Could rubber tyre foundations help protect buildings during earthquake?

Many homes in Lombok have been destroyed. Image: EPA/Adi Weda.

At the time of writing, 436 people have died following an earthquake in the Indonesian island of Lombok. A further 2,500 people have been hospitalised with serious injuries and over 270,000 people have been displaced.

Earthquakes are one of the deadliest natural disasters, accounting for just 7.5 per cent of such events between 1994 and 2013 but causing 37 per cent of deaths. And, as with all natural disasters, it isn’t the countries that suffer the most earthquakes that see the biggest losses. Instead, the number of people who die in an earthquake is related to how developed the country is.

In Lombok, as in Nepal in 2015, many deaths were caused by the widespread collapse of local rickety houses incapable of withstanding the numerous aftershocks. More generally, low quality buildings and inadequate town planning are the two main reasons why seismic events are more destructive in developing countries.

In response to this issue, my colleagues and I are working on a way to create cheap building foundations that are better at absorbing seismic energy and so can prevent structures from collapsing during an earthquake. And the key ingredient of these foundations is rubber from scrap tyres, which are otherwise very difficult to safely dispose of and are largely sent to landfill or burnt, releasing large amounts of carbon dioxide and toxic gases containing heavy metals.

Rubber-soil mixture

Previous attempts to protect buildings from earthquakes by altering their foundations have shown promising results. For example, a recently developed underground vibrating barrier can reduce between 40 per cent and 80 per cent of surface ground motion. But the vast majority of these sophisticated isolation methods are expensive and very hard to install under existing buildings.

Our alternative is to create foundations made from local soil mixed with some of the 15m tonnes of scrap tyre produced annually. This rubber-soil mixture can reduce the effect of seismic vibrations on the buildings on top of them. It could be easily retrofitted to existing buildings at low cost, making it particularly suitable for developing countries.


Several investigations have shown that introducing rubber particles into the soil can increase the amount of energy it dissipates. The earthquake causes the rubber to deform, absorbing the energy of the vibrations in a similar way to how the outside of a car crumples in a crash to protect the people inside it. The stiffness of the sand particles in the soil and the friction between them helps maintain the consistency of the mixture.

My colleagues and I have shown that introducing rubber-soil mixture can also change the natural frequency of the soil foundation and how it interacts with the structure above it. This could help avoid a well-known resonance phenomenon that occurs when the seismic force has a similar frequency to that of the natural vibration of the building. If the vibrations match they will accentuate each other, dramatically amplifying the shake of the earthquake and causing the structure to collapse, as happened in the famous case of the Tacoma Narrows bridge in 1940. Introducing a rubber-soil mixture can offset the vibrations so this doesn’t happen.

A promising future

The key to making this technology work is finding the optimum percentage of rubber to use. Our preliminary calculations echo other investigations, indicating that a layer of rubber-soil mixture between one and five metres thick beneath a building would reduce the maximum horizontal acceleration force of an earthquake by between 50 and 70 per cent. This is the most destructive element of an earthquake for residential buildings.

We are now studying how different shaped rubber-soil mixture foundations could make the system more efficient, and how it is affected by different types of earthquake. Part of the challenge with this research is testing the system. We build small-scale table models to try to understand how the system works and assess the accuracy of computer simulations. But testing it in the real world requires an actual earthquake, and it’s almost impossible to know exactly when and where one will strike.

The ConversationThere are ways of testing it through large scale experiments, which involve creating full-size model buildings and shaking them to simulate the force from recorded real earthquakes. But this needs funding from big institutions or companies. Then it is just a question of trying the solution on a real building by convincing the property owners that it’s worthwhile.

Juan Bernal-Sanchez, PhD Resarcher, Edinburgh Napier University.

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

 
 
 
 

What does the fate of Detroit tell us about the future of Silicon Valley?

Detroit, 2008. Image: Getty.

There was a time when California’s Santa Clara Valley, bucolic home to orchards and vineyards, was known as “the valley of heart’s delight”. The same area was later dubbed “Silicon Valley,” shorthand for the high-tech combination of creativity, capital and California cool. However, a backlash is now well underway – even from the loyal gadget-reviewing press. Silicon Valley increasingly conjures something very different: exploitation, excess, and elitist detachment.

Today there are 23 active Superfund toxic waste cleanup sites in Santa Clara County, California. Its culture is equally unhealthy: Think of the Gamergate misogynist harassment campaigns, the entitled “tech bros” and rampant sexism and racism in Silicon Valley firms. These same companies demean the online public with privacy breaches and unauthorised sharing of users’ data. Thanks to the companies’ influences, it’s extremely expensive to live in the area. And transportation is so clogged that there are special buses bringing tech-sector workers to and from their jobs. Some critics even perceive threats to democracy itself.

In a word, Silicon Valley has become toxic.

Silicon Valley’s rise is well documented, but the backlash against its distinctive culture and unscrupulous corporations hints at an imminent twist in its fate. As historians of technology and industry, we find it helpful to step back from the breathless champions and critics of Silicon Valley and think about the long term. The rise and fall of another American economic powerhouse – Detroit – can help explain how regional reputations change over time.

The rise and fall of Detroit

The city of Detroit became a famous node of industrial capitalism thanks to the pioneers of the automotive age. Men such as Henry Ford, Horace and John Dodge, and William Durant cultivated Detroit’s image as a centre of technical novelty in the early 20th century.

The very name “Detroit” soon became a metonym for the industrial might of the American automotive industry and the source of American military power. General Motors president Charles E. Wilson’s remark that, “For years I thought what was good for our country was good for General Motors, and vice versa,” was an arrogant but accurate account of Detroit’s place at the heart of American prosperity and global leadership.

The public’s view changed after the 1950s. The auto industry’s leading firms slid into bloated bureaucratic rigidity and lost ground to foreign competitors. By the 1980s, Detroit was the image of blown-out, depopulated post-industrialism.

In retrospect – and perhaps as a cautionary tale for Silicon Valley – the moral decline of Detroit’s elite was evident long before its economic decline. Henry Ford became famous in the pre-war era for the cars and trucks that carried his name, but he was also an anti-Semite, proto-fascist and notorious enemy of organised labor. Detroit also was the source of defective and deadly products that Ralph Nader criticized in 1965 as “unsafe at any speed”. Residents of the region now bear the costs of its amoral industrial past, beset with high unemployment and poisonous drinking water.


A new chapter for Silicon Valley

If the story of Detroit can be simplified as industrial prowess and national prestige, followed by moral and economic decay, what does that say about Silicon Valley? The term “Silicon Valley” first appeared in print in the early 1970s and gained widespread use throughout the decade. It combined both place and activity. The Santa Clara Valley, a relatively small area south of the San Francisco Bay, home to San Jose and a few other small cities, was the base for a computing revolution based on silicon chips. Companies and workers flocked to the Bay Area, seeking a pleasant climate, beautiful surroundings and affordable land.

By the 1980s, venture capitalists and companies in the Valley had mastered the silicon arts and were getting filthy, stinking rich. This was when “Silicon Valley” became shorthand for an industrial cluster where universities, entrepreneurs and capital markets fuelled technology-based economic development. Journalists fawned over successful companies like Intel, Cisco and Google, and analysts filled shelves with books and reports about how other regions could become the “next Silicon Valley”.

Many concluded that its culture set it apart. Boosters and publications like Wired magazine celebrated the combination of the Bay Area hippie legacy with the libertarian individualism embodied by the late Grateful Dead lyricist John Perry Barlow. The libertarian myth masked some crucial elements of Silicon Valley’s success – especially public funds dispersed through the U.S. Defense Department and Stanford University.

The ConversationIn retrospect, perhaps that ever-expanding gap between Californian dreams and American realities led to the undoing of Silicon Valley. Its detachment from the lives and concerns of ordinary Americans can be seen today in the unhinged Twitter rants of automaker Elon Musk, the extreme politics of PayPal co-founder Peter Thiel, and the fatuous dreams of immortality of Google’s vitamin-popping director of engineering, Ray Kurzweil. Silicon Valley’s moral decline has never been clearer, and it now struggles to survive the toxic mess it has created.

Andrew L. Russell, Dean, College of Arts & Sciences; Professor of History, SUNY Polytechnic Institute and Lee Vinsel, Assistant Professor of Science and Technology Studies, Virginia Tech.

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