Top Project in St. Petersburg
The implementation of the project unique not only for St. Petersburg but also the whole of Russia and Europe, the Lakhta Center Public and Business Complex housing the headquarters of Gazprom, has entered the home stretch. The main building has reached its design height of 462 m.
Sergey Nikiforov, Lakhta Center chief engineer, told the Construction Weekly about the project features.
— Sergey, what makes the project you’re implementing unique?
— The easiest way to answer this question is to list some technical parameters of the object.
The pile field of Lakhta Center consists of 2,080 bored piles. 264 of them (with a diameter of 2 m and depth of 82 m) are installed directly under the tower. Their total length is 15.8 thousand meters and total load is 670 thousand tons. The height of the diaphragm wall (a protective underground structure enclosing the tower foundation) is 30 meters.
Concreting the lower foundation slab of the Lakhta Center tower is inscribed in the Guinness World Records as the longest continuous concrete pouring in the world. More than 19.62 thousand cubic meters of concrete were poured over 49 hours without a stop.
Floor slabs and pillars of the tower are composite, made of metal and concrete in a ratio of 60 to 40. The main structure ensuring the skyscraper stability — the reinforced concrete core with communication systems, elevator equipment, technical rooms, etc. inside — has the highest fire-resistance rating, REI240 (ability to withstand fire for 4 hours without changing the properties of concrete and steel).
I suppose these few facts are enough to grasp that the design is really unique.
— What challenges did you face when building the skyscraper?
— Of course, difficulties are always present. There are probably no projects without them, especially when it comes to such a large-scale construction as Lakhta Center. During the design and construction process we faced problems of various kinds. First, there were natural challenges. In our case, these are the proximity to the Gulf of Finland as well as groundwater and wind load. Prior to the construction commencing, we performed all sorts of tests (including aerodynamic ones) to consider the influence of these factors on the object.
There were also technical issues concerning the use of modern technologies and materials as well as the implementation of complex geometry due to the architectural concept of buildings. The work was carried out in several stages. First, a thorough calculation of all units and structures was performed using special computer programs. Then, mock-ups of the elements were made and exposed to appropriate loads to ensure the calculation accuracy. And only after that the complex structures were manufactured. Furthermore, preliminary "training" assembly was performed on the ground prior to their installation at height.
The third group of challenges was related to the construction coordination. The Lakhta Center tower is the highest building in Europe, and therefore the scope of works is enormous, so a lot of things depend on clarity of actions and coherence between various structures and companies. The logistics is extremely complicated considering a lot of operations are performed simultaneously at the construction site: arrangement of temporary utilities, delivery and warehousing of structures and materials, machinery movement, construction works themselves, etc.
— What kinds of work during the erection of the Lakhta Center tower would you call unique?
— The scope of the project, complex architectural form, specifics of the object geography necessitated the use of unique materials and technical solutions. They were applied literally at every construction stage.
Moving bottom-up, we need to start with the drilling technology we used to install piles to a depth of 82 m. The proximity of the sea and abundance of groundwater added difficulties to the process. It was decided to use the casing system instead of bentonite slurry when performing the works. At that time, we managed to avoid groundwater in the wells. I guess no one in the world had used such a technique. The quality of operations was inspected with special probes and visual examination cameras which were lowered into the wells. Only after making sure that they were clean and absolutely dry, we would begin to dip metal frames and pour concrete.
We used high-performance concrete for the structures of the core and pillars. Self compacting concrete was used in the foundations due to the reinforcement complexity and power, and the rate of pouring the 3.6 meters thick lower plate. After many tests, we managed to discover a mixing formula which is optimal for our object.
We also used the technology of steel-concrete structures which, I hope, will now be more widely applied in Russia. As cores, we used high-strength steel shapes, around which concrete was poured. So, we produced a unified composite structure. This technique enabled us to significantly increase the speed of building the tower.
To erect the core, considering its size and geometry, we used a very interesting technology of self-elevating formwork which allowed us to perform these works carefully, skilfully and almost uninterrupted.
A lot of both cold- and hot-formed glass is used in the project implementation. Only because of this, we managed to realize the architectural ideas of the tower project developers and effectively organize the internal space of the object.
This is a high-rise building, and we used high-strength steel and concrete on office floors too in order to keep the building structures as small as possible. Many interesting methods were applied to organize the engineering systems of the complex. Of course, skyscraper construction is impossible without up-to-day high-speed elevator equipment.
That means, as you can see, unique technical solutions are used in the construction of Lakhta Center from piles to the spire. You can safely say that this is an object created with the use of the latest technologies.
— Are these Russian or foreign technologies?
— Lakhta Center is a world-class project, and it uses up-to-date international know-how. However, we must keep in mind that any direct transposition of solutions implemented somewhere else into our environment is simply impossible. Each project of this scale is unique, and the technologies must be adapted to specific conditions and problems. In other words, we had to update existing know-how.
At the same time I can say that Russian expertise and domestic materials were used when handling these problems. For example, the formula of concrete mixtures that we used is absolutely unique and has been optimized exactly for our conditions.
— When will we see Lakhta Center in all its beauty?
— Commissioning of the object is scheduled for autumn 2018. However, we should understand that it means the end of engineering works and commissioning. That is, the facilities will be built and take their final forms, but the arrangement of internal spaces will still go on. Future tenants will settle in Lakhta Center not earlier than 2019.
Information
Lakhta Center is a public and business complex under construction in Primorsky district of Saint Petersburg which will house the Gazprom headquarters and open public spaces. It comprises a skyscraper and multifunctional complex. The overall area of the facilities is 400,000 sq. m. The office space will occupy about two thirds of the complex. Lakhta Center has become the northernmost skyscraper in the world and the tallest building in Russia and Europe, 88 meters higher than the Moscow high-rise Federation Tower and inferior only to the 540-meter high Ostankino TV tower which is considered an engineering structure rather then a building.
Opinion
Alexey Synchikov, project manager at AECOM (the company providing construction supervision on behalf of the customer for the Lakhta Center multi-functional complex):
— АЕСОМ started to work with the customer back in 2007, when the project was planned to be implemented on Sverdlovskaya Embankment. In 2011, a decision was made to move the project to Lakhta, and we were invited to supervise geotechnical surveys and consult on the design of the facility substructure at the new site.
The difficulties of this projects implementation include, first of all, insufficiency of Russian regulatory base for high-rise construction and the unique character of the facility itself. Thus, to solve the emerging engineering challenges, the customer had to invite the following research institutes: Gersevanov Research Institute of Bases and Underground Structures (NIIOSP), Gvozdev Research Institute of Concrete and Reinforced Concrete (NIIZHB), Koucherenko Research Institute of Building Constructions (TSNIISK), and others. АЕСОМ participated in discussion of these challenges, since we were to supervise compliance of the actual works with the requirements of technical procedures and recommendations.
Huge research work was being conducted from the earliest stage. First, we validated engineering and processing decisions “on paper”. Then laboratory research was conducted, to prove the theory. Some unique and complex construction works (such as concreting of massive structures) required experimental check on the construction site, as laboratory conditions are always a bit different from real life. Following the results of special research (including sampling and required laboratory examination), we took either a final decision, or adjusted the engineering solutions when necessary.
Another challenge was the scale of the project. For example, to pour concrete for the foundation, 13 different batching plants operated simultaneously, and 17 pumps were pouring concrete non-stop for 49 hours. We had to examine every plant for compliance with the requirements: use of modern equipment, a quality assurance system, and a number of other criteria (e.g., storage of inert materials) — and choose the ones for the project. This is just one example. Unique engineering solutions on steel structures, facades, object safety and security required particular attention from all project stake-holders. I am glad that АЕСОМ made its humble contribution to the project that is now known all over the world.
Harijs Cika, Director General of PERI Russia:
— PERI participated in the construction of Lakhta Center, the highest building in Russia and Europe. We provided a comprehensive engineering solution for in-situ concreting from the foundation to the top floors of the tower. We also used formwork and scaffolding systems by this German company to construct the multi-functional building. In total, 7.2 tons of equipment was supplied to the site.
In construction of sky-scrapers, it is crucial to ensure safe and comfortable working environment for the workers. Just imagine the emotional stress that construction workers experience even at the height of 20 meters when there is no wall or fence. So, what is to be said of the height of Lakhta Center? An open horizon is a big danger. The probability of accidents in such conditions is very high. Not only can site workers be hurt but also cars and pedestrians in the proximity to the erected building. This is especially true in dense urban development. A perimeter fence also protects from the weather: wind, rain, snow. Especially, if the construction site is in a northern region or on the shores of a gulf, as is the case with Lakhta Center.
For the core of the Lakhta Center tower, PERI engineers designed an effective formwork solution based on a self-lifting system. As a result, formworks without a crane and regardless of weather conditions sped up the construction.