The case for steel
Nick Barrett starts a series of articles that will provide designers with a comprehensive outline of why their choice of constructional steelwork represents the value for money option with an overview of the case for steel.
The case for using steel as a construction material in the UK is overwhelmingly strong, so much so that it dominates the market as a building framing solution and for longer span bridges to a greater extent than anywhere else. Why do designers increasingly find structural steelwork to be the first choice building material?
Safety record sets steel apart
Health and Safety is often cited as the priority by developers, designers and contractors alike, and one way to show that safety is truly being put first is to select steel. The sector enjoys an enviable safety record. Most of the work is already done by the time steelwork arrives on site, in the factory-controlled conditions of the fabricating shop where the latest machinery ensures safer working conditions for fully trained, skilled workforces.
On site operations are inherently safer than with alternative materials. In place of gangs of shuttering joiners and other trades, constructional steelwork is erected quickly and safely by small teams of certified specialists, overseen by erection experts with a wealth of experience. Work at height takes place in the secure environment of a mobile platform in which operatives are secured with fall arrest equipment.
BCSA members have been at the fore of developing innovative safety systems that benefit all workers on projects they are involved in, like edge protection systems and safe loading and unloading procedures.
Vibration standards easily achieved
The long span solutions offered by steel are easily achieved without any special strengthening being required to meet even the strictest requirements for vibration performance in the National Health Service.
Floors provided to these ‘hospital specifications’ are lighter than concrete alternatives. Assessing structures for performance in use is easily achieved with steel framed buildings, using calibrated, proven design rules.
Post-tensioned concrete flat slabs raise their own vibration issues, and in some parts of the world previously high profile supporters of this technique are turning their backs on it in favour of steel.
Careful detailing is needed whatever framing solution is adopted to ensure that a building achieves the required acoustic performance. Tested details are available free for steel solutions. Steel infill walls are lighter and narrower than concrete block equivalents.
Steel is the sustainable solution
Steel has possibly the strongest sustainability case of all construction materials. As it is so easily recycled steel in use represents a positive store of value to society. Concrete on the other hand leaves a substantial legacy problem that threatens to blight some potential redevelopment sites.
Using steel lengthens the life of buildings as they can be easily extended vertically and horizontally and adapted to the changing needs of building users. When it is decided to completely redevelop, the sale of scrap steel helps defray development costs.
Floors in steel framed buildings commonly provide all the thermal mass that is required for efficient heating and cooling.
Proven performance in fire
Steel has a proven performance record in fire, whereas other materials have at best patchy test histories and as a result their performance in real fires can only be guessed at. The steel sector has consistently funded comprehensive research over a period of many years so that the performance of steel in a fire can be reliably forecast. The cost of fire protection has fallen considerably over the past 20 years or so and intumescents are now routinely applied offsite. New design techniques using finite element analysis are highlighting where fire protection can be safely and cost effectively eliminated, and where additional protection could be best applied.
Quality assured product
All steel sourced from Corus, the UK’s leading steel manufacturer, is CE marked, with all that implies in terms of guaranteed quality and provenance. Use of 3-D modelling, CE marking, numerically controlled fabrication and offsite production all add up to steelwork being a high quality product supplied to site with minimal defects. Steelwork contractors now commonly cooperate with designers and clients to such an extent that key structural solutions can be trialled before going to site using mock ups, as was done at Heathrow Terminal 5 by Severfield Rowen for client BAA.
Cost effective framing solutions
For many, the financial case for using steel is perhaps the strongest. The cost of constructional steelwork has fallen significantly in real terms over the past 20 years thanks to massive productivity improvements made by Corus, steelwork contractors, intumescent paint manufacturers and others in the supply chain that have been shared with clients.
Independent studies consistently show that steel provides the most economic solution in most cases – the market obviously agrees as steel now commands over 70% of the market for multi storey buildings. Value engineering usually results in steel being chosen in preference to any concrete alternatives that might have been considered.
The strength of the steel supply chain, from the Corus steelworks and mills through fabrication to erection on site, is one of the most striking characteristics of the UK construction market.
There is a wide range of highly skilled and experienced steelwork contractors able to tackle the most complex and technically challenging projects and play an active role in developing cost effective and innovative design solutions. They ensure a competitive tendering environment, compared to projects using other materials that might at best attract only two bids.
The supply chain has a long history of producing innovative solutions. Corus for example recently introduced its rebranded quality assured CE marked Advance range of steel sections, bringing new standard section sizes to the UK market for the first time.
Steelwork contractors have invested heavily in state of the art CNC machinery which means continuous improvements in quality and productivity, all to the benefit of designers and building owners and users.
Shallow depth floor solutions are one of the factors that set steel framed buildings apart. Despite the claims that may be made by others from time to time when it is required to have floors accommodate services steel provides the shallower solutions. Slimflor solutions or bespoke fabricated beams provide very shallow floors to meet the most demanding client needs. Solid slab concrete floors are heavy, with cost implications for both the structures and foundations of buildings.
Steel solutions deliver longer spans with column free spaces, small columns, lightweight solutions, shallow floors and integrated services.
Underpinning all this is the huge investment in research and development and technical and marketing support provided by Corus, the BCSA and the Steel Construction Institute. The sector carries out a great deal of development work of its own and cooperates with universities in the UK and worldwide to ensure continuously developing technical excellence.
Technical support is offered to designers on a scale unprecedented in construction. Everything that can be provided to make designing in structural steelwork easy is made available.