Let it rise
Some very interesting design ideas are being explored by designers known to relish the physical challenges of structural engineering. The metal of choice: steel
Steel can never go out of fashion. It is one metal that has had maximum impact on mankind. As an engineering material, it is of great help to architects, civil and structural engineers, designers, consultants, metallurgists and project owners.
There’s something unique to steel too. During an economic downturn, prices of most products are expected to fall.
However, steel prices rise as demand falls. There is a term the industry has: steelflation.
As the focus on developing infrastructure across the country gains momentum, the steel industry has responded by adjusting its product mix. As an alloy of iron and carbon, it is the latter that modify the allotropic changes that iron displays during heating and cooling.
There are a host of different types of steels used in steel framed buildings. Some of the principal products include structural sections, which includes universal columns and universal beams; steel plates; hot finished hollow sections which are available in different shapes such as round, square, rectangular and oval.
Demand for steel has also escalated by leaps and bounds and is now enjoying a resurgence that was last experienced in the 1980’s.
Market share has swollen from 25% 25 years ago, to in excess of 71% in 2007, so much so that the construction market in the UK is now one of the most steel intensive in the world. This has now filtered down to India as well. Hence we see mergers and acquisitions on a large scale.
Knowledge of the physical benefits of steel is continually increasing among the community using it. Hence manufacturers have realised that to constantly innovate on new technologies requires their willingness to work with its customers on technical development of products.
This creates benefits for users not only in the construction process, but also in the lifetime performance as part of the overall building package. Innovation has been spurred on by competition with other materials – notably concrete.
The launch of branded steel products for construction comes at a time when consumers are becoming increasingly brand conscious. M Aggarwal of SSH Agrotech (P) Ltd says: “No more are customers, especially in the construction industry, ignorant about reputed brands. Among rebars, brands like Tiscon, Sail, Elegant and SRMB enjoy a status in the Indian market.” Knowing the quality of the TMT bars customers prefer, industry leader Tata Steel makes it a point to actively engage structural engineers and architects so as to disseminate product brochures about steel products.
Consumers also need to be alerted to the fact that large plants, specifically automatic rolling mill plants, manufacture good quality products compared to local manufacturers. Manufacturers using imported TMT plants (quenching plants) accepted worldwide for their quality – such as Thermex from Germany, Tempcore from Belgium or Jettherm from the US – are able to add both to their brand image and quality of steel rebars.
Structural steel has also seen constant innovations since the last decade or so.
“Corus has a patented technology. Bi-Steel has been around for some years. But Corefast – an innovative, rapid-erect modular building core system created by fabricating Bi-steel panel modules off-site – is growing beyond its earlier security sector applications into the construction mainstream.
Corefast can significantly reduce on-site construction time, and can typically be erected up to six times faster than an equivalent concrete core. In addition, it delivers a highly accurate structure with superior strength and stiffness, says Darayus Shroff, general manager, Corus.
Another product from the Corus stables is ComFlor 60, an innovative new composite floor profile that offers lightweight steel decking for all multi-rise buildings. Using roll-forming techniques, it gives an exceptional unpropped spanning capability of up to 4.5 metres with reduced concrete usage.
Engineered with optional closed ends, it provides an acoustic performance and fire protection, with no requirement for filler blocks. Additionally, its profile has been specifically designed with trough stiffeners and side laps to guarantee centrally placed sheer studs – reducing the need for on-site checking.
It must be remembered that for maximum benefit, predominantly high tensile steel in grade 355 is used for construction applications.
With the construction industry increasingly aware of the need to use sustainable materials that ensure product durability and low maintenance costs, the use of SS rebars has assumed paramount importance. As SS mirrors carbon steel in all physical and load bearing properties, it may be replaced ‘like for like’, and also be connected to carbon steel without fear of increased galvanic corrosion to the parent carbon steel.
Authentic stainless reinforcing bars also have low magnetic permeability. When used in bridges, SS reinforcement also reduces the concrete requirement, and eliminates expensive bridge deck surface treatments. The only thing going against SS rebars is their high cost, which is in part due to their high nickel content.
Steel offers the construction industry a chance to offer high quality buildings while also taking into consideration the environmental impact.
Cost is no more a deterrent when specifying building materials, but speed and predictability of construction programmes, design flexibility and sustainability are becoming key considerations.
Some of the benefits that steel offers are:
Structural Efficiency – Steel is inherently strong yet also has a high strength-to-weight ratio. Thus it makes for comparatively ‘light’ structures that often require fewer and lighter foundations.
Its long span capabilities allow designers to create flexible spaces than can facilitate changes of use during the life of a building and so help extend its useful life.
Off-site construction – By its very nature, steel based construction is exclusively off-site giving rise to more predictable construction programmes, along with cost certainty, and construction quality.
Offsite – Steel is inherently off-site. All steel construction components are manufactured off-site, in factory-controlled conditions, ensuring consistency, quality, reliability and fewer defects.
What little waste is generated is efficiently captured and is 100% recyclable. Off-site manufacture combined with rapid erection on-site increases economic efficiency and reduces the chance of delays.
Tie-ups of steel
Recently, British structural steel major Severfield-Rowen entered into a joint venture with a subsidiary of India’s O P Jindal Group to create a structural steel joint venture based in Bellary and Mumbai.
JSW Steel, which is part of the O P Jindal Group, has a capacity of about 5 million tonnes per annum (mtpa) and plans to expand to 32 mtpa by 2020. The new company, JSW Severfield Structures, will be based next to JSW Steel’s Vijayanagar works in the Bellary district of Karnataka. It will design, make and build structural steelwork projects in Indian markets.
The total investment cost of the 50/50 joint venture is about £30 million. The joint venture will work on everything from oil and gas projects to stadiums.
Severfield-Rowen has worked on numerous high-profile projects including Arsenal’s Emirates Stadium. It is currently providing structural steel for a closing roof for Wimbledon’s Centre Court. The company is the only structural steel contractor for the London 2012 Olympic Stadium.