Timber Footbridge at National Forest Visitor Centre
Buro Happold has provided structural engineering for an innovative timber footbridge, sponsored by Next plc, at the 'Heart of the National Forest Visitor Centre'.
One of several focal points and structures within the 'Heart of the National Forest Visitor Centre' development, the timber footbridge is approached from a lake and amphitheatre, and if viewed from below forms the gateway to the Dunblane memorial. The bridge spans approximately 12m with a curved deck, which is 2.5m in width at its widest point, and it provides a platform to view the new Visitor Centre.
The chestnut footbridge provides an excellent demonstration of a sustainable and 'green' timber construction and helps form the network of interesting walkways around the Visitor Centre. It is constructed in green and unregularised chestnut, a species of timber, which is durable and does not need any preservative treatment.
The deck of the bridge is constructed of round-wood beams – cross-beams – supporting oak joists and finished with 19mm thick oak planks nailed to the joists. The deck is supported by round-wood posts, which at deck level are connected to the cross-beams and pinned at foundation level to the abutments. The posts are arranged in a 'fan' shape with the central post at the shallowest angle to the horizontal. Vertical loads on the bridge deck put the posts into compression, while the post at the shallowest angle has the largest force in it. This force is transmitted to the abutment, which therefore has to be able to resist this large almost horizontal force. The stainless steel handrail is supported off the regularly spaced posts.
Chestnut poles soar through the deck, providing support and enabling pedestrians to touch the structure and enjoy the feel of the chestnut. In contrast to the irregularity and solidity of the timber, the handrail is in minimalist stainless steel.
The bridge was designed by landscape architect Faulks Perry Culley and Rech and consultant Buro Happold, and built by Carpenter Oak and Woodland. Client is the Heart of the National Forest Foundation.
