与时间赛跑！中国救援队平安归来，背后的细节有这些

On Feb 17, a Chinese rescue team returned from Turkiye at Beijing Capital International Airport, after an intense rescue operation following the devastating earthquake that hit the region on February 6. They spent ten days and nights working with rescue teams from various countries, racing against time to save lives.

Wang Tao is the deputy director and researcher of the Institute of Engineering Mechanics (IEM), China Earthquake Administration (CEA). Wang joined the rescue team to Turkiye as an expert in structural safety which was instrumental in understanding how to save lives underneath dangerous ruins as well as keeping the rescue team safe from harm in the process.

It means a lot. There is always hope of finding survivors. On Feb 18, 296 hours after the earthquake, three residents were rescued. So “never give up” is the rescue team’s mantra. As long as there are people or potential signs of life on the scene, we will never give up.

Initially, the rescue team could work quickly on surface-level searches but soon came into difficulty when deeper searches were required. Deeper searches needed large machinery to move the rubble. Protection of life is much more complex at this stage because without the machinery, people trapped at deeper levels are at greater risk of not being found in time, yet the vibrations from the machinery may cause significant structural damage and cause even more loss of life. Therefore, how to use large machinery scientifically still needs further exploration.

The local people were very friendly towards the Chinese rescue team and offered a lot of help and support. For example, when we were moving people out of the ruins, they took the initiative to line up nearby to help; when we were working, they also voluntarily gave us some water and food, and even when they saw us on the road, they would say “hello” and “thank you” as we passed.

This kind of gratitude is sincere. At the same time, our rescue team was working really hard. I am an expert in structural safety. Some firefighters in the Chinese rescue team had to go into the ruins to rescue people. The space inside may be very small, as well as the space for operating equipment. As a result, they could only claw at the ruins by hand. We often worked all night. Every time we heard that there were people buried below, we were full of grit and determination to try our best to save people. This kind of spirit really moved me. The spirit of the entire Chinese rescue team is very encouraging.

During the rescue, we often encountered aftershocks. Once, at around nine or ten o’clock in the evening, we were working in a ruin. Because the structure was not stable, we made a lot of supporting plans in advance to protect it. Later we happened to experience aftershocks. The tremor was quite forceful. Fortunately, the entire ruins did not collapse within the operating space. We were all safe. In terms of safety, we took the supporting measures to protect the ruins. Meanwhile, there were observers to watch aside so as to ensure the safety of the team.

Local people in Turkiye are aware of earthquake resistance measures. Their houses are made of concrete with steel bars inside. First, in terms of material selection, the quality of concrete and the structural types of steel bars of some rather old houses are insufficient. For example, reinforced concrete columns generally have stirrups. The stirrup spacing is an important aspect of seismic capacity. But in Turkiye, the stirrup spacing of the beams and columns is too large, so the stirrups will not effectively play a binding role, thereby decreasing the seismic capacity for turbulence.

Second, it’s common for houses in this region to adopt a plate-column structure which is close to the wall, rather than the common square column. The advantage is that it has a relatively high lateral resistance capacity. Architectural elements that do not protrude are easier to incorporate into the building. However, if it is arranged in a precarious position, it is easy to make one part of the building strong while the other weak. Even if the house is balanced in its design, due to the effect of horizontal movement caused by earthquakes, the more rigid columns may be damaged first under major pressure, and the remaining ones cannot bear the load of the upper structure, and therefore collapse is more probable. 

In addition, we found that the hardest-hit areas in Antakya were basically along the banks of the river and many buildings collapsed. I think there may be something wrong with the foundation of the buildings. The soil of river banks is often soft. The choice of the structural form of the pile foundation and the underground is especially important. I guess this was not factored in when construction began.

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