How to Reinforce Prefabricated Floor Slab Houses

The reinforcement of prefabricated floor slab houses should be based on the results of safety assessments, selecting targeted methods. Common reinforcement methods and implementation points are as follows:

I. Selecting Reinforcement Methods Based on Damage Types

1. Insufficient Local Load-Bearing Capacity

   • Section Steel Reinforcement Method: Install section steel at the four corners of the prefabricated slab, transforming the original four-sided support into an eight-sided support, significantly enhancing the floor slab's load-bearing capacity. This method is suitable for scenarios with increased loads, such as additional floor construction.
   • Carbon Fiber Adhesion Method: Adhere carbon fiber cloth using epoxy resin to enhance the structural flexural capacity. For example, a 1982 prefabricated slab office building in Shanghai was renovated into a hotel using this method, resulting in a load-bearing capacity increase of over 40%.
   • Plywood Reinforcement Method: Requires professional design, adding wooden plywood or steel plates at the bottom of the slab, fixed with bolts to form a composite structure, suitable for scenarios with specific spatial constraints.

2. Crack or Deformation Issues

   • Steel Mesh Reinforcement Method: Lay Φ4-Φ6 steel mesh on the surface of walls or floor slabs, plaster with cement mortar to a thickness of ≥30mm, effectively inhibiting crack propagation.
   • Steel Plate Adhesion Method: Adhere steel plates to both sides of cracks using structural adhesive, with a typical plate thickness of 4-8mm, fixed with anchor bolts to ensure tight connection, suitable for reinforcing beams, slabs, and other components.

3. Foundation Issues

   • Foundation Reinforcement: For uneven settlement foundations, methods such as expanding the foundation base area, adding ground beams, or grouting to reinforce the soil can be employed. For example, strip foundations can be widened by 300-500mm on both sides and reinforced with steel bars to enhance overall stability.

4. Overall Stability Enhancement

   • Grouting Reinforcement Method: Inject cement-based grout into foundation or wall voids, filling and compacting to improve overall structural integrity, suitable for soft foundations or wall cavity repairs.
   • Additional Support Reinforcement Method: Add steel supports or concrete columns at wall corners or floor slab mid-span to reduce structural deformation risks, ensuring reliable connection with the original structure.

II. Principles for Handling Special Cases

1. Post-Fire Houses: If prestressed steel bars lose strength due to high temperatures, the structure has lost its load-bearing capacity, and reinforcement costs may exceed reconstruction costs, it is recommended to directly demolish and rebuild.
2. Cracking Due to Foundation Settlement: If settlement continues to develop, simply reinforcing walls or floor slabs cannot solve the problem. A comprehensive assessment of reinforcement costs versus reconstruction costs is needed, prioritizing the safer option.

III. Key Construction Considerations

1. Professional Assessment First: Before reinforcement, a qualified institution must be commissioned to conduct a structural safety assessment, clarifying the location, extent, and cause of damage to avoid blind construction.
2. Detail Control:
   • Carbon fiber cloth adhesion requires controlling the ambient temperature ≥5℃, applying adhesive evenly to avoid voids;
   • When adhering steel plates, the plate surface must be polished to expose the metallic luster, with structural adhesive thickness controlled at 2-3mm;
   • During demolition work, real-time monitoring of the support system's stress is required, prohibiting the use of heavy hammers to prevent secondary damage.
3. Environmental Protection and Safety: During construction, the work area must be enclosed to control dust and noise, with waste classified and disposed of properly; for high-altitude work, protective scaffolding must be erected to ensure personnel safety.
4. Acceptance and Maintenance: After reinforcement, load tests and deformation monitoring must be conducted, and the structure can only be put into use after passing inspection; regularly inspect reinforced areas and conduct a comprehensive assessment every five years.

Optimization Suggestions for Non-Structural Issues: If the house has no structural hazards but poor living conditions, you can apply for old community renovation subsidies, prioritizing crack repair, pipeline replacement, or adding insulation layers, which have a higher cost-benefit ratio than blind reinforcement. All reinforcement projects must be designed by professional structural engineers, and the construction team must possess special operation qualifications to ensure the scientific nature of the plan and construction safety.