Mesh setup
The user may control the shape of the finite element mesh. The Mesh setup dialogue offers a whole range of parameters.
Mesh
1D elements (1D members)
Minimal length of beam element |
If a 1D member of a structure is shorter than the value here specified, then the 1D member is no longer divided into multiple finite elements even though the parameter above (Average number of tiles of 1D element) says so. |
Maximal length of beam element |
If a 1D member of a structure is longer than the value here specified, then the 1D member will be divided into multiple finite elements so that the condition of maximal length is satisfied. |
It is necessary to generate more than one finite element on cables, tendons (prestressed concrete) and 1D members on subsoil. For more information about this issue see book Advanced calculations, chapter Analysis of a beam on elastic foundation versus mesh size. NOTE: This parameter also controls the size of finite elements for beams with a phased cross-section. |
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Generation of nodes in connections of beams |
If this option is ON, a check for "touching" 1D members is performed. If an end node of one 1D member "touches" another 1D member in a point where there is no node, the two 1D members are connected by a FE node. If the option is OFF, such a situation remains unsolved and the 1D members are not connected to each other. The function has the same effect as performing function Check of data. |
Generation of nodes under concentrated loads on beam elements |
If this option is ON, finite elements nodes are generated in points where concentrated load is acting. This option is not normally required |
Generation of eccentric elements on members with variable height |
If a beam is of variable height, the generator automatically generates eccentric finite elements along the haunch. Moreover, if this option is ON, the eccentricity of the elements may vary along the element, i.e. the start-node of the element may have different eccentricity than the end-node of the element. If this option is off, the eccentricity along individual finite elements is constant and the eccentricity changes in steps in nodes along the haunch. |
Division on haunches and arbitrary members |
Specifies the number of FE generated on a haunch. |
Division for integration strip and 2D - 1D upgrade |
Specifies the number of section which are generated on integration strip or on the beam after 2D-1D upgrade performance. |
Mesh refinement following the beam type |
Specifies the mode of refinement on 1D members. None The refinement is applied to 2D members only. Beams and columns The refinement applied to 1D members the type of which is adjusted to "beam (80)" or "column (100) All 1D members The refinement applied to all 1D members. |
2D elements (slabs)
To generate predefined mesh |
If ON, the generator first tries to generate in every slab a regular quadrilateral finite element mesh complying with the adjusted element-size parameters. Only if required, additional necessary nodes are added to the mesh. If OFF, the finite element mesh nodes are generated across the slab and the nodes are the elements are then created from the nodes. |
Maximal out of plane angle of a quadrilateral |
This value determines whether a spatial quadrilateral whose nodes are not in one plane will be replaced by triangular elements. This parameter is meaningful only for out-of-plane surfaces – shells. The assessed angle is measured between the plane made of three nodes of the quadrilateral and the remaining node of this quadrilateral. |
Predefined mesh ratio |
Defines the relative distance between the predefined mesh formed by regular quadrilateral elements and the nearest edge. The edge may consist of an internal edge, external edge or border of refined area. The final distance is calculated as a multiple of the defined ratio and adjusted average element size for 2D elements. |
Average number of tiles of 1D element
For static linear calculation, value 1 is normally satisfactory. On the other hand, there are several configurations when finer division is required in order to obtain accurate results.
These are:
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beam laid on foundation requires a fine division – see chapter Analysis of a beam on foundation versus mesh size.
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dynamic calculation when a great number of eigenfrequencies is required – see chapter Natural vibration analysis versus mesh size
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buckling calculation
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non-linear calculations
Division on haunches and arbitrary beams
The number defined here determines the "precision" that is applied in modelling of the variable cross-section along a haunch. The higher the number, the more the model reflects the real shape. See chapter Analysis of a haunch versus mesh size.
In addition, the same rules as for a standard member must be followed here as well.
Generation of eccentric elements on members with variable height
The midline of the finite element model of a haunch-beam may be either straight (following the midline of the original "non-haunched" beam) or "curved" (following the real midline of the haunch beam corresponding to the centre of gravity of the cross-section).
See chapter Analysis of a haunch versus eccentric elements.
Average size of cables, tendons, elements on subsoil
Specifies the number of finite elements generated on a beam laid on foundation.
See chapter Analysis of a beam on foundation versus mesh size.
The procedure for the adjustment of mesh parameters
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Call menu function Setup > Mesh.
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Adjust the parameters (see above).
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Confirm with [OK].
The finite element mesh may be previewed using function Mesh generation under tree menu Calculation.
07/10/2013