London, April 25:
Researchers from the University of Sheffield in south Yorkshire have developed a cheap and simple technology to repair earthquake-damaged buildings and make them safe and habitable.
Recent tests showed that a damaged building repaired using the technique could withstand a major earthquake. The technology involves wrapping metal straps around each floor of the building which are then tensioned either by hand or using compressed air tools.
It is designed for use on reinforced concrete frame buildings — a common construction technique around the world. Unlike other repair methods, it does not require expensive materials or a high-level of technical knowledge, making it ideal for use in the developing world.
“The strapping works very much like a weightlifter’s belt, by keeping everything tightly compressed to reduce tension on the concrete columns of the structure,” said lead researcher professor Kypros Pilakoutas.
Concrete works well under compression but not when pulled under tension and this is why it has to be reinforced for use in construction.
When the reinforcement is faulty or damaged, it can be very expensive to repair.
“Our method not only makes the building stable again very quickly, but it increases the building’s ability to deform without breaking, making it more able to withstand further earthquake movement,” Pilakoutas added.
The team tested the technique on a full-scale, two-storey building which had inadequate reinforcing to withstand earthquakes.
The building was constructed on a specially designed ‘shaking table’ which can simulate ground movement caused by earthquakes.
During the first test, the building was very near collapse following a small earthquake similar in scale to a magnitude 4 on the Richter scale having about 10,000 times less energy than the Haiti earthquake.
The building was then repaired using the post-tensioned metal straps and retested. The researchers were unable to make the building fall during a major earthquake similar in scale to the magnitude of 7.
According to professor Pilakoutas, the new technology will not only speed up the response to major earthquakes but could also prevent the damage happening in the first place.
The cost of the materials for a typical small building column is about 20 pounds and it would take a crew of two people around two hours to complete the strengthening.
“Ideally, governments should not wait until a disaster happens but should be identifying buildings at risk and taking steps to make them strong enough to withstand any future earthquakes,” the team said.
Recently, assistant professor William Barnhart from the University of Iowa in the US showed that GPS and satellite data can be used in a real-time, coordinated effort to fully characterise a fault line within 24 hours of an earthquake, ensuring that aid is delivered faster and more accurately than ever before.
The technique will be most useful in the developing world.
On an international scale, it dramatically reduces the time between when an earthquake happens, when buildings start to fall down, and when aid starts to show up, Barnhart wrote. (IANS)