Structures - steel. Structures - steel

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1 Structures - steel This section includes summary sheets for the following technical solutions: Assemble structures on site and move into place; Steel with high recycled content; and Lightweight bridge decks. Designing out Waste - Part 2: Technical Solutions 117

2 Technical solution: Structures steel Assemble structures on site and move into place Application: Various structural elements for highways, railways, utilities, harbours, docks and waterways, and power generation. Off Site Construction. Off site manufacture of steel elements ensures better quality workmanship with minimal waste production and has been a feature of steel construction for many years. Assembling structures on site and then moving them into place has the potential to significantly change operations on site, reducing the number of site activities and changing the construction process into one of a rapid assembly of parts that can provide many environmental, commercial and social benefits. Assembling structures in this way is one of a group of approaches to more efficient construction sometimes called Modern Methods of Construction that also include prefabrication, improved supply chain management and other approaches. It should be noted that these techniques are already extensively applied in the building construction industry from which many lessons can be learned. Assembly on site is now frequently used as a method of construction of road, rail and foot bridges. In replacement situations, the new structure is built alongside the existing one, which is then demolished and the new structure moved into place as a unit. The main driver for this method of construction is that it minimises closure or disruption of the road or railway, but it also allows more efficient construction of the new structure with reduced waste compared to constructing it in stages while keeping the road/railway functioning. The existing structure can then be demolished or dismantled more efficiently, allowing greater recovery and reuse of its materials for future projects. In all cases, the methods of construction need to be considered at the preliminary design stage. WRAP (2007) Current practices and future potential in modern methods of SCI (2009) Benefits of off site steel construction in urban locations provides advice for the building sector which may be more generally relevant. Waste reduction: has the potential to reduce waste produced on site. Cost reduction: efficient prefabrication may reduce costs. Recycled content: most steels have a high recycled content. Programme: minimises disruption to transport networks by rapid on site assembly of the structure reducing construction timescales. Carbon footprint: minimises delay to road, rail and other users so improving fuel efficiency. Other environmental benefits: less disruption in terms of noise, dust, and vibration because of faster 118 Designing out Waste - Part 2: Technical Solutions

3 Technical solution: Structures steel Steel with high recycled content Structures - steel Application: Steel usage in the construction of highways, railways, utilities, harbours, docks and waterways, power generation and in the development of brown- and greenfield sites. Reuse and Recovery. In general there is a highly developed market for steel recycling and about 40% of the steel produced in the world is from recycling. This means that steel purchased for construction is likely to have a high recycled content and also that steel scrap arising on site will have a market value. Steel can sometimes be reclaimed from site and put to direct use elsewhere without recycling. Waste reduction: surplus or waste steel is normally sold to a scrap merchant for recycling. Cost reduction: there is an associated cost recovery in the reclamation or recycling of steel. Recycled content: increases the recycled content of the scheme. Programme: no impact on programme. Carbon footprint: the recycling process requires lower levels of resource than primary steel production. Other environmental benefits: no waste generation. Reduced resource depletion. A high proportion of the steel used in the construction industry is already produced by recycling and there are generally no limitations on its use for any purposes. All steel has a recycled content that varies between 10% and 100% and steel construction products are highly recycled. Recent research by the Steel Construction Institute has found that on average, 84% of UK s construction steel is recycled and a further 10% reused. The location of scrap merchants is readily researched on the internet and many websites are available to identify the nearest merchant to a particular UK postcode. The properties of the recycled steel are the same as those of the virgin material and the relevant British Standard specifications apply, e.g. BS EN 10293:2005 Steel castings for general engineering uses. BS EN :1997 Founding. Technical conditions of delivery. General. BS EN :2000 Founding. Technical conditions of delivery. Additional requirements for steel castings. BS 4483:2005 Steel fabric for the reinforcement of concrete. Specification. BS 4449:2005+A2:2009 Steel for the reinforcement of concrete. Weldable reinforcing steel. Bar, coil and decoiled product. Specification. Designing out Waste - Part 2: Technical Solutions 119

4 Technical solution: Structures steel Lightweight bridge decks Application: Rapid construction of bridges. Off Site Construction. Fibre reinforced plastic (FRP) decks may provide an effective solution in cases where the advantages of light weight, rapid construction and corrosion resistance outweigh the additional material cost. FRP decks are likely to be used in combination with conventional materials in the design of new bridges and replacement of understrength decks in existing bridges. Waste reduction: factory production minimises waste. Cost reduction: minimises installation and traffic delay costs, although material costs may increase. Recycled content: n/a Programme: light weight decks can be rapidly assembled and lifted into place with a mobile crane. Carbon footprint: reduction in lorry movements as more linear metres can be carried per delivery. Other environmental benefits: less use of concrete and steel. Less disruption in terms of noise, dust, and vibration because of faster Lightweight decks are ideal for the construction of footbridges or limited facility bridges (i.e. farm crossings, cycle routes, etc). The main structural members are normally designed using conventional materials, however where FRP main beams are used higher material factors are appropriate for ultimate and serviceability limit state designs. FRP decks may be more costly than decks formed from conventional materials and, for this reason, their use is normally only considered where speed of construction significantly reduces costs and/or environmental impacts. The design of FRP bridges and highway structures is covered by the HA Departmental Standard BD90 www. standardsforhighways.co.uk/dmrb/vol1/ section3/bd9005.pdf Guidance is also given in CIRIA Report C564 on Fibre-reinforced polymer composites in 120 Designing out Waste - Part 2: Technical Solutions

5 This information is an extract from Designing out Waste: a design team guide for civil engineering Designing out Waste: a design team guide for civil engineering was originally published July To downloaded the full guide visit: While we have tried to make sure this document is accurate, we cannot accept responsibility or be held legally responsible for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. This material is copyrighted. You can copy it free of charge as long as the material is accurate and not used in a misleading context. You must identify the source of the material and acknowledge our copyright. You must not use material to endorse or suggest we have endorsed a commercial product or service. For more details please see our terms and conditions on our website at