12 November 2013

Teesside Bridges: 1. Middlesbrough Transporter Bridge

I was very lucky recently to join a weekend study tour of the bridges and structures of north-east England, organised by the British Group of the International Association for Bridge and Structural Engineering (IABSE). Previous British IABSE study tours had taken participants to Switzerland and France. I had greatly enjoyed the Swiss trip (and missed out on France), and wondered whether north-east England could possibly be anywhere near as interesting or enjoyable.

I needn't have been concerned. While much of the pleasure of the tour was the chance to meet and spend time with fellow bridge designers, it soon became obvious that we were to visit some splendid and fascinating bridges.

The first stop on the trip was the Middlesbrough Transporter Bridge. This is one of only six transporter bridges worldwide which remain operational (the others are in Newport, Bilbao, Rochefort, Osten, and Rendsburg). We visited it while it was closed for a major refurbishment (structural steel repairs and repainting), but were lucky enough to get a guided tour to the top of the bridge from the contractor, and of the machine house by one of the bridge's electricians.

The bridge was opened in 1911, nearly four decades after Charles Smith first proposed the concept of an "aerial ferry" bridge. Smith's idea was taken up by French engineer Ferdinand Arnodin, who designed several transporter bridges. The bridge at Middlesbrough, however, was designed by Georges Imbault, of Cleveland Bridge & Engineering Co Limited.

Unfortunately, we didn't have time to photograph the bridge from a proper distance, but most of the website links at the end of this post have plenty of photos. Seen in profile, it's a particularly fine structure. The four towers support cantilevering trusses, joined at mid-river by a hinge, and held down behind the towers by cables anchored vertically to the ground. It's the hinge that makes the bridge particularly attractive, I think. Several of the other surviving examples, particularly those designed by Arnodin, are suspension bridges with stiffening trusses, lacking the simplicity of the Middlesbrough design.

As part of the bridge's refurbishment, a lift will be installed at the south end, allowing more regular public access to the walkway level. The staircase that we climbed was steep and, on a windy day, terrifying enough for a group of hardened bridge enthusiasts, let alone the general public.

The trip to the top of the bridge, and the opportunity to quiz one of the engineers working on the refurbishment, was a great start to the study tour. Much of the repair and repainting work at high level is being undertaken from the upper transporter carriage, a high-level platform which rolls along the support girders and from which the bridge gondola is hung. This is both safe and reduces greatly the amount of temporary containment required when removing existing paintwork. However, several other parts of the bridge can be reached only with the use of roped access.

We also had a very interesting look around the bridge's machine house. As this was not in operation, most of the protective covers for the machinery and electrical equipment had been removed. What you can see in the photos is therefore quite different to what would normally be visible. It was particularly interesting to observe the difference between the original control panel, with massive fuses and electrical contacts, and the modern push-button panel.


Further information:


Anonymous said...

What are those thingies in the first machine-room photo, that look like curved sliding contacts?

The Happy Pontist said...

That's some kind of power feed device for the original motor. I assume it's no longer used, as there is a new motor. As I understand it, the controller rotated the device with the circular contacts, this could bring more contacts into position simultaneously, and hence increased the power delivered to the motor.