Prefabricated Panel Houses in the 5.12 Earthquake
In the 5.12 earthquake, the seismic resistance of prefabricated panel houses was limited, and they suffered relatively severe damage. There are potential safety hazards in their subsequent use, and reinforcement or demolition should be carried out according to the actual situation.
I. Seismic Resistance of Prefabricated Panel Houses The seismic resistance of prefabricated panel buildings is limited, and the seismic standards for prefabricated panel houses built in different periods vary. For the old prefabricated panel buildings constructed in the 1970s and 1980s, the standard at that time only required them to withstand a magnitude-6 earthquake. They were severely damaged in the Wenchuan earthquake, basically collapsing into flat shapes. Nowadays, new buildings incorporate prestressed technology and can theoretically withstand earthquakes of magnitude 7 - 9. However, their actual seismic resistance is greatly affected by the construction team. If the construction team cuts corners and the steel bar joints are not properly welded, the seismic resistance will be directly halved.
II. Damage to Prefabricated Panel Houses in the Earthquake In the 5.12 earthquake, prefabricated structural houses suffered relatively severe damage. For example, the prefabricated structural houses in the Hangkong Huayuan Community in Weizhou Town, Wenchuan County, were moderately damaged and classified as dangerous buildings during the earthquake. Although they were simply reinforced after the earthquake for residents to live in, after experiencing multiple earthquakes and aftershocks, the houses reinforced in 2008 developed cracks again. Mianzhu City in Sichuan was severely affected by the 5.12 earthquake, with 80% of the buildings in the urban area being prefabricated panel houses, posing a high risk.
III. Post-earthquake House Assessment and Handling Post-earthquake emergency safety assessments of buildings are classified into three levels—"usable", "temporarily unusable", and "prohibited from use"—based on the impact on human life safety. When aftershocks cause new damage or destruction to buildings, those that have already undergone emergency assessments as safe or pending should be reassessed. For old prefabricated panel houses, if reinforcement is desired, steel plates can be attached to the old buildings and shear walls can be added, which can increase their seismic resistance by 1 - 2 magnitudes. However, in high-intensity areas above magnitude 8, it is recommended to conduct professional assessments and demolish them if necessary. Some prefabricated panels in Mianzhu have been in use for more than 35 years, and some houses are full of cracks inside, posing significant safety hazards and requiring careful handling.
