Selection and Application of Prefabricated Slabs for Large-Span Houses

The selection and application of prefabricated slabs for large-span houses require comprehensive consideration of factors such as span, type, design requirements, and usage limitations.

I. Maximum Span and Type Selection
The standard spans of ordinary prestressed concrete hollow prefabricated slabs are concentrated between 2.4 meters and 6.0 meters, with 3.9 meters, 4.2 meters, and 4.8 meters being the most common. When the span exceeds 6 meters, ordinary hollow slabs, due to insufficient deflection and crack resistance, need to be replaced with channel slabs, T-beams, or cast-in-place structures, or specially designed reinforced prefabricated composite slabs. For example, by optimizing the internal framework structure and applying high-strength steel wires, the ultimate span of some special prefabricated slabs can reach 8 meters or even over 10 meters. However, such products are non-standard customizations and have extremely high requirements for the connection structure of support nodes. The national standard 'Code for Design of Concrete Structures' recommends that the applicable span of prefabricated components should not exceed 12 meters, and special demonstrations are required for spans exceeding this limit. For a 6-meter span, prestressed slabs must be chosen instead of ordinary cement slabs, as the latter are prone to bending beyond 3 meters, while prestressed slabs with a standard thickness of 120 millimeters can support spans of over 7 meters.

II. Design Requirements and Construction Specifications
The design of large-span prefabricated slabs requires professional engineers to calculate the floor load-bearing capacity, ensuring that the load-bearing capacity per square meter is not less than 760 kilograms. High-strength steel with a yield strength of 500 megapascals should be used for reinforcement, replacing the old-fashioned 335-megapascal steel. During installation, the length of the slab ends resting on the walls should not be less than 10 centimeters, and stirrups should be inserted at the joints to enhance integrity and prevent cracking. In addition, the transportation and hoisting of prefabricated slabs must be strictly controlled to prevent internal hidden cracks caused by collisions, which could affect structural safety.

III. Usage Limitations and Alternative Solutions
In earthquake-prone areas, prefabricated slabs are prone to disintegration during vibrations due to their poor integrity. It is recommended to prioritize the use of cast-in-place concrete structures, which can achieve an earthquake resistance level of 8. If the budget is limited and the area is not earthquake-prone, prefabricated slabs can be chosen, but the connection design of the nodes must be strengthened. For industrial plants or large public buildings requiring spans of 15-20 meters, designers often adopt prefabricated hollow floor systems or bidirectional ribbed floors, achieving column-free large spaces through spatial structure optimization.

IV. Practical Application Scenarios
Prefabricated concrete hollow floors are widely used in multi-story residential, commercial, educational, medical, and industrial buildings. Their advantages lie in fast construction speed and high industrialization level, but strict quality control is required from production to installation to ensure compliance with specifications.