HomeInfrastructureSend for the skyhooks! The reconstruction of Albrighton bridge

Send for the skyhooks! The reconstruction of Albrighton bridge

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The Victorian footbridge at Albrighton station is a fine structure. It’s Grade II listed and obviously everyone’s pride and joy. Carefully restored in 2013, it is resplendent in its fresh coats of paint, clearly visible from Station Road that passes beneath the station platforms.

Clearly visible eh?

Yup, you can’t miss it with its main span supports smack over the eastern abutment.

Now that’s fine if you’re looking for an historic footbridge from the road, but it’s not that fine if you have the task of replacing the bridge under the footbridge foundations.

The footbridge is in the way.

Credit: David Millar.
Credit: David Millar.

Time for reconstruction

The original bridge under the railway between Wolverhampton and Shrewsbury was constructed in 1849. How do we know with such certainty? Well, it’s written in large letters on the cast-iron parapets that survive to this day. (In fact, the date on the beams is 1848, which is when they were cast rather than when they were installed.)

They, too, are everyone’s pride and joy. They, too, get in the way.

Station Road underbridge is a relatively modest structure. It is heavily skewed and was reconstructed in the late 1890s. This, in turn was reconstructed in 1935. It carries two tracks and the 1935 structure consisted of a central girder and two outer girders with a troughing deck.

The station’s platforms were reconstructed at the same time, with trusty Dorman Long 24-inch deep girders supporting the precast concrete slabs.

In common with many similar structures, it was showing its age and the time had come for it to be reconstructed once again. But, this time, the track-carrying components were not everyone’s pride and joy. Rusting and dripping wet, it was time for them to go.

Amco is Network Rail’s framework contractor on this part of the network. They worked with designers Tony Gee and Partners to reconstruct the 1930s bridge, taking in the complex task of preserving the heritage material. David Millar was Amco’s senior project manager for the work responsible for both managing the design of the temporary arrangement and being the Contractors Responsible Engineer (CRE) on site when it was installed.

All bridges require an element of preparatory works – utilities to check and avoid, and site facilities to set up. However, because of the footbridge and the cast-iron parapets, this bridge reconstruction job had more than its fair share of challenges.

Credit: David Millar.
Credit: David Millar.

Audacious temporary works

Time is strictly limited, even during an out-of-the-rules extended possession. The project was allocated a 73-hour possession but, even within this budget, there was little time to spend scratching around the foundations of the footbridge so that new cill beams could be installed.

The solution was to adopt some very audacious temporary works. A tower was erected tight against the side of the platform retaining wall, heavily weighted with concrete blocks. Beams were then threaded under the top landing of the footbridge, cantilevering out from the tower.

In all, some 19 tonnes of kentledge weights were used in the tower, and this was sufficient for the footbridge to be supported by the cantilever beams. This whole arrangement allowed work to take place below the footbridge footings.

The precious cast-iron parapets were carefully protected so that they would not be damaged in the main possession.

All this temporary work made the site very difficult to work in, so it was important to carry out as much work in the days prior to the possession without affecting the running lines.

Credit: David Millar.
Credit: David Millar.

Road and station closures

With the station closed to passengers for two weeks, the platforms over the road were dismantled and the abutments on each corner were excavated as far as possible, with Amco teams working night and day shifts.

The roadway dips down steeply under the railway which meant that, in order to create a level working platform for the 1000-tonne crane, substantial quantities of Navi Mats (350 in total) were needed to create a working platform for the crane and its outriggers.

All this preparatory work was carried out with a road closure that was taken two weeks before the Easter weekend. This enabled materials to be stockpiled, except for the major items which were transported down from Scotland, after a full scale trial erection, and held at a nearby service station until required to arrive ‘just in time’.

These major items included the large cill beams – 65 tonnes each – and the two Network Rail standard U-decks, each also weighing in at 65 tonnes. The cill beams, manufactured in Ireland by Shay Murtagh Precast, were shipped across to Lanarkshire Welding in Scotland, which fabricated the steelwork, for the trial erection.

Also included were the two new 56-tonne platform units, also fabricated by Lanarkshire Welding, to replace the old platform that had been dismantled. These mated up with upstands on the cill units, and were designed to connect up to the original 1849 cast-iron edge beams, a feature in the design that turned out to be very complex to achieve.

Credit: David Millar.
Credit: David Millar.

Applying Christmas’ lessons

Network Rail’s project manager Stephen Townley was keen to draw on lessons learnt over the Christmas period when overruns had occurred on West Coast main line works. It was a deliberate tactic to make all components as large as practical – after all, there was a 1000-tonne crane available and it seemed logical to use its capacity to the full – and fitting together smaller precast items can often lead to delays, no matter how precisely the items have been constructed.

The main possession started at 01:00 on 15 April 2017. The first task was to remove the track, carried out by 1st in Rail. The rails were cut and drawn back to be reused, while the life-expired timber sleepers were scrapped.

With the track out of the way, it was time to remove the existing bridge structure, which had a central girder rather than being two separate spans. Having examined the logistics of cutting up the steelwork in-situ, it soon became clear that the easiest way forward was to remove the entire structure in one go. Again, Baldwins’ 1000-tonne crane was available, so why not make best use of it?

Sam Evans and Sons of Widnes undertook the demolition of the bridge and the handling of spoil and backfill materials. Lifting beams were positioned below the deck and it was not long before the 87-tonne bridge was airborne. The record drawings proved to be accurate, as the structure had been landed originally on cast bearings rather than being bolted down directly to the abutments.

Credit: David Millar.
Credit: David Millar.

Tonnes of spoil – plus cupcakes!

With the old deck out of the way, excavators set about reducing the abutments down to a saw cut that had been made earlier. Despite the ever-present temporary works, something like 300 tonnes of spoil was loaded away.

Once a level surface having been created on the old abutments, it was time to lift in the large cill beams. To get them to fit into the tight space available took some ‘teasing’ of brickwork. Learning from previous experiences, this was not a surprise, even if it was a little frustrating on the night, and had been worked through in Delivery of Work in Possessions (DWWP) workshop sessions before the possession.

Taking 300 tonnes of spoil out meant something like 300 tonnes of new backfill had to go back in, all transported in bulk bags from a road-rail access point 200 metres east of the station. After that, the new spans went in without issues and the new platforms were landed on the cill beam upstands.

With the deck waterproofing pre-installed, the decks were handed to the pway team which made swift work of installing the track in time for signal testing and handback on time (with four hours to spare).

Along with the impressive list of materials and components used, it mustn’t be forgotten that substantial quantities of cake were consumed. It pays to give attention to the concerns of local residents, one of whom rewarded the workforce with an unending supply of cupcakes.

In the days following the possession, the platform surfacing, lighting and furniture were completed. So, too, were the final complex connections that fused the new construction with the last remaining elements of IK Brunel’s GWR cast-iron parapets.

After that, the temporary works were dismantled and the vista of the footbridge and the cast iron parapets has been restored to be everyone’s pride and joy once again.

This article was written by Grahame Taylor

Read more: Taking the Northern line to Battersea



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