Redhayes Bridge

• UK's first major highway infrastructure project designed and constructed to Eurocodes
• Linear and nonlinear analysis to determine section sizing
• Detailed pedestrian moving-load and steady-state analysis

Parsons Brinckerhoff was commissioned by Devon County Council to undertake a feasibility study, outline and then detailed design for a new pedestrian and cycle bridge near Exeter, UK. The resulting 82m span twin-arch bowstring bridge was developed with the aid of LUSAS bridge analysis software and on completion was believed to be the first major highway infrastructure project designed and constructed to Eurocodes in the UK.

Redhayes bridge provides a segregated pedestrian and cycle crossing spanning 82m across the cutting immediately north of Junction 29 of the M5 motorway. The bridge is a key part of a green travel corridor serving a number of developments and planned developments to the East of Exeter. It provides an elegant landmark structure in a prominent location and re-establishes a route that was lost when the motorway was originally constructed.

Parsons Brinckerhoff built LUSAS models to undertake both linear and nonlinear analyses of the structure. Geometric nonlinearity was modelled to investigate the sensitivity of the structure to second order large-displacement effects, and on the basis of these findings, it was established that initial section sizing could be performed using the results of a first order analysis simplifying the superposition of load effects.

Buckling behaviour was investigated accounting for both geometric and material nonlinearity and the modal dynamics established with LUSAS to find the vertical, transverse and twist modes and frequencies. The primary modes were then used for more detailed pedestrian moving-load and steady-state analysis in accordance with the requirements of the UK National Annex to BS EN 1991-2 using the LUSAS Pedestrian Load Wizard.

The main arch of the bridge was erected alongside the motorway and following a night closure was lifted into position in February 2011. After finishing works were completed it was open for public use later in 2011.