Strength of Solid Tree Stems
The strength of tree stems to resist bending in the wind is associated with the cross-sectional area of the stem. Strength is proportional to the diameter of the stem to the fourth power (DIAMETER). Small increases in diameter yield large increases in strength. This publication presents a theoretical examination of relative strengths of round stems as modeled by bending moments in solid cylinders. Resistance to torsional forces (twist) are two times that of bending forces.
The link address is: http://warnell.forestry.uga.edu/service/library/index.php3?docID=401&docHistory%5B%5D=12&docHistory%5B%5D=413