11.0 - Installation - Floor deck and shear studs
SMD products should only be installed by those competent and trained to do so. Specific reference should also be given to the BCSA Code of Practice for Metal Decking and Stud Welding and, as a minimum, the following procedure should be followed.
Prior to commencement of deck installation, a system of fall protection (refer section 10) and safe access must be in place. This should form part of the overall safe system of work agreed by all parties and detailed in the project specific Risk Assessment and Method Statement (RAMS).
Decking bundles should only be opened if all the sheets in the bundle can be fixed or left in a safe condition at the end of the shift. Consideration must be given during periods of bad weather to any unfixed sheets as these must be secured at the end of each day by using a temporary strap secured to the frame or decking.
Where supports are to receive shear studs, top flanges must be unpainted and free from grease or rust that might adversely affect the weld. Refer to Fixings section (page 24) for guidance on minimum bearings.
Access to level
Wherever possible, the decking installation should be planned to commence from the corner of a building or phase, so that the number of leading edges are limited. The recommended means of access to and egress from the workface should be either temporary Haki type stair or permanent fixed stair with handrail.
Laying decking sheets
Using the access provided, the installer should straddle the first bundle of decking to remove the banding. The first decking sheet will then be pushed out onto the steelwork to be used as a working platform from which to lay the remaining sheets in that bay. Decking sheets should then be lapped, lined up and fixed into place once the adjacent bay has been laid and the troughs of the decking have been lined through. During installation, cumulative measurements of across the bay width should be taken to ensure the effective product cover width is consistently achieved.
Cutting / notching
Decking sheets are typically delivered to site at the correct square cut length. Where decking ribs sit over beams that are to receive welded shear studs, around columns and other protrusions, notching and/or cutting of the deck will be required. This should be carried out by trained operatives using suitable disc cutters (petrol, cordless, electric or pneumatic) with appropriate blade, plasma cutters or similar approved equipment. For some contracts, cutting will be carried out off-site prior to delivery (refer to section 13.5), in these instances the sheets will be delivered to site at the correct length and shape for installation with only minor notching required around columns and handrails.
Fixing of the deck and edge trim to the supporting steelwork or walls will typically be carried out using low velocity powder (‘shot-firing’) or gas-actuated cartridge tools. In certain circumstances, the use of self-tapping screws may be necessary.
Refer to section 4.6 - Fixings for recommended fixing types and spacings.
At side laps, the deck sheets must be stitched together using self-tapping screws, installed with suitable screw guns, at maximum 1.0m centres. In addition to stabilising the joint, these help minimise grout loss experienced during concreting.
Sealing and finishing off
Gaps up to 5mm are acceptable as they are not sufficient to allow concrete aggregate to escape.
Note: The decking is not intended to provide a watertight finish and a degree of fines and water seepage (grout loss) is to be expected from the panel ends and joints.
In areas where it is essential to reduce grout loss to a minimum, the addition of tape at all butt joints and side laps may offer an economical solution, it should be noted that this is not standard practice and must be discussed at pre-tender stage.
Generally supplied in 3.00m standard lengths, each length should be tethered during installation using the holes provided. The edge trim must be fixed to the perimeter supports at maximum 750mm centres, with restraint straps installed to the top of the upstand leg/tick at centres as indicated in the Edge Trim & Flashings section using self-tapping screws.
Forming holes and openings
Where trimming steels are provided, the decking sheets may be cut to suit the size of the opening and edge trim installed. Where there is no supporting steelwork, the voids will have to be decked over. The opening should then be formed by the concreting contractor who will box out the opening prior to pouring the concrete. Refer to Section 5.6.
It is the Steelwork Contractors responsibility to ensure the supporting structure is in a stable condition, adequately restrained and handed over as 'safe to access' prior to proceeding with the deck installation. Any additional support plates or angles required around columns, penetrations or splices must also be provided by the Steelwork Contractor.
Refer to BS EN 1993 or BS5950 in Lateral Restraint section for more information
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