An open letter on the “generalised tipping curve” of the SIM pulling tests, the “dynamic” SIM wind load analysis and VTA

Abstract

Current methods such as the Visual Tree Assessment (VTA) of Mattheck and the pulling tests of Wessolly (SIM) and others will be analysed here. A number of authors have asserted since 1998 that their “generalised tipping curve” (GTC) would predict the uprooting of trees by extrapolating small values of stembase tilt angle under a static pull, and that 100% of the maximum or critical uprooting moment (Mcrit) would be reached at 2.5º. However, evidence elucidated from literature and pulling tests strongly suggest that a very different tipping curve (similar to a curve published in 1965 by a comparatively unknown researcher) has been used instead for the pulling tests, where 1º = 100% Mcrit. That curve will be called the SIM curve herein. A number of related researchers report contradictory findings, by showing either uprooted trees that had obeyed the GTC (0.25º) or trees that had perfectly obeyed the SIM curve (1º) which is confusing. This paper also analyses highly-cited and influential proclamations regarding the GTC and the “dynamic” versus “quasi-static” WLA, that may have, quite simply, sprouted from unconscious research bias.