Earthquake Prefabricated House Design Code

The design code for earthquake-resistant prefabricated houses should be formulated in accordance with the seismic standards of different periods and current regulatory requirements, as detailed below:

Seismic Standards for Prefabricated Houses in Different Periods

Early prefabricated houses (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, namely, remaining intact under minor earthquakes, being repairable under moderate earthquakes, and not collapsing under major earthquakes. In areas with a seismic intensity of 6 degrees, seismic structural measures were generally not required. 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, making them prone to issues such as slab joint cracking and slab detachment during earthquakes.

Later prefabricated houses (after 1990) implemented the GBJ11-89 code and subsequent standards, significantly improving their seismic performance. It explicitly required that prefabricated slabs must be reinforced with a cast-in-place composite layer and prohibited pure bare laying. It also mandated the installation of closed ring beams on each floor and structural columns at the four corners and stair corners, enhancing the overall integrity and seismic resistance of the houses.

Current Regulatory Requirements

New construction, expansion, and renovation of housing construction projects should be seismically fortified in accordance with relevant national regulations and mandatory engineering construction standards. No unit or individual may reduce the seismic fortification standards. Survey and design units must conduct surveys and designs in accordance with mandatory engineering construction standards and be responsible for their quality, ensuring that the houses meet seismic requirements. If new technologies or materials specified in the survey and design documents for housing construction projects may affect the seismic safety of the projects and there are no national technical standards, they should be tested and approved in accordance with relevant national regulations before use.

Seismic Fortification Objectives

When subjected to frequent earthquakes, the general functions of the city should remain normal. When subjected to earthquakes equivalent to the seismic fortification intensity, the general functions of the city and its lifeline systems should remain basically normal, and important industrial and mining enterprises should be able to resume production normally or quickly. When subjected to rare earthquakes, the city's functions should not be paralyzed, critical systems and lifeline projects should not suffer severe damage, and no serious secondary disasters should occur. These objectives provide clear directions and requirements for the seismic design of prefabricated houses, ensuring their safety and functionality during earthquakes.