Inertia Consulting Ltd was appointed to design and supervise the temporary works for the Spinningfields Footbridge, a 52m curved inverse arch catenary footbridge spanning the River Irwell in Manchester in a tight urban location.
Our brief was to design:
• Crane foundations for a 1,000 tonne crane lift and bridge support system to be used during assembly.
• A temporary steelwork splice, tie and counterweight system for the bridge’s inclined support piers.
• A support trestle, jacking and lifting system to support the lightweight bridge sections during transportation, on‐site assembly and cable stressing, and which could also be used as lifting beams during installation.
Councillor John Merry, Leader of Salford City Council
Before developing our designs, our team attended the site to carry out detailed investigations into existing structures, including the location of services and buried tunnels underneath the site, so we could ascertain the precise requirements for temporary support and the best construction methodologies to be used.
As the existing arch structures and near-surface ground deposits were unsuitable for spread foundations to be laid, we designed piled foundations to the site’s bedrock that were capable of bearing the load.
For the trestles, our team designed a system that could be jacked and slid to accommodate changes in the bridge’s profile during catenary stressing, to avoid the development of locked-in forces in the trestles. And for the lift, we designed the trestles to unbolt at the top to release the lift beams, with the lift arrangement designed so that the curved structure didn’t rotate during installation.
Throughout the temporary works, our team were onsite to provide construction supervision services, manage Health & Safety and ensure compliance with specification and statutory requirements. The project was successfully delivered, with the added benefit that our innovative construction methodologies reduced the client’s costs.
Our experience in off‐site element construction and the design of crane foundations and lifting and support systems meant we could save our client money by adopting innovative construction methodologies to deliver complex temporary works in a logistically difficult location.
As with all our projects, our aim was to design and deliver a cost-effective, buildable and durable solution to the highest safety and quality standards, whilst ensuring minimum disruption whilst the works were taking place.