Llanfairpwll Station Footbridge
Refurbishment design and specification, including the remediation of defective structural members, for a lattice girder passenger footbridge.
Llanfairpwll Station is a popular tourist attraction due to its extended name, 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”. The station footbridge was originally constructed over 100 years ago with original cast and wrought iron members remaining to most of the structure. The original treads and decks would have originally been constructed from timber, but these had since been removed and replaced with steel plate decks and treads which were suffering from corrosion, unsurprisingly given their setting within a coastal environment. A temporary footbridge was installed and the existing footbridge was removed using a crane and slings and transported to the contractor’s workshop for refurbishment.
Part of the client’s brief was to explore the possibility of replacing the severely corroded steel treads and deck with a GRP alternative satisfying a live load of 5kN/m². jnpgroup worked with a third party to develop a cost-effective GRP solution for the deck and treads that would also extend the service life of these elements to the minimum requirement of 25 years with minimal maintenance costs. This solution utilised a foam core box beam made from glass polymers surrounded in GRP/FRP (glass/fibre reinforced plastics) which would form the structural beams to the product spanning the supports. A prototype was manufactured with a 1.8m span and it was sent for independent load testing which showed it satisfied the loading requirements. Upon receipt of the testing data jnpgroup specified this new product within the refurbishment designs and submitted them together with the test data for Network Rail’s approval. The refurbishment designs were accepted, and the product was installed.
The product was advertised in IStructE’s January 2017 publication of ‘The Structural Engineer’ and the August 2017 publication of ‘Rail Engineer’ magazine, alongside a case study written by Network Rail’s Route Asset Engineer. The case study can be found via: https://www.railengineer.uk/2017/08/18/the-worlds-longest-footbridge/.
JNP Group services provided:
- Footbridge inspection.
- Development and approval of innovative GRP/FRP solution for deck and treads.
- Non-complex design submission:
- remedial design to extend the life of the footbridge and repairs to defective members.
- Inspection and attendance at workshop to agree replacement members and refine design proposals.
Project Value: £395k
Client: Network Rail, Wales Route