FAILURE CRITERIA FOR TREES

Summary A field study of hollow tree trunks has shown an upper limit of hollowness of 70 per cent of the radius prior to failure, i.e. with a ratio of solid wall thickness t over a radius R > 0.3 tree breakage will be avoided. Wind throw has also been studied as an alternative failure mode. The ratio RW/R=root plate radius/stem radius produces a curve which decreases with increasing stem radius R. Both criteria can be used to assess the safety of trees adjacent to the public highway. The assessment procedure has been recommended to replace intuitive assessment by verified failure criteria.