What is a composite steel deck floor?
A composite steel deck floor is a floor system in which profiled steel sheeting serves as permanent formwork for concrete cast on site. The sheets usually have a trapezoidal or re-entrant (dovetail) profile and are galvanised, typically by the Sendzimir process. Once the concrete has hardened, steel and concrete act together: the sheet takes tension, the concrete compression. The Dutch term is staalplaatbetonvloer. You find this floor mainly in steel-framed buildings and in renovation work.
How does it work?
- Composite action. Embossments or indentations in the sheet stop the concrete from slipping along it, so the sheet acts as (part of) the bottom reinforcement.
- Reinforcement. A mesh is usually placed near the top to control shrinkage cracking. To achieve the required fire resistance, extra bars in the ribs may be needed, because the unprotected sheet weakens quickly in a fire.
- Light. Thanks to the ribs, less concrete is needed than in a solid slab. Lightweight concrete makes it lighter still.
- Fast. The sheets are easy to lay. Where they can be walked on, several storeys can be prepared before any concrete is poured.
Design follows Eurocode 4 (EN 1994-1-1), usually using the span tables of the decking manufacturer.
Application
- Fix the sheets straight away to the steel beams as the manufacturer specifies, before anyone walks on them. Loose sheets can slide or tip.
- Prop where required. Whether the deck needs temporary propping during the pour depends on profile, gauge and span. Follow the manufacturer’s tables.
- Close the edges with edge trims and seal the rib ends at the supports so no concrete escapes.
- Openings for services and stairwells are formed with trimmer joists or extra reinforcement, as the structural engineer specifies. Don’t cut through ribs afterwards.
Common mistake: dumping the concrete in one tall heap. The local load can permanently deform or even collapse the sheet; spread the concrete across the area immediately.
Related terms
- Sendzimir galvanizing
- Filigree
- Hollow-core slab floor
- Trimmer joist
- Reinforcement
- Fire resistance
- Light steel frame floor
- Steel connection
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