Brunel’s Swivel Bridge
Cumberland Basin
Condition assessment
May 2006
Ian Duncan : Engineer
Introduction
It was decided at the Group’s last meeting that it might be useful for there
to be a preliminary report on the
structural condition of the bridge, with a longer term view of arriving at a
reliable estimate of the costs for
repair and renovation of the structure. I offered to undertake the preliminary
survey.
The meeting further discussed whether it was appropriate that this Group
should take responsibility for the
R+R of a structure which was in the ownership of the City. This will be an
ongoing discussion, but on the
basis that this survey would be done in the interests of the Group, as well as
the City, the meeting
conformed that a preliminary survey should be carried out.
Condition of the structure
The structure is generally in good condition. There are a few locations where
corrosion has set it but these
seem to be isolated and relatively straightforward to repair. The worst of these
are illustrated below:
Less severe corrosive deterioration occurs sporadically and this degree of
corrosion would be
reparable by grinding and painting with a suitable protective paint.
The left hand picture above shows what looks like an extensive area of
surface corrosion which has been
grit blasted clean and protected by painting. A similar extensive area occurs on
the southern inside surface
of the web and in both cases occurring at the bottom of the web. If this was
corrosion then there are no
signs of its continuing activity. The right hand picture is another example of
sporadic corrosion which, in my
view, could be ground down or grit blasted and made good quite easily.
The underside of the structure appears not to have received much attention.
Surface corrosion is quite
extensive on the cross beams and on the bottom chord members. However, from a
limited view it does
appear as though the corrosion can be dealt with by grit blasting followed by a
protective treatment.
The wrought iron work appears, at a cursory inspection, to be in a condition
for which repairs can be
made relatively easily. However it will be essential to lift the bridge so that
easy access can be made to
all surfaces.
Finally, the timber decking is in a very poor state and will need to be
replaced.