Prefabricated Slabs on Brick-Concrete Buildings

The prefabricated slabs used on brick-concrete buildings are a common floor form in early construction, featuring various aspects such as structural characteristics, safety hazards, renovation limitations, and governance directions.

1. Structural Characteristics
   The prefabricated slab brick-concrete structure consists of brick walls and prefabricated hollow floor slabs. The prefabricated slabs are placed on the brick walls through simple overlapping, lacking effective connections between slabs, resulting in poor overall integrity and insufficient seismic performance. This structure was widely used from the 1970s to the 1990s to address housing shortages. However, it has inherent defects according to current building safety standards, such as weak joint connections and poor lateral resistance.

2. Safety Hazards
   Prefabricated slab buildings are at significant risk of damage during earthquakes. For example, during the 1976 Tangshan earthquake, this type of building suffered severe damage due to the detachment of prefabricated slabs and the collapse of walls, with stairwells becoming the weakest structural links. Additionally, the design life of prefabricated slab buildings typically does not exceed 30 years. Older buildings commonly face issues such as foundation settlement, aging pipelines, and poor sound insulation, with some even experiencing collapse. Material aging, connection failure, and insufficient structural integrity are the main sources of risk.

3. Renovation Limitations
   Renovations such as elevator installations require cutting walls and removing beams, potentially damaging the already fragile structural integrity. If the elevator shaft is rigidly connected to the main body of the old building, it may increase the structural load and pose fire safety risks, such as obstructing ventilation and lighting in stairwells. However, if the building is rated as Class A (structurally safe) or Class B (individual components are dangerous but do not affect the main structure), non-structural parts such as roofs and pipelines can still be renovated through old community renovations.

4. Governance Directions
   According to the '15th Five-Year Plan for Urban Renewal', the governance of prefabricated slab buildings requires classification and disposal based on safety assessment reports (divided into Classes A, B, C, and D):

• Class A/B buildings: Priority should be given to improving living quality through renovations, such as reinforcing non-load-bearing components and updating pipelines;
• Class C buildings: Repair and reinforcement are required, such as adding structural columns, ring beams, or carbon fiber cloth reinforcement;
• Class D buildings: They should be included in the demolition scope and demolished and rebuilt in conjunction with urban renewal projects.
  After 2001, the use of prefabricated floor slabs has been prohibited in the country. Existing buildings that have not been demolished must meet safety requirements through reinforcement.