How to Replace Prefabricated Beams in a House

Replacing prefabricated beams in a house requires strict adherence to structural safety principles and construction should be carried out according to standardized procedures. The specific steps are as follows:

1. Structural Assessment and Plan Formulation

Before construction, entrust a professional institution to conduct a safety assessment of the overall structure of the house, focusing on checking the crack width of the prefabricated slabs (repair is required if it exceeds 0.3 millimeters) and the connection status between the prefabricated slabs and the ring beams (replacement is required if the bolt corrosion rate exceeds 30%). Based on the assessment results, formulate a beam replacement plan, specifying material specifications (e.g., the steel beam section should be ≥ 200*200 millimeters), construction steps, and safety measures. For beam replacement in old rural houses, it is necessary to report to the local authorities in advance and complete the approval process.

2. Erect Temporary Support System

Set up steel pipe supports every 1.2 meters along the length of the prefabricated slabs, and use H-shaped steel beams for underpinning at key nodes to ensure the stability of the floor slab during construction. If wall-to-beam conversion is involved, fix the structures on both sides with supports before removing the interior walls to avoid overall collapse due to local instability. The support system must pass the inspection by a structural engineer before proceeding to the next stage.

3. Demolition and Hole Drilling

• Demolition of Prefabricated Slabs: The original prefabricated slabs should be removed entirely or broken up. Directly drilling holes in the slabs is prohibited to prevent damage to the internal steel bar structure.
• Hole Drilling for Wall-to-Beam Conversion: Drill holes at specified positions on the floor slab or wall for inserting steel bars or pouring concrete. After drilling, immediately reinforce the supports to prevent deformation of the floor slab due to insufficient load-bearing capacity.

4. Installation and Reinforcement of New Beams

• Installation of Steel/Concrete Beams: Install new beams above the removed positions and drive columns into the interior of the walls on both sides to enhance stability.
• Steel Bar Insertion and Grouting: Remove the original filling material from the slab joints, insert No. 6 deformed steel bars, and pour C30 fine aggregate concrete; when converting walls to beams, increase the density of stirrups (5-7 per meter) to improve shear resistance.
• Addition of Structural Columns: Add 240*240 millimeter structural columns at the four corners of the house, tie them with No. 6 and No. 8 steel bars, and connect them to the floor slab to form an overall load-bearing frame.

5. Curing and Inspection

• Concrete Curing: The bottom formwork supports should be retained for at least 15 days in summer and at least 20 days in winter. During this period, regular watering should be carried out for curing to ensure the strength meets the standards.
• Structural Inspection: After construction is completed, a professional team should conduct an inspection, focusing on checking the stability of the new beams, the quality of steel bar connections, and consistency with the approved plan.

Precautions:

• Construction should follow the principle of 'demolishing from the middle to the sides and symmetrically', with the daily demolition amount not exceeding 30% of the total floor slab area.
• The use of heavy hammers for impact demolition is prohibited to avoid vibration damage to the foundation or surrounding structures.
• The entire process should be guided by a structural engineer and carried out by a professional construction team to ensure safety and compliance.