How to Reinforce Prefabricated Panels in Old Houses

Reinforcing prefabricated panels in old houses requires selecting scientific methods based on the structural condition. Common reinforcement methods and construction key points are as follows:

I. Core Reinforcement Methods

1. Grouting Reinforcement Method Inject cement-based or chemical grouting materials under high pressure to fill voids inside walls or foundations, enhancing overall strength and seismic resistance. Suitable for situations with fine cracks or loose foundations, effectively preventing deformation expansion.

2. Steel Mesh/Profile Steel Reinforcement Method

   • Steel Mesh Reinforcement: Lay bidirectional steel mesh on the surface of walls or floor slabs, and spray fine aggregate concrete to form a composite structure, enhancing shear resistance.
   • Profile Steel Reinforcement: Install L-shaped or channel steel at the four corners of prefabricated panels to construct an octagonal support system, directly improving the load-bearing capacity of the floor slabs, especially suitable for floor slabs with large spans.

3. Steel Plate Bonding/Carbon Fiber Reinforcement Method

   • Steel Plate Bonding Reinforcement: Use structural adhesive to bond steel plates to cracked or deformed areas, compensating for original structural defects with the tensile strength of the steel plates. Ensure there are no voids at the interface between the steel plate and the base material.
   • Carbon Fiber Bonding Method: Apply high-strength carbon fiber cloth along the direction of force to form a lightweight and high-strength reinforcement layer. The construction is convenient and corrosion-resistant, suitable for renovation projects with limited space.

4. Foundation Reinforcement Enhance the foundation's load-bearing capacity by expanding the foundation's base area, adding ground beams, or injecting reinforcement agents (such as epoxy resin). For houses with uneven settlement, pile foundation underpinning technology should be combined to adjust the force distribution.

II. Key Construction Control Points

1. Preliminary Assessment

   • Detect the width of cracks in prefabricated panels (cracks > 0.3mm require treatment) and the rust rate of connecting bolts with ring beams (bolts with a rust rate > 30% require replacement).
   • Use laser distance meters and rebar scanners to locate the distribution of internal rebar, avoiding damage to the original structure during reinforcement.

2. Temporary Support System Set up steel pipe supports every 1.2 meters along the length of the prefabricated panels, and use H-shaped steel beams for underpinning at key nodes to ensure structural safety during construction. When dismantling, follow the principle of "middle first, then sides," with a daily dismantling area ≤ 30% of the total area.

3. Panel Joint Treatment After removing the original filling material, implant Φ6 threaded rebar (spacing 200mm), pour C30 fine aggregate concrete, and vibrate it densely to form a continuous load-bearing strip.

4. Constructional Column Addition Add 240×240mm constructional columns at the four corners of the house, using Φ6 and Φ8 rebar tied into cages, reliably connected to the floor slabs through embedded parts to enhance overall stiffness.

III. Handling of Special Situations

• Houses with fire damage or severe settlement: If the strength of prestressed rebar is lost or foundation cracks exceed limits, the reinforcement effect is limited, and it is recommended to demolish and rebuild.
• Non-structural issues: Through subsidies for old residential area renovations, prioritize addressing issues such as leakage and aging pipelines, supplemented by the addition of insulation layers to improve living comfort.

After reinforcement is completed, ultrasonic testing, load tests, and other acceptances should be carried out to ensure that the deviation between the load-bearing capacity and the design value is ≤ 5% before the house can be put into use.