Load-Bearing Capacity of Prefabricated House Slabs
The load-bearing capacity of prefabricated house slabs has no fixed value and is influenced by factors such as type, specification, thickness, span, reinforcement, and load type, typically ranging from 150 to 500 kilograms per square meter. Here is a detailed analysis:
Type and Specification: Concrete hollow slabs are commonly found in rural self-built houses and old residential building floors, with a national standard uniformly distributed load of 200 to 250 kilograms per square meter. For example, a hollow slab that is 3.6 meters long and 0.6 meters wide has an area of 2.16 square meters and a total load-bearing capacity of 432 kilograms. Solid prefabricated slabs are sturdier than hollow slabs and are often used in kitchens, bathrooms, and other areas with heavy loads, capable of bearing 250 to 300 kilograms per square meter. Solid slabs produced by large factories, with sufficient reinforcement and high concrete grades (C30 and above), can have a load-bearing capacity of up to 300 kilograms per square meter. Prestressed prefabricated slabs generate prestress by tensioning high-strength steel wires, resulting in stronger crack resistance and load-bearing capacity. For spans within 3 meters, they can bear 300 to 400 kilograms per square meter; for spans over 4 meters, the load-bearing capacity remains at 250 to 300 kilograms per square meter, which is 20% higher than that of ordinary prefabricated slabs of the same span.
Thickness and Span: Thickness directly affects the load-bearing capacity. A 10-centimeter-thick prefabricated slab has a load-bearing capacity of 150 to 250 kilograms, while a 12-centimeter-thick one can reach 250 kilograms. In terms of span, the shorter the prefabricated slab, the stronger its load-bearing capacity. For example, a hollow slab with a 2.4-meter span can bear 250 kilograms per square meter; a 3.6-meter span reduces it to 200 kilograms per square meter; and spans over 4.2 meters may only have a load-bearing capacity of 150 to 180 kilograms per square meter.
Reinforcement and Load Type: Prefabricated slabs with thicker and denser reinforcement (such as 8-millimeter steel bars spaced 15 centimeters apart) have stronger load-bearing capacities. Prefabricated slabs are sensitive to concentrated loads, with different impacts from uniformly distributed weights and weights concentrated at a single point. For example, a prefabricated slab that can bear 200 kilograms per square meter may be fine with 200 kilograms of sand evenly spread, but placing a 300-kilogram safe in a 1-square-meter area may crack the slab.
Historical Standards and Ordinary Concrete Prefabricated Slabs: In the 1970s and 1980s, the design value for live loads in residential buildings was specified as 150 kilograms per square meter, taking into account a safety factor of 1.2 to 1.4. Ordinary concrete prefabricated slabs can bear a maximum of about 500 kilograms per square meter, roughly equivalent to the weight of five adults. National standards stipulate that residential floors must be able to bear at least 200 kilograms of live loads, and when considering the self-weight of the floor, the total load-bearing capacity can reach about 760 kilograms.
