Prefabricated Floor Slab Structure of Houses
The prefabricated floor slab structure of houses is a building system with prefabricated slabs as the main components. Its core components are factory-prefabricated cement slabs, which enable rapid construction through standardized production and on-site assembly. However, it has limitations such as weak earthquake resistance and poor integrity. Modern technology has developed improved prefabricated structures.
1. Structure and Types of Traditional Prefabricated Slabs
Traditional prefabricated slabs are made in factories by nailing wooden molds, arranging steel bars, and pouring cement. They are divided into two types: solid slabs and hollow slabs. Hollow slabs reduce the amount of non-load-bearing concrete through internal holes, achieving lightweight while maintaining structural strength. Their dimensions are designed according to the room span and the lifting capacity of the machinery, and they are commonly found in the floor slabs of early residential buildings and roof insulation layers. Most residential buildings constructed in China before 1985 adopted this type of structure. However, existing buildings generally have problems such as weak earthquake resistance, poor sound and heat insulation, and a service life of about 30 - 50 years. Some regions have initiated demolition or renovation projects.
2. Application Scenarios and Defects of Traditional Prefabricated Slabs
- Rural self-built houses: Prefabricated slabs are still used in some rural areas due to their fast construction speed and low cost. However, they have poor integrity, and the slab joints are prone to water leakage; their earthquake resistance is weak, and it is necessary to enhance structural stability by setting up reinforced concrete ring beams; their local load-bearing capacity is limited. For living rooms or master bedrooms with a span exceeding 3.6 meters, it is recommended to use cast-in-place slabs or thickened prefabricated slabs with structural reinforcement.
- Urban renovation policies: Since 2022, China has implemented renovation policies, focusing on the repair of prefabricated slab buildings and only demolishing those that meet the criteria for dangerous buildings. This reflects that their structural safety can no longer meet modern earthquake resistance standards.
3. Improvements in Modern Prefabricated Floor Slabs
Modern prefabricated structures, such as composite slabs, adopt a composite design of bidirectional steel bars and truss bars. Unlike the prefabricated slab technology in the 1980s, they significantly improve the overall structural integrity and earthquake resistance. In addition, prefabricated prestressed reinforced concrete hollow floor slabs enhance stiffness through prestressing technology, are lightweight, and have good earthquake resistance, making them suitable for high-rise buildings; cast-in-place concrete hollow floor slabs form cavities by embedding internal molds, reducing the amount of concrete and increasing the span. They also have sound and heat insulation properties and are suitable for large-span public buildings.
4. Special Applications of Hollow Floor Slabs
Hollow floor slabs achieve performance improvements by optimizing their internal structure:
- Prefabricated prestressed hollow slabs: The internal longitudinal channels save materials and are lightweight, making them suitable for high-rise buildings.
- Cast-in-place hollow slabs: Cavities are formed through standardized construction processes (such as surveying and setting out, and the installation of thin-walled tubes), reducing the overall cost. They have been widely used in schools, shopping malls, and other scenarios.
