Professor Guo Xun Interviewed by Sichuan Daily: Why were Buildings Damaged Seriously in Earthquakes? Listen to the Experts of Aseismic Structures

Soon after the 6.17 Yibin Earthquake, Prof. Guo Xun of IDP, a member of the expert group of the Emergency Management Department, went to the earthquake stricken area to carry out the assessment and investigation of the damage to buildings. On June 19, Prof. Guo Xun was interviewed by a reporter from the column of "Sichuan Newspaper Observation" of Sichuan Daily to answer the common questions about the earthquake resistance of buildings and the existing problems after the earthquake. The following is the full text:

Ren Hong, observer reporter of Sichuan Daily

At noon on June 18, 2019, Guo Xun, a researcher from the Institute of Disaster Prevention and Technology, as one of the expert group members sent by the Emergency Management Department, arrived in the disaster area and kept on investigating the earthquake damage of buildings.

"Considering the magnitude of the earthquake, it can be said that the housing damage is very serious." On the afternoon of June 19, after visiting Gongquan town in Gongxian County and Shuanghe town in Changning County, Guo Xun told reporters. As reported in the third briefing of Changning Earthquake Relief Headquarters on June 17, June 19, the earthquake caused 20185 houses collapsed and seriously damaged, and 75713 buildings damaged.

"Most of the collapsed houses are old rural houses. One of the main characteristics of these houses is" scattered. " Guo Xun said that due to the lack of necessary connections between columns, beams, slabs, roofs and walls of old civil and brick concrete structures, especially the lack of ring beams and structural columns in brick concrete structures, ground shaking, house disintegration, and burying residents and furniture are the main causes of casualties.

In the disaster area, Guo Xun saw a lot of "standing ruins". Although these houses did not fall, they showed obvious "Deviation" because of the "weak outside and strong inside" or "weak front and strong rear" in design. The internal injuries were serious and could not be repaired. In addition, some houses in the disaster area are of lime sand brick masonry structure, which is difficult to be reinforced due to the low wall strength and serious damage. In the extreme earthquake area (Shuanghe town and Gongquan town), a large number of house parapets (low walls around the building roof), brick guardrails, staircases out of the roof, etc. collapsed seriously due to loose connection with the main structure.

What makes Guo Xun even more worried is that after participating in earthquake rescue many times, he found that some residents were not very clear about whether their houses were safe or not, and still stayed indoors at risk. “It seems that all parts of some houses are complete. There is no obvious collapse and damage. There are only some cracks, but in fact they have suffered serious ‘internal injuries’ and are not suitable for living.” Guo Xun reminds, for example, if you see that there are vertical cracks in the wall supporting the beam, there are cross cracks in the bearing wall, and there are horizontal cracks in the root of the parapet, you should ask professional institutions to make an assessment, and you should not live blindly. Some people think that the construction of frame structure is safe, and this understanding is not correct. Guo Xun said, "if there are ‘brittle, partial, single’ buildings, even the frame structure of the building, seismic resistance will be reduced."

To reduce the damage caused by the earthquake, Guo Xun proposed to build "resilient urban and rural areas". "The main reason why earthquakes cause casualties and property losses is that buildings cannot withstand earthquakes. And we can use civil engineering related methods and measures to reduce disaster losses, such as building houses that are "complete but not scattered, extended but not brittle, uniform but not biased, redundant but not single." He suggested that such a theory be transformed into design and construction norms and applied to post disaster reconstruction to enhance building toughness.