Beams in Prefabricated Slab Houses
The beams in prefabricated slab houses are of various types, widely used, and require rigorous structural design. They cannot be randomly removed, and the number of floors is also restricted by the structure.
Types and Applications of Prefabricated Beams
Prefabricated beams are one of the main prefabricated components in prefabricated concrete frame structures. Common types include prefabricated solid beams and prefabricated composite beams. These beams are prefabricated in factories and then transported to construction sites for installation and fixation. They have been applied on a large scale in areas such as long-span viaducts, prefabricated buildings, and municipal engineering projects.
Definition and Classification of Composite Beams
Composite beams are beams with concrete poured in two stages. First, a prefabricated beam is made in a prefabrication yard. Second, after the prefabricated beam is hoisted and placed at the construction site, concrete is poured on the upper part to form an integral whole. According to their load-bearing performance, they can be classified into two types: "one-stage load-bearing composite beams" and "two-stage load-bearing composite beams". In the former, reliable supports are provided under the prefabricated beam during the construction stage, and the load is transferred to the supports. After the post-poured concrete in the composite layer reaches a certain strength, the supports are removed, and the entire cross-section bears the load. In the latter, no supports are provided under the simply-supported prefabricated beam during the construction stage, and all the loads during this stage are borne by the prefabricated beam.
Structural Design of Composite Beams
Taking the "two-stage load-bearing composite beam" as an example, the structural design is divided into two stages. The first stage is before the concrete in the composite layer reaches the design strength value, and the prefabricated components are calculated as simply-supported components. The second stage is after the concrete in the composite layer reaches the design strength value, and the composite components are calculated as integral structures. At this time, both the construction stage and the service stage should be considered. During structural design, calculations such as the flexural bearing capacity of the normal section, the shear bearing capacity of the inclined section, the shear bearing capacity of the composite surface, the maximum crack width, and the maximum deflection value are required.
Handling of Beams in Prefabricated Slab Buildings from the 1990s
In discussions on the renovation of prefabricated slab buildings from the 1990s, most people recommend not smashing the beams in bedrooms and instead opting for edge wrapping or ceiling installation. These beams may have been added for structural reasons, and randomly smashing them may pose safety hazards, such as the prefabricated slabs not having sufficient overlapping length and falling.
Floor Number Limitations for Prefabricated Slabs with Small Beams
Structures consisting of prefabricated slabs with small beams can have a maximum of 3 to 4 floors. They have poor integrity and are directly prohibited in earthquake zones with an intensity of 8 degrees or higher. In areas with an intensity of 6 or 7 degrees, the slabs should be 80 millimeters when attached to walls and fixed with ring beams.
