Archive research informs modern designs

While our work to refurbish Rochester’s bridges is all about the future, the best way to go about the task is by taking note of the past. This means many of the preparations for the project have involved research in our historic archives.

The archives, which stretch back more than 600 years, cover a range of topics linked with the Trust’s history, and for the purposes of this blog post they include a wealth of information about the bridges: how they were built; maintenance reviews; what changes have been made; and more – all of which proves invaluable when working on an historic structure such as the Old Bridge.

One item of note relates to the ugly lighting on the cross-girders over the Old Bridge. That’s right, we did just use the word ugly in relation to something on everyone’s favourite bridge, but there’s no point in calling it otherwise. The current lighting over the roadway was only ever meant to be temporary and it doesn’t take an expert to see it’s not in keeping with the aesthetics of the beautiful Old Bridge.

We’ve already told you about DW Windsor, the company responsible for producing prototypes of our new ornate lighting, and within their remit was the design for a new cross-girder bracket to support replacement lighting over the roadway.

Before they got to work, DW Windsor was provided with an outline design by Bridge Engineer Arcadis, but in order for them to produce accurate designs to fit and suit the Old Bridge more information was required.

This is because it wasn’t a simple case of handing over the plans for the Old Bridge – the cross-girders on those drawing are different to the ones we have today. It’s not initially obvious when you look at historic photos, but the original cross-girders – also known as ‘wind bracings’ – were lattices, whereas today they are plate girders.

Fortunately, our Bridge Archivist at the time of this research, the late Dr James Gibson, was able to quickly locate a file of 110 documents which included tenders, plans, accounts, engineer’s certificates, and correspondence covering just over two years from 26th February 1948 to 5th May 1950. Within this were the contract drawings for the upgraded cross-girders – exactly the information required to ensure the accurate development of prototype light fixings.