Design of buildings affected by reduced rigidity resulting from wall openings and detachable as well as demountable joints


Project duration: 04/2022 - 01/2026

Buildings/load-carrying structures must be erected in a way that they are able to carry the occurring loads in a safe and reliable manner. The 3D load-carrying structure is often split up into easier to handle, flat 2D-elements. In the course of this transformation assumptions are made which may lead to conservative design results, neglecting e. g. wall-sections reaching "over a corner". As a consequence of conservative calculations, forces to be transmitted by the joints/fasteners tend to be too high. The internal forces as well as deformations of shear-loaded cross laminated timber (CLT) walls are also significantly influenced by openings (e. g. doors and windows). In the corners of such opening zones ("singular points") occur for which no transparent and rational calculation methods are currently known. Therefore, the calculation of stresses and the verification of the shear-loaded CLT walls requires the intervention of an expert. However, this is contrary to the need for an efficient design to maintain future competitiveness, which would be made possible by increasing digitization in the construction sector or applying modern planning methods such as "Building Information Modelling (BIM)". This research project is intended to provide the necessary foundation for the implementation of the afore mentioned points. In addition, this project will investigate in which cases and under which geometric limitations and other constraints verification-free openings can be implemented in solid timber constructions. Furthermore, variant studies and construction details for alternative construction methods (such as a "balloon frame" load-carrying system with walls ranging over several floors and suspended ceilings) will be carried out and their practical applicability analyzed.

The design of the fasteners and connections in the wall-ceiling joint is influenced by structural modeling and its resulting forces, which subsequently interact with the mechanical parameters of the joining technology. Unlike other fields of technology, such as mechanical engineering, the joining technology in timber engineering is not systematically structured. To be able to sensibly implement the equation "Building system (and components) = (standardized) building product + (standardized) joint" the specification and definition of principles and fundamentals therefore seem to be absolutely necessary. With the project "CLT_WALL_mod+joint" dynamic development of the solid timber construction method, resulting from contributions from the Austria Timber Industries, will be supported and further developed. Increased efficiency and optimization of joints (e. g. through multi-functional joints enabling simultaneous "load-carrying" and "air-tightening") due to an improved modelling in the first part of the project, the trend towards sustainability becomes increasingly realistic. Due to the connection technology currently used in timber engineering, components cannot be reused without damage or even destruction. This is not in-line with the requirements regarding sustainability. Therefore, the systematic development of detachable and demountable joining techniques for timber construction is required. This aspect will be taken into account in the project by designing, calculating and testing joint prototypes with the aim of providing an innovative trend for the branch.

The main objectives of the project are:
(I) regarding building modelling
a. Creation of a basis for an automatized 3D-calculation of multi-story 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")

(II) regarding joining technique
e. Systematization 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 detachable 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.