Seismic Mitigation of Prefabricated Houses

The seismic mitigation performance of prefabricated houses varies depending on specific circumstances, with significant differences observed across different construction periods, structural systems, and reinforcement measures.

Early prefabricated houses had relatively weak seismic performance. Those built before 1990 mostly adhered to the old seismic code TJ11-78, which had lower seismic standards. Their structural flaws were evident: they lacked core seismic components such as structural columns and ring beams, with prefabricated slabs directly placed on brick walls without integral connections. This design led to issues like slab joint cracking and slab detachment during earthquakes, resulting in poor overall structural stability. For example, in moderate earthquakes, the connections between walls and prefabricated slabs might fail due to stress concentration, potentially triggering structural collapse.

The seismic performance of later prefabricated houses improved significantly. The GBJ11-89 code and subsequent standards implemented after 1990 imposed stricter requirements on the seismic design of prefabricated houses: prefabricated slabs had to be reinforced with cast-in-place composite layers and pure exposed laying was prohibited; each floor was mandated to have closed ring beams, with structural columns added at the corners and stair corners. These measures enhanced the overall integrity and ductility of the structures, significantly improving their seismic resistance. For instance, the cast-in-place composite layers effectively transmitted seismic forces, reducing relative displacements between prefabricated slabs and walls and preventing local damage.

New prefabricated house systems demonstrated excellent seismic mitigation performance. Some innovative structural systems achieved efficient seismic mitigation through technological optimization:

• Post-earthquake recoverable rapid-assembly multi-story prefabricated steel structure system: This system employed replaceable buckling-restrained beam-column joints and buckling-restrained braces with U-shaped steel plate dampers. After an earthquake, energy-dissipating components could be quickly replaced based on damage inspection, resulting in short repair times and low costs.
• Sandwich concrete composite exterior wall panels: These panels featured flexible connections with the main structure, exhibiting outstanding seismic performance. In shake table tests simulating a magnitude-9 earthquake, the exterior wall panels remained intact without detachment or severe cracking, effectively protecting the main structure.

Reinforcement measures can enhance the seismic mitigation capacity of existing prefabricated houses. For early prefabricated houses, seismic performance can be strengthened through the following approaches:

• Structural reinforcement: Installing steel frames or pouring concrete within walls to increase stiffness; laying steel mesh at joints to improve connection strength.
• Seismic isolation technology: Installing seismic isolation bearings to reduce seismic force input by extending the structure's natural vibration period.
• Material optimization: Using high-ductility cement plaster to enhance wall crack resistance and prevent brittle failure.

These measures can address the structural flaws of early prefabricated houses in a targeted manner, significantly improving their seismic mitigation capacity.