Scientists have designed a “skin” that senses when concrete structures are damaged

Image: Bittbox via Flickr, reproduced under creative commons.

Concrete is pretty great, isn’t it? It’s strong, it’s cheap, it’s easy to use. Let’s hear it for concrete!

On the downside, though, it’s also prone to cracking – if there are swift changes in temperature, for example, or if it’s bearing too much weight. Cracks in concrete structure are annoying at the best of times, but if said structure is holding, say, nuclear waste, they can also be disastrous.

So a team of scientists from North Carolina State University and the University of Eastern Finland have developed plans for a “skin” that would flag up cracks or damage to the concrete’s surface. Their idea involves installing electrodes at the edges of a structure, then applying electrically conductive copper paint across the concrete. The electrodes would emit a constant, low-level current across the surface of the painted “skin”, monitored by a computer. If the surface was weakened, cracked or damaged, the paint would become less conductive, and the computer would sense a change in the signal. You can even analyse the data to produce a map of the damage.

Here’s a cracked piece of concrete, alongside a computer rendering of the damage:

Image: Aku Seppänen.

So far, the researchers have only tried the method out on small, 1m long pieces of concrete, but they’re hoping to test on bigger areas. Dr Mohammad Pour Ghaz, one of the paper’s co-authors, said the team were keen to show the method could work on “real-world structures”.

 
 
 

Istanbul is building a 47km monorail network to deal with its crippling traffic congestion

A metro train crosses the Istanbul's Goldern Horn. The line opened last February. Image: Ozan Kose/AFP.

Istanbul has tried to combat its notorious traffic levels with nearly every type of public transport under the sun – buses, metrobuses, suburban and subway trains, trams, funiculars, cable cars, ferries, sea taxis, and the ever-popular shared taxi vans known as dolmush – but all to little avail. The city regularly tops road congestion rankings in Europe and beyond.

Now, for its latest projects, the city municipality has decided that the sky is no longer the limit.

Eight monorail lines will connect a number of neighbourhoods on both the European and Asian sides of the city, carrying 200,000 passengers a day. When completed, the 47 km-long system, called the Havaray, will be the first major monorail system in Europe. The municipality also hopes to span two cable car lines across the Bosphorus.

Turkey’s largest city is in desperate need of traffic relief. Three million private cars clog Istanbul’s roads; around 20,000 more join them every month, in addition to around 5,000 buses and 17,000 taxis.

These numbers, combined with central Istanbul’s old, narrow streets and the ever-busy bridges, create hour-long traffic jams: researchers found that the speedy 12-minute drive between the districts of Bakirkoy and Mecidiyekoy turned into a 115-minute crawl at peak time. In Europe, only Moscow has higher road congestion levels.

Such traffic jams not only annoy commuters, but cause significant economic damage. Travel delays and high petrol consumption in Istanbul cost the Turkish economy an estimated 6.5bn lira (around £1.8bn) each year.

The mayor of Tuzla, a district on the Asian side which will be connected to the Kartal neighbourhood via a three-kilometre monorail, therefore greeted the project with enthusiasm: the Havaray would be a “milestone” for Istanbul, he said.

Yet the city’s Chamber of Urban Planners is unsure whether the project will have any impact on Istanbul’s traffic. “You need a general plan,” said Akif Burak Atlar, the Chamber’s secretary-general. “Not just connecting two hills with a cable car, or connecting two provinces with a monorail.”

He worries that the Havaray’s separate lines will not be integrated into the wider public transport system, comparing the new schemes to the subway and metrobus stations at Mecidiyekoy. “They were opened in different times and it took five years for them to connect these stations. You couldn’t reach one station from the other,” he said.

Although the chamber supports investments into any kind of public transport, Atlar favours expanding the existing railway network over building a completely new system such as the monorail. “I was thinking, this is not what you learn at school. You bring a project like this in front of a jury, you fail at school.”

Istanbul's rapid transit network, as of September 2014. Click to expand. Image: Maximilian Dörrbecker via Wikimedia Commons.

Professor Mustafa Ilicali, a transportation consultant for the municipality, agrees: “Expanding railways will be Istanbul’s only saviour,” he told Turkey’s Anadolu Agency in October.

The municipality has launched several railway projects, and plans to add more than 600 km to its existing 150 km-long metro network within the next five years. In 2013, it completed the Marmaray railway, which links the Asian and European sides underneath the Bosphorus.

The Marmaray was expected to carry 1.5m passengers each day, reducing Istanbul’s traffic by 10 to 20 per cent. Yet one year after it was opened, just 110,000 commuters took the Marmaray every day.

Clearly, expansion is not enough: the municipality also needs to encourage commuters to swap their cars for buses, trams and trains, for example by reducing ticket prices, Atlar says.

“When you look at the railway use in Istanbul and compare it with Tokyo, New York, Paris, London, Berlin – it’s not more than 15 per cent. In Tokyo it’s more than 95 per cent,” he said. “More integrated, more comfortable and cheaper public transport will solve the traffic problem.”

Although he is undecided about the monorail, Atlar is critical of the municipality’s dream of a cable car ferrying commuters from Europe to Asia. “You can do it as an attraction. Cable car slowly crosses the Bosphorus, you can take pictures, nice for you, enjoy it – it’s for tourists."

He adds a warning about the need to maintain a protected view. “You have to be careful about the silhouette of the Bosphorus,” he says. “There is a law – if you act according to law, it shouldn’t be possible to build anything like that.”