DCL-56 Underbridge Renewal Design

Client: Story Contracting
Location: Oxfordshire
Discipline: Structural and Geotechnical Engineering

FJD Consulting have delivered the structural and geotechnical design for the replacement of DCL/56 Old River Cherwell Underbridge, which carries the railway over the River Cherwell in King's Sutton near Banbury. The structural design comprised the detailed design of a 9.6m wide Network Rail Standard Design (NRSD) Type-E steel half-through bridge and production of the associated Form A document and drawings.

After a five day disruptive possession at the end of July 2024, the new 240-tonne bridge deck was lifted into place on a piecemeal basis using two special rail-mounted ‘Kirow’ cranes, and is now operational, providing safe and reliable journeys for passengers and freight on the on the Didcot to Chester line.

Our involvement comprised the delivery of the option selection report, Structures Form A, Form B, AFC, and as-builts and and integration of the Permanent Way design. The form of construction necessitated new piled substructures so our geotechnical team was brought in to provide inputs into Form A document, and the production of GIR and GDR Reports and preliminary design and check of calculations for pilecaps, and improvements to the river channel construction to mitigate scour. Harnessing our longstanding partnerships with Permananent Way Designers, we were able to supply GRIP4 and GRIP5 Track design as part of our package.

As the site is a low-lying floodplain in close proximity to the Old River Cherwell, the area around the DCL-56 bridge is known to be prone to flooding, especially during periods of heavy rain. FJD collaborated on site with the Environmental Agency representative, and modeled the changes to the existing river channel and designed the ChoirMesh and tie in solutions for this element of the works.

FJD has worked collaboratively with Story to provide a feasible installation solution of the new 240-tonne deck. FJD has provided early design input with regards to the weights of the deck elements, consulting on the installation method, and providing consistent support during site installation.

Our design solutions and TQs have ensured that the Programme was met on site. E.g. early refusal of piles on site resulting in shorter piles. This involved quick and responsive re-design based on additional site information and agreement with the CAT3 checker.

We were responsive to all Technical Queries during the construction phase, providing reactive responses to critical issues on site. Most TQs were responded within 72 hours, even when this required CAT3 checker involvement. This helped keep cost and programme on track.

FJD has also collaborated directly with the steel fabricators, bearing manufacturers and Story site team to ensure that all proposed details are feasible and easy to build on site.