Force Transmission in Prefabricated Slab Buildings
The force transmission methods in prefabricated slab buildings are mainly divided into vertical load transmission and load transmission under horizontal seismic actions, as detailed below:
Vertical Load Transmission
The vertical loads in prefabricated slab buildings, such as self-weight, occupant activities, and furniture, follow a clear transmission path, primarily relying on the collaborative action of the prefabricated floor slabs and supporting structures. 1. One-way Slab Load Transmission Mechanism When rooms are arranged with prefabricated slabs, they typically adopt a one-way slab configuration. A one-way slab is defined as a slab where the ratio of the long side to the short side is greater than 2, causing the load to be primarily transmitted along the long side direction. For example, a prefabricated slab measuring 4 meters in length and 1 meter in width will concentrate its load through the long side to the supporting beams or walls below, forming a clear “slab→beam/wall” path. This design simplifies the load transmission path, facilitating structural calculations and construction. 2. Role of Supporting Structures Supporting beams or walls, as key load-transmitting components, must possess sufficient stiffness and load-bearing capacity. Beams transmit loads further to columns or foundations through bending deformation, while walls directly transfer forces to foundations through compression. For instance, in a frame structure, the prefabricated slabs transmit loads to the frame beams, which then transfer them to the columns and ultimately to the foundation; in a brick-masonry structure, the slabs are directly placed on the walls, which distribute the forces to the foundation.
Load Transmission Under Horizontal Seismic Actions
Under horizontal seismic loads, prefabricated slab buildings require connection details to achieve overall collaborative behavior and prevent local damage. 1. Criticality of Connection Details Connections between prefabricated slabs and between slabs and supporting structures (such as welding, bolting, and post-poured concrete) are central to horizontal load transmission. Proper connections ensure that all slabs share loads vertically and horizontally, forming an “integrated floor system”. For example, during an earthquake, the horizontal force on one prefabricated slab is transmitted through the connections to adjacent slabs, which then transfer it to the supporting structures and ultimately to the foundation. 2. Impact of Integrity on Seismic Resistance If connections are weak (such as relying solely on dry connections), relative displacements between slabs can occur during an earthquake, leading to interrupted load transmission or even structural collapse. Therefore, codes require that prefabricated slab connections meet shear and tensile resistance requirements and enhance integrity through construction measures (such as adding shear keys and reserving steel bar overlaps). For example, some prefabricated buildings adopt a “composite slab” technique, where a cast-in-place layer bonds the prefabricated slabs with post-poured concrete, significantly improving horizontal load transmission capacity.
Summary
The force transmission in prefabricated slab buildings is characterized by “vertical load transmission through one-way slabs” and “horizontal collaborative behavior through connection details”. During design, it is essential to focus on the load transmission path along the long side of the slabs, the load-bearing capacity of supporting structures, and the reliability of connection details to ensure the safety of the structure under both conventional loads and seismic actions.
