Prefabricated Slab House Beam Modification Plan Diagram

There is no direct plan diagram for modifying beams in prefabricated slab houses, but it can be carried out through two methods: side-form grouting and hole-opening grouting. The specific plans and precautions are as follows:

I. Beam Modification Methods

1. Side-Form Grouting Method When installing the formwork, one piece should be installed vertically and the other piece should be installed obliquely, with the oblique surface used for grouting. Alternatively, a small concrete conveyor can be used to inject the grout through holes opened at the edge of the formwork. This method is suitable for reinforcing the connection between prefabricated slabs and walls or for repairing local beams.
2. Hole-Opening Grouting Method Directly open holes in the floor slab (non-prefabricated slab), bind the reinforcement bars, and reinforce the supports. Then, install the formwork and pour the mixed concrete through the holes. For long beams, multiple holes should be opened to avoid voids and ensure dense concrete filling. This method is suitable for overall beam modification or structural adjustments with large spans.

II. Key Construction Steps

1. Reinforcement Bar Configuration The bottom reinforcement bars should be 25 deformed steel bars, with a higher density of stirrups than those in newly constructed beams (5 to 7 per meter). The waist reinforcement bars should be tied at a position 15 to 20 centimeters from the bottom reinforcement bars. The reinforcement bars should be derusted and straightened in advance to ensure good adhesion with the concrete.
2. Support Reinforcement Before hole-opening grouting, provide adequate support for the entire floor slab to prevent it from collapsing after wall removal. The supports can be steel pipe scaffolding or wooden beams, and the load should be calculated with a safety factor reserved.
3. Concrete Pouring The concrete should be mixed in proportion with moderate fluidity to avoid segregation. During grouting, it should be vibrated in layers to ensure density. Long beams should be poured in sections, with each section not exceeding 1.5 meters in length to avoid cold joints.

III. Curing and Formwork Removal

1. Side-Form Removal: The side form can be removed after 24 hours, but care should be taken to avoid colliding with the beam.
2. Bottom-Form and Support Curing: In summer, curing should last at least 15 days, and in winter, at least 20 days. During this period, water should be applied daily to keep the concrete surface moist. Insufficient curing can lead to insufficient strength or cracking.

IV. Case Reference In a renovation project of an old prefabricated slab house in Hubei, the first-floor space was opened up by modifying a load-bearing wall into a beam, transforming it into a workshop. The bottom wall removal required waiting for 15 to 20 days to ensure that the concrete strength of the beam reached the design requirements. After renovation, a load test should be conducted to confirm structural safety.

V. Precautions

1. Before construction, a professional structural engineer should assess the load-bearing capacity of the house to avoid the risk of collapse caused by blind modification.
2. Modifying beams in prefabricated slab houses involves structural safety, so construction specifications should be strictly followed, and it is recommended to be carried out by a qualified construction team.
3. After renovation, the beam should be regularly inspected for cracks or deformation, and hidden dangers should be dealt with in a timely manner.