In recent years, modern engineered timber construction has established itself as a high-performance construction method. Its applications range from one- and two-storey residential, office, educational, and hall buildings to multi-storey buildings. Connections in these buildings play a central role, as they must be executed efficiently. Screwed end-grain or near-end-grain connections with inclined screws enable particularly high-performance connections. They are used, among other applications, in main-to-secondary beam connections with system connectors, as well as in tension connections with metal plates as outer member, such as those found in moment connections. In addition to failure of the fasteners, however, brittle failure modes can also occur in the timber at these connections. These include, in particular, splitting failure and block shear failure. For some of these brittle failure modes in timber, design approaches do not exist, or existing approaches only partially capture the complex failure mechanisms, which can lead to an overestimation of the load-bearing capacity.
The research project “brittleSCREWjoints” investigates three practice-relevant connection configurations:
- system connectors in slender secondary beams, where splitting may occur in the lower region near the end grain,
- system connectors in stocky secondary beams, where local three-dimensional block shear failure may occur,
- and tension strap connections with external steel plates and inclined screws, where block shear failure may also occur.
Based on a comprehensive analysis of existing design models, standards and approvals, the governing failure mechanisms are investigated using existing models, numerical simulations and experimental investigations. Timber products, connector arrangements, screw dimensions and geometric boundary conditions relevant to practical applications are considered. Particular emphasis is placed on load transfer, the location and development of the governing crack and fracture surfaces, and the influence of key geometric parameters, particularly the screw arrangement and connector geometry.
The aim of the project is to develop practice-oriented design models. This will allow brittle timber failure in screwed end-grain and near-end-grain connections to be reliably accounted for and will provide a basis for practical design verification, implementation of the models in design software, and their incorporation into standards and guidelines.
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.