Nottingham Enterprise Zone Footbridge

Bespoke design of a 50m footbridge featuring weathering steel main span and mild steel approach ramps

The challenge

The project was a success, with a key benefit being the use of weathering steel for the main structure, as it avoids the need for maintenance – and associated disruption – during the bridge’s designed ‘in service’ life.

Engineering Consultancy

The project posed multiple challenges, including:

• Bespoke design and construction of weathering steel grade hollow rectangular sections that would form the main deck of the bridge to meet the requirements of the brief whilst complying with industry standards BS EN 1983-1-1 and BS EN 1983-1-8.

• Ascertaining the right order in which to assemble the deck panels, bearing in mind that welded rectangular hollow sections need to have similar design characteristics to hot-formed ones.

• Using an advanced FEM shell model to provide the required curve effect for the approach ramp elements, which needed to be curved in plan and sloping at the same time.

• Carrying out a Human Induced Vibration Check using advanced design methods such as FEM shell/strut modelling and time history analysis to ascertain the level of vibration caused by pedestrians and whether this could be tolerated by the bridge and approach ramps.

“Inertia provide an excellent service and work hard to meet our tight schedules. We also change requirements at short notice and Inertia are quick to respond. We value their service and advice and look forward to a continuing successful relationship in the future.”

Aaron Fisher, Technical Manager, Briton Fabricators Ltd

The outcome

The success of this project was ensured by the innovation, knowledge sharing and experience of the professionals working on the project. Collaboration and communication were key to enabling the project team to meet the required delivery dates. It was vital for Inertia to keep tight control over the design process, and the preparation of drawings.

By constantly checking and validating the project geometry to accommodate ad hoc changes to the design, we could continue to meet our client’s fabrication and installation needs whilst avoiding time-consuming exchanges of information between the design and drafting processes.

On a practical level, the use of weathering steel for the main deck structure was the right choice as it doesn’t need any maintenance during its designed “in service” life. This avoids the need to close the railway tracks to carry out maintenance, which is expensive for the client and disruptive to the travelling public.

The project team

• Nottingham City Council – Client
• Eurovia – Principal Contractor
• Inertia Consulting Ltd – Superstructure Designer
• Nottingham City Council – Substructure Designer
• Briton Fabricators Ltd – Steelwork Fabricator