Connections in Timber Structures

Every timber structure includes connections of some kind. Connections link the single timber members with each other, transferring the loads from one element to the next. Due to their complex force and deformation behavior, connections are key elements in the design of timber structures, especially when building wide spanning and high rising structures. It is of highest importance to make connections as efficient as possible to allow for competitive design of timber structures.

Our research

Over many years, comprehensive knowledge in experimental and numerical research on connections in timber structures has been built up at Linnaeus University. In various projects, we investigate the mechanical behavior of connections at different length scales from the local embedment behavior of dowels up to large joints for timber structures. This includes a large range of wood-based materials, connectors and connection types. Based on the research outcomes, we develop computational simulations and propose design recommendations for exploiting the knowledge in the calculation and design of timber structures.

Wood interface to the connectors

Due to the inherent anisotropic mechanical nature of wood and wood products, a complex stress state in the wood below the interface with the connectors is evoked. This makes numerical modeling of these local effects very challenging.

To develop a thorough understanding of the complex mechanical behaviour of the wood interface to the connectors, we carry out a large range of experimental studies at the Department of Building Technology at Linnaeus University. Embedment test of steel dowels in wood and wood products, loaded under various angles to the fiber direction of wood, can be named as one example. Results from these tests are a valuable input to numerical tests on the single-fastener connection scale, as well as for standardization.

Single-fastener connections

The diversity of connection types in timber structures seems to be sheer endless, which makes it cumbersome to investigate all of them by experiments. Thus, at Linnaeus University, we utilise and enhance numerical models for predicting the mechanical behavior of single-fastener connections since more than a decade.

We develop numerical models of different complexity, from advanced scientific models to engineering approaches. These models are validated by comparison of their predictions with experiments, using our unique testing facilities of the in-house laboratory. We especially aim to make our research accessible to our industry partners and the timber engineer community in general, by participating in international platforms to further develop timber engineering design standards.

Multiple-fastener joints

Based on a profound knowledge of the single-fastener behavior, we can use numerical models of different complexity to predict the behavior of the entire joint. We apply these models to different types of joints and experimentally validate them, ranging from moment-loaded dowel connections to nailed connections of OSB-sheathing in timber frame structures. These examples highlight the versatile application spectrum of our numerical models.

Joints in timber structures

We then further exploit our numerical connection models, supported by experimental investigations, by applying them in the analysis of timber structures, in order to study their global behavior and load distribution. Other application examples are timber-framed shear walls and prefabricated timber modules.