13.7 - Off-site cutting
What is it?
Typically metal deck sheets are delivered to site in packs with square cut ends, to be cut to suit on site. The SMD ‘Off-Site Cut’ service involves cutting the sheets to exact shape and size required at the factory prior to delivery to site. Any small notches or alterations are then undertaken on-site using a bespoke plasma cutting tool developed for metal deck construction.
The service was developed originally to meet the environmentally sensitive requirement to ‘Reduce Noise’ for deck installation in London. The extent of cutting required depends on the complexity of the project, but the benefits the service offers (detailed below) have now seen the service adopted on a number of large city centre contracts.
Benefits
- • Reduce noise pollution on site - <70dB at source compared to 110dB when using petrol driven disc cutters
- • Reduction in site wastage and difficulty in scrap removal
- • Cutting undertaken in a controlled factory environment
- • Wastage recycled at source
- • Reduction in time working at height
- • Less wastage = Reduction in delivery vehicles
Involve SMD early in the project alongside the Steel Fabricator and Principal Contractor. This enables details to be developed to minimise the impact and cost of the off-site cutting requirement.
When should it be adopted?
The ‘Off-Site’ service may not be necessary for many contracts, but can be essential in certain locations where:
- • The site is located in a particularly environmentally sensitive area
- • Where noise pollution could create a nuisance to adjacent buildings
- • Projects with large volumes of decking and where a high degree of splayed (or raking) cutting is required, to reduce the on-site programme.
Off-Site Design
It is important to involve SMD early in the process for ‘Off-Site’ contracts as there may be design implications or the potential to develop a more enhanced ‘Off-Site’ option. The design process for off-site cutting differs from standard projects; set-out points must consider column sizes and utilise flashings to minimise the requirement for site notching, further limiting any site wastage.
The detailing and drawings are modelled in a 3D environment using Tekla; using the fabrication model for this service is a must to ensure sheet sizes provided reflect the exact frame being erected. Therefore, sharing of models and utilising BIM principles is an essential part of this service (refer to Fig 13.7b).
Cutting Process
With direct control over the manufacturing facility, a designated cutting area (Refer Fig 13.7c), specifically trained labour, detailing cut part drawings and a detailed QA procedure at our factory, the quality of our ‘off-site’ cutting service is assured.
Installation - decking by numbers
Packs are delivered to site with the sheets already cut to suit the required size and splay. Packed in a safe manner to minimise risk during offloading (refer to Fig.13.7d).
With each cut sheet given a unique identity number (shown on the drawing), the installation on site becomes a decking by numbers process (refer to Fig 13.7e).
Any small notches or alterations required around handrail pots or unforeseen details are then accommodated using a plasma cutting unit.
Plasma Cutters
Where plasma cutters are required, SMD use Hypertherm Powermax30® AIR units to undertake operations.
This small air plasma cutter includes its own built-in air compressor so you can use the Powermax30 AIR anywhere there’s single-phase power.
Dual-voltage, you can use it as a 120v plasma cutter or at 240v.
Take ‘Off-Site’ further….
For some projects there may be solutions to take the ‘Off-Site’ construction ethos further to suit specific building requirements and details. One case study of this was at London Bridge Place, London. For this contract bespoke sheet widths were produced, ‘Off-Site’ cut and then delivered to the steelwork contractor for installation into pre-detailed and designed perimeter modules. These modules were then delivered to site and erected with the majority of the perimeter section of deck sheets already in place (refer to Fig 13.7g).
This bespoke ‘Off-Site’ design offered yet more site benefits by:
- • Further reducing ‘work at height’
- • Minimal time working at the building perimeter
- • Minimising the risk on high-rise buildings
Engaging SMD early in the design process is essential to ensure the benefits of ‘Off-Site’ construction of metal decking are maximised and realised!
Go to NEXT section
