Lakhta Center – a large scale project of the construction of a modern business area in the north-west of Saint Petersburg. Opening in 2018.
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Lakhta Center. 462 Meters above Sea Level
Steel cores of the vertical columns of Lakhta Center high-rise building
— The key topic of the forum (100+ Forum Russia) is special technical conditions (hereinafter STC) for high-rise buildings. Could you tell us how difficult it was for Lakhta Center to approve the technical conditions?
In our project there are conditions for fire safety STC, or rather, requirements to ensure fire safety and the general technical conditions for the facility as a whole, including the design and the construction. And these special technical conditions accompany us throughout the project, live with us as a constantly changing document where we regularly record the latest ideas, optimizations and improvements that are to be approved by the federal authorities. Generally speaking, this is a separate work that is not much associated with the design, but it is very important to reflect in these documents all innovations that we want to bring into our complex. But the point is that not all innovations that we want to use are described exhaustively in the existing regulations. And the main task is to find the right paragraph in the regulations that can describe these. If there is no such a paragraph, we try to cover this with STC.
Moreover, the project has one more element introduced by us, which required not only the issuance of special technical conditions, but also the application of the method of calculation. I mean composite structures. Vertical structures – columns; and horizontal structures – floor slabs. Horizontal slabs are very often used by bridge-builders. There is nothing new in this field. But we are one of the first who use such vertical structures in Russia. And recently we have made another update to the documents in order to close the issue with the composite structures. We conducted a series of field tests, and the leading institutions prepared the revised methodology for the calculation of our structures, as a result STC for the use of these structures were developed and approved by the Ministry of Construction.
— You mentioned composite structures. Could you share the details of the technology?
We have chosen the most profitable and reliable solution for the project implementation – composite structures. This is a perfect combination of steel and concrete. We have exploited all advantages of steel – speed, ease of erection in the cold season and at height. And we borrowed the advantages of concrete such as its fire resistance, the similarity of yield and shrinkage of the outer perimeter of the tower and the core. Steel in a composite (steel concrete composite) structure takes up to 17%, including reinforcement elements. The rest is concrete. What is more, we use the concrete of high grade B 80 to get the optimal strength of the materials. And these are our columns that are installed on the perimeter to ensure the building stability.
In fact, the skeleton of the building is as follows: there is a circular reinforced concrete core in the center of Tower, from which steel girders radiate being supported by the steel concrete composite columns installed on the perimeter of the facade. In addition to steel – rigid reinforcement that we insert into the columns, we also have additional reinforcement – traditional reinforcement bars installed on the perimeter of the columns.
Furthermore, due to the transition from pure steel to composite, we have got a definite advantage with respect to the time frames and the selection of lifting equipment. A column of pure steel with the height of 4.2 meters is very heavy. We need a lot of such columns on the lower floors. And although the designers initially considered the possibility of the application of steel structures made of standard steel slabs (the editor’s note: slab is a plate, big piece; in metallurgy – a semi-finished product of the metallurgical production: steel billet of rectangular cross section with a large width to height ratio – up to 15), after the detailed analysis of the schedule and the construction procedure with the construction manager it was decided to make the columns as composite structures.
1. Record-setting base
The reliability of the complex foundation is ensured by 2,080 piles.
Piles with the diameter of 2 meters installed under Tower are used for the first time in the world.
The bottom plate of the center foundation will require 20,295 cubic meters of concrete. Simultaneous filling of such volume will also be done for the first time.
2. 20 football fields of glass
Glazing area of the complex is 130,000 square meters. One glazed unit of the facade will weigh 740 kg. This is the first use of such volume of facade glass for a high-rise facility.
3. Smart facade
The air space between the glazing layers will provide thermal insulation and natural ventilation, which will reduce the costs for heating and air conditioning.
Glazing area is 85% of the total facade area.
4. Independent lighting
The lighting system is fully automated. Dimmable LED lamps change color and intensity depending on the level of natural lighting providing comfort to inhabitants of Tower. The blinds are also controlled automatically with account of the position of the sun.
5. Top-level speed and comfort
A total of 96 lifts are in Lakhta Center. Lifts’ speed is 8 meters per second.
6. Entrance arch is larger than the bridge span over the Neva
The maximum span of the trusses of the main entrance arch is 98 meters, which is more than the length of the largest span of the Trinity Bridge. The height of the arch is almost 24 meters.
7. Architecture with a wingspan
Large spaces of lobbies of the multifunctional building will be created through the use of 36-meter steel Vierendeel trusses. The span is larger than the wingspan of the Airbus A320.
8. Cold generators for cost saving
Cold is accumulated during hours of low load and lower temperature and is used during the period of the highest cooling demand reducing the load on the network. Taking into account the double-rate system, the saving will be up to 15%. CO2 emissions will be reduced.
9. Smart recycling
Vacuum pneumatic waste disposal system: improved hygiene, reduced CO2 emissions, sorted waste; garbage removal is required 20 times less often than when a conventional system is used.
Runoff water is used secondarily for watering lawns, technical needs, cooling towers.
Excess heat from the work is reused for heating.
10. Smart home: building management system
All MEP systems of the complex are controlled from a single control point.
The system allows professionals to monitor and manage MEP systems from any point of the building. Monitoring data are automatically transmitted to MChS (Emergency Control Ministry) in case of emergency situation (data on condition of the structures of the building, the work of water, electricity and heat supply systems).
Interior Design of Atrium of Lakhta Center
— Are any other innovative technologies used in the project of the center?
Speaking of the construction of skyscrapers in general, first of all, it is worth mentioning that high-strength materials are used. We mean both the concrete (B 60, B 80 concrete grades) and the high-strength steel (355, 465 steel classes). These are the materials that are to be used at height. Without them, the building elements are either very cumbersome, or their shape does not fit the geometry designed by the architect. One more system appeared; it considers that steel and concrete are used together. This is a composite cross-section of flooring when a corrugated sheet is placed on a steel beam and anchor bolts are welded to the steel beam through this corrugated sheet. As a result, when we pour concrete from the top, we get a permanent formwork. It is a very interesting and promising technology that is effectively and widely used in high-rise construction.
One more solution that is used is worth mentioning: self-compacting concrete (SCC). It is concrete that displaces the air due to its own weight. In order to displace the air out of the ordinary concrete, to lay it and vibrate it, a vast number of vibrators are required. This means additional time, additional equipment and, accordingly, additional costs. When self-compacting concrete is considered, it is enough to fill it in a form and that is all. But it has a major disadvantage. It is very sensitive to the external environment. If during the pouring it rains or the cement and water ratio is chosen incorrectly or the additive is calculated incorrectly, its consistency may be impaired. But if you can cover the surface and execute works taking into account the outdoor air temperature and humidity then this material is simply irreplaceable for densely reinforced structures.