The Northallerton School & Sixth form campus was undergoing an extensive construction and refurbishment programme to upgrade the existing infrastructure and increase its overall capacity. Linking the East and West sections was a key component within these works to ensure safe passage over the A684 for both students and staff.
MAC Consulting were the Principal Designers and Project Managers for the overall scheme. JME Consultants were brought in by Lynas Engineers to assess the existing footbridge and specify remediations, liaise with the relevant authorities and design anti-trespass measures. The timescales were extremely tight; we were instructed in April with the bridge needing to be opened by the start of the new school year (September).
After initial consultations with North Yorkshire County Council Bridges Team and the client, a design concept and programme was established enabling us to meet the deadlines. A Principal Inspection in accordance with CS 450 and a Ground Investigation report were commissioned to specialists, both were completed and returned to JME Consultants in June. At the same time, JME Consultants completed the initial assessment of the bridge from a walkover survey along with preliminary drawings and prepared the Approval in Principal document. All of these documents along with a proposed Traffic Management Plan helped form the Approval in Principal document which was submitted to NYCC Bridges Team (the Technical Approval Authority) in June and signed off with only minor comments being received.
Work then proceeded on the assessment of the existing structure (taking into account existing section thicknesses of the plated box sections) and the new anti-trespass enclosures via 3D analysis software and hand calculations. One of the key items which required consideration was the replacement of the existing pin joint at the midspan of the deck. A replacement pin detail was carefully designed to ensure that it could be installed during one overnight bridge possession. Other key items were ensuring that the bridge did not pose any unacceptable risks to the bridge users; these risks were cutting risks from corroded bridge elements and the slipping risk due to the existing anti-slip surface finish having failed. The enclosures needed to be designed in a way to ensure that they would not cause any issues for future inspections or bridge maintenance works.
Construction issue drawings and a Designers Risk Assessment were issued to the winning tenderer in early August with works commencing during overnight possessions August Bank Holiday. Certificates C and D were issued to the Technical Approval Authority in August and countersigned.
