dk nkf - Nordisk Konservatorforbund Danmark
dk nkf - Nordisk Konservatorforbund Danmark
dk nkf - Nordisk Konservatorforbund Danmark
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sold to the Falkland Islanders and remained as a<br />
floating storehouse. This was extremely fortunate<br />
because she would almost certainly have been sold<br />
for scrap if she had been too expensive to repair in<br />
the Northern hemisphere.<br />
In 1937 the harbour master became concerned<br />
about her condition. He ordered that she should be<br />
removed from the harbour and scuttled in a nearby<br />
cove (see Figure 11). There she stayed until, in<br />
1970, she was salvaged and returned to the Great<br />
Western Dockyard in Bristol, the dockyard that<br />
Brunel had built for her construction. Owned by<br />
a trust, operating as an independent museum, she<br />
was partially restored between 1970 and the mid<br />
1990s. At this point the trustees decided that she<br />
should in future be treated as a museum object, and<br />
that the traditional shipyard approaches used in her<br />
restoration should be replaced with conservation<br />
methods.<br />
Fort Brockhurst Bridge, by contrast, was built by<br />
the army from a kit of parts in 1862. Several similar<br />
examples, dating from the period, are located<br />
nearby. The bridge provides access over a moat to<br />
Fort Brockhurst, one of a number of forts built in<br />
the 1860s to protect Portsmouth and its strategically<br />
important harbour. The fort remains physically<br />
largely unaltered, although it currently serves as a<br />
store for objects from English Heritage’s extensive<br />
reserve collections. These include stonework,<br />
textiles, jewellery, and furniture from many periods.<br />
It was crucial that the fort retain safe vehicular<br />
access.<br />
Condition and Treatment ~<br />
Fort Brockhurst Bridge<br />
The bridge had lasted for almost 150 years before<br />
receiving conservation treatment. As can be seen in<br />
Figure 2, the bridge was re-inforced on at least two<br />
occasions before receiving full conservation and<br />
restoration to its original function in 2004.<br />
The bridge was constructed from a combination of<br />
wrought and cast iron. Generally, cast iron was used<br />
for elements such as the support columns, hand-rail<br />
stanchions, bridge-deck plates and the landing beam<br />
of the drawbridge. Riveted wrought-iron beams were<br />
Figure 3. Corrosion of the wrought iron<br />
used where tensile strength was required. The owners<br />
of the bridge, English Heritage, had specified the<br />
design life of the treatment should be as long as was<br />
reasonably practicable. For this reason, it was decided<br />
to dismantle everything except the cast iron columns<br />
and treat the bridge in the conservation workshops.<br />
The main conservation issues to be addressed were<br />
corrosion of the wrought iron and some fracturing<br />
of the cast-iron elements.<br />
The main structural elements of the bridge were<br />
composite riveted wrought iron I-beams. These<br />
were constructed from plates and angles.<br />
The horizontal plates, particularly the upper ones,<br />
were heavily corroded. It was decided to de-rivet<br />
the beam and to cut down plate No. 2 to become a<br />
new plate No. 1. A new plate No. 2 was made from<br />
mild steel because wrought iron is in very short<br />
supply in the UK and it can be next to impossible<br />
to obtain high-quality replacement material in the<br />
large sizes.<br />
The engineers had determined that if more than 60%<br />
of the thickness of a material remained then it could<br />
be left un-repaired. Minor areas that were below this<br />
threshold (small holes for example) were repaired<br />
by welding in small patches or the application of<br />
weld metal to build up the required thickness.<br />
Cast-iron elements were visually inspected and dye<br />
penetration tests were conducted if fractures were<br />
suspected. Fractured cast-iron elements were metal-<br />
stitched together.<br />
All iron elements were cleaned to SA3 and zinc<br />
metal-sprayed.<br />
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