Precast concrete construction
Precast concrete construction refers to the creation of structures using prefabricated components made of reinforced concrete, the so-called precast concrete parts , the production of such precast concrete parts , as well as structures that were essentially built with precast concrete parts . Precast concrete construction is used in both building construction and civil engineering as a complex system or as a single prefabricated part in mixed buildings. The range of prefabricated components used ranges from individual ceiling panels , supports and girders to wall panels and finished, multi-shell facade elements to prefabricated rooms, for example complete prefabricated bathrooms or prefabricated garages. The precast concrete parts used are manufactured in pre-fabricated concrete factories in halls in reserved forms that can be reused after the component has hardened and formed. Precast concrete construction places special demands on both the planners (modular construction) and those carrying out the work, both in the factory and on the construction site.
commitment
Today, precast concrete construction is mainly used for the construction of large apartment buildings, commercial buildings, hotels, office buildings, but also for parking garages, bridges, towers, tunnels and masts. Even railway sleepers are now precast concrete parts. Sewers are often made of precast concrete pipes and conventional masonry usually come precast concrete floors are used. System parts developed by the respective providers are usually used. Especially for larger construction projects with special design requirements, individually designed prefabricated components and systems can also be produced cost-effectively.
The advantage of precast concrete construction consists primarily of the advantages of industrial production of series components with corresponding cost efficiency, quality assurance and weather-independent production. At the construction site, shorter construction times, shorter drying times and less of the wage-intensive construction site work are added as advantages. Basically, it can be said that the advantages, especially the cost savings, increase significantly with the size of the respective components and the number of identical parts used.
A disadvantage is that sometimes extra-wide heavy transports are necessary and powerful cranes have to be used on the construction site. Planning restrictions for the floor plan or the design also have to be taken into account, since the required grid and reduced part diversification restrict the design freedom here. The task of the planning is to find an optimal compromise.
historical development
The first houses in which prefabricated elements were used as large plates in reinforced concrete construction were built in 1910 in the Forest Hills Gardens project in Queens , New York . Named after the engineer and architect Grosvenor Atterbury , the construction principle was also known in Europe as the Atterbury system . The first project in which panel construction was used in Germany was the Neues Frankfurt project (1925–1930), for which a factory was built specifically for the production of large panels. In 1926, the first German prefabricated housing estate was built in Berlin-Lichtenberg , district of Friedrichsfelde , based on designs by the then town planning officer Martin Wagner . Multi-shell concrete slabs weighing up to 7 tons were poured on site.
The Unité d'Habitation (apartment) of Le Corbusier was as Every system works the model of modern prefabricated buildings. Corbusier presented the core of the idea with the Pavillon de l'Esprit Nouveau in Paris in 1925 . The residential units were built between 1947 and 1965 in four French locations and in Berlin . Corbusier saw his building design as the ideal solution for mass repetition in many places. He wanted to achieve a high level of profitability through standardized series production . This economic efficiency and widespread use should enable the majority of the population to enjoy increased living comfort and alleviate the housing shortage after the Second World War .
.JPG)
Prefabricated prefabricated buildings used for residential purposes were particularly widespread in the German Democratic Republic . A first large-scale test building was built in 1953 in Berlin-Johannisthal . The expansion of the city of Hoyerswerda became an "experimental field" in this area. The industrial residential building in prefabricated construction was realized there for the first time in the GDR since 1957 on a large scale with residential building systems specially developed for this purpose.
The construction process with prefabricated concrete parts was based on the ideas of modern architecture that had already emerged in the Bauhaus . Due to the economic advantages, entire housing estates , high-rise office buildings , industrial and other large buildings are often built from factory-made precast concrete parts .
application
Design and planning
The decision to use precast concrete parts usually has economic reasons and from then on it determines the entire planning, from design to logistics to execution. For example, a grid has to be developed in the design, which represents an optimal compromise between usage-optimized space dimensions, maximum manageable component sizes and economical logistics. The aim is to meet the various requirements for use and architectural design of the buildings with as few different components as possible. Depending on the grid chosen and the static requirements, various design approaches are possible. For larger halls, systems with separate supports, ceiling beams and wall and ceiling panels in a wide variety of variations are usually used. For example, separate and specially shaped prop heads are possible, which in turn enable uniform props, as well as U-shaped or cassette-shaped ceiling panels that combine the ceiling and any necessary intermediate supports in one component. In offices, hotels or residential buildings, self-supporting wall and ceiling panels are usually used as the most economical solution due to the smaller spans.
When planning and designing the individual components, care must be taken to ensure that they can be easily shaped after casting and that they have dimensions that ideally enable transport without a heavy load permit. The parts can be multi-shell, angular or highly complex. When it comes to surface design in the visible area, there are a number of options for avoiding a typical concrete look. Polished surfaces, structures, patterns or sand or sandstone structures in all imaginable colors, the so-called architectural concrete, are possible here .
The necessary connections are of particular importance when planning precast concrete parts, which on the one hand must meet static requirements, but on the other hand should also be designed in an appealing manner. When designing these connections, you can either optically emphasize the seams and supports as a grid or dissolve them with shadow gaps, concealing surface structures or overlaps.
Manufacturing
Precast concrete parts are industrially manufactured in precast concrete plants as large or special series. There are limits to the shapes that can be realized. In addition to the size, the shaping required after the concrete has hardened also plays a role here. Ideally, the mold should be left undamaged so that it can be reused. As a rule, this is done using slightly conical components with appropriate shapes. If this is not possible or desired, multi-part shapes with the disadvantage of a seam are used. Only as a last resort are disposable forms, so-called lost forms, used. The statically required reinforcement steel and, if required, supply pipes are inserted into the molds during the production of parts and the mold is then poured with concrete. For better compaction of the concrete, the molds stand on vibrating tables ( external vibrators ) or it is sufficiently compacted by hand with internal vibrators . Multi-shell wall elements can be produced by setting in concrete in two runs, as can more complex components. However, it should be noted that due to the manufacturing process, one side cannot be a visible side and also has certain dimensional tolerances. After sufficient curing time, the parts produced in this way can be switched off.
For the assembly of the precast concrete elements, systems are provided that enable simple and non-positive connection on the construction site. On the one hand, there are recesses with exposed connection reinforcement, so-called casting pockets or, especially in the case of plates and large panels, weld-on plates embedded in concrete. Often there are also brackets for transport in the parts.
On the construction site, the parts are transported to the intended location by crane, partially supported on neoprene bearings or placed in mortar . After the alignment, the connections are frictionally connected by concreting the pockets with the exposed and now overlapping connection reinforcements or, in the case of parts with weld-on plates, these are firmly welded to the components corresponding to the weld-on plates, then poured with concrete or later, during expansion, covered with screed or plaster. If there are joints, these are permanently elastic sealed with joint sealing compound .
Systems
There are a number of manufacturers of precast concrete parts who offer self-developed prefabricated parts and prefabricated part systems in large series for all imaginable purposes. In the area of residential construction, the most well-known systems are certainly the prefabricated buildings of the former GDR housing systems M 10 , Q3A or WBS 70 .
Norms
transport
For the road transport of precast concrete parts, the maximum permissible dimensions of vehicles according to §32 StVZO are decisive. This results in the following maximum dimensions:
- Normal transports with a unit weight of up to 26 t and a dimension of 10.80 m × 3.40 m.
- Lengths of up to 16.50 m and heights of up to 4.90 m are possible on a sloping stand vehicle.
- Common heavy transporters are able to transport concrete parts individually or in pairs with 84 t and a maximum length of 55 m.
When using the required cranes, it should be noted that the load-bearing capacity decreases quickly as the outrigger increases. Precise construction site planning is particularly important here.
Job description precast concrete manufacturer
literature
- Roman Hillmann: Precast Aesthetics - The emergence of your own expression in buildings made of prefabricated reinforced concrete parts. In: Adrian von Buttlar, Christoph Heuter (Ed.): Monument! Modern. 1960s architecture. Rediscovery of an era. Jovis, Berlin 2007, ISBN 978-3-939633-40-2 , pp. 80–87 (architectural-historical treatment of the topic).
- Tihamér Koncz : Handbook of precast construction. Volume 1-3. Bauverlag, Wiesbaden / Berlin 1973, ISBN 3-7625-0416-4 / ISBN 3-7625-0594-2 / ISBN 3-7625-0326-5 .
- Konrad Weller: Industrial Building: Volume 1 - Basics and development of industrial, energy and resource-saving building . Kohlhammer, Stuttgart / Berlin / Cologne / Mainz 1986, ISBN 3-17-008880-7 .
Individual evidence
- ↑ Le Corbusier's residential unit "Typ Berlin" - facsimile of the original edition from 1958 with an updated appendix, WEG Corbusier-Haus, Förderverein Corbusierhaus Berlin e. V. (Ed.), JOVIS Verlag Berlin 2008, ISBN 978-3-86859-005-0 .
- ↑ DBV leaflet: precast concrete elements made of architectural concrete ( Memento of the original from September 28, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ 32 Dimensions of vehicles and vehicle combinations ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
