Regression Models for the Description of the Behaviour of Modern Timber Joints

Joints in timber structures are today typically designed in a simplistic manner, i.e., by assuming linear elastic behaviour or neglecting their real stiffness by assuming ideal pinned or fixed conditions. While such assumptions may be acceptable for simple structures, they do not reflect the real behaviour of joints in complex structures, and could, in some cases, lead either to an over-conservative or even unsafe design. Therefore, a more accurate and realistic representation of the nonlinear behaviour of joints with mechanical fasteners is needed. The most common modern timber joints with mechanical fasteners are realized with dowels, bolts, glued-in rods, or self-tapping screws. In this paper, an overview of the impact of the most influential parameters on the shape of the load-displacement curves of these joints under common static loading is given. The joints were differentiated according to the characteristics of their nonlinear load-displacement behaviour. Different analytical models from the literature for the description of the load-displacement curves of timber joints were reviewed. The performance and suitability of these models for describing the variety of nonlinear load-displacement behaviours of joints were evaluated and the advantages and limitations of each model were identified. It was found that the Richard–Abbott model is the most suitable to parametrize a variety of timber joints and to capture the variability of the test data by its parameters. Such an analytical model can be used to incorporate a parametrized, more realistic, nonlinear load-displacement representation of the behaviour of joints in reliability analyses, structural design software, and design guidance for modern timber structures.

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