PSI - Issue 64

Iryna Rudenko et al. / Procedia Structural Integrity 64 (2024) 1216–1223 I. Rudenko and Y. Petryna / Structural Integrity Procedia 00 (2019) 000–000

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3.4. Proposed approach for BIM-based FE model generation The proposed approach for BIM-based FE model generation allows the user to vary complexity and element dimensionality of the FE model. The basis of the BIM model is an IFC file, that contains geometry as well as material properties of the structure. Afterwards, the IFC file is enriched with FEM and SHM relevant information. Subsequently, an ANSYS APDL file is generated. To reduce the amount of information stored, the loads are not included in the IFC file. They should be added manually to the ANSYS APDL file. The IFC files are created and visualized in the open-source software Blender together with the BlenderBIM Add-on. The basis of BlenderBIM Add on is the open-source software library IfcOpenShell, that allows to work with IFC files through C++ and Python. IFC allows objects to have one or more geometric representations. This advantage was used to vary the element dimensionality of the FE model. For each object two geometric representation types were considered: SweptSolid and Tessellation, as shown in Fig. 2. The SweptSolid representation ( IfcSweptAreaSolid ) describes a 3D solid by sweeping of a 2D cross-section along a path, see buildingSMART International Limited (2024b). The cross-section is represented by a subtype of IfcProfileDef . It is possible to define arbitrary profiles by points and curves, for example, in case of IfcArbitraryClosedProfileDef , as well as to use one of the parametrized profile definitions, such as IfcRectangleProfileDef . Then, only height and width of a rectangle should be specified. When using the Tessellation representation type, the surface of the object is described by triangles and polygons. The IFC file contains a list of vertex coordinates IfcCartesianPointList3D , the faces IfcIndexedPolygonalFace , that are defined by indices referencing a list with vertex coordinates, and the set of faces being bound by polygons IfcPolygonalFaceSet . The SweptSolid representation type is used to describe the geometry of the structure, that will be meshed with 1D, 2D and 3D finite elements. This way, mapped meshing can be used in most of the cases, and a high-quality FE mesh is ensured. The Tessellation representation type is used for the objects, that could be difficult to describe by SweptSolid and should be meshed with solid finite elements. For example, building elements with complicated geometry, that cannot be represented by sweeping of a cross-section along a path or with a lot of voids.

Fig. 2. Different geometric representation types: Tessellation and SweptSolid.

The material properties are defined by using the class IfcMaterial with property sets Pset_MaterialCommon and Pset_MaterialMechanical . To add the FEM relevant information to the objects a new property set Custom_Pset_FE_ANSYS is created. This property set contains the information on finite element dimensionality, type, size as well as section offset and whether this object should be used for structural analysis in general. The boundary conditions are defined according to the IFC schema through the classes IfcStructuralConnection and