04 Feb Fixings for Composite Decks
After laying the deck it must be fixed to the supporting steelwork. Powder (shot-fired) or gas actuated, or screw fixings can be used for this depending on the application. Below is a list of common applications and support materials.
Fixing to structural supports
When steel beams are to receive thru-deck welded shear studs, Hilti X-U 15 shot-fired fixings or X-P14 G3 MX gas-fired fixings should be used to secure the deck during installation.
Where studs are not required for composite action, the Hilti X-ENP 19 should be used. These fixings are required for the increased resistance of the nails, as typically beams will have been designed with a restrained top flange.
Where decking is required to provide lateral restraint and no thru-deck welded shear studs are specified, the fixing type should be checked by the engineer to ensure adequate shear resistance is provided by the fixing type and frequency, refer to https://smdltd.co.uk/tgn-online/4.4_-_Lateral_restraint_and_diaphragm_action.
Masonry & Concrete
Fixings to masonry should be either Drill & Hammer Anchors (Spit P370) or shot-fired fixings (Hilti X-SW or Spit CR9).
Timber & Glulam
When fixing to timber or glulam beams, shot firing is not recommended. Instead self-drilling screws should be used, such as; Hilti S-MD55Z, Fixfast DF12 5.5mm.
To stop the deck profile spreading during concreting, the sheets must be fixed together. For SMD floor decks, self-tapping screws (typically Hilti S-MD01Z 4.8 x19) must be installed at a maximum of 1.0m centres.
Decking must be fixed at a maximum spacing of 300mm centres (300/333mm dependent on profile) at the end of each sheet and 1 per 600mm (For TR60+ 333mm or 666mm respectively) at intermediate supports. Fixings should be located a minimum of 20mm from the end of the sheet and where more than one fixing per trough is specified, the spacing between fixings in the direction of deck span is to be >45mm. The table below indicates the spacings for the various SMD floor deck profiles: