Solution

Diamonds needs a closed circumference to create a plate. If that is not the case, the plate definition is ‘broken’: you get an ‘invalid’ plate (or wall).

Diamonds (since version 2023) selects these invalid plates when you generate the mesh.

• Click ‘OK’ to close the message.
• Fix the invalid plate(s).
  • Either you delete them and create them again
  • Either you run the projection function on the circumference although this doesn’t always fix the issue.

Solution

This error can have 2 main causes: either an error in the geometry or either unsuitable mesh size. The latter occurs less often.

Cause 1: error in the geometry

Many things can go wrong in the geometry. We’ve listed the most common mistakes.

• Make sure there are no tie rods on surface borders.
  A tie rod can only be loaded with axial force. But when a tie rod is on the edge of a surface, it can no longer meet that axial behaviour.
• Check for invalid plates.
  • If you have a large model, try to isolate the elements causing the problem.
    Remove a part of the structure, try to generate the mesh. If the error remains, remove more of the structure and try again until you only have a small part left. If the error is gone, you removed to much.
  • When use the short cut ALT + click on a plate, you select the plate together with its borders.
  • Do ALT + click on each plate and check if the selected border makes sence.
    

    Makes sence	Makes no sence

  • When you’ve found the invalid plate, select the plate (no the borders) and hit CTRL + ALT + DEL . This will remove the plate, but not the borders. Regenerate the plate .
• Verify the geometry of the model.
  If there are problems with the mesh, this is most often the cause.

Cause 2: mesh size

• Check if you’ve used a suitable mesh size.
• Try a few variations on the mesh size. If the error remains and you’ve followed the article above, the mesh size is probably not the cause (but the geometry).

A point, will always result in a node in the mesh.

The same frame contains 19 nodes.

The number of nodes depends on the chosen mesh size.

How to show the point numbers:

• Opt for a wireframe representation .
• Go to the mesh configuration .
• Click on  and select the option Point number. Hit ‘OK’ to close the window.
• If necessary, change the font size and set symbol size to ‘0’ to increase the readability of the model.

• Opt for a wireframe representation .
• Go to the mesh configuration.
• Click on  and select the option Show node number. Hit ‘OK’ to close the window.
• If necessary, change the font size and set symbol size to ‘0’ to increase the readability of the model.

• Go to the menu Select  > Point number.
• Enter the desired point number and hit OK.
• Diamonds will select the relevant point. Click on  to only show the selection.

What you can do with 2500 mesh nodes highly depends on the choosen mesh size. Below are some example structures with 2400-2500 mesh nodes and an acceptable mesh (not too fine and not too course).

Bar structures

For bar structures, 2500 mesh nodes corresponds to approximately 300 bars.

2D Bars license

3D Bars license

Plate structures

For plate structure, there is no equivalent in number of plates. It depends on the size of the plates and the choosen mesh.

2D Slabs license

3D Structures license  

In your own Diamonds model

In your own Diamonds model, the number of mesh nodes is displayed at the elastic analysis. In the image below, there are 221 mesh nodes.

1. The size
2. The regularity
3. The free borders

1. Size

Play with the maximul element size to obtain a mesh that is not too big or not too small in relation to the dimensions of the model. By this we mean:

• • Make sure you have about 8 mesh triangles along the shortest side of the plate.
    6-7 is fine, 10 is also fine. But 30 is too many. And 3 is too few.

    Good	Too small	Too Big

  • Make sure that thin plate strips contain at least 2 mesh triangles.
    You can play with advanced mesh settings (minimum element size refinement factor and minimum side distribution) or refine the mesh locally.
    If you can’t get 2 mesh triangles in it, you should consider not modeling that strip.
  • Make sure that each plate edge contains at least 1 mesh node.
    The mesh dimensions are adjusted to the dimensions of the floors. But those mesh dimensions are often too coarse for narrow (masonry) walls. If you want an adequate result in those walls, you must make sure that each plate edge contains at least 1 mesh node.

    Bad
    Good

  • Remove unnecessary points and lines, because each point in the geometry, will become a mesh point.

Good	Bad

2. Regularity

Each mesh triangle only fulfills the equilibrium equations over its surface, regular triangles give better quality of results. Avoid elongated triangles by playing the maximum and minimum size.

Good	Bad

3. Free borders

Diamonds checks the consistency of the model by searching for free edges (= edges where no other plates connect), thus where the model begins and ends. Free edges are highlighted in a bright green color. Check if the free edges are in the right place!

Free edges where they should be	Free edges where they should NOT be

Solution

After launching the elastic analysis, in the analysis progression dialog, Diamonds will show you the number of

• mesh nodes (.)
• mesh lines (-)
• mesh triangles (Δ)

[NL]: De rekenkundige bewerking heeft geresulteerd in een overloop. 

[FR]: L’opération arithmétique a provoqué un dépassement de capacité.

Solution

• Verify the geometry of the model.

Your request has caused the following error: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

[NL]: Uw vraag heeft de volgende fout veroorzaakt: De index valt buiten het bereik. Deze mag niet negatief zijn en moet kleiner zijn dan de grootte van de verzameling. Parameternaam: index.

[FR]: Votre demande a provoqué l’errur suivante: L’index était hors limites. Il ne doit pas être négatif et doit être inférieur à la taille de la collection. Nom du paramètre index.

[ES]: Su solicitud ha provocado el siguiente error: El índice establa fuera del intervalo. Debe ser un valor no negative e inferior al temaño de la coleccíon. Nombre del parámetro: index

Solution

• Verify the geometry of the structure. Make sure all walls are perfectly straight (check out the solution in this article).
• Send the model (*.bsf-file) to the support desk (support@buildsoft.eu) for further analysis.

• first you generate the mesh using logical sizes (see below)
• second you should verify the used mesh size!!

The mesh window consists of two parts: one for plates and one for bars.

Plates

Basic parameters

• Maximum element size: 3 to 4 times the plate thickness
  The maximum element size determines the general fineness of the mesh.

Maximum element size: 1,0m

Maximum element size: 0,8m

Maximum element size: 0,6m

• Minimum element size: 1,5 to 2 times the plate thickness
  The minimum element size determines the fineness of the mesh around small lines and points that are very close to each other. Don’t set the minimum element size equal to the maximum element size. Only for standard models (like a 4 sided supported plate) a minimum element size of 0m is acceptable.

Advanced mesh parameters

These parameters are hidden for a reason: only in specific cases it is relevant to change them!

• With triangle subdivision
  Checking this option will create a smaller mesh with unmodified minimum and maximum elements sizes by connection the mid points on each mesh triangle side.
  
  In times when it took a while to generate this mesh, this option had his advantages. But in current times this option has less advantages, because badly chosen min/max element size will result in an even worse mesh when you check this option. If you want a smaller mesh, simply change the min/max element size. In calculation time it will not make a difference, but in the quality of the result it will.

Without triangle subdivision

With triangle subdivision

• Minimum edge division (= the number of mesh points along the boarder of a plate/wall) and refinement factor (= the number of mesh point in the field of a plate/wall)
  A good mesh size for the floors, can be too coarse for some walls. Setting the mesh size smaller, will give a good smaller mesh in those walls, but will be too fine in the floors. By increasing both parameters simultaneously, you can obtain a good mesh those smaller walls.

• Options to determine the mesh algoritm.

(default option)

Bars

• Number of divisions: 8 recommended
  A beam is simply supported and loaded with self-weight. The shape of the moment line is parabolic.
  
  With 8 divisions the parabolic shape is well approximated.
  • With more divisions the calculation time will increase, while the results don’t benefit.
    Only for an isolated beam on an elastic foundation, it can be meaningful to request more divisions (see this example).
  • With less divisions the calculation time will decrease, but the parabolic shape will be less detailed.
    In larger models (with bars mainly loaded with axial force), the number of divisions can be set 4 or 6 divisions to limit the calculation time.

2 divisions

4 divisions

8 divisions

16 divisions

• Minimum element size: 0,1m recommended
  With the minimum element size, you can request less divisions in shorter bars.
  • With a minimum element size equal to 0,0m, all bars have the same number of divisions (8), regardless their length.
  • With a minimum element size equal to 0,1m, the number of mesh elements in the shorter beams is reduced. Resulting in less calculating time. Since the complete behaviour of the truss is important and not the behaviour of every bar seperatly, the mesh shouldn’t be so detailed.

8 divisions + minimum element size: 0,0m

8 divisions + minimum element size: 0,1m

Solution

• Hit Cancel to close the error.
• “#348” is the number of the bar that’s causing trouble. Remember the number.
• Go to the Geometry Configuration .
