Scientific researchers analyze the causes of building collapse

In the past two days, Wang Tao, a provincial scientific researcher who went to Turkey to participate in the rescue of the 7.8 magnitude earthquake, sent back the rescue situation on the spot and analyzed the causes of the collapse of the building. With the joint efforts of all of us, as of the 10th, the Chinese rescue team has successfully rescued three people. 00 on the

7th, the Chinese rescue team took a chartered plane from the Capital Airport to fly to the disaster area. After arriving in Turkey, Wang Tao, a scientific researcher, arrived in Antakya City, Hatay Province, Turkey, on the 8th after a five-hour drive, and immediately carried out field work in accordance with the requirements of the mission. After

entering the disaster area, we mainly observed 16 residential buildings, all of which are concrete slab-column (short-limb wall) structure, with about 10 floors. All these buildings collapsed or collapsed in the form of laminations, which was the first strong earthquake collapse. It is preliminarily judged that the main reasons for the collapse are insufficient bearing capacity, less steel bars, low concrete grade, strong directivity of slab columns, and it is very easy to collapse to one side if the arrangement is uneven. This area is located in the floodplain area, and it is estimated that the foundation is not very reliable, but there is no sand liquefaction around it, only there is a water on the way to the residential area.

The earthquake caused the collapse of many buildings in the disaster area , and the living space was limited. With the joint efforts of all of us, as of the 10th, the Chinese rescue team has successfully rescued three people.

On the 11th, Wang Tao continued to participate in the search and rescue work in Antakya City, encountered a six-storey reinforced concrete apartment completely collapsed in the earthquake, forming a cascade of ruins. The beam and column reinforcement of the building is sufficient, but the longitudinal reinforcement is plain round reinforcement, the connection is lapped, and the bond force is insufficient, which does not meet the requirements of seismic design. At the same time, concrete stones turn yellow and brittle, resulting in low strength of concrete and brittle failure.

In the search and rescue target area, the section size of some building columns is too small, the minimum size of the first floor column of the 10-storey building is about 300 × 800 mm, which reaches 18 MPa under its own weight. Considering its low concrete strength, the axial compression ratio is too high, and the seismic margin is insufficient . This is also one of the reasons why many building floors collapse or completely collapse. Wang Tao, deputy director of the Institute of Engineering Mechanics, China Seismological Bureau, structural safety expert of

China Rescue Team: I think we can say from several aspects. One aspect is that Turkey's seismic force level is indeed relatively high, and then the fortification intensity here is about 0.3 G of the seismic acceleration value, but it actually reaches 0.6 G. This is an objective reason for doubling the (fortification standard).

In terms of housing, there are also some problems in its quality. According to Turkey's seismic design code, everyone should strictly abide by it, but it may not be satisfactory in the implementation process. In terms of architectural details, we found that its materials are not very standardized. The main stress steel bar is round steel bar, and the bond force between it and concrete is not very good.

The second aspect is that the quality of concrete is not very good. We can see that its stones already have yellow stones. Maybe its own strength is not very high, and the overall strength of concrete will not be too high. In the process of looking at the concrete ruins, we also found that there are many honeycombs and pits in the process of pouring the concrete itself, and the quality of vibration may not be very good. So in essence, the quality of concrete can be regarded as a crisp and brittle material, and the overall strength of concrete may not be very good.

Thirdly, I think there may be some problems in its building foundation, especially on the first day when we saw many buildings staggering in the floodplain of the river, we think there may be some problems in its building foundation.