Foundation of Prefabricated Frame Structure Houses

The design of the foundation for prefabricated frame structure houses needs to be comprehensively considered in combination with structural characteristics, construction conditions, and load transfer requirements. The following explains from three aspects: foundation characteristics, adaptation to construction conditions, and special structural design:

1. Core characteristics of frame building foundations
The frame structure consists of columns, beams, and floor slabs forming the load-bearing system, with walls only serving as enclosures and partitions, not participating in structural load-bearing. Therefore, foundation design needs to focus on strengthening the following two points:

• Prefabricated slab layout and foundation plan optimization: By reasonably planning the positions of prefabricated slabs, uneven foundation loading can be reduced; optimizing the foundation plan layout in combination with geological conditions, such as using independent foundations or constructing basements in areas with weak foundations, can significantly improve structural adaptability. Independent foundations disperse column bottom loads to the foundation, reducing the risk of local settlement; basements increase the overall anti-overturning capacity by increasing the depth of burial, especially suitable for soft soil or filled soil areas.
• Clarity of load transfer paths: The loads of frame structures are transferred step by step through columns-foundations-foundations. Foundation design needs to ensure that the load transfer paths are short and direct. For example, independent column foundations need to ensure that the foundation bottom area meets the foundation bearing capacity requirements while controlling the foundation height to avoid punching shear failure.

2. Impact of construction conditions on foundation selection
The soil quality of the foundation is a key factor in selecting the foundation form:

• Hard soil, native soil, or rock layers: These foundations have high bearing capacity and low compressibility. Independent foundations are the preferred choice due to their convenient construction and low cost. The construction process includes excavation of foundation pits, pouring of cushions, binding of steel bars, erection of formwork, and pouring of concrete, with a short construction period and mature technology.
• Soft soil or filled soil areas: If the foundation bearing capacity is insufficient, foundation treatment (such as replacement filling, dynamic compaction) or the use of raft foundations or pile foundations is required to enhance overall integrity. For example, raft foundations disperse loads by increasing the foundation bottom area, suitable for sites with poor foundation uniformity; pile foundations transfer loads to deep soil layers by embedding pile ends into the bearing layer, suitable for high-rise or heavy-load frame structures.

3. Special design requirements for two-story steel structure factory buildings
Steel structure factory buildings form a spatial framework through beams, columns, and purlins, with the load transfer path being: roof/floor loads → purlins → main beams → columns → foundations. The foundation design needs to focus on the following aspects:

• Column base anchoring nodes: The connection between the column base and the foundation needs to determine bolt specifications, weld thickness, and stiffener layout through calculations. For example, rigid column bases need to ensure that the bolt shear and tensile bearing capacities meet design requirements while reducing local stress concentration through stiffeners; pinned column bases need to control rotational stiffness to avoid excessive structural lateral displacement.
• Foundation uplift resistance design: Steel structures have light self-weight, and wind loads or seismic actions may cause uplift forces on the foundation, requiring the addition of uplift-resistant piles or expansion of the foundation bottom area to meet anti-overturning requirements. For example, in coastal or windy areas, column foundations need to be equipped with uplift-resistant steel bars or use extended foundations with greater burial depths.