Specification for Cement Prefabricated House Beams

The specifications for cement prefabricated house beams cover aspects such as span, materials, structure, reinforcement, construction, and special requirements, and must strictly adhere to standards to ensure safety and durability.

Span Range

The span of ordinary cement prefabricated beams typically ranges from 2 to 8 meters, suitable for conventional residential or small buildings. With special designs (such as prestressed concrete, truss, or arch structures), the span can be extended to 10-20 meters. For example, prestressed concrete beams generate pre-compression stress through tensioned reinforcement, achieving spans of 10-15 meters; truss structures disperse loads through triangular units, allowing spans of 15-20 meters; arch structures transfer loads using axial pressure, enabling spans exceeding 20 meters, but require attention to the lateral thrust's impact on foundation stability.

Material Strength

Beams must use high-grade cement (such as C40, C50, or higher) and high-strength reinforcement (such as HRB400, HRB500) to enhance load-bearing capacity. Material strength directly affects the beam's flexural and shear resistance, especially in scenarios with large spans or heavy loads, where high-strength materials can reduce cross-sectional dimensions and optimize structural efficiency.

Structural Design

• Prestressed Concrete Beams: Counteract tensile stresses generated by loads through pre-compression stress, suitable for medium to large spans.
• Truss Structures: Composed of triangular units with rods, efficiently dispersing loads, commonly used in large-span industrial buildings or public facilities.
• Arch Structures: Utilize the arch's axial pressure to transfer loads, allowing large spans but requiring additional handling of lateral thrust, often used in bridges or special buildings.

Reinforcement Method

• Main Reinforcement Diameter: Not less than 12mm, with secondary reinforcement diameter not less than 8mm, ensuring collaborative work between reinforcement and concrete.
• Reinforcement Spacing: Not exceeding 200mm, with distances from walls and beam bottoms not less than the reinforcement diameter to avoid local stress concentration.
• Bending Requirements: Reinforcement bending radius not less than twice the diameter, with bending angles conforming to design requirements to prevent reinforcement fracture or concrete cover spalling.

Construction Techniques

Concrete vibration compactness, curing humidity and temperature control, and prestressed tensioning accuracy must strictly adhere to the "Code for Acceptance of Construction Quality of Concrete Structures" (GB 50204-2015). For example, during the curing stage, humidity must be maintained at ≥95%, with temperature controlled at 20±2℃ to avoid cracking or insufficient strength.

Other Considerations

• Pre-camber Setting: As span increases, the beam's self-weight and deflection control become more challenging, requiring pre-camber (typically 1/300-1/500 of the span).
• Foundation Treatment: Foundation settlement may cause beam cracking, necessitating adequate foundation bearing capacity (such as using pile foundations).
• Seismic Design: In seismic fortification areas, calculations must be performed according to the "Code for Seismic Design of Buildings" (GB 50011-2010), with additional structural measures (such as denser stirrups) implemented.