Prefabricated Columns in Brick-Concrete Structure Houses

In brick-concrete structure houses, prefabricated columns are generally not used alone as the main load-bearing components. They need to be paired with cast-in-place structural columns to enhance stability. If prefabricated columns are used, they must strictly meet regulatory requirements, but the use of cast-in-place structural columns is more recommended.

The Special Nature of Structural Columns Limits the Application of Prefabricated Columns

In brick-concrete structures, structural columns are core components that enhance overall integrity and stability, typically constructed using cast-in-place reinforced concrete. Their key design requires simultaneous construction with the walls, achieving reliable connections through a “step-back and step-forward” masonry method (stepping back by 6 cm, stepping back every five layers, and stepping forward by 6 cm on the sixth layer). This method forms an integrated load-bearing system through the interlocking structure of the walls and structural columns. Prefabricated columns, however, cannot achieve simultaneous masonry, making it difficult to ensure connection strength with the walls, especially under horizontal loads such as earthquakes, where there is a risk of disconnection.

Integrity Requirements Restrict the Reliability of Prefabricated Column Joints

Structural columns need to form an integrated load-bearing framework with ground beams and ring beams through vertical reinforcement (e.g., 4φ12) and stirrups (spacing ≤ 250 mm). The cast-in-place process ensures continuous anchoring of reinforcement at the joints, while the connections of prefabricated columns require secondary pouring or mechanical connections, resulting in joint strength typically lower than that of cast-in-place structures. According to seismic design codes, the connection between structural columns and ring beams in brick-concrete structures must meet the principle of “strong joints, weak members.” The joint treatment of prefabricated columns is difficult to achieve this requirement and may become a structural weak point.

Construction Codes Explicitly Limit the Use of Prefabricated Columns

The current standard, Code for Design of Masonry Structures (GB 50003-2011), requires that columns in brick-concrete structures be poured simultaneously with the floor concrete to avoid discontinuities that affect structural integrity. Prefabricated columns need to be connected to the upper and lower structures through reserved reinforcement or post-pouring strips, but the shrinkage of the secondarily poured concrete can easily lead to joint cracking, and the extended construction period may increase costs. Additionally, the transportation and hoisting of prefabricated columns require extra equipment, further limiting their economic viability in brick-concrete structures.

Alternative Solutions and Recommended Practices

If prefabricated components are required, it is advisable to prioritize non-critical load-bearing parts such as prefabricated concrete floor slabs and ensure that structural columns are still constructed using cast-in-place methods as per regulations. For special cases where prefabricated columns must be used, the following measures should be taken to ensure safety:

1. Install shear keys or steel connectors between the prefabricated columns and walls;
2. Use high-strength grout or fine aggregate concrete for secondary pouring in joint areas;
3. Conduct rigorous seismic calculations to ensure that joint bearing capacity is not lower than that of cast-in-place structures.
   However, considering cost, construction difficulty, and safety, cast-in-place reinforced concrete structural columns remain the optimal choice for brick-concrete structure houses.