Encasing old buildings in cheap plastic mesh could help save lives in earthquake-prone cities like Kathmandu

Few buildings in Kathmandu were specially engineered to withstand earthquakes. Image: Getty.

When a 9.0 magnitude earthquake hit Japan in March 2011, I was on the 9th floor of a 20-storey Tokyo hotel. The quake was one of the five most powerful since modern record-keeping began in 1900, and it lasted for around three minutes – an unusually long time.

Countless lives were saved by Japanese engineering. The tsunami that followed – and the resulting Fukushima meltdown – was a terrible tragedy, but the earthquake itself could also have caused far greater loss of life. It actually did very little damage relative to its magnitude.

The fact that buildings like the one I was in, and thousands of others, remained intact shows just how important good earthquake engineering is.

In Nepal, which was recently struck by a series of quakes, the largest of which was of 7.8 magnitude, the problem is quite different. A combination of poverty, a lack of specialised knowledge and poor regulation mean most houses were never built to such standards in the first place. Therefore it is these houses that retrofitting efforts – and my research in the country – must focus on.

As recent events have reminded us, it is collapsing structures that kill people during earthquakes, and very rarely the shaking itself. Engineers, through intensive and persistent analysis of past earthquakes, have mastered the art of building houses to resist shaking and to avoid collapse.

However, such earthquake-resistant buildings are expensive and require specialised knowledge and skills – it’s not something any old builder/architect combo can knock out overnight. There are specialised MSc courses and even doctorates in the subject – and engineers need continuous professional development to keep pace with the latest research. Japan has these skills and resources in abundance; a poorer nation such as Nepal, not so much.

Tokyo’s skyscrapers are built to sway. Image: Antonio Tajuelo.

Houses in Nepal are built with traditional knowledge and often without any engineer’s visit – the technical term is non-engineered buildings – and it is difficult to make them withstand earthquakes of large magnitudes.

In such scenarios, it is often prudent to rein in expectations and aim for the “least bad” outcome, by increasing the time it takes for the house to collapse. If, instead of two seconds, the building collapses in 12 seconds it may give the occupants enough time to escape.

The collapse of non-engineered masonry buildings is one of the greatest causes of casualties in major earthquakes around the world. Yet, by definition, these non-engineered structures remain largely outside of the scope of modern engineering research, focused as it is on new technologies and new buildings (fancy new quake-proof skyscrapers command significantly more funding than the unglamourous task of seismic retrofitting). This means that the majority of those at risk often remain so.

Even where research is focused on non-engineered housing, there are still significant social and economic challenges before implementation. It’s all very well asking people in Tokyo to pay a premium for seismic proofing, but Nepal’s gross national income per capita is $730 – just two dollars a day.

My research is aimed at developing retrofitting techniques which will prevent or prolong the collapse of adobe (mud brick) houses in strong earthquakes. We used common plastic packaging straps to form a mesh, which is then used to encase structural walls.

A mesh-enclosed house in Pakistan, before a covering mortar layer is applied. Image: Macabuag et al.

Tests showed that the proposed technique effectively prevents brittle masonry collapse and the loss of debris. We then trained rural masons in Nepal, gave a public “shake-table” demonstration and retrofitted a real house.

A clear ‘shake-table’ victory for the retrofit model house. Macabuag et al.

This implementation project proved effective at reaching rural communities – but it also highlighted the fact that government subsidies are still required to give low-income people the incentive to safeguard their homes against the next big earthquake.

Subhamoy Bhattacharya is Chair in Geomechanics at University of Surrey.

This article was originally published on The Conversation. Read the original article.

 

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Everything you ever wanted to know about the Seoul Metro System but were too afraid to ask

Gwanghwamoon subway station on line 5 in Seoul, 2010. Image: Getty.

Seoul’s metro system carries 7m passengers a day across 1,000 miles of track. The system is as much a regional commuter railway as an urban subway system. Without technically leaving the network, one can travel from Asan over 50 miles to the south of central Seoul, all the way up to the North Korean border 20 miles north of the city.

Fares are incredibly low for a developed country. A basic fare of 1,250 won (about £1) will allow you to travel 10km; it’s only an extra 100 won (about 7p) to travel every additional 5km on most lines.

