Do Prefabricated Houses Resist Earthquakes Now?
Whether prefabricated houses can resist earthquakes depends on specific circumstances and cannot be generalized.
Impact of Construction Era on Seismic Performance: Old prefabricated slab buildings from the 1970s to 1980s were mostly designed according to the 'Code for Seismic Design of Buildings' (TJ 11 - 78), with a general seismic fortification intensity of 6 - 7 degrees, and some areas (such as Beijing) designed for 7 degrees. Due to technological limitations at the time, component connections often used simple steel bar overlaps or mortar joints, resulting in poor integrity and weak seismic resistance. They could withstand earthquakes of magnitude 6 - 7 (corresponding to an intensity of 6 - 7 degrees), but offered little protection above magnitude 8. Houses built before the 1980s could resist earthquakes of intensity 6 degrees, while newly built ones could reach 7 degrees, but their seismic resistance was still inferior to that of cast-in-place reinforced concrete houses. Modern prefabricated assembled buildings, designed according to the current 'Code for Seismic Design of Buildings' (GB 50011 - 2010), can achieve a seismic intensity of 7 - 9 degrees depending on regional fortification requirements. They use high-strength concrete, prestressed technology, and steel bar sleeve connections, significantly improving their integrity and seismic performance. For example, assembled shear wall structures can withstand earthquakes above intensity 8 degrees, depending on design and construction quality. There is also a claim that cement 'prefabricated houses' used in rural areas of Henan can withstand magnitude 8 earthquakes.
Impact of Design Codes on Seismic Performance: Prefabricated houses built before 1990 mostly followed the old seismic code TJ11 - 78, which had lower seismic standards, did not clearly define the 'three-level seismic fortification' theory, and generally did not require seismic structural measures in areas with an intensity of 6 degrees. Such houses often lacked core seismic components like structural columns and ring beams, with prefabricated slabs directly placed on brick walls without overall connections, making them prone to problems during earthquakes. The GBJ11 - 89 code implemented after 1990 and subsequent standards explicitly required that prefabricated slabs must be reinforced with a cast-in-place composite layer, prohibited pure bare laying, and mandated closed ring beams on each floor and structural columns at the four corners and stair corners, significantly improving seismic performance.
Impact of Construction Quality on Seismic Performance: Even if the design meets 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, can all reduce the seismic resistance of the house.
