Framing schematics for a complete building structure
Most steel buildings use eithier composite or Slimdek flooring. For both the various structural components - slab, beams and columns - are brought together to form the complete building structure.
Composite construction
The composite frame uses a combination of composite slab and beam elements and has proved very efficient for multi-storey construction
The traditional composite frame comprises primary and secondary beams rigidly connected to the floor slab using shear studs. The composite action developed between the beams and slab enables shallower beam depths to be used.
Floor slabs generally comprise composite metal decking with in situ concrete. These span onto the secondary beams.
Estimates of structural sizes can be made using simple guidelines
Primary beams can be sized according to the following:
- maximum span = 15m
- Floor beam depth = span/20
- Roof beam depth = span/25
Secondary beams can be sized according to the following:
- maximum span = 12m
- Floor beam depth = span/25
- Roof beam depth = span/30
Composite slabs are typically 125 to 150mm thick (overall) and can span up to 3.5m
Column sizes are largely dependent on the number of floors supported as shown in the table below.
| Floors | UC | SHS |
| 1 | 152 x 152 | 150 x 150 |
| 2-4 | 203 x 203 | 200 x 200 |
| 5-8 | 254 x 254 | 250 x 250 |
| 9-12 | 305 x 305 | 300 x 300 |
| 13-40 | 356 x 356 | 400 x 400 |
Slimdek uses ASB's to achieve a shallow overall construction depth.
The Slimdek structure comprises shallow slimfloor beams within the depth of the floor slab. The newly developed Asymmetric Slimfloor Beam (ASB) is designed specially for this, and a rectangular hollow section with a bottom flange plate (RHSFB) is advised for edge beams. The beams support the floor slab on their bottom flange.
Floor slabs may comprise precast concrete slabs (slimfloor) or deep metal decking with in situ concrete (Slimdek). The latter enables composite action to be developed in the supporting ASB beams, and provides good opportunities for service runs.
Estimates of structural sizes can be made using simple guidelines
ASB beams can be sized according to the following:
- maximum span = 7.5m
- Beam depth = 300mm
Floor slabs are typically 300mm thick (overall) and can span up to 9m
Column sizes are largely dependent on the number of floors supported as shown in the following table.
| Floors | UC | SHS |
| 1 | 152 x 152 | 150 x 150 |
| 2-4 | 203 x 203 | 200 x 200 |
| 5-8 | 254 x 254 | 250 x 250 |
| 9-12 | 305 x 305 | 300 x 300 |
| 13-40 | 356 x 356 | 400 x 400 |
