Identification of the M-V Toppling Failure Condition of Simplified Root Plates in View of Tree Stability Assessment

Tree stability assessment represents a key issue for risk management of urban areas, where the problem of falling trees is also exacerbated by the ongoing climate change. In this context, Geotechnical Engineering can provide a valuable contribution in the development of new engineering-based approaches to evaluate tree resistance to overturning. Trees can indeed be conceptually assimilated to “living” structures whose root-plates play the role of direct foundations subjected to a complex combination of vertical (V ) and toppling (M ) loads, mainly due to self-weight and wind gusts. During the loading process, rotations of the stem become larger and larger and geometrical effects (2nd order effects) may signif-icantly increase the toppling action. By analyzing a set of available laboratory experimental results on a small scale tree root prototype, the paper presents a the-oretical framework for the definition of the failure condition, by evidencing how the toppling of the tree corresponds with the loss of controllability of the system along the imposed loading path. Disregarding such mechanism may lead to large overestimations of the system toppling resistance.