Validation of strength and flexibility of sengon (Paraserianthes falcataria) by experimental tree-pulling test and numerical simulation

Abstract

Stability assessment of trees is considered important in urban areas to detect possible occurrence of tree failures that often result in disastrous damages. Tree-pulling test is a low-cost, well-known method that has been practiced by researchers and practitioners alike from several decades ago. From the method, a number of parameters related to the physical characteristics of the tree can be further derived. However, the tree-pulling test has only been widely practiced mostly for tree species in subtropical region, such as pines, spruces, and birches. In this paper, a tree-pulling test on sengon (Paraserianthes falcataria), a tree native to Indonesia is reported. Such a study is imperative as sengon is among the most commonly planted tree species in the urban areas of Indonesia and there have been alarming reports of falling sengon trees. Two kinds of tree-pulling test are conducted. i.e. destructive and non-destructive. From these experiments, the critical force that results in a breakage as well as the fl exibility of sengonare obtained. Numerical simulations are also carried out. The results arecompared and they show a good fi t to the experimental data, justifying the assumed linearly elastic behavior.

Effect of Dimensional Variables on the Behavior of Trees for Biomechanical Studies

“…[46] found that uniformly tapered stems (i.e., those of Cryptomeria japonica trees) subjected to wind and snow loads had breaks located between 50% and 70% of the tree's height, while In ref. [43] showed trunk break at 13.5% H. The distribution of stresses along the stem is influenced not only by the horizontal load considering the wind, but also by the moments applied considering the branches and by the horizontal components of the selfweight, which appear due to the deflection of the trunk. Furthermore, stresses are affected by diameter variation, which impacts the moment of inertia of the transversal section of the trunk.…”

“…Comparing deflection values using literature is complex because different authors use different measurement methodologies. Some of them consider only the inclination of the root plate [15,17], and others consider the inclination of the root plate and the deflection of the stem together [26,33,43], as in this study (Figure 2). Furthermore, the deflection is influenced by geometric tree parameters such as height, diameter, and taper [24], and also by mechanical properties of the trunk and root wood, as modulus of elasticity [15].…”

“…Therefore, the comparison with literature is focused on the analysis of the general order of magnitude of the values obtained and the coherence of behavior, considering geometric parameters of the trees and properties of the wood adopted by different In ref. [43] uses two trees with the same height (H = 20 m) and diameters at breast height (DBH = 24.5 cm and 24.8 cm), both same species with density 300 kg•m −3 and modulus of elasticity in bending 3584 MPa. The horizontal pulling force, with a magnitude much lower (maximum 2.25 kN and 1.65 kN) than those used in this research (5 kN to 15 kN), was applied at 12.23 m and 12.20 m (about 60% H).…”

“…The closest condition to compare our data is in scenario 1, where the tree with H = 20 m (Table 1) was subjected to a horizontal load of 5 kN at 55% H (Table 4). For a horizontal load of 1.65 kN, the average displacement at the point of load application obtained by [43] was 1.5 m. If we apply a composition of differences of DBH (24.7 cm/91 cm = 0.27) and modulus of elasticity (3584 MPa/10387 MPa = 0.34) calculated by multiplying these differences (0.09), the expected displacement (0.14 m) will be of the same order of magnitude as those obtained in this paper (0.293 m in Table 4).…”

Városi fák vizsgálati módszerei

“…A dőlésveszély pontos meghatározására használható módszer, melyben az imitált szél erősségét és a törzs megdőlésének mértékét is rögzítik (1. ábra). Régóta ismert és alkalmazott, alacsony költségű módszer [34]. A vizsgálatok alapján a hajlítónyomaték maximuma pozitív korrelációt mutat a gyökérzet méretével, a gyökerek átmérőjével, valamint a korona kiterjedésének mértékével [36].…”