- By Rebecca Morelle and Alison Francis
- BBC News Climate and Science
Structural and civil engineers from the UK have traveled to Turkey to help survey the damage caused by last month’s powerful earthquake.
They collect geological data and conduct detailed analyzes of why so many buildings collapsed.
Working with her Turkish colleagues has uncovered examples of poor construction, including large pebbles mixed into concrete, weakening its strength.
But the sheer force of the quake also caused some devastation.
The ground movement was so great in some areas that it exceeded the resistance of buildings.
The group includes industry experts and leading academics and has conducted major earthquake assessments for the last three decades.
They will combine their findings with research from Turkish teams and other civil engineers to learn lessons from the earthquake and find ways to improve the construction of buildings to make them more resilient.
“It’s important to get the full picture, rather than just looking at a snapshot of an individual asset or building,” explains Professor Emily So, Director of the Cambridge University Center for Risk in the Built Environment, who is co-leader of the Investigation.
“The successes of the still intact and fully functional buildings are just as important as the collapsed neighboring buildings.
“And having that distribution, that overview, is really key to what we can learn from this earthquake.”
The 7.8 magnitude earthquake struck southern Turkey near the Syrian border on February 6, followed by violent aftershocks.
More than 50,000 people lost their lives in the region when buildings collapsed.
After the devastation, building codes and practices in Turkey came under scrutiny. Now the EEFIT team is conducting technical assessments of the performance of buildings in the area.
Structural engineers from Turkey working with the team have already identified some problems.
Samples of concrete from a collapsed building in Adiyaman have revealed that it contains stones 6 cm long. They come from a nearby river and were used to fill the concrete.
“This has serious effects on the strength of the concrete,” says Prof. So.
And it was found that steel rods in the concrete, which are supposed to reinforce it, are smooth instead of ribbed.
This means the concrete won’t stick to them, which in turn weakens the structure.
In Turkey, many older buildings collapsed during the quake, but some modern ones also failed.
After a major earthquake in Iznit in 1999, new building codes were introduced and Prof. So says newer buildings should have fared better.
“I think it’s really important that we recognize these and actually test them to find out why these new buildings that would have been built to code have failed so much,” she told BBC News.
The EEFIT team is also analyzing the nature of the quake.
dr Yasemin Didem Aktas, co-leader of the expedition from UCL in London, said the earthquake was extremely powerful.
“Even the aftershocks were the size of a decent-sized earthquake,” she said.
The quake also caused large ground displacements.
“During an earthquake, the ground shakes horizontally and vertically. Often the vertical component is much less and negligible compared to the horizontal movement. However, very high vertical accelerations were also recorded in this event.”
Some areas saw a process called liquefaction. It turns solid ground into a heavy liquid – like very wet sand – a telltale sign of this is a toppled or sunken building.
“I think the characteristics of the events also played a very important role in the devastation that we’re seeing,” added Dr. Aktas added.
But buildings can be designed to be earthquake-proof.
Ziggy Lubkowski, head of the seismic team at Arup design and engineering firm, which has dispatched engineers to Turkey for the survey, said: “What we try and do when we design buildings is to prevent the loss of human life.
“The basic design principle is to allow damage within the building. This damage absorbs the energy of the earthquake, ensuring the building is still upright but not collapsing.”
There are also components such as dampers, which act like shock absorbers when the building moves back and forth, and rubber mounts, which are attached under a building and absorb the energy of an earthquake.
But all this costs money.
“These increases in structural cost of the building can be in the order of 10 to 15% depending on the type of building,” says Ziggy Lubkowski.
“But when you think about it, the expansion costs of a building often outweigh the structural costs of a building. In the end, the additional construction costs are not that much higher.”
The United Nations has estimated that the cost of clearing and rebuilding after Turkey’s earthquake could exceed $100 billion.
The EEFIT team says the results, which will be released in the coming weeks, could help set new building codes to prevent the devastation caused by this earthquake from happening again.