At the heart of this project was the restoration of the historic Grade II* Barmouth Viaduct. The viaduct is the longest timber bridge in Britain. It survived two world wars, a near-miss with a live naval mine in 1946, and an infestation of marine Teredo worms and is now the heart of the local community. However, the viaduct was built over 150 years ago, and parts of the viaduct were rotting and decaying. Therefore, Network Rail chose to invigorate this viaduct and return it to its former glory.
Prior to starting, the project team completed a large full scale structural testing utilising old timber sections. The contractor TXM was hired to accurately measure the maximum weight that can be expected from the crane lifting the timber sections. Following this, that weight was exerted on the full-scale model of the spans. This innovative testing was completed in Marine Parade, which is near the site location, allowing an accurate depiction of how the structure would behave with a crane lifting span sections out being placed next to the removed section. The testing concluded that the timber structure would be able to take over 160% of the expected load. Therefore, this enabled for the unconventional placement of the crane next to the removed sections safely.
Furthermore, the timber was sustainably sourced using Gilmour & Aitken. These contractors provide sustainable tropical timber, their tree extraction techniques ensure that the areas where the trees are removed benefit from the tree removal rather then suffer. The specially picked Greenheart trees were used to ensure that it matched the existing timber structures and will not cause any major structural integrity problems.
In addition to this, the project unconventionally used the scaffolding as a longitudinal support system for the span sections. The way that the scaffolding was constructed, not only increased the overall structural stability of the spans when working near the removed sections, but it was also moveable. The project ingeniously utilised the tide cycle to lift and move the scaffolding while requiring minimal reconstruction. This resourceful engineering allowed for a faster and safer turnaround time for moving the scaffolding in between sections.
Three Winning Facts:
- Like for Like restoration of the timber sections of the Grade II* Barmouth Viaduct
- Innovative nonintrusive testing of the capacity of the existing viaduct
- Bespoke utilization of the environment surrounding the site location