Prefabricated modular architecture: characteristics and applications of the dry construction system |

(by R. Petruzzelli) There prefabrication is the general term by which we refer to any component manufactured in a different place from the last placement site. With reference to the building sector, it means the off-site construction of building elements, building components and / or subsystems of buildings.

These forged in the factory, in a highly controlled environment thanks to the use of technologically set machinery and subject to continuous checks, respect the predefined performance in the design phase and are ready to be assembled in the factory or transported to the installation site where the phases will follow. by Assembly.

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The potential of prefabrication

Given the above, it is possible to outline the following potentialities of prefabrication and consequently of the dry construction system:

  • environmental sustainability: the design and use of cold connections and joints minimize the use of chemical substances such as adhesives and resins and avoid the use of mortars whose packaging requires a large amount of water and therefore a consumption of resources.
    Furthermore, the assembly and disassembly of modular prefabricated structures in the factory or on site considerably reduces the waste traditionally produced on site with consequent simplification of the phases of waste separation as well as recycling of materials and reuse of components. This contribution, for the benefit of respect for the environment, is enhanced thanks to the versatility of the module, since it can be adapted to meet different needs during its life cycle;
  • speed of realization: production times compared to traditional architectures are short as the manufacturing companies provide a range of modules with a “turnkey” formula. These are complete and functional modules, equipped with every finish and systems already installed. The times that elapse from production to use, in this case, depend only on the transport from the warehouse / company to the site and on the assembly times if there are more modules for the spatial definition;
  • flexibility: intrinsic characteristic due to being able to add, subtract and modify the components of the modules, creating highly flexible spaces that meet the specific needs of each client;
  • ease of transport: the predetermined dimensions allow the transport on ordinary vehicles such as ships and mobile cranes of modules assembled in their spatial configuration or transported in flat pack mode. In this case, each module is disassembled into its components, in particular the base and the cover become elements of the packaging, inside which all the plant elements, structural and otherwise, are inserted with the components necessary for assembly. This transport system allows a reduction in volumes and the possibility of not carrying out exceptional transport with a consequent increase in costs;
  • manageability: The composition of the dry layering, due to its ease and decomposition, is oriented towards the optimization of maintenance times and phases. In fact, during the life cycle of the structure, it is possible to remove or restore a component without the need to damage other portions making up the product. The speed of the localized intervention guarantees the carrying out of activities in the spaces without particular interruptions.
Fig. 1_How to transport the assembled module
Fig.2_Flat pack transport mode

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The degrees of the prefabrication and the dimensional definition of the module

There dry layered construction it is the result of the juxtaposition of different components, with different degrees of complexity and specialization. In fact, support profiles, panels and stratifications of insulating materials are used which overall define the product.

The start of a design process requires, upstream, the choice of the manufacturing grade to be adopted in order to better evaluate the convenience ratio between the performance offered by the prefabricated components and the overall system. In general, the degree of prefabrication refers to the complexity and dimensions of the prefabricated components that lead to the final configuration of the product.

They can be distinguished four degrees of prefabrication:

  1. the materials: columns and beams of different materials such as wood or steel;
  2. the components: individual elements such as stairs, fixtures whose installation requires particular attention to connections, alignments and stability checks;
  3. the panels2D systems: two-dimensional elements, whose degree of prefabrication is about 60%, used to create structural walls, floors and roofs;
  4. the forms3D systems: also known by the term of PPVC (Prefabricated Prefinished Volumetric Construction) are three-dimensional structural units, the degree of prefabrication of which rises up to 85%, or in the case of the presence of internal finishes up to 95%.
Fig.3_Prefabricated module

Generally off-site construction adopts a single system or a hybrid system, combining the different degrees of prefabrication. The definition of the dimensions of the modules requires reference to the standards defined by the International Organization for Standardization (ISO). In particular, the ISO 668: 2020 standard specifies container sizes, functionalities, applications and structural limits. Compliance with the limit dimensions defined by the above, allows the ease of transport with special ordinary means.

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The following are the standard dimensions of the most used containers in the building sector:

  • 20 ‘ISO container with external dimensions: width equal to 2,438 m, length of 6,058 m and a maximum height of 2,896 m;
  • ISO 40 ‘containers with external dimensions: width 2,438 m, length 12,192 m and maximum height of 2,896 m.

The dimensions of the containers are such, as mentioned, that they can be transported on articulated lorries but it should be noted that the maximum height is equal to 2,896 meters. In relation to the aforementioned dimensions, the ranges of modules available on the market have a minimum height of 2.20 m, followed by 2.50 m and 2.70 m. For these values, transport can be carried out on trucks equipped with cranes for lifting and positioning the modules, respecting the limit values ​​set by the Highway Code.

If the size of the modules exceeds 2.70 m, the transport becomes a exceptional transport, as defined in art. 61, paragraph 6 of the Highway Code. This is the case of the basic units intended for school use, for which the minimum internal height is set at 3.00 m, pursuant to the ministerial decree of 18 December 1975, except for exceptions. The execution of an exceptional transport involves a greater burden that affects the overall cost of the realization, for this reason companies can resort to the flat pack mode.

The article is from Rosa Petruzelli, building engineer at the Algeco Company. She has always been passionate about design and construction, she faces every new project with enthusiasm, aiming for the search for an efficient solution. Her strong curiosity and determination lead her to explore new cultures and sectors because she is convinced that wealth lies in knowledge.

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Prefabricated modular architecture: characteristics and applications of the dry construction system |