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 k c 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.