Railway engineers don’t often get the opportunity to dismantle and rebuild a piece of railway heritage. That’s why working on a well-known station footbridge in Anglesey was such an exciting project for Network Rail’s asset engineer and externally appointed structural designers. The work was carried out at the beginning of 2017 as part of the plans to build a bigger and better railway for passengers.

Llanfairpwll station is a popular tourist attraction due to the extended name it is often known by – Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch – which translates to “St. Mary’s Church in the hollow of white hazel near a rapid whirlpool and the Church of St. Tysilio near the red cave”. People visit the station to take photographs of the famous sign and often use it as a starting point to explore Anglesey and the North Wales coast.

Even the name itself is a piece of railway history. It was ‘invented’ in the 1860s to be the longest place name in Britain and to attract tourists. At 58 characters (only 51 letters as ‘ch’ and ‘ll’ are regarded as single letters in Welsh) it is the second longest place name in the world*. To make life simpler for passengers and for ticketing websites, the official name of the station is Llanfairpwll, with the three-letter code LPG.

But back to the bridge…

Philosophy

Whenever possible, when carrying out footbridge refurbishments, the Wales route removes any spans crossing the track and transports them to a controlled environment. Of course, this is only practical where a temporary footbridge can be installed on the site and the general logistics of the surrounding area allow for the hoisting and lifting of a bridge span onto a low level loader.

This philosophy is driven by three factors – the results of inspections of previous bridge refurbishments completed on the Wales route over the last five years, the importance for the control of salt contamination, especially in coastal areas, and the safety of passengers using stations during refurbishment works.

In addition, it was important to work with partners Arriva Trains Wales to ensure that the works were completed during the winter and spring in order to cause minimal disruption, with the station and surrounding area being such a popular tourist destination.

As it was

Network Rail’s structural assessment programme confirmed that the footbridge in Llanfairpwll could not support the minimum required live loading of 5.0kN/m². Considering the station’s high footfall, this was a concern. Therefore, the buildings asset team, based in Cardiff, decided to restrict the number of passengers that could physically stand on the bridge span.

Prior to the Flying Scotsman passing through during 2016, Herras fencing was installed to the deck span to physically minimise the loaded width of the footway. A full repair and refurbishment was imminent, so the installation of this fencing was only deemed a short-term restriction.

A desktop study confirmed that the layout of the station allowed for a temporary footbridge to be installed and the existing span could be hoisted onto a low level loader and transported to a workshop. The footbridge trestles and staircases would remain on site, encapsulated with a scaffold system for full access and covered to protect the structures from the elements during the onsite refurbishment of these parts.

Network Rail tries to avoid any site painting works during the winter months, but negotiating access to the site with third parties took longer than anticipated and delayed the start date for the project.

The lift

During January 2017, a temporary Layher footbridge was installed, complete with a temporary lighting installation and the required lux-level testing. This was all completed and in operation by 19 January.

The existing footbridge was closed and the footbridge structure was prepared for span removal. This included removing the handrails, lighting and the connection fixings securing the bridge to the trestle frames at either end.

The lift was carried out on a Saturday night under possession using a crane and slings. The bridge was slowly hoisted and manoeuvred towards a low level loader in the car park and transported to Centregreat’s workshop in Cardiff, 210 miles away.

The reveal

Once the bridge span had been removed and the bare frame of the structure had been shot blasted back to bare metal, engineers were able to inspect the Victorian structure up close and appreciate the sheer simplicity of the bridge. The overall impression was quite promising and it appeared to be a relatively intact structure.

The inspection revealed that the bottom chord of the lattice truss had previously received strengthening plates, but it wasn’t until the plates were removed that the true extent of corrosion could be seen. Once it was decided that a full renewal was required of the bottom chord, engineers worked alongside Centregreat’s steelwork fabricators to design and detail a new bottom chord that would reinstate the transfer of forces between the top and bottom chord of the truss.

Salt contamination

Even with the strictest of site controls, it is very difficult for a contractor to control the level of salt contamination, particularly in coastal environments. However, the Wales Route did succeed with one footbridge refurbishment during the summer of 2016. The site was located in one of the highest recorded areas for airborne salts and, for logistical reasons, the footbridge could not be removed off site, so the footbridge was constantly monitored, jet washed and retested to prove that salt contamination was within acceptable limits before the application of paint layers.

Although the footbridge span at Llanfairpwll was removed for refurbishment in a factory environment, the stairways and trestle frames had to remain. With full site encapsulation, the trestle frames and stairways were shot blasted back to bare metal ready for repairs and strengthening.

The contractor had to ensure that the soluble salt traces left on the shot blasted on-site structures were monitored and, where required, further jet washing was carried out and tested before each paint layer could be applied.

As well as repairs and painting, the main span of the bridge, the stair treads, risers and landings were totally replaced with structural GRP panels and treads, specially made by Polydeck using its unique foam core support structure which matched the new footbridge span. The GRP deck also provides a durable, aesthetically pleasing and slip-resistant walking surface

Unaligned colour scheme

The specific requirement for the colour scheme was that it should not relate to any branding. Therefore the Railway Heritage Trust developed a suitable painting scheme for the North Wales coast. The architect at the time for the regional railways in the North West generally used dark green, beige and red. These colours, in particular the dark green and beige, worked well with a variety of materials and were well suited to rural locations.

The reinstatement

By mid-March, the structures were completed and about to be reunited. On 25 March, the refurbished span was hoisted and manoeuvred back onto its support trestles. By the 29th, the sparkling footbridge was completely trial lit with new energy saving LED lights, which would eventually be lit within the new handrail system.

The £395,000 project to upgrade and restore this historic footbridge was completed by mid-April. The benefits of the span removal, strict control of salt contamination and an understanding and respect for Victorian heritage were there for all to see.

All that was left to do was to dismantle the temporary footbridge and clear the site, ready for a new season’s tourists to arrive.

Darren McKenna is an asset engineer – buildings fabric on the Wales Route of Network Rail.


*The world’s longest

Those wondering why Llanfairpwll station, at 51 letters (58 characters), is only the world’s second longest place name should visit a hill at Hawke’s Bay. According to Land Information New Zealand, the hill is called Taumatawhakatangihangakoauauotamateapokaiwhenuakitanatahu (57 letters) although there are even longer forms of the same place name with up to 105 letters. It’s 85-character version, Taumatawhakatangi­hangakoauauotamatea­turipukakapikimaunga­horonukupokaiwhen­uakitanatahu, features in the Guinness Book of Records as the longest place name. But locals simply call it Taumata.


This article was written by Darren McKenna.


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