Could this new anti-earthquake technology protect cities from destruction?

The Marina District of San Francisco in October 1989, after it was hit by an earthquake measuring 7.1 on the richter scale. Image: Getty.

Protecting cities from earthquakes is still a grand challenge that needs addressing, as recent disasters in Nepal, Japan, Haiti, and Chile show. Significant progress has been made in understanding seismic activity and in developing building technology – but we still don’t have a satisfactory way of protecting buildings on a large scale.

For new buildings, anti-seismic technology is today considered quite advanced, and it is possible to build individual structures that can withstand the vast majority of recorded earthquakes. Devices such as isolation systems and dampers, which are designed to reduce the vibrations – and, as a consequence, the damage – induced by earthquakes, are successfully being employed in the design of new buildings.

But large numbers of buildings exist in earthquake zones that don’t have built-in protection. That's particularly true in developing countries where replacing them or introducing stricter – and more expensive – building codes aren’t seen as an option. More than 130,000 houses were destroyed by the earthquake in Nepal in April 2015.

What’s more, these technologies are rarely used for protecting existing buildings, as they generally require substantial alteration of the original structure. In the case of heritage buildings, critical facilities or urban housing, especially in developing countries, traditional localised solutions might be impractical.

This means there is a need for alternative solutions that protect multiple existing buildings without altering them using a single device. At the University of Brighton, we have designed a new vibrating barrier (ViBa) to reduce the vibrations of nearby structures caused by an earthquake’s ground waves. The device would be buried in the soil and detached from surrounding buildings, and should be able to absorb a significant portion of the dynamic energy arising from the ground motion with a consequent reduction of seismic response of between 40 and 80% per cent.

In need of protection. Image: Narendra Shrestha/EPA.

The idea behind this technology was to look at buildings as an integral part of a city model, which also includes the soil underneath them and the interaction between each element, rather than as independent structures. Each ViBa can be designed to protect one or more buildings from an earthquake; but also it forms part of a network of devices placed at strategic locations in order to protect entire cities.

The ViBa itself is essentially a box containing a solid central mass held in place by springs. These allow the mass to move back and forth and absorb the vibrations created by seismic waves. The entire structure is connected to the foundations of buildings through the soil to absorb vibrations from them. The box’s exact position underground would depend on how deep the surrounding foundations went; it could even be placed on the surface.

As the ViBa is designed to reduce all vibrations in the soil, it could also be used to insulate buildings against ground waves from human activities such as road traffic, high-speed trains, large machinery, rock drilling and blasting. In this way, the technology would be able to absorb a larger quantity of energy than traditional measures used to insulate railways such as trenches or buried sheet-pile walls.

Starting construction

The problem with the ViBa is its size – it would need to be at least 50 per cent of the mass of the average building it was protecting – and how much money it would cost to build and install as a result. So compared to current technologies to protect single buildings it would likely come with a much higher price tag. But as the ViBa can be designed to reduce the vibrations of more than one building, or for buildings of historical importance for which current technologies are impractical, it can still be considered as a viable solution.

So far we have only modelled how the ViBa would work, using computers and prototypes in the lab. To be deployed in the real world we would need to do a lot more experimenting to understand exactly how it would work, and to make sure it didn’t produce any damaging side-effects on the surrounding buildings. We would also need to work with industry to work out how to build and install it in the most cost-effective way.

But our latest research suggests the ViBa is a viable alternative strategy for protecting buildings from earthquakes. In the long term, it could lead to safer cities that are better equipped to deal with disasters and ultimately save lives. The Conversation

Pierfrancesco Cacciola is assistant head of the School of Environment and Technology at the University of Brighton.

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

 
 
 
 

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.