Prefabricated Load-Bearing Beam for Housing

The prefabrication of load-bearing beams for housing is a key technology in prefabricated concrete structures, and its design and construction must strictly adhere to specifications to ensure structural safety.

I. Core Functions and Cross-Sectional Forms of Prefabricated Beams

As horizontal load-bearing components, prefabricated beams primarily bear vertical loads transferred from floor slabs and transmit them to vertical components such as columns or shear walls. Their cross-sectional forms are diverse, with common types including:

• Rectangular beams: Simple in structure, suitable for conventional span scenarios;
• T-shaped beams: Increase the moment of inertia of the cross-section through flanges, enhancing flexural capacity;
• Cross beams and flower-basket beams: Often used in complex joints or large-span structures to optimize load distribution.

II. Key Control Points in the Design Phase

1. Reinforcement Connection at Beam-End Joints:

   • Common methods include grouted sleeve connections (mature technology, ensuring fullness of grout), mechanical connections (such as straight-thread sleeves), and post-cast joints (enhancing integrity).
   • Connection quality directly affects the seismic performance of the structure and requires experimental verification of connection strength.

2. Stability During Transportation and Hoisting:

   • Prefabricated beams can weigh several to tens of tons, necessitating precise calculation of lifting points during hoisting to avoid concrete cracking.
   • Temporary supports should be added during storage and transportation to prevent lateral instability; for large spans, it is recommended to use dedicated transport frames for fixation.

III. Operational Specifications in the Construction Phase

1. Installation Sequence and Temporary Supports:

   • Follow the principle of "columns first, then beams," installing the lower-story prefabricated columns before immediately hoisting the beams of that story, and setting up temporary supports in the beam-column joint area. These supports can only be removed after the joint concrete reaches the design strength (usually C30 or above).
   • High-strength mortar (approximately 10-20mm thick) should be laid between the beam bottom and column top contact surfaces to ensure uniform load transfer.

2. Prestressing Technology for Large-Span Beams:

   • For prefabricated beams with spans exceeding 8 meters, prestressed tendons (such as steel strands) should be used to reduce deflection and cracks. Anchorage plates should be set at the beam ends, and the tendons should be protected by grouting and sealing after installation.
   • Prestressing tensioning should be carried out in stages to avoid local compressive failure of the concrete.

3. Handling of Reserved and Embedded Components:

   • Reserved and embedded components such as lightning protection grounding and pipeline penetrations through beams must be accurately positioned during the prefabrication stage to avoid structural damage from later slotting.

IV. Prefabricated Applications in Rural Self-Built Housing

Rural self-built housing can adopt prefabricated formwork for integrated pouring of reinforced concrete. The dimensions of load-bearing beams should be determined based on the span and roof load:

• Reinforcement Configuration: The larger the load-bearing coefficient, the thicker the reinforcement model (such as HRB400 grade), with corresponding increases in beam thickness and height;
• Structural Requirements: Stirrup densification zones should be set at beam ends to enhance shear capacity; for large spans, it is recommended to use double-row reinforcement layouts.