Suspended concrete floors are most often used in commercial construction and high-rise buildings.
Suspended concrete floors are rare in residential construction in the United States but are common in commercial construction. The American Concrete Institute (ACI) maintains standards for the construction of suspended concrete slabs, providing requirements for the design and construction of suspended floors.
Specifications
The ACI standards require that certain significant specifications be included in the contract documents for a suspended slab design. These specifications include the size and geometry of any supporting framework, the details of reinforcement within the concrete, the specifications of shear connectors that connect the slab to the supports, the location of construction joints, the specification of any metal deck that supports the slab, the specifications of any shoring that supports the structure and the design tolerances of all elements of the structure.
Reinforcement
Internal reinforcement of suspended concrete slabs is typically either conventional iron reinforcement or post-tensioned reinforcement. Post-tensioned reinforcement is a type of reinforcing structure that is under tension and is more effective at preventing deflection, or sagging, of the slab when the concrete is subjected to a weight load. Post-tensioned reinforcement is commonly used when the slab must span larger distances.
Metal Decking and Supports
Suspended slabs are often supported by a steel framework, and the supported slab is considered to be either composite or noncomposite. In a composite slab design, the concrete slab and steel framework are mechanically connected in such a way that the two elements work together to support loads on the slab. In a noncomposite design, the slab and the framework function independently to bear weight loads. In some designs, a metal deck supports the slab, and in these designs the deck typically serves as a form for the concrete when it is poured and remains in place after the concrete has hardened.
Inspections
Inspection of suspended concrete floors is difficult because the floor is often hidden beneath other elements of the structure, and structural deficiencies can be nearly impossible to detect. The deterioration of internal reinforcement is one of the most serious threats to the strength of a suspended concrete slab, and inspectors should be alert to any sign of rusted reinforcement, such as rust on the surface of the concrete. If signs of rust are seen, or the inspector suspects any other structural problems, a specialist should be consulted.
Tags: concrete floors, commercial construction, concrete slab, concrete slabs, construction suspended