Thursday, 26 July 2012

After suspension bridges – what about Cable-Stayed bridges

Cable-stayed bridges seem to be taking over from suspension bridges so after discussing at Hungerford and Clifton, I thought I’d investigate this type. Although many have been built in the last 50 years or so, the design has been around for much longer. Some notable early bridges are either cable-stayed or a combination of suspension and cable-stayed:  the Victoria Bridge, Bath (1836) the Albert Bridge across the Thames (1872) and the Brooklyn Bridge in New York (1883)

Victoria Bridge and Albert Bridge
 The first modern cable-stayed bridge is usually quoted as the Strömsund Bridge in Sweden, built in 1955.

Strömsund Bridge

Since that date may have been built: the Queen Elizabeth II bridge which takes the M25 over the Thames and the Second Severn Crossing are two in the UK.

Second Severn Crossing

Probably the most famous is the Millau Bridge in France, designed by the French structural engineer Michel Virlogeux and British architect Norman Foster, it is the tallest bridge in the world. It also has the highest structure in France – one of the piers at 343M is taller than the Eiffel Tower (323M). The Millau has 7 piers and 8 spans. This, I believe, makes it the longest cable-stayed span in the world. Interestingly Wikipedia, in it’s list of longest cable-stayed bridges, doesn’t include the Millau because the others have longer approach bridges which are not cable-stayed.

Millau Bridge
The main difference between suspension and cable-stayed bridges is that in the latter, much of the weight of the bridge is taken by the cables to the anchorages which need to be substantial. In cable-stayed, the weight is taken to the piers. Also multiple-span suspension bridges are not possible.

Monday, 23 July 2012

Another recycled construction – Hungerford Bridge and the Clifton Suspension Bridge, Bristol

Another ‘green’ construction , but much older than the Olympic stadium is the Hnngerfrod Bridge across the Thames from Charing Cross to the South Bank near the Festival Hall. The original bridge was built by Isombard Kingdom Brunel in 1845. It was a suspension bridge linking the north bank of the Thames with the Hungerford Market – hence the name. 

When the railway company extended their track to the new Charing Cross station in 1859, they replaced the suspension bridge with a wrought iron gifder bridge designed by John Hawksmoor. At this stage, the suspension links were reused for the Clifton Suspension Bridge which still spans the Clifton Gorge in Bristol. 

We rather take for granted today engineering standards but in Brunel’s day, they didn’t have any standard components. Brunel had to calculate the size and strength of the links needed for his design. All the links were individually cast on site and tested to ensure they were strong enough to support the calculated weights. That they are still in use today supporting the Clifton bridge is a tribute to Brunel’s engineering skill.

The Olympics are nearly here – I’ve had a look at the stadium design

While the stadium doesn’t have the same iconic look as the Beijing “Bird’s Nest” stadium, it has a number of interesting features. One is that it is a very green building – I haven’t been able to find out how green, but one reference says “Most, if not all, of the structure was made with recycled materials like rejected plastic crates and excess concrete from other areas of the park”

The architect Peter Cook has also designed the stadium so that after the games the top sections can be removed, reducing the capacity from 80,000 to 25,000. The stadium has been shortlisted today for the Stirling Prize – the RIBA’s annual architecture prize. The full shortlist can be seen at The Guardian’s comments are at

More info about the stadium:

Wednesday, 4 July 2012

A good day

A good day for two reasons. Firstly an important day for physics: CERN has confirmed with nearly 100% certainty that the Higgs Boson exists. I won’t try to explain - or understand it but it is a very significant confirmation of the explanation of matter. It’s existence was forecast in 1964: earlier models couldn’t explain mass (weight to us) until this particle was added to the models. The whole elementary particle and quantum mechanics world is fascinating but difficult to take in: electrons - whose existence is fundamental to our modern high-tech world - don’t exist as ‘things’ in the sense that we understand, rather they have a probability that places them over a range of locations with a most likely location. When in university, I played with tunnel diodes - devices that have negative electrical resistance which can be explained by this probability theory. Light normally behaves as waves but can also exhibit characteristics of particles - photons. Proving the existence of these elementary particles is a complex game: they only exist for fractions of a second and need complex mechanisms to detect their existence. 

The second ‘good day’ reason was a Young Enterprise event at the Cooper School, Bicester. Sell for Success is a day of business games to give students an intensive introduction to enterprise and business skills. Groups of year 11 (5th form in old currency) students have to design, market and finance a game console. We had five groups of about a dozen each today from a range of Oxford schools. I played the role of Supplier of the consoles - manufactured in India. Each company has to decide on the spec for the console, sort out financing (another adviser plays bank manager) and market the device once they’ve decided on all the options. They don’t make a real console, of course, but do make a mock-up and have to make a presentation to the judges and the rest of the students. 

It’s a high-pressure day, particularly as most of the groups come together for the first time so they have to build themselves into a team very rapidly before negotiating with bank manager and me. They all did exceptionally well, gelling as teams very rapidly and having great fun. I’m sure they have started to develop a range of skills that they will find very useful whatever career they chose. One of the teachers reported that several had said that based on their experience of the day, they want to take part in the YE Company Programme during the next academic year. This involves groups of students forming their own companies and developing and selling products or services: no business games, this is for real.

Apart from the fun of the day, all the students today were great. Youngsters get such a bad press these days but everyone I saw today was well behaved, courteous and mature. Not the image one sees in the press.

Altogether a great day!