Structural analyses of common planted trees in Singapore

Abstract

Structural evaluation of a large living structure like a mature tree is needed using its own mechanical properties since the failure of large matured trees would cause safety concerns to the public. Green wood properties of three common planted trees in Singapore with distinct tree shapes, i.e. Swietenia macrophylla (broad-leafed Mahogany), Syzygium polyanthum (Salam) and Pterocarpus indicus (Angsana) had been established in this study. A portable 3-point bending test machine was used for the branches breaking test to determine the modulus of rupture (MOR) and modulus of elasticity (MOE) of tree species. Pterocarpus indicus had the best performance among these 3 tested species with the highest value of MOR and MOE while Swietenia macrophylla had the highest toughness. The selection of tree species for roadside planting can utilize these test data as reference. Root architecture of a tree is one of the utmost factors to the tree’s stability. The numerical simulation of the tree - root model had been established to evaluate the maximum stresses and total deformations of the tree. The results showed the maximum stresses usually occurred on the connection of trunk-lateral or lateral-sinker root. The comparison of effectiveness of the windward roots and leeward roots was done by cutting the lateral roots of tree model and applying the bending moment induced by wind loading from different directions. It was discovered that the windward lateral root contributed most to the stability of the tree. All the simulations were modelled in static structural of ANSYS™ by applying the earth gravity force and bending moments under wind loading.