Design of Prefabricated Components
The primary advantage of prefabricated structures is that they perform similarly to cast-in-place structures. These prefabricated systems consist of components such as prefabricated columns, shear walls, composite beams, composite panels, stairs, balconies, and more. However, the adjustment factors used in structural calculations differ slightly from those applied to traditional construction.
When designing prefabricated structures, secondary beams are often omitted to reduce the number of assembly parts and simplify on-site construction. It is essential to consider the boundary conditions of the cross-sectional dimensions of components based on the manufacturing capabilities of the factory. Without this knowledge, the designed components may not be producible. For shear walls, the layout should facilitate easy assembly and disassembly during construction.
The load transfer method for floor slabs depends on the type of panel produced by the industrial manufacturer. If a double-sided composite panel is used, the load transfer method remains unchanged. However, if a unidirectional prestressed composite panel or a unidirectional prestressed hollow panel is employed, the load transfer should be adapted to opposite-side and unidirectional force transmission. Floor slab reinforcement should be designed to resist non-primary stresses by using envelope design techniques, considering construction direction and cast-in-place thickness for two-way slabs.
When using software like PKPM for prefabricated structure calculations, note that factors such as periodic reduction, beam stiffness increase, and torque reduction differ slightly from traditional designs. These variations must be carefully accounted for during the design process.
In construction drawings for prefabricated structures, it is important to minimize the number of sleeves in edge components of columns or shear walls to reduce costs. Additionally, when arranging shear walls in prefabricated systems, beyond traditional design considerations, keep the following in mind:
(1) Prefer arranging more L-shaped and T-shaped shear walls while limiting the addition of flanges, especially on exterior walls, to avoid scattered disassembly of wall components.
(2) There are two common approaches regarding the length of flanges in shear wall structures:
The first approach involves leaving a door jamb of at least 200mm at door and window openings, as illustrated in Figure 1. For L-shaped exterior wall flanges, the length is generally limited to 600mm or less, while T-shaped flange lengths are typically kept under 1000mm. This helps prevent issues during concrete pouring caused by excessively long edge components.
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