It is generally believed that only sports structures, parking spaces, warehouses, industrial workshops, and, probably, large malls can be built of steel. While for housing, the metal is unfitted. Actually, it is not the case.
With the steel
In recent years, steel structures have been actively applied in the construction of residential compounds. The secret of the growing popularity of this material is simple: with structural elements, buildings are erected literally within months. They are assembled on a construction site like a construction kit. In this case, any “wet” processes are ruled out. In order to install a multi-storey building from metal structures, there is no need to involve a crowd of people: some 5-6 assemblers will be enough. While at the construction of high-rise buildings, the metal is simply critical — most of the skyscrapers are built just on a steel frame.
Let alone the “original” niche of the metal where it is almost the king — a steel technology particularly took roots in parking spaces: constructing from metal, one can get a parking lot without columns. First of all, it is due to the fact that fewer columns is required, and secondly because such columns have smaller dimensions. Needless to say that parking in such a space is more convenient, while the parking lot is several times cheaper.
According to INFOline agency, by the end of 2017, the number of products made for the purpose of being used in construction amounted to 3.5 million tons, which is 4% more than the previous year. In addition, a steady trend of increasing the production of metal structures has been observed for several years.
However, we would be insincere if we said that steel construction does not involve any troubles. They exist and they are more than a few. Some of such troubles were discussed by a representative of Ferro-Story company Igor Danilov at a recent seminar “Steel Construction” held by the Association of Steel Construction Development (ARSS). The company is building three 17-storey residential blocks with a stylobate part on a steel structural element. The project envisages a monolithic core with a grid of columns along the perimeter. Metal structures are fastened with high-strength bolts.
‘The first thing we faced was the lack of a market for qualified contractors specializing in steel construction’, says Igor Danilov. And if such a contractor can be found, the cost of its services is quite high. Actually, there are not enough project solutions on the “steel” market either. But the bottom line here, according to Igor Danilov, is, perhaps, the unpreparedness, ignorance about the peculiarities of steel technology both on the part of the customer and the end user.
‘Abroad, for example, the buyer does not have any problem with the metal beams of a structure, which project somewhere’, Igor Danilov continues. ‘The real estate buyer simply does not pay attention to them. Whereas our customers have made a severe condition: beams should not be visible anywhere. We have found a way around by pushing the beam to the ceiling. This solution kills two birds with one stone — it performs the fireproof function and ensures a smooth ceiling without an offset’.
Conclusions that were made during the construction are the following: the metal enjoys plain shapes; when designing, it is better to involve assemblers; when reducing metal consumption, remember that this can lead to a cost overrun since you will have to purchase the higher-strength metal, which can be more expensive; check everything yourself and make sure that your customer knows where to place the order for metal structures.
There is a video available on the Internet, made by one of the Chinese construction companies. A 57-storey building has been constructed within 19 days. It was assembled from blocks prefabricated at a plant. Is it a possible timeframe?
‘Yes it is’, believes Denis Konin, who is in charge of the high-rise building and structure sector at the Research Center of Construction n.a. Kucherenko (TsNIISK). ‘But what must be understood is that prior to that, the building modules had been prefabricated at a factory for a year. While the building itself had been designed for two years. In total, 3 years and 19 days!’
‘And yet, I suppose that the future belongs to quick-assemble modules’, Denis Konin admits. ‘And now not just a steel but also a composite construction is becoming increasingly popular, with the core of the building being made of a steel frame while the surrounding grid of columns is made of composites.
This, by the way, gives the building an extraordinary lightness. Metal structures allow reducing the load on the footing, which is important for high-rise buildings. The use of light and flexible steel structures can be particularly seen in seismically unstable areas. So, for example, in the tower of Akhmat in Grozny, the concrete, with its great weight and rigidity, has proved inappropriate while the light steel has turned out to be very useful.
Are the standards too tight?
So what impedes the advancement of steel construction on the Russian market? That was the question the participants of a recent press breakfast arranged by the Association of Steel Construction (ARSS) have raised. Alexander Danilov, Director General of the Association of Steel Construction, cites the following figures. Steel-frame buildings account for just 17% in Russia, whereas the total amount of such houses abroad accounts for 70%. Despite a steady upward trend, Russia still has a long way to go.
‘At present, the emphasis has shifted, in many respects, from the design and construction process to the process of project coordination and validation’, admits the head of ARSS, Alexander Danilov. ‘That is, the developer had to move from the construction site to bureaucratic offices’.
Due to “failures” in the area of the regulatory framework, there is often a need for developing special technical conditions for steel-frame buildings. This requires coordination with the Ministry of Construction, as well as with the key research institutions, something that results in the delay of a design process and brings the project to bureaucrats. Therefore, many developers do not dare to use steel structures, despite their advantages.
‘What is the obstacle? First and foremost, these are Russia’s tight standards for metal-framed buildings’, said a senior partner of Thornton Tomasetti Corporation and Director of its Moscow branch, Leonid Zborovsky. ‘They make “steel” buildings more expensive. What do I mean? For example, fire protection requirements. In Russia, the requirement for fire resistance of metal structures is four hours. It is during this time that firemen are supposed to be able to get to the flame base and extinguish the fire.
In Europe, the requirement is two hours, that is, in two hours, a fire brigade should be on the site and extinguishing the fire. In order to comply with the fire resistance standards adopted in Russia, the flame-retardant coating of the metal must be much thicker. This leads to a considerable increase in the cost of a building as a whole.
Another standard is wind resistance, the swinging of a high-rise building on exposure to the wind. A critical factor here is the acceleration during swinging. In Russia, a very small amount of acceleration is considered permissible, while in Chile, China, and many other countries this figure is almost twice as big! That is, the permissible amplitude of the swing is wider. What does this mean? This means that in Russia, in order to comply with the standard, the building must be more “rigid”. And this also leads to a considerable increase in price. As a result, compared with the concrete, the metal is at a disadvantage. If Russia introduces the European standard, the cost of construction will be much lower.
Indeed, at present, the Association has actively taken on the regulatory framework. National state standards for metal building structures and light steel thin-walled ones are being developed. The Catalog of Metal Structures Manufacturers, the National Standard for Rolling of Building Structures and other state standards have already been released.
‘Light steel thin-walled structures based on the cold-rolled profile, being quickly erectable ones, can provide an immediate solution to the problem of housing for orphans, military, as well as of temporary buildings in areas of natural disasters’, says Tatyana Nazmeyeva, project director at the ARCC engineering center. Our interlocutor has emphasized that when designing with the use of light steel thin-walled structures, it is essential to employ a coefficient of operation conditions, otherwise, we will get the structure’s fragility.
According to the head of the ARSS, Alexander Danilov, the Association does its best to make steel construction develop more rapidly. Basically, the practice of steel construction, which is expanding every year, provides food for thought, as well as experience and options for new technical solutions. Therefore, steel construction definitely has a future. But what the future is going to be, depends on all of us — the construction community in general.