The story of Prague’s most dominant bridge and how it was tested using tanks

Photo: Petr Brož, CC 3.0 license

For today’s episode of Czech History I’ve come here to Nuselský most or Nusle Bridge which joins two parts of the city. Completed in 1973, the bridge serves as a major artery for six lanes of North-South traffic and even the city’s metro. Every single day countless thousands of commuters rely on it.

Photo: Petr Brož, CC 3.0 license
It is possible of course to walk across - and people do - using the two available sidewalks. It’s noisy here but the view is magnificent. In the distance you can see Vyšehrad, the seat of kings, Prague Castle, and all around, the city. From up here, in places, it’s 40 metres down. What is the bridge’s history? To find out more, I spoke to the original designer, architect Stanislav Hubička.

“The idea to build a bridge over Nusle Valley, connecting Pankrác plain with Prague’s Karlov, goes back to the First Republic. And, from as way back as 1933, it was clear the bridge would serve mass and public transport. It was conceived from the start that the bridge would have a section (originally for trams) and later for the metro to travel across.”

The very first plans for a bridge over the valley go back even earlier, to the turn of the 20th century: in 1903 engineer Jaroslav Marjanko, for example, proposed a steel design for the almost half-kilometre span. But it was not until the late 1950s that the issue was tackled head on, in answer to the rise of new development and housing on Pankrác plain. As the number of developments grew, so did the need for a major new bridge and it happened the design by Svatopluk Kobr, Vojtěch Michálek and Stanislav Hubička was chosen.

“I was only 30! I was chosen for the project because two years prior I had won the first prize for the design of the opera house in Ostrava – a solo project five years after completing my studies. Of course you have an enormous team of people on such an undertaking; you sort of have to get things in underway and make sure that the project meets expectations. The structure had to sing, so to speak, not groan. I had a lot of help and I focussed largely on the design of the columns, the supports and the underside of the bridge.”

Photo: Jklamo, CC 2.5 license
The plan was to construct the bridge from reinforced concrete. Though grey and somewhat grim, the enormous structure even today appears to soar: although gray, it is impressive, not oppressive, in large part thanks to the row of twin columns which support it. Stanislav Hubička says it was an essential part of the design: that the massive bridge should not feel overbearing but light, far above. The architect once again:

“I came up with a lot of ideas and basically we agreed that the row of twin support columns would diverge at an angle as they rose up funnel-shaped. The design was basically inspired by branches in Nature: open, subtle, allowing light and shadow through, ‘thin’ in the areas where they bore the greatest weight. It is this balance between the span of the bridge and the columns which creates drama and tension. For me that was very exciting.”

Construction of the bridge began in 1965 but there were some major modifications along the way: key changes were introduced as a direct result of Cold War politics. Original metro cars based on an effective Swedish design were replaced by much heavier Soviet-built trains. This caused no end of engineering problems which were a real sore spot, the architect says:

“Soviet experts decided that Russian trains would be used. We had designed the bridge and the tunnel inside to carry a light Swedish carriage and our own ČKD made an even better variation of the same. And then the news came: Russian carriages would be used. They were twice as heavy and had a lower chassis, meaning the whole design of the platform had to be changed.”

But by 1973 the bridge was ready, as it happens 25 years after the Communist putsch of February 1948, which the Communists exploited to their full advantage. But before it could be put into use, the bridge – originally named after the first Communist President Klement Gottwald – had to be properly tested. That, Stanislav Hubička says, is a fascinating chapter in itself:

“Heavy load tests were conducted, both static and dynamic. The statistic test saw more than 60 Russian tanks, weighing 35 tonnes each, driven onto the bridge and parked in rows along the sides. Then trucks brought in 3,000 tonnes of sand and gravel. And that’s not all. After this test, the tanks were driven back and forth... a full 600 times! There were sensors hooked up to a laboratory desk to measure the impact. You want to know what the maximum sag under all that weight was? 16.5 millimetres! A mere seventh of what was allowed.

“After that dynamic tests were conducted by firing rockets off the bridge. I have a photograph of one taking off. So that was it. The bridge did very well: it passed with flying colours.”

One sobering element in its history is that Nusle Bridge soon became a magnet for suicide jumpers, something the architect says no one on the team ever foresaw. Over the years, hundreds of people leapt to their deaths below, before a tall fence was erected to dissuade others. More effective was an overarching metal strip which is practically impossible to get over. When the strips first went up, TV stations showed seasoned rock climbers unable to get more than a leg over, proving that for most any attempt would be a futile task. That has had a largely positive effect.

Nusle Bridge, as it was renamed in 1990, is not a typical Prague wonder but it is well-worth seeing – and the view is fantastic. As architect Stanislav Hubička says, it will still be here after many of us are gone, lasting a full one hundred years.

“That’s the benefit of reinforced concrete. Two years ago I read there were some concerns about the material and material fatigue and so on... but they confirmed that the worries were unfounded. 100 years is guaranteed.”