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2023-05-16
Overview
Graphical User Interface and Settings
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Mesh Settings

The 'Mesh Settings' dialog box manages general specifications for the generation of the FE mesh. You can open this dialog box by selecting Mesh Settings on the Calculate menu, or by using the list button Mesh Settings .

  1. List Button "Mesh"
    List Button "Mesh"

  1. == General ==
  1. In the General tab, you can adjust the default mesh size used by RFEM when generating the FE mesh.

  1. 'General' Tab in 'Mesh Settings' Dialog Box
    'General' Tab in 'Mesh Settings' Dialog Box
  1. === General Settings ===
  1. The 'Target length of finite elements' controls the mesh size by which the FE mesh is created. The shorter the FE length is, the more close-meshed the mesh will be and the more accurate the results will usually be. However, the amount of data to be calculated and the computing time increase as well, since additional equations must be solved for every additional FE node. A fine-meshed mesh also results in singularity effects occurring more frequently.
  1. #banner.importantThe preset mesh size of 50 cm (1.64 ft) is suitable for many surface structures. For models with small dimensions, you should reduce the target FE length accordingly. == Members == The Members '''tab''' controls how the FE mesh is created on members.
    'Members' Tab in 'Mesh Settings' Dialog Box
    'Members' Tab in 'Mesh Settings' Dialog Box
    If necessary, you can adjust the 'Number of divisions' for result diagrams, special member types, and determining extreme values. If you increase the divisions, you can achieve a refined result diagram. In most cases, however, the default settings are sufficient. The 'Divisions for straight members with the material category Concrete' have an influence on the nonlinear calculation of reinforced concrete members in the cracked state. Thus, the [https://www.dlubal.com/en-US/products/rfem-fea-software/add-ons-for-rfem-6/design/reinforced-concrete-design/concrete-design-members-and-surfaces Concrete Design], you can determine the stiffness (uncracked/cracked) in each finite element for the deformation analysis, among other things. The 'Member divisions for large deformation analysis option Activate ' also allows you to select beams for calculations according to the large deformation analysis by intermediate nodes and thus determine it with a higher accuracy. The number of divisions entered for special types of members will be applied. If the check box 'Activate member divisions for straight members' is selected, members that are not integrated in surfaces are also divided. RFEM creates FE nodes on the free members and takes them into account in the calculation. You can specify a minimum division or a value for the FE length LFE . With the 'Use division for members with nodes lying on them' option, you can generate FE nodes at member locations where other members are connected to the member, but have no connection to it. #banner.textsurfacesTab
    'Surfaces' Tab in 'Mesh Settings' Dialog Box
    'Surfaces' Tab in 'Mesh Settings' Dialog Box
The most accurate results are obtained for finite elements that are as close as possible to the shape of a square. For a square, the diagonal ratio D1/D2 = 1. The limit value ΔD for this diagonal ratio is preset to 1.8 as the 'Maximum ratio of FE rectangle diagonals'. If you reduce the value, more triangular elements will be created. On the other hand, a value that is too large leads to the generation of elements with very acute or reflex angles. This may result in numerical problems. A curved surface is covered by plane elements in the FE mesh. The inclination angle α defines the 'maximum inclination of a single quadrangle element out of the plane'. This value describes the angle between the normals of two elements (see image [[#image025717 Inclination Angle α]]). If the allowable inclination angle is exceeded, they are subdivided into triangular elements. ">image025717
Inclination Angle α
Inclination Angle α
If you have defined the model as '2D | XY | plate' (see Base chapter), a 'mesh refinement along the lines' is possible ( '''in preparation''' ). This allows you to create smaller FE elements on all lines in order to better approximate, for example, results along supported lines. The relation Δb refers to the global mesh size. It describes the edge distance of the refinement from the lines.
  1. The 'Integrate unutilized objects into surfaces' option allows you also to create FE nodes on objects that do not have any specific function for a surface (for example, free nodes without support or load, constructional lines in surfaces). This function is deactivated by default to avoid statically insignificant objects distorting the FE mesh.
  1. You can set the 'Shape of Finite Elements' by three options:
  1. * Triangles and quadrangles: default setting
  2. * Triangles only: Option, if quadrangles result in very distorted mesh
  3. * Quadrangles only: option for increased accuracy of results
  1. For additional control options, use the 'Generate similar squares where possible' and 'Triangles for membranes' check boxes.
  1. If the 'Mapped mesh preferred' option is set, RFEM tries to adjust the FE mesh to the border lines of surfaces. You can define this type of FE mesh generation separately for each surface ('Edit Surface' dialog box, 'Mesh Refinement' tab).
  1. Mapped Mesh of Surface
    Mapped Mesh of Surface
  1. A mapped mesh is exclusively composed of quadrangles. In general, a mapped mesh provides "more accurate" results. Moreover, as less unknown factors occur in the equation system, this method is recommended for generating the mesh.
  2. == Solids ==
  1. The Solids tab controls how the FE mesh is created on solids.
  1. 'Solids' Tab in 'Mesh Settings' Dialog Box
    'Solids' Tab in 'Mesh Settings' Dialog Box
  1. If you activate the 'Mesh Refinement on Solids with Close Nodes', RFEM performs a mesh refinement for solids whose nodes are very close to each other. In this way, the nodes are correctly determined with the FE mesh. The mesh size of the solid arises from the shortest distance of the nodes.
  1. The 'Maximum number of elements' represents the upper limit of the 3D elements created.
  1. You can access the 'Target length of finite elements for soil solids' check box if the [https://www.dlubal.com/en-US/products/rfem-fea-software/add (license required). This allows you to specify a specific default mesh size LFE for soil massifs and to generate coarser solid meshes without "mesh refinements".
  2. == Quality Criteria - Surfaces ==
  1. The Quality Criteria - Surfaces tab manages the quality specifications for the generation of 2D elements.
  1. 'Quality Criteria - Surfaces' Tab in 'Mesh Settings' Dialog Box
    'Quality Criteria - Surfaces' Tab in 'Mesh Settings' Dialog Box
  1. === Quality Criteria ===
  1. This dialog section specifies various criteria that are checked after the FE mesh has been generated. If you deactivate a criterion, RFEM does not perform the corresponding check.
  1. For each check type, you can define the value as of which a 'warning criterion' and a 'failure criterion' apply.
  1. === Color Display ===
  1. After generating the FE mesh, the report shows the 'number of elements' that meet the quality criteria as well as those for which there is a problem. This allows you to evaluate the consistency of the FE mesh.
  1. You can also check the quality of the FE mesh on the model: Activate the mesh quality in the 'FE Mesh' category in the 'Navigator - Display'.
  1. Displaying Mesh Quality
    Displaying Mesh Quality

  1. == Quality Criteria - Solids ==
  1. The Quality Criteria - Solids tab manages the quality specifications for the generation of 3D elements.
  1. Tab "Quality Criteria - Solids" in Dialog Box "Mesh Settings"
    Tab "Quality Criteria - Solids" in Dialog Box "Mesh Settings"
  1. === Quality Criteria ===
  1. This dialog section specifies various criteria that are checked after the FE mesh has been generated. If you deactivate a criterion, RFEM does not perform the corresponding check.
  1. For each check type, you can define the value as of which a 'warning criterion' and a 'failure criterion' apply.
  1. === Color Display ===
  1. After generating the FE mesh, the report shows the 'number of elements' that meet the quality criteria as well as those for which there is a problem. This allows you to evaluate the consistency of the FE mesh.
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