WOOMI Wood meets minerals

Timber construction offers great potential when it comes to extending, expanding and reinforcing existing buildings. Thanks to its high strength-to-weight ratio, timber allows buildings to be extended without placing excessive strain on the existing structure. To achieve this, timber must be joined to mineral-based materials. The aim of the project is to develop joints and suitable design methods for connecting the two building materials.

There is currently no common design approach for retrofitted connections between mineral building materials and timber. Instead, the calculations are carried out separately:

• Concrete: Design in accordance with Eurocode 2 is largely limited to metal attachments with no or minimal clearance from the concrete. The design of the anchoring of timber attachments is based on simplified load transfer models, in which the timber component is not taken into account and the force is ideally transferred to the anchor at the centre of gravity of the timber.
• Timber: The fastening element in the timber component is designed in accordance with Eurocode 5, analogous to a steel sheet-timber or timber-timber connection. However, due to concrete spalling in front of the fastening element, a certain distance between the components must also be taken into account here.

This separate approach leads to a complex and inefficient design, in which the actual load-bearing capacity of the connections cannot be fully utilised.

The core objective of the project is to develop high-performance, cost-effective and practically feasible connections between timber and concrete. To this end, the current state of knowledge regarding the interaction between timber, fasteners and concrete must be documented and expanded. The aim is to establish a fundamental mechanical and stochastic understanding of cross-material connections under static and dynamic loads. By developing realistic mechanical models of the load-bearing behaviour of mechanical connections and taking into account varying influencing factors, approaches for design models for connections between timber and mineral building materials can be derived.

WOOMI is a collaborative project between the KIT Timber Structures and Building Construction and the Fastening Technology Department of the Institute for Construction Materials (IWB) at the University of Stuttgart. It is also supported by a project committee comprising SMEs, industry partners and trade associations.

The project is funded by the European Regional Development Fund (ERDF) as part of the Holz Innovativ Programme (HIP) of the State of Baden-Württemberg.