The trains are reasonably quick: maximum speeds of 62mph and average operating speeds of around 20mph make them comparable to London Underground. But the trains are much more spacious, air conditioned and have wi-fi access. Every station also has protective fences, between platform and track, to prevent suicides and accidents.

The network

The  service has a complex system of ownership and operation. The Seoul Metro Company (owned by Seoul City council) operates lines 5-8 on its own, but lines 1-4 are operated jointly with Korail, the state-owned national rail company. Meanwhile, Line 9 is operated jointly between Trans-Dev (a French company which operates many buses in northern England) and RATP (The Parisian version of TfL).

Then there’s Neotrans, owned by the Korean conglomerate Doosan, which owns and operates the driverless Sinbundang line. The Incheon city government, which borders Seoul to the west, owns and operates Incheon Line 1 and Line 2.

The Airport Express was originally built and owned by a corporation jointly owned by 11 large Korean firms, but is now mostly owned by Korail. The Uijeongbu light railway is currently being taken over by the Uijeongbu city council (that one’s north of Seoul) after the operating company went bankrupt. And the Everline people mover is operated by a joint venture owned by Bombardier and a variety of Korean companies.

Seoul’s subway map. Click to expand. Image: Wikimedia Commons.

The rest of the lines are operated by the national rail operator Korail. The fare structure is either identical or very similar for all of these lines. All buses and trains in the region are accessible with a T-money card, similar to London’s Oyster card. Fares are collected centrally and then distributed back to operators based on levels of usage.

Funding

The Korean government spends around £27bn on transport every year: that works out at 10 per cent more per person than the British government spends.  The Seoul subway’s annual loss of around £200m is covered by this budget.

The main reason the loss is much lower than TfL’s £458m is that, despite Seoul’s lower fares, it also has much lower maintenance costs. The oldest line, Line 1 is only 44 years old.


Higher levels of automation and lower crime rates also mean there are fewer staff. Workers pay is also lower: a newly qualified driver will be paid around £27,000 a year compared to £49,000 in London.

New infrastructure is paid for by central government. However, investment in the capital does not cause the same regional rivalries as it does in the UK for a variety of reasons. Firstly, investment is not so heavily concentrated in the capital. Five other cities have subways; the second city of Busan has an extensive five-line network.

What’s more, while investment is still skewed towards Seoul, it’s a much bigger city than London, and South Korea is physically a much smaller country than the UK (about the size of Scotland and Wales combined). Some 40 per cent of the national population lives on the Seoul network – and everyone else who lives on the mainland can be in Seoul within 3 hours.

Finally, politically the biggest divide in South Korea is between the south-west and the south-east (the recently ousted President Park Geun-Hye won just 11 per cent of the vote in the south west, while winning 69 per cent in the south-east). Seoul is seen as neutral territory.  

Problems

A driverless train on the Shinbundang Line. Image: Wikicommons.

The system is far from perfect. Seoul’s network is highly radial. It’s incredibly cheap and easy to travel from outer lying areas to the centre, and around the centre itself. But travelling from one of Seoul’s satellite cities to another by public transport is often difficult. A journey from central Goyang (population: 1m) to central Incheon (population: 3m) is around 30 minutes by car. By public transport, it takes around 2 hours. There is no real equivalent of the London Overground.

There is also a lack of fast commuter services. The four-track Seoul Line 1 offers express services to Incheon and Cheonan, and some commuter towns south of the city are covered by intercity services. But most large cities of hundreds of thousands of people within commuting distance (places comparable to Reading or Milton Keynes) are reliant on the subway network, and do not have a fast rail link that takes commuters directly to the city centre.

This is changing however with the construction of a system modelled on the Paris RER and London’s Crossrail. The GTX will operate at maximum speed of 110Mph. The first line (of three planned) is scheduled to open in 2023, and will extend from the new town of Ilsan on the North Korean border to the new town of Dongtan about 25km south of the city centre.

The system will stop much less regularly than Crossrail or the RER resulting in drastic cuts in journey times. For example, the time from llsan to Gangnam (of Gangnam Style fame) will be cut from around 1hr30 to just 17 minutes. When the three-line network is complete most of the major cities in the region will have a direct fast link to Seoul Station, the focal point of the GTX as well as the national rail network. A very good public transport network is going to get even better.