20 April 2014

Tyneside Bridges: 4. Gateshead Millennium Bridge

I'm still (very slowly) writing up bridges from the second day of last year's IABSE Study Tour of north east England. At last, we came to the mightiest bridge of the tour, the Gateshead Millennium Bridge.

Because I'm struggling to find time to write for this blog, I'm mainly just going to offer you a series of photos with brief comments. But really, this bridge can speak for itself.

This is the classic view of the bridge, taken from the north bank of the Tyne. The weather was fairly miserable when I visited, but that doesn't detract much from this remarkable view.

From a distance, it's not just the arch which is striking, it's also the slenderness of the deck. There's a lot of metal in that deck, but it doesn't look like it from here.

Viewed from the west, the deck appears less slender, as from this side you're looking at the main deck edge girder, not the sharp edge of a walkway cantilever.

The arch is kite-shaped in cross-section, with a curved front face and a sharp rear edge. This simple feature provides the vast majority of the bridge's visual interest, offering a fresh and interesting geometry from almost every perspective.

The deck offers a game of two halves, separating foot from cycle traffic and employing two different surfaces. On the right hand side of the second image, the deck hides a stiff steel box girder. This curves in plan to make it long enough to gain the sufficient navigational height over the river without making pedestrian gradients too steep. On the left hand side, lighter weight aluminium deck panels are supported on transverse cantilever arms.

The two halves are separated by a step and a perforated metal "hedge", which acts as a windbreak and also incorporates space for seating.

A glass "shed" at the south end of the bridge sits above the machine control room, and provides space for the bridge operators to receive guests. A matching glasshouse at the north end is available for other use, e.g. exhibitions, but was unused when I visited.

Each end of the bridge is supported on a giant steel hinge. Below this, a steel fin protrudes downwards. Hydraulic rams act against this fin to raise (or lower) the bridge, and their action has to be carefully coordinated to prevent twist occurring.

The form of bridge is fundamentally inefficient when considered as a moveable structure: it is unbalanced in almost every position, and therefore the loads on the rams are considerably greater than the loads borne by most moveable bridge machinery. The foundations must resist commensurate forces.

On our visit, we were lucky enough to get access both to the hydraulic ram pit and also to the bridge control room. This is the main control panel.

It's a hugely impressive piece of both engineering and architecture, quite deserving of its many accolades and awards. It has been suggested that this is one of the most expensive footbridges ever built, and that's probably true, especially for the width of obstacle crossed. But it's a hugely iconic structure, a tribute to the ingenuity and perseverance of its designers, and certainly one of the most lasting monuments to have emerged from the turn of the millennium.

Further information:


Pete said...

Thanks again for a great write up - any chance of doing a post for graduates with recommendations and tips for becoming a good bridge engineer? I'm sure theres a lot of grads like me who read your posts a lot, and we'd definitely appreciate it. Thanks as usual,

Anonymous said...

Unquestionably a great engineering and architectural accomplishment. I always cite this bridge as a brilliant example of engineering creativity. Nevertheless, I still wonder about the issues raised in your third-from-the-end paragraph. How is the bridge performing and how will it perform as it gains age and use are the questions I would ask if I was the Owner.

The Happy Pontist said...

Pete, I'll consider that.

For now ... work on the best projects you can, with the best people you can. I learned a great deal from an older engineer early in my career, and was lucky to work on a wide variety of very different schemes. If you have to move jobs to find that, do it.

Never turn down a challenge. If you think something will be tough, take it on. You learn little from the tasks you know will be easy.

Finally, take every opportunity to learn. You can learn from most situations, including visits to real bridges of all types. But ask yourself: who are the best bridge engineers working today? Or last century? If you can't answer those, then go and find out. And learn stuff you don't immediately need - store it for the future. Perhaps keep a notebook or sketchbook. That way you'll be much better prepared when the challenges and opportunities do come along.

Imre Laufer said...

Pete, I'd add one more thing to the tips on how to become a good engineer:

Be always ready to question and evaluate "ready-made solutions". This is especially true if the answer to your "Why?"-question is only a simple "We used to do it like this for ages", or something similar.
This helps not only to "wire together" the different and detached things that you've learned in school, but - especially with the help of an older, more experienced engineer - you can quickly get "the feeling" about important or lesser important aspects of a problem.

Of course, you will many times find that a "We used to do it like this for ages" solution is indeed a good one, but then you already know the "why" behind it. And perhaps more importantly, you'll be able to recognize your limits. This may sound a bit odd, but remember that one cannot be an expert in everything, and you'll be responsible not only for your work, but also for yourself and - even more important - your family. Of course, if you know your limits, then you probably know already how to expand them.

I admit that my 6 years of working experience aren't too much. But the above points are maybe the most important lessons I've learned so far from both working at a larger engineering company and as a freelancer.

Brandon Mills said...

Hello Happy Pontist! I was on this tour with you. And I have been aware of your site for some time. This was certainly a great tour. Kind Regards.