Prefabricated Concrete House Design

Prefabricated concrete house design should adhere to the principles of standardization and modularization, achieving efficient construction through factory-prefabricated components and on-site assembly. The core steps include determining design parameters, splitting the structural system, and designing node connections.

1. Pre-design Conditions and Determination of Basic Parameters Key parameters must be defined based on the building's purpose, climate, and geological conditions. Taking a two-story rural self-built house as an example, the seismic fortification intensity is typically set at 7 degrees, with a basic wind pressure of 0.4 kN/m², a floor live load of 2.0 kN/m², and a roof live load of 0.5 kN/m². Unifying the building modulus is crucial for cost reduction; generally, 300 mm is used as the basic modulus, with bays set at 3.6 m, 3.9 m, or 4.2 m, depths at 4.5 m or 5.1 m, and floor heights at 2.8 m or 3.0 m. Once the modulus is unified, the variety of components decreases, mold turnover rates increase, and overall costs can be reduced by 15%-20%.

2. Selection of Structural System and Splitting of Prefabricated Components For buildings up to three stories, the assembled monolithic concrete frame structure is preferred, with all columns, beams, and slabs prefabricated and the node areas cast with concrete on-site to form an integral structure. Specific splitting rules are as follows:

• Columns: Split one per floor, with common cross-sections of 400 mm × 400 mm or 500 mm × 500 mm, and a single weight controlled between 3-5 tons.
• Beams: Main beams are split at mid-span, with a cross-section of 300 mm × 600 mm; secondary beams have a cross-section of 250 mm × 500 mm, with a single span not exceeding 6 meters.
• Floor Slabs: Composite slabs are used, with a prefabricated base slab thickness of 60 mm, a cast-in-place layer thickness of 80 mm, a total thickness of 140 mm, and a single slab area not exceeding 6 square meters.
• Other Components: Non-load-bearing components such as stairs, balconies, and air conditioning panels are all prefabricated, with dimensions meeting transportation width limits of 2.5 m and height limits of 4 m.

3. Node Connection Design Node connections must ensure the overall integrity of the structure, with strength not lower than that of the components themselves, and verified through finite element analysis and full-scale testing:

• Column-to-Column Connections: Utilize sleeve grouting connections, with vertical reinforcement reserved at the top of the lower column and grouting sleeves embedded at the bottom of the upper column. After injecting high-strength grout, a continuous load-bearing reinforcement is formed, with a tensile strength exceeding 500 MPa.
• Beam-to-Column Connections: Achieve rigid connections through a combination of a corbel plate and post-cast concrete. The prefabricated beam end is reserved with a slot, placed on temporary supports at the column side, with the beam bottom reinforcement welded to embedded parts in the column, and the upper reinforcement overlapped in the node core area. Post-casting C40 micro-expansion concrete integrates the beam and column.
• Floor Slab-to-Beam Connections: The胡子筋 (hooked reinforcement) at the slab end extends into the post-cast strip at the beam side, with an anchorage length not less than 15 times the钢筋直径 (reinforcement diameter), ensuring effective load transfer.

All connection nodes must adhere to the principle of 'strong nodes, weak components' to avoid structural failure due to node failure.