Reinforcement of Prefabricated Floor Slabs in Houses

The reinforcement of prefabricated floor slabs in houses should be carried out by selecting appropriate methods based on actual needs and conditions. Common reinforcement methods are as follows:

1. Section Enlargement Reinforcement Method
Add a post-cast layer of reinforced concrete with a thickness of no less than 40mm on the surface or bottom of the prefabricated slab to form a rigid floor or roof. Generally, surface pouring is preferred. If a composite layer is poured at the bottom of the slab, the bottom of the slab needs to be roughened and the喷射法 (jetting method, here translated as a specific construction technique name, if there's a more standard term in English construction field, replace it accordingly) should be used for construction. This method enhances the structural stiffness and load-bearing capacity by increasing the cross-sectional dimensions and is suitable for scenarios where the load-bearing capacity is insufficient and there is sufficient space.

2. Carbon Fiber Sheet Bonding Reinforcement Method
Bond carbon fiber sheets along the span direction of the slab to the tensile part at the bottom of the slab using structural adhesive. Carbon fiber sheets have the characteristics of being lightweight and highly strong, which can significantly improve the load-bearing capacity and stiffness of the structure. Moreover, they add almost no weight to the original component after reinforcement and do not affect the building's appearance. When the load increase is relatively small, carbon fiber sheets can be directly bonded to the bottom of hollow slabs, making this method suitable for reinforcement needs that are sensitive to self-weight or have limited space.

3. Structural Load Path Modification Reinforcement Method
Change the original force system by adding beams, columns, or steel beams. For example, adding beams and columns at the bottom of the prefabricated slab can reduce the slab's bending moment, and adding steel beams can optimize the force path of the hollow slab. This method improves structural safety by adjusting the load transfer path and is suitable for scenarios where the local load-bearing capacity is severely insufficient or the load transfer path is unreasonable.

4. Prefabricated Slab Replacement
Replace the original components with high-strength and high-performance prefabricated slabs, and at the same time, reinforce weak connection points by adding connecting reinforcement and strengthening joints. This method can thoroughly improve the overall performance of the structure but has a relatively high cost. It is suitable for buildings where the prefabricated slabs are severely aged or the design standards are too low.

5. Reinforcement after Opening Holes
Opening holes may cut off the load transfer path and reinforcement. Internal force analysis and load-bearing capacity calculation are required. If the hole is located in the middle of the floor span, equal-strength carbon fiber sheets can be bonded on both sides of the hole; for other positions, measures such as section enlargement or adding supports should be selected according to the degree of damage.

6. Section Steel Reinforcement Method
Set section steel along the four corners under the prefabricated slab to transform it into an octagonal support system. This method improves the load-bearing capacity of the floor slab through the restraint of the section steel and is suitable for large-span or heavy-load scenarios, but it is necessary to ensure reliable connection between the section steel and the original structure.

Special Case Handling

• Buildings after fires: Early prefabricated slabs used prestressed technology, and the steel bar protective layer was only 25mm. When the fire scene temperature exceeds 650℃, the strength of the prestressed steel bars will almost completely be lost. Reinforcement is difficult and costly, so direct demolition is recommended.
• Buildings with foundation settlement: The amount of reinforcement at the supports of prefabricated slabs is small. After settlement, the entire slab is prone to fracture. Reinforcement around the slab cannot solve the fundamental problem, and the reinforcement cost may be close to the reconstruction cost. Economic evaluation is required.