The bridge between mechanical and civil engineers

Rochefort Transporter Bridge

Rochefort Transporter Bridge

Last night I was reminded of the fascinating world of moveable bridges. From the glorious transporter bridges of ports and river estuaries to hulking swing bridges of the New Jersey railroad, these projects would make interesting interdisciplinary case studies for civil and mechanical engineers.

The lightbulb went on when I found this fantastic set of animations on Wikipedia showing the movements of different types of moveable bridges. For me part of the wonder of civil engineering is the scale of the projects. When those massive structures start to move, well, I just have to sit down. But as well as wonder, I think they offer really valuable learning.

A conclusion of research interviews I carried out last year about developing engineering skills for industry was that engineering employers want graduates who can work with people from other backgrounds to solve engineering problems. In my experience as a civil engineering student we felt miles apart from our mechanical cousins down the corridor. Crudely, we were concerned with things that stayed still, and they were concerned with things that moved. Civils courses that had the word ‘dynamic’ in the title were considered hard and we knew our engineering relatives were studying a more difficult degree!

One of the challenges in giving students opportunities for interdisciplinary working is the siloed nature of university departments. This is a problem not just across engineering but also in the built environment. I know of major institutions whose civil engineering and architecture students never meet – at least in any formal capacity. So I am increasingly on the look-out for projects or topics that can bring different disciplines together. And a moveable bridge could be just the ticket.

At the Constructionarium, where engineering students build scaled versions of engineering structures using real materials, plant and processes, two of the bridge projects on site require already significant movement of the superstructure to complete the structure. At Millau the students construct bridge piers in the gorge and slide the deck units across from the gorge sides. At Kingsgate the two halves are the bridge a constructed on either bank of the river and then rotated into position to meet in the middle – I am still struck by the elegance of this construction method.

Moving a bridge deck once as part of the construction sequence is a starting point, but the real crossover with mechanical engineering begins when the bridge requires a permanent mechanism to make the movement repeatable. At their simplest, moveable bridges require bearings to move the deck units, but a more challenging project would be to have to include hydraulic rams to make get the deck to to lift or swing.

The aim of the crossover is to give students from either bank of this engineering divide the chance to understand the perspective of the people from the other side so that they might work together better in the future. For the civil engineer that might mean understanding how mechanisms are modelled, the dynamic forces on moving elements and the tolerances required to get the structure to work. For mechanical engineers that might mean understanding how a piece of mechanical plant fits into a civil engineering structure and understanding the practicalities of construction on site.

But as well as the educational reasons for wanting to develop a moveable bridge-themed student project, I have a more personal reason. When I lived in New Jersey I’d often take the train to New York, and I would stare out of the window in wonder at the host of moveable bridges of every type that the railroad uses between Jersey City and Elizabeth. We just don’t have the same proliferation of moveable bridges in the UK (maybe we paid more to put our railways on viaducts?).

A couple of years later I had a Saturday job in an office adjacent to Thomas Hetherwick’s roll-up bridge. We’d get people visiting the bridge every day and one time I got chatting to a retired engineer from the states, who it turns out had been a very senior member of staff at the US’s largest moveable bridge specialists. He had worked on and knew a great deal about many of those bridges that I had seen out of the train window in Jersey. Hearing that I was studying engineering, he told me all sorts of fascinating stories.

Six months later after leaving that job, I dropped by to see my old colleagues, and the receptionist gave me an envelope stuffed full of pictures and reports that that engineer had posted me from the states, without a return address – I had no way to say thank you. To make things worse, I then managed to lose this treasure trove. If I am able to contrive to get a moveable bridge project set up at the Constructionarium, it willl be my way of saying thank you to that generous-minded engineer.