Menai suspension bridge footway panel replacement

In 1938 footways were installed on either side of the bridge to allow pedestrians to safely cross. A survey conducted in 2020 identified that the footway panels on either side of the road were showing significant signs of spalling to the soffits which would require remedial work. The existing surfacing needed to be removed, and the existing panels which spanned between the cantilevered concrete beams needed to be taken out and replaced with new precast footway panels.

Solution

From an initial plan to use in situ poured concrete it was decided instead to carry out accurate surveys of each individual panel and to pre-cast off-site. This would reduce time and disruption on-site and provide a superior quality solution with the panels being produced in a quality-controlled, factory environment. One of the main challenges to the project was that all the existing panels were different shapes and sizes with no two units being the same. This meant that the replacement precast panels would have to be produced individually to a specific bespoke size. A modified A-frame system was used to lift the existing panels out and to replace the new panels back in, all in the same day shift.

Menai Suspension Bridge – Footway Replacement Film

Find out more in this video from the Spencer Group.

How we helped

We supplied 71 precast panels which were custom manufactured to a +/- 3mm tolerance, based on site measured dimensions. The panels ranged in weight from 0.75 tonnes to 1.34 tonnes. The project was an exacting one in that every panel was unique in shape and size which meant the mould for each one had to be modified. “Once a site survey was done we had 10 days to convert the dimensions to drawings, have the units manufactured, and provide sufficient time for each of the panels to cure and harden” said Tim Evans, Director of Bespoke for Poundfield. “On average we achieved 60N+ after only 5 days and in some cases in excess of 100N after 28 days. Working closely with the Spencer Group, we did this every week for a period of 8 weeks to fit in with a planned installation programme to ensure there were no delays on site.”

“Each of the panels were of excellent quality and manufactured to our tight tolerance of +/- 3mm. The team at Poundfield are easy to do business with and the communication throughout the project has been very collaborative.” – Spencer Group

Award winning project

In May 2021 the project won the Bridges Management Award at the Bridge Design and Engineering Awards.

Comments on the project from the judges included:

“Change of design approach to adopt precast panels – the quality of finish is clear. Temporary works challenging.”

“Impressive quality control of panel casting through detailed survey. A-frame panel lifting and debris capture positive. Some good solutions here for what were some maintenance issues on an iconic bridge.”

“Demonstrated good inspection and maintenance processes and innovative use of installation equipment for the panels.”