Non-linear modelling of the in-plane seismic behaviour of timber Blockhaus log-walls

This paper investigates the non-linear modelling of the cyclic behaviour of Blockhaus timber log-walls under in-plane lateral loads. The structural behaviour of Blockhaus log-walls in the examined loading condition strictly depends on the geometry – thus on the deformability and ultimate resistance – of the adopted corner joint, namely the joint between perpendicular log-walls. The presence of metal fasteners is in fact minimized and the structural interaction between the basic timber components is provided by simple mechanisms such as notches, tongues and grooves, multiple surfaces in contact. In this paper, a computationally effective FE-model is developed, in order to predict the cyclic behaviour of an entire Blockhaus log-wall once the cyclic behaviour of the adopted corner joint is known. The model uses non-linear hysteretic springs to describe the joint behaviour, where all typical features such as pinching behaviour, strength and stiffness degradation can be considered. By comparing the numerical and the experimental predictions of the cyclic response of full-scale Blockhaus log-walls, a general good agreement is found. Simulations confirmed the high flexibility of the studied structural systems, as well as the significant effect of possible openings such as doors and windows on their global resistance to in-plane lateral loads. In conclusion, the presented study confirmed that the proposed modelling approach can be used to estimate the load-carrying capacity and vulnerability to seismic events of Blockhaus shear walls, and that the same model could be extended to full Blockhaus buildings.