Buildings investigated by UK team

Earthquake destruction

The damage in the earthquake zone was widespread

Engineers and scientists from the UK have traveled to Turkey to investigate the damage caused by last month’s powerful earthquake.

They are collecting geological data and carrying out detailed assessments of why so many buildings collapsed.

Work with their Turkish colleagues has already revealed some poor construction – large pebbles have been mixed into concrete, weakening its strength.

But the sheer strength of the earthquake also led to some of the devastation.

In some areas, the ground movement was so great that it exceeded what buildings had been designed to withstand.

The research is being carried out by the Earthquake Engineering Field Investigation Team (EEFIT).

The venture is a collaboration between academia and industry, and has carried out assessments of major earthquakes over the last three decades with the aim of improving how we build in earthquake zones.

“It’s important to get the full picture, rather than just looking at a snapshot of a single asset or a single building,” explains Professor Emily So, from Cambridge University who is co-leader of the expedition.

“The successes of the buildings that are still intact and perform perfectly well, are as important as the neighboring buildings that have collapsed.

“And actually having that distribution, having that overview, is really key to what we can learn from this earthquake.”

The Magnitude 7.8 earthquake struck on February 6 in southern Turkey close to the Syrian border and was followed by powerful aftershocks.

More than 50,000 people lost their lives in the region as buildings collapsed.

In the wake of the devastation, there has been scrutiny of building codes and construction practices in Turkey. Now the EEFIT team is carrying out technical evaluations into the performance of buildings in the area.

Structural engineers from Turkey, who are working with the team, have already found some problems.

Samples of concrete taken from a collapsed building in Adiyaman have revealed that it contains 6cm-stones embedded within it. They have come from a nearby river and have been used to bulk the concrete out.

“That has some serious implications on the strength of the concrete,” says Prof. So.

And steel bars inside the concrete, which should reinforce it, have been found to be smooth and instead of ridged.

This means the concrete does not cling to them, again weakening the structure.

In Turkey, many older buildings collapsed during the earthquake, but some modern ones also failed.

New building codes were brought in after a major earthquake in Iznit in 1999, and Prof. So says newer buildings should have fared better.

“I think it’s really important that we recognize those and actually do the testing, to find out why these new buildings, which should have been built to code, would have failed in such a way,” she told BBC News.

The EEFIT team is also analyzing the nature of the earthquake.

Dr Yasemin Didem Aktas, co-leader of the expedition, from UCL in London, said that the earthquake was extremely powerful.

“Even the aftershocks were as large in magnitude as a decent-sized earthquake,” she said.

The earthquake also caused major ground shifts.

“In an earthquake, the ground shakes in a horizontal and vertical fashion. Often the vertical component is much lower, and negligible compared to the horizontal movement. However, this event recorded very high vertical accelerations as well.”

Some areas also saw a process called liquefaction. It turns the solid ground into a heavy fluid – like very wet sand – a telltale sign of this is a building that’s toppled over or has sunk.

“I think the characteristics of the events also played a very important role in the devastation that

we are seeing,” Dr. Aktas added.

But buildings can be designed to be earthquake resilient.

Ziggy Lubkowski, who leads the design and engineering company Arup’s seismic team, said: “What we try and do when we design buildings is to prevent loss of life.”

“The basic design principle is to allow some form of damage within the building. That damage absorbs the energy of the earthquake, and ensures that the building still stays upright, but does not collapse.”

Components such as dampers, which act like shock absorbers as the building sways to and fro, and rubber bearings, which are fitted underneath a building and absorb the energy of a quake, can be added.

But all of this costs money,

“Those increases, in terms of the structural cost of the building, may be in the order of 10 to 15%, depending on the nature of the building,” says Ziggy Lubkowski.

“But actually, if you think about it, the fit-out costs of a building often outweigh the structural costs of a building. So at the end of the day, the additional structural costs are not that much more.”

The United Nations has estimated that the cost of rebuilding in the earthquake hit region could exceed $100 billion.

The EEFIT team’ say their findings, which will be published in the coming weeks, will reveal lessons that can be learned so the devastation that has been seen is not repeated.

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