HOW THE WOOD OF HOLLOW AND LEANING TREES RESISTS FAILURE

Within the scope of a field study on hollow and mostly leaning eucalyp tus trees (Eacalyptus obliqua, Eucalyptus globulus) in Tasmania (Austr alia), the strength properties were determined with the help of the Fr actometer III. The Fractometer III is a pure mechanical device for the determination of strength properties of wood. With the Fractometer II I it is possible to measure the compression strength, the radial and t angential bending strength, and the shear strength of wood from an inc rement core. The objective of the investigation was to find out, if tr ees obviate different kinds of failure by variation of the correspondi ng strength property of by variation of all measured strength properti es. The measurements on biochemically meaningful spots showed, that tr ees distribute their strength properties stress controlled. Neverthele ss it is possible, that sometimes two strength properties are controll ed by one stress-state, for example the values of the shear-strength a nd the tangential bending strength are high along the neutral axis of bending or above openings of a tree.