Rawcliffe Bridge

Overview

Mason Clark Associates were appointed in June 2019 by East Riding of Yorkshire Council to carry out intrusive Post Tensioned Special Inspection (PTSI) works on Rawcliffe Bridge near Goole. The bridge is a three span Post-Tensioned bridge consisting of two balanced cantilever approach spans and a central drop in span, spanning over the Dutch River.

The PTSI results identified that the bridge was suffering from a range of defects to its Post-Tensioning systems, affecting the safety of the structure and requiring significant load restrictions over the bridge.

Tasks / challenges

Mason Clark Associates’ (MCA) bridge engineers undertook a thorough inspection of the structure, carrying out non-destructive and non-invasive investigations and intrusive Post Tensioned Special Inspection (PTSI) works to try and determine the condition of the main structural elements of the bridge. Challenges were faced in terms of the logistics of the work, to drive around the bridge involved a 10-mile detour. Also, there were farms on both sides of the river who needed the bridge for transport purposes as part of their livelihoods, there was concern for local farmers in the event that the bridge was to be totally out of action. A traffic management plan was implemented to work around local farmers. This helped us to minimse full-closure periods. Part of this involved reducing the road width and installing traffic lights to allow a single lane of traffic to feed through. We worked to coordinate necessary periods of full closure with the most beneficial seasons and time of year.

Activity

The bridge required major strengthening and carriageway narrowing works with the application of a novel anti-corrosion pacification system to the deck tendons enabling the reopening of the bridge to unrestricted traffic.

The £800,000 scheme included:

• Temporary re-alignment of the EA Flood Defences to enable hydro-demolition of the abutments.
• Installation of temporary stabilisation works to maintain the equilibrium of the bridge during the removal of Post-Tensioned Macalloy abutment anchors.
• Hydro-demolition of the abutment, replacement of the Macalloy bars and reinstatement.
• Carriageway layout redesign and installation of new parapets.
• Utilisation of ‘Post-Tech PTI Impregnation System’ to the deck tendons, being first bridge in the UK to use the novel anti-corrosion system.

Results

We managed to successfully coordinate the opening and closure of the bridge around the concerns and requirements of local businesses and farmers, managing to open the bridge in a restricted way, ahead of schedule.Closures were kept to a minimum throughout by carrying out phased testing, finding defects and taking appropriate action. Working on this project increased our appreciation of the value of thorough testing – as well as one of the Macalloy bars being below the requisite strength, we found that some other steel tendons that were post-tensioned were not fully grouted. Hence, this helped us increase our awareness of the importance of extensive investigation and testing over visual inspection.