Creates or modifies plane and 3D curved structural areas.
Modifies structural areas' properties.
Structural areas are planar or curved surfaces for the structural calculation. Each area is assigned properties (element thickness, group number, material, bedding properties, loads, etc.). In a 3D system, the positioning/eccentricity of elements is also determined from the nodes.
Lines, arcs, polylines and splines can be used to define the boundaries. Structural areas describe areas that can contain openings, columns, walls and beams. They are written into the structural database (.CDB) when the drawing is exported. The program SOFiMSHC creates finite elements from these for the structural calculation.
A detailed description of these properties can be found in the chapter ‘SAR – Structural area’ and the following chapters of the manual SOFiMSHC.
With the systems 2D Slab, 2D Frame and 2D prestressed slab, permanent and variable loads can be directly applied during the creation of structural areas. These can be viewed and modified in the loads tab of the structural area dialog box where there is, to the right of the dialog box, a button named Edit structural area default loads. The loads tab is only available for use when modifying an existing structural area.
Each structural area can be assigned its own mesh density. The settings specified in the meshing tab are used independently of the general mesh density defined in the export dialog box.
Each structural element is assigned a local coordinate system. Exported finite elements are created with the same local coordinate systems. This also affects any locally applied loads!
If the local coordinate system of a structural element requires modification, this can be done using the Align Elements command.
The coordinate system of structural areas may be orientated towards another structural element. If such an assigned area is marked, a little symbol like a lock is shown. Behind of this lock there is the kind of the assigned element an its number. To change the alignment click on the symbol of the lock. All properties of the alignment can be changed now. To save this modifications press the green check mark, to cancel press the red cross.
The assigned group number can easily be modified via command Assign Group and Construction Stages.
For creation of a structural area, the following options are available for use:
Creates structural elements from AutoCAD elements. This option supports the creation of structural elements from regions, solids, 2D areas and other 3D AutoCAD bodies. Thus almost any geometry can be used as a basis for a structural element.
Don’t delete the original AutoCAD geometry. The structural area get all information about the geometry out of the original AutoCAD geometry. If the AutoCAD element is deleted, the structural area couldn’t change the geometry anymore.
Segment on geometric axis
Creates elements with reference to an axis. For this option the following input possibilities are available:
Between all placements: The elements are created from the first placement of the axis up to the last.
Use the segment closest to the picked point: One element is created between the two placements nearest to the picked point on the axis.
The grip points of elements bound to an axis change their type. Instead of the square a small arrowhead can be seen. This arrowhead can be dragged to another placement. This changes the assignment of the element.
Pick Lines or Curves–Select Points
Creates a closed polygon as the boundary of the element. When selecting lines or curves, the input type can be
switched between either option by pressing the down key (as shown in the command line and at the cursor text). The picked
points can be selected from the drawing or can be entered using cartesian coordinates. During input, a preview is available.
The input can be ended by pressing the
enter key. In a 3D system, this option is only available for use in the XY plane,
although this need not be in the plane located at the origin.
After selection of a line or curve using the
Pick Lines or Curves option, it can be useful to select a point by which the
end of the next line is defined. The
Pick Points option is available in the context menu during input.
Creates a rectangular element with the input of two diagonally opposite points. In a 3D system, this option is only available for use in the XY plane, although this need not be in the plane located at the origin. Please note that the rectangle will always be created with reference to the current coordinate system. If a rotated rectangular area is to be created, the coordinate system must first be modified accordingly.
Point in Area
Creates a closed polygon as the boundary of an element. A point within a closed polygonal element can be input. The boundary lines of that closed element are used as the boundary for the element. Ensure that the boundary is closed and that the point selected is not too close to a re-entrant corner, since the program, in this case, may be unable to find the boundary. In 3D systems, this option is available only in the plane where the origin is currently defined.
With this selection option, an additional Boundary Options Mode selection is available in the sidebar.
Set Working Plane
Because certain selection options only are available in the current working plane, it is possible to rest the working plane to a user defined position. For this the following options are available:
3Points: The coordinate system is aligned by defining 3 points (origin, X-axis and Y-axis).
Element: The orientation of the coordinate system is set with the selection of an object.
The working plane remains in place until the command to create the element is closed.
Each element is given a name and a number that is shown in the drawing. This is the internal number of the element which is used for identification.
It is possible to define a thickness of the area element here.
To define slabs with variable thickness, there are two options. Either via the edges tab or via the structural points general tab. Please notice, in the second case the slabthickness has to be set to zero.
Using the Meshing Parameters options allows to control the mesh density on each structural area. When the drawing is exported, the density assigned to these areas
will override the general definition given in the
Export dialog box.
Using one or a combination of the Intersection Properties allows to disable the intersection with the respective structural element types.
In this tab, support and bedding values for the created structural area elements can be defined (although not for the boundary of the area).
Activating the radio button Beddingfactor as Material will set the bedding values specified for the structural area’s material to be used.
The effect of a loss in tensile strength of the bedding can only be calculated with a non-linear analysis with the program ASE. The mixing of global and local support conditions is possible only in a limited manner. For example, if a global direction support condition is selected, the local direction supports will become unavailable but the local moment supports may be used. Supports unavailable for use will be automatically greyed out by the program.
In 3D or 2D prestressed slab systems, the position of the area element in relation to its nodes can be defined. Because of the normal force effects, the calculation can only be carried out using the program ASE.
The calculation of internal forces in an orthotropic panel is described further in the TALPA and ASE (Chapter 2: Theoretical Principles) manuals. The orthotropy of a panel can be controlled directly by the specifying thicknesses or by specifying a cross section.
In this case, the orthotropic behaviour option should be activated and a cross section entered for TX and/or TY orthotropic thickness values. The input possibilities for the panel thickness will then be greyed out. The stiffness of the cross section is taken over a 1m width (in the local direction of the panel). For the self-weight of the element, this input is not considered.
This tab (becomes available only when modifying existing elements) is filled, when exactly one element is chosen.
In a table all outer edges of an area are recorded. In case, a line is marked, the affected line in the drawing is highlighted and the coordinate system of the edge is displayed. Edge properties could also be modified with command Area Edge Properties.
The entry in column Thickness is used to define variable thicknesses of slabs. Each edge of the area may have a different thickness and the program would generate a haunched slab. This definition overwrites the thickness of the slab on tab general.
To create a variable thickness along an axis, the name of the variable must be defined in the column Thickness From Axis Variable. All variables present in the drawing are displayed in the drop-down list. In order to calculate the thickness of the generated finite element, a perpendicular is drawn from the assigned main axis to the edge of the structural area. A set variable overwrites the value of the thickness on the general tab. If an undefined variable is set, the thickness of the slab is set to 0.
Along the chosen edge hinges between two adjacent structure areas could be generated. If a hinge is activated, a spring value may be given (editboxes on the left side). In this case, a connectingspring (no hinge) would be generated.
If the tick boxes of the hinges are activated, according to the system and switches, input fields according to spring values are activated. In this case, spring values could be entered and no hinge, but spring actions will be generated. Please notice, the direction oft he hinge is like the direction of the edge of the area.
In the mesh generation a row of nodes parallel to the constraint is generated according to the set distance. This is especially needed for verifying constraints. Generally, the program generates the elements and the nodes. This then generates a second row of nodes in order for the elements to form the stipulated line elements. The new nodes would then be coupled with existing (and perhabs supported) nodes.
In the loads tab, which becomes available only when modifying existing elements, loads that are applied directly to an area can
be defined or modified. Loads that were created in the
Loads for Structural Area dialog when the SE areas were created can
be modified with the
Edit Structural Area Default Loads... button to the right of the dialog box. Loads on area elements are
displayed by default as text below the area description. Loads can also be viewed as a shaded area, the settings for which can
be found in the Visualisation.
Edit Structural Area Default Loads Icon:
A detailed description of the loading possibilities can be found in the chapter ‘AREA – Free Area Loading’ of the manual SOFiLOAD.