Women from Turkey check their destroyed building, in Kahramanmaras, southern Turkey, Photo / AP
We can’t prevent earthquakes but engineers and architects have the knowhow to design structures that can keep residents safe.
Home is supposed to be a refuge. But when an earthquake strikes, it can become lethal. It is not the quake that kills but the house itself; collapsing structures, falling floors, crumbling walls.
The powerful earthquakes that shook south-eastern Turkey and northern Syria on February 6 reduced entire streets and city blocks to rubble. These were modern blocks built, like almost all our buildings today, of concrete reinforced with steel, just like it says in the architectural textbooks. How could they have failed so badly?
“We as engineers have the knowledge to build a building that could withstand anything,” says Dr Yasemin Didem Aktas, an Ankara-born structural engineer specialising in seismic structures who teaches at UCL in London. Yet, she adds, after the 1999 earthquakes centred on İzmit, “we saw the ruins of the buildings which had collapsed. There was concrete we could crush in our hands, we saw [the wrong] sand substituted in concrete, shortcuts in construction.
“Since then Turkey has strong regulations, state of the art, but it is not how buildings are being built.”
According to the Turkish Environment and Urbanisation Ministry, in 2018 more than 50 per cent of all buildings in the country, almost 13 million structures, had been constructed illegally. Despite frequent earthquakes, only very few older buildings were retrofitted with extra protection or reinforcement. In fact, in 2018 the Turkish government launched an amnesty in which owners of buildings constructed after 1999 could (for a small fee, of course) have them legitimised.
Turkey and Syria might be uppermost in our minds right now but they are very far from alone in facing real and potential disaster. A map showing the confluence of population density and areas of seismic activity is deeply unsettling. Bands of bright spots glow across northern India, Malaysia, Indonesia, Japan and all the way down the west coast of North, Central and South America in a dense, almost unbroken line.
The central California stretch of the San Andreas Fault is estimated to suffer an earthquake of a magnitude of 6 or above every 22 years. The fault’s last event with a magnitude comparable to the Turkey-Syria earthquakes was in 1906. Measuring 7.8 (the Turkey-Syria earthquakes on February 6 measured 7.8 and 7.5), it destroyed San Francisco. Devastating quakes in nations with strong building codes including those in Christchurch, New Zealand and Tohoku, Japan in 2011 powerfully demonstrated that destruction cannot all be blamed on the poor regulation, corruption or shoddy construction found in some developing economies.
Still haunted by the folk memory of the Great Kantō earthquake of 1923, which flattened the traditional wooden buildings of historic Tokyo and Yokohama and claimed 140,000 victims, Japanese engineers and manufacturers have continued to innovate. From hydraulic dampers and huge movement-compensating pendulums to meshes that wrap buildings in stabilising nets, new engineering ideas, both complex and seemingly simple, keep coming.
Well-known architects including Kengo Kuma and Sou Fujimoto are continuing to propose elegant architectures of increased stability. Shigeru Ban, who designed temporary homes using cardboard tubes, string and tarpaulin after the Haiti earthquake of 2010, has also designed simple earthquake-resistant houses from cheap materials which can be built by communities without outside help.
At the other end of the scale, the largest buildings employ base isolation, in which sliding or shear supports allow the structure to decouple from its base during violent shaking. For taller buildings “tuned mass dampers”, essentially weights of steel or tanks of water high up in the towers, help reduce extremes of movement. The same devices are used to reduce the speed of sway in, for instance, New York’s skinnyscrapers.
If, a century ago, the Great Kantō earthquake tragically illustrated the limitations of historic and early modern buildings in resisting shaking, more recent seismic events in Kobe, Hebei and Mexico City have demonstrated that it is not heavily engineered skyscrapers but the now ubiquitous, recently built midsized apartment blocks of fast-growing cities that have become the most vulnerable and dangerous class of building.
“There are different ways buildings can go wrong,” says Aktas. “There are often economies made in the construction process, cheaper materials substituted, poor quality used in concrete or reinforcement bars omitted to save money. But there is also what happens post-occupancy; building owners adding extra floors or even removing structural columns or walls on the ground floor to put in, for instance, a supermarket.”
This is known in seismic-speak as a “soft first storey”, a ground floor with higher ceilings than the rest of the building and, perhaps, large shop windows, all of which lead to reduced structural strength exactly where it is most needed.
The aftermath of the recent earthquakes has also highlighted another urban situation in which extensive public space is needed for gathering after disasters when structures may still be unsafe. “There were many of these designated spaces [across Turkey],” says Hakan Topal, a Turkish artist and engineer living in Brooklyn, “often public parks and squares...but they were built over with shopping malls.”
It might be counterintuitive but engineers and architects design for damage, or at least accept it. “We design for life safety,” says Aktas. “In these kinds of extreme events a degree of damage helps to dissipate the energy of the earthquake. We can be happy with that, but it should happen in a way that does not affect the structural stability of the building. What we’re seeing on pictures and on TV, these collapsed and pancaked and crumbling structures, tell me we will need to understand better what happened here.”
Aktas’s expression “pancaked” has cropped up across the coverage of the aftermath of these earthquakes. It describes a collapse in which the joints between walls and floors fail and the floors pile down on to each other like a stack of pancakes, crushing residents with no warning. It usually indicates that some stage of the construction process has been compromised.
Structural engineer Hanif Kara, founder of London-based AKT II, tells me “these look like failures caused by very basic constructional mistakes. The joints, the connections between vertical columns and horizontal slabs, are not properly connected. You would imagine that the knowledge of how to build to withstand earthquakes is widespread enough but my instinct is that it was not done.”
In Turkey, Aktas says, “the retrofitting of old neighbourhoods to meet new seismic regulations has been used as a tool for gentrification”. Condemned as unsafe, historic buildings were torn down rather than reinforced. Politicians, she says, realised these historic places, often close to the centres of cities (most visibly in Istanbul), were rife for redevelopment and this was just the excuse they needed for the social cleansing of the existing, working-class residents.
“Erdoğan used construction as a tool to develop the economy, nothing could get in its way,” says Topal. He also says that as part of a populist policy, “there was a suggestion that a business-friendly government meant getting rid of the ‘elite’: the architects, engineers and academics”. The bureaucrats who supervise building regulation (always unpopular in a real-estate-driven economy) look like an easy cut.
Engineers, as Aktas says, can design for almost any eventuality, to withstand almost any earthquake. But most people would not choose to live in a massive concrete box with tiny windows, and contractors would not make much money building them.
Perhaps the biggest problem is the way we build, the ingrained conventions. The kinds of rectangles and cubes that might be the most convenient to put up and to live in make for surprisingly fragile structures. Small compromises in construction, weak joints and bad connections can easily and fatally undermine structural integrity. To watch a model of a three or four-storey building wobbling like jelly before it collapses entirely on a simulator provokes a queasy realisation of our vulnerability.
There are, however, simple retrofitting measures that can make a huge difference. Diagonal brackets in the corners radically but relatively discreetly increase stability in the kinds of torsion experienced in an earthquake, for instance. Motion dampers installed on alternate floors can be enough to counter the worst damage and the danger of collapse.
“In Indonesia,” Kara tells me, “they’ve built shelters inside houses, one room which is stronger than the others so that if there is an earthquake the residents have somewhere secure to go.” A very different kind of safe room.
Much of California has been effectively retrofitted with retroactive anti-seismic measures. Los Angeles and Santa Monica have both made retrofitting all vulnerable buildings mandatory but plenty of other cities continue to resist.
David Cocke, president of both the Earthquake Engineering Research Institute and Structural Focus in Gardena, California, says: “Things are getting better, particularly in California, but we are always in danger of becoming complacent. The events in Turkey are terrible but we need to use the attention of the press that they generate, to use that emotion. We have a window of a few months while it is fresh in people’s minds and we need to take advantage to push regulation.”
History, as ever, is rich in inspiration. After the 1755 quake that destroyed the city of Lisbon, architects and engineers came up with the Pombaline Cage. This was a system of timber framing using vertical posts, beams and diagonal reinforcements all infilled with masonry. The system took advantage of the flexibility of timber and the solidity and fireproof qualities of stone. The city’s new Baixa district was entirely rebuilt using these methods.
From the Andes to Indonesia, bamboo has proved a remarkably resilient material. Now enjoying a renaissance due to its sustainability (certainly in comparison to carbon-heavy concrete), bamboo is flexible, lightweight, able to be locally grown and a renewable resource. Colombian architect Simón Vélez builds complex, beautiful buildings using bamboo and he has inspired others across the Pacific (and the wider world) to use it too. Quick to grow and simple to handle, it can be employed by small communities without heavy equipment. Even if damaged by tremors, bamboo buildings are easy to repair and, if they partially collapse, less lethal than concrete slabs.
Engineering company Ramboll developed earthquake-resistant bamboo houses in Lombok, Indonesia, with cross-braced structures and woven screens. Rural Urban Framework’s House for All Seasons in China’s Shaanxi Province employs concrete alongside mud brick to create a low-slung, low-tech, earthquake-resistant architecture that builds simply and elegantly on local languages of construction.
For architect Yasmeen Lari, the Pakistan earthquakes of 2005 were a spur to the design of a series of community-constructed dwellings (instructions available on YouTube) designed to be resistant to quakes and floods, while also suitable as both emergency relief and long-term housing. Cross-braced for stability but simple and cheap, they begin to address the huge problems of homelessness in the aftermath of disaster, which often leads to more deaths than the event itself.
Very different is Noriyosha Morimura’s Television House in Japan’s Suita City, a high-tech dwelling set on a V-shaped base designed to isolate the structure from tremors. In his monumental ensemble in Chengdu, the Sliced Porosity Block, architect Steven Holl used the extra diagonal bracing needed for earthquake protection as a device to disrupt the architectural grids, creating curious geometries and a little surprising aesthetic relief. In Japan, Studio Sklim’s Hansha Reflection House employed traditional Japanese carpentry techniques combined with reinforcement to create a very contemporary earthquake-resistant dwelling.
The harsh truth, however, is that most of the world’s residential construction is not regulated at all — or, if it is, its effectiveness is eroded by corruption and neglect. It is difficult to accept that each earthquake brings with it seemingly endless human tragedy. But even in the poorest cities, measures can be taken to ensure that it is buildings rather than residents that sustain the worst damage.
“The issue just needs to be kept in the public consciousness,” says Kara. “We need to educate about the importance of good construction and the UN needs to be doing much more here.”
“We should recognise that this was a very powerful earthquake. We would always have expected damage,” says Aktas. But a magnitude 7 earthquake hits the earth somewhere about once a month — a quake measuring 6.3 shook New Zealand this week. Mostly they happen where there are no people; wherever they strike, the earth doesn’t care. So we must. By building better.
Written by: Edwin Heathcote
© Financial Times
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