Derivation of buckling design curves via FE modelling for in-plane compressed timber log-walls in accordance with the Eurocode 5

In ‘Blockhaus’ systems the structural capacity derives from surface interactions and friction mechanisms between multiple timber logs stacked horizontally one upon each other. Unlike masonry or concrete walls, timber log-walls are characterized by the absence of a full structural interaction between the basic components, hence resulting in ‘assembled’ rather than ‘fully monolithic’ structural systems characterized by high flexibility of timber and usually high slenderness ratios. The current Eurocode 5 for timber structures, however, does not provide formulations for the prediction of the critical load of log-haus walls under in-plane compressive loads. In this work, based on past experimental tests and detailed Finite-Element (FE) models, extended numerical investigations are performed on timber log-walls. A wide number of configurations (more than 900) characterized by different geometrical properties, timber log cross-sections, number and position of door and window openings, presence of in-plane rigid (RF) or fully flexible (FF) inter-storey floors, as well as initial curvatures and/or load eccentricities, are analyzed under monotonic in-plane compressive load. Careful consideration is also given to the influence of additional out-of-plane pressures (e.g., wind pressures) combined with the in-plane compressive load. In accordance with the buckling design approach proposed by the Eurocode 5 for timber columns, non-dimensional buckling curves are then proposed for timber log-walls under in-plane compression. These curves are based on an accurate calibration of the kc buckling coefficient and the related imperfection factors on the results of the numerical parametric study. The developed simple and conservative approach for the design of log-walls can be proposed for implementation in the new generation of the Eurocode 5.