Seismic Resistance of Prefabricated Houses

Whether prefabricated houses are seismic-resistant depends on specific circumstances and cannot be generalized.

Construction era is a key factor: Prefabricated houses built in the early period (before 1990) generally have weaker seismic resistance. These houses mostly followed the old seismic code TJ11-78, which had relatively low seismic standards and did not clearly define the “three-level seismic design” theory (i.e., “no damage in minor earthquakes, repairable in moderate earthquakes, and non-collapse in major earthquakes”). In areas with a seismic fortification intensity of 6 degrees, the code even did not require the adoption of seismic structural measures, resulting in a lack of core seismic components such as structural columns and ring beams in the houses. The prefabricated slabs were directly placed on brick walls without overall connection, making them prone to problems such as slab joint cracking and slab detachment during earthquakes, which could potentially lead to house collapse in severe cases.

Code upgrades significantly improve seismic performance: The GBJ11-89 code and subsequent standards implemented after 1990 put forward clear requirements for the seismic resistance of prefabricated houses. For example, prefabricated slabs must be reinforced with a cast-in-place composite layer and pure bare laying is prohibited; it is mandatory to set closed ring beams on each floor and add structural columns at the four corners of the house and the four corners of the stairs. These measures have significantly enhanced the overall integrity and collapse resistance of the houses, greatly improving the seismic performance of prefabricated houses built later.

Construction quality directly affects seismic effect: Even if the design complies with seismic codes, construction quality can still be a “weak link”. If the construction party擅自修改设计 (unilaterally modifies the design, such as reducing the number of structural columns and ring beams) or cuts corners (such as insufficient concrete strength and shortened curing time), the seismic performance of the house will be weakened. For example, problems such as unbound reinforcement in structural columns and non-dense concrete pouring may cause components to fail prematurely during earthquakes.

Summary: The seismic performance of prefabricated houses needs to be evaluated comprehensively based on the construction era, code implementation, and construction quality. Early houses have weaker seismic capacity due to code lag and structural defects; later houses have significantly improved seismic performance through code upgrades and structural reinforcement; and construction quality is the “last mile” to ensure seismic effect and requires strict supervision.