© 1987 Heron Publishing—Victoria, Canada
Structural analysis of tree trunks and branches: tapered cantilever beams subject to large deflections under complex loading
J. Morgan (1) and M. G. R. Cannell (2)
1. Department of Civil Engineering, University of Edinburgh, King’s Buildings, Edinburgh EH9 3JU, Scotland / 2. Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EH26 OQB, Scotland / Received May 13, 1987
Summary
The dimensions, deflections and support costs of tree trunks and branches can be deduced using the structural theory for cantilever
beams. However, elementary theory applies only as long as deflections are small, and complex analytical solutions are required
to account for complex taper and patterns of loading. This paper describes a method that copes with large deflections, any
patterns of taper, and any patterns of distributed loading, point loading or externally applied bending moments. A beam is
considered to be composed of a series of short segments, such that each has only a small deflection, and each can have specified
dimensions, Young’s modulus and loading. The transport matrix method of structural analysis is used to determine the end conditions
of each segment and of the whole beam. The method is verified by comparing predicted deflections with deflections (a) calculated
using an analytical solution by Bisshopp and Drucker (1945), (b) calculated and measured for sapling tree trunks by Leiser
and Kemper (1968), and (c) measured on tapered and untapered plastic rods.
