Flat Plate
The flat plate is a two-way reinforced concrete framing system utilizing a slab of uniform thickness, the simplest of structural shapes.
Flat Plate System Introduction
A flat plate is a one- or two-way system usually supported directly on columns or load-bearing walls. It is one of the most common forms of construction of floors in buildings. The principal feature of the flat plate floor is a uniform or near-uniform thickness with a flat soffit which requires only simple formwork and is easy to construct.
The floor allows great flexibility for locating horizontal services above a suspended ceiling or in a bulkhead. The economical span of a flat plate for low to medium loads is usually limited by the need to control long-term deflection and may need to be sensibly pre-cambered (not overdone) or prestressed.
An economical span for a reinforced flat plate is of the order of 6 to 8 m and for prestressed flat plates is in the range of 8 to 12 m. The span ‘L’ of a reinforced concrete flat-plate is approximately D x 28 for simply supported, D x 30 for an end span of a continuous system, to D x 32 for internal continuous spans.
The economical span of a flat plate can be extended by prestressing to approximately D x 30, D x 37, and D x 40 respectively, where D is the depth of the slab.
Advantages of the System:
- Simple formwork and suitable for the direct fix or sprayed ceiling
- No beams—simplifying under-floor services
- The minimum structural depth and reduced floor-to-floor height.
Disadvantages of System:
- Medium spans
- Limited lateral load capacity as part of a moment frame
- May need shear heads or shear reinforcement at the columns or larger columns for shear
- Long-term deflection may be controlling factor
- May not be suitable for supporting brittle (masonry) partitions
- May is not suitable for heavy loads.
flat plate construction
Source
thanks to
civil digital
Er.SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)
Structural Engineer
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