|
Return
to Items for Decision
Return
to Item 2
|
Division(s):
Brightwell-cum-Stowell, Warborough, Benson
|
ITEM CMDT2 - ANNEX 1
CABINET
MEMBER FOR TRANSPORT – 14 SEPTEMBER 2006
SHILLINGFORD
BRIDGE SIGNALISATION
The Bridge Problems
The
bridge was constructed in 1826 and carries the classified, but unnumbered
Shillingford to Wallingford road over the River Thames. The bridge comprises
three main stone arch river spans with a number of smaller brick/masonry
built flood arches. The road over the bridge currently extends from parapet
to parapet, providing a 6.5m wide two-way carriageway with no defined
footways. A concrete slab was constructed over the three main arches in
1974 as a rudimentary strengthening measure.
The
bridge is a Grade II listed structure and any alterations are subject
to the County Council obtaining listed building consent.
The
bridge has been assessed as adequate to carry 40 tonne vehicles positioned
centrally in the carriageway. However its ability to sustain HGV loading
adjacent to the parapets is not adequate. This is confirmed by recent
inspections that have identified lateral cracking of the bridge arch barrels,
typically caused by differential movement between the arch barrels and
spandrel walls.
The
original stone and brick used in the construction of the bridge is frost
susceptible with surface water percolating through to the arch barrels,
almost every element of the external surface exhibits some areas of deterioration
or erosion.
In
addition, the existing pilaster parapets are structurally inadequate with
regard to lateral vehicle impact loading and have suffered collision damage
on numerous occasions, due in no small part to the lack of clearance between
road traffic and the parapet faces. A subsidiary issue is with regard
to pedestrian safety as clearly it is currently far from ideal that there
are no footways at all over its entire 100m length.
The proposed solution
The
proposed solution is designed to address the issues above. Introducing
footways will serve to move all vehicles away from the weaker edges of
the bridge, reducing vertical loading and vibration there whilst also
reducing the likelihood of vehicle impacts with the parapets. In addition
the footpaths will significantly improve pedestrian safety across the
bridge.
To
enable the carriageway over the bridge to be singled traffic will need
to be controlled by traffic signals.
To
undertake these changes it is proposed to remove all surfacing down to
the concrete slabs, repair the slabs where required and then waterproof
them to prevent surface water seeping through the structure and causing
further damage to the arch barrels and spandrel walls below.
It
is then proposed to construct two raised 1.8m wide footways over the bridge
adjacent to each parapet, leaving 3.0m between the kerbs for the new carriageway.
Ducting
for the traffic signals will be incorporated into the footways during
construction. Subject to Listed Building approval it is proposed to use
a buff coloured york-stone for the paving, channels and edgings with grey
granite for the kerbs.
Longer Term Measures
Once
the structure has dried out after perhaps a year or more it is proposed
to follow on from this improvement scheme with an extensive stone work
repair scheme which will require separate listed building consent and
consultation with English Heritage and the Environment Agency. These measures
are subject to funding being available within the Local Transport Plan.
Return to TOP
|