Abstract
This work deals with the innovated complex process of tree risk assessment, from precise geometrical tree shape acquisition to building and analyzing a finite element model under specified load. The acquisition of the 3D geometry of the tree was performed by means of terrestrial laser scanning. Obtained point cloud was optimized and additionally converted to a 3D CAD model, representing the bearing skeleton compound of trunk and main branches. For structural analysis purposes, a finite element model (FEM) was built in the form of beam structure fixed to the ground. Particular beams were defined by geometry, material properties of wood, and cross sections. An acoustic tomography was applied for determination of the precise cross section on investigated locations of an analysis model. Finite element analysis performed on the computational model shows the bearing capacity and deformations of the whole tree structure caused by combinations of load cases like self-weight and static equivalent of wind load. The results of the structural analysis called attention to potentially dangerous places within the tree structure with extreme node displacements or tensile stresses on beams. Thus, we observed a maximal horizontal displacement of 280.4 mm in node N34 and dangerous tensile stress in node N26, where it reaches +23.6 MPa. After filtering some beams with an abnormal cross section geometry, the finite element analysis of the whole tree structure showed the highest tensile stress of +8.8 MPa and highest compressive stress of −8.9 MPa. The suggested method can be applied generally for the prediction of potentially risky tree suspected of breakage and especially for monumental trees, where the presented method can be mostly applicable.
Highlights
Mill. viathe high precise acquisition mentioned in body 4 ofsingle this article, wecordata reconstructed main architecture of both outer and inner body of the single tree via high precise acquisition hardware of terrestrial laser scanner (Figure and via acoustic tomograph both outer and inner body of the single(outer) tree Tilia cordata high precise acquisition hardware of terrestrial laser scanner and acoustic tomograph
The process of modelling and structural analysis of a single tree was carried out in three main steps: point cloud acquisition and processing supplied by the terrestrial laser scanning (TLS), conversion of point model into 3D CAD model consisting of the bearing axial skeleton and cross-section definition, and the structural analysis of the finite element model with respect to acting load
Our methodology brings a new vision to this topic with the use of highly precise up-to-date technology provided by terrestrial laser scanning and acoustic tomography
Summary
Finite element analysis performed on the computational model shows the bearing capacity and deformations of the whole tree structure caused by combinations of load cases like self-weight and static equivalent of wind load. We observed a maximal horizontal displacement of 280.4 mm in node N34 and dangerous tensile stress in node N26, where it reaches +23.6 MPa. After filtering some beams with an abnormal cross section geometry, the finite element analysis of the whole tree structure showed the highest tensile stress of +8.8 MPa and highest compressive stress of −8.9 MPa. The suggested method can be applied generally for the prediction of potentially risky tree suspected of breakage and especially for monumental trees, where the presented method can be mostly applicable.
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