
presented. The advanced polymer composites used for the upgrading system are
manufactured from a factory-made hot melt pre-impregnated high modulus and
ultra high modulus carbon fibres; the polymer system is an epoxy. The
composite is bonded to the steel structural member with a compatible film adhesive; the
two components are then fabricated in one operation onto the structure. The
compaction is performed under a vacuum assisted pressure of 1 bar and two cure
temperatures are used, one at 650C
for 16 hours and the other at 800C
for 4 hours; the length and time of cure are dependent parameters. The FRP
structural and material characteristics and the beam test results are
presented. It is shown that some slight damage to the adhesive from the
vibrational forces, during the cure period, did occur but the strain to
failure of the high modulus CFRP composite took place well into the non-linear region
of the steel beam and the high modulus carbon fibre composite supported 10%
greater load than the ultra high modulus carbon fiber composite as a result of
the low strain to failure of the latter carbon fibre. It is noticed, however,
that half the thickness of the ultra high modulus CFRP composite is used
compared with the high modulus CFRP. This allows the yielding of the steel beam
to occur at a similar load value for the two upgrades and prevents a severe
brittle failure of the composite beam.