Building modelling under consideration of stiffness-reducing wall openings and detach-, as well as demountable joints


Project duration: 04/2022 - 01/2026

Buildings/load-carrying structures have to be erected in a way to carry the occurring loads in a secure and reliable manner. The real spatially (3D) acting load-carrying structure is often split up into easier to handle, plane 2D-elements and the members are then analysed on this basis. In the course of this transformation assumptions have to be made which often lead to conservative design results. As a consequence, the forces to be transmitted by the joints/fasteners – in particular in the wall-ceiling-joint – tend to be too high. Further the internal forces as well as deformations of shear-loaded cross laminated timber (CLT) walls are also significantly influenced by stiffness-reducing openings (e. g. doors and windows). In the corner of the openings local zones occur ("singular points") for which no transparent and rational calculation methods are known so far. The complexity is further increased by the fact, that the internal forces additionally depend on the mechanical properties – in particular the slip modulus – of the joints and that the mentioned factors interact.

In recent decades, digitalization in the construction sector and the application of modern planning methods like “Building Information Modelling (BIM)” have lead to a strong change in the traditionally applied methods towards software-supported, automated computation. However, due to the issues described above and the associated complexity, the calculation of stresses and the verification of shear-loaded CLT walls still requires the intervention of an expert. This is in contradiction to an efficient, at least partially automated, planning and design to maintain competitiveness in the future. The intention of the project “CLT_WALL_mod+joint” is to provide the basis for the implementation of the above-mentioned areas. In addition, the question in which cases and under which geometric and other boundary conditions openings without verification can be implemented in massive timber constructions will be investigated. Furthermore, variant studies and construction details for alternative construction methods, like e. g. "balloon frame" like load-carrying systems with walls ranging over several storeys and suspended ceilings) will be carried out and examined upon their practical implementation.

Unlike other areas of technology, such as mechanical engineering, the connection technology in timber engineering is not systematically structured throughout. However, for a targeted development, expressed by the equation "Building system (and components) = (standardized) building product + (standardized) joint" the specification and definition of principles and fundamentals seems to be absolutely mandatory. The activities in the project "CLT_WALL_mod+joint" will help to maintain the dynamic development of the massive timber construction method, which has taken place with significant contributions from the Austrian Timber Industries.

In addition to an increased efficiency (e. g. through multi-functional joints enabling at the same time “load-carrying” and “air-tightening”) and optimization joints through an improved modelling, another requirement becomes increasingly important: Due to the connection technology currently used in timber engineering, the components cannot be removed from the existing structure without damage, and often not even without destruction. In order to contribute to a sustainable development, it is therefore necessary to systematically develop detach- and demountable connection technology for timber constructions. This aspect is taken into account in the project by designing, calculating and testing joint prototypes with the aim of providing an innovative trend for the industry.

The main objectives of the project are:
(I) regarding building modelling
a. Creation of a basis for an automatized 3D-calculation of multi-storey CLT buildings (= Basis for Building Information Modelling (BIM))
b. Development of a comprehensible, rational calculation and verification procedure for CLT-walls with openings
c. Definition and preparation of geometric and other boundary conditions for verification-free openings (e. g. dimension and position of openings; similar to the rules in masonry design)
d. Variant studies and development of construction details for alternative building methods (e. g. "balloon-frame" like)

(II) regarding jointing
e. Systematisation of jointing technology in timber engineering and systematic development of efficient, easy-to-use, detachable and demountable joints for CLT-walls (incl. joinery and robot production) 
f. Development and testing of prototypes for selected detach- and demountable jointing systems

Funding programme Collective Research

Collective Research | General Programmes

The funding of cooperative research projects (sector projects) in Collective Research supports pre-competitive research projects which do not include any directly exploitable product and process or service developments.

Collective Research stands for cooperative research projects for whose results are made available to the industry and is open to all topics.