Seismic Standards for Prefabricated Houses

The seismic standards for prefabricated houses need to be determined based on specific circumstances, primarily influenced by three factors: design, construction, and regulatory standards.

Design Perspective

Prefabricated houses built in different periods exhibit significant differences in seismic standards. Early prefabricated houses (built before 1990) mostly adhered to the old seismic code TJ11-78, which had relatively low seismic standards. It did not clearly define the 'three-level seismic fortification' theory (i.e., no damage in minor earthquakes, repairable in moderate earthquakes, and no collapse in major earthquakes), and seismic structural measures were generally not required in areas with a seismic intensity of 6 degrees. These houses often lacked core seismic components such as structural columns and ring beams. The prefabricated slabs were directly placed on brick walls without overall connection, resulting in poor seismic performance. Later prefabricated houses (built after 1990) implemented the GBJ11-89 code and subsequent standards, explicitly requiring that prefabricated slabs must be reinforced with cast-in-place composite layers and prohibiting pure bare laying. They also mandated the installation of closed ring beams on each floor and structural columns at the four corners and stair corners, significantly improving seismic performance. Modern prefabricated assembled buildings are designed according to the current 'Code for Seismic Design of Buildings' (GB 50011-2010). Depending on regional seismic fortification requirements, they can achieve a seismic intensity of 7-9 degrees. They employ high-strength concrete, prestressed technology, steel bar sleeve connections, etc., significantly enhancing overall integrity and seismic performance. For example, assembled shear wall structures can withstand earthquakes above magnitude 8.

Construction Perspective

Construction quality directly affects seismic performance. Even if the design complies with seismic codes, unauthorized design modifications or shoddy workmanship during construction, such as reducing the number of structural columns and ring beams, insufficient concrete strength, or shortened curing times, will all reduce the seismic performance of the house. Article 28 of the 'Regulations on the Quality Management of Construction Projects' clearly stipulates that construction units must carry out construction in accordance with engineering design drawings and construction technical standards, and must not unauthorizedly modify engineering designs or cut corners.

Regulatory Standards Perspective

Relevant regulations impose clear requirements on the seismic resistance of prefabricated houses. Article 38 of the 'Construction Law of the People's Republic of China' requires that when construction enterprises prepare construction organization designs, they should formulate safety technical measures based on the characteristics of the construction project. For professional engineering projects, special safety construction organization designs should be prepared, and safety technical measures should be taken. Article 19 of the 'Regulations on the Quality Management of Construction Projects' clearly states that survey and design units must conduct surveys and designs in accordance with mandatory standards for engineering construction and be responsible for their quality, ensuring that the houses meet seismic requirements.