The useful life and service life of buildings are often far apart. If a property is no longer fit for purpose, it is usually demolished, even though it would still be perfectly usable. Even if individual parts of the building are damaged, the entire building usually has to go. This is because in most cases it is cheaper to build a new building than to convert or renovate the existing one. However, this approach does not conserve resources. In the MOHOHO project, an interdisciplinary team from the Institute of Architectural Technology and the Institute of Timber Construction and Wood Technology at Graz University of Technology, together with corporate partners Kaufmann Bausysteme and KS Ingenieure, has developed a system for a modular timber high-rise building whose flexible adaptability is intended to extend its useful life and service life. A patent application has been filed for this system. The project was funded by the Austrian Research Promotion Agency FFG.

Circularity

“The construction industry is responsible for around 60% of global resource consumption and almost half of global waste generation and global emissions of climate-damaging gases,” says Christian Keuschnig from the Institute of Architectural Technology at TU Graz. “Therefore, circular R-strategies such as refurbishment, repair or reuse were very important for us in the MOHOHO project in order to develop a building system that offers a CO2-reduced alternative to conventional construction methods in high-rise construction and can be used for different purposes for as long as possible.”

This has been achieved through the combination of modular and skeleton construction. In modular construction, completely prefabricated room modules made of wood are used, which are stacked next to and on top of each other. Skeleton construction offers a supporting structure for free and therefore flexible floor plans that can be adapted by inserting or removing partition walls. These recyclable skeleton modules consist of a cross-laminated timber floor and glulam supports. The prefabricated skeleton modules can be joined quickly and securely using the connection node developed as part of the project.

The connecting node also enables load redistribution, which means that the failure of individual supports does not lead to the collapse of the entire building, which firstly increases robustness and therefore safety and subsequently enables the targeted repair of individual modules. In addition, an elastomer bearing integrated into the node ensures a high level of sound insulation between the units.

Repairable support structure

To replace a module or individual elements, it is necessary to disconnect the supply lines for electricity, water and heating and expose the connections. The node is designed so that a lifting cylinder can be inserted between the spacers, which slightly lifts the support above. This allows the spacers to be removed and a shear plate redirects the forces after the lifting cylinder is lowered. This relieves the pressure on the components below and creates the necessary space for the replacement process. In addition to accessibility, the individual elements must be able to be dismantled to ensure a repairable construction. In mathematical terms, a building with this construction system can be up to 24 storeys high, although a concrete core is absolutely necessary from a height of more than six storeys, which significantly increases the consumption of resources and CO2 emissions.

“With MOHOHO, we have combined the advantages of modular timber construction, such as the high degree of prefabrication and the short construction time, with the advantages of skeleton construction,” says Christian Keuschnig. “The prefabrication of the modules in a production hall under controlled conditions enables higher quality and traceability of the joints compared to on-site assembly and ensures shorter construction times as well as reduced noise and dirt pollution. The repairability and flexibility of the construction system should significantly extend the service life and useful life of the building. During dismantling, the modules can either be reused directly or separated according to type. We are already planning a follow-up project in which we want to test and check all of these things in practice.”

[Source: 19.12.2024 | TU Graz news | Forschung |Autor: Falko Schoklitsch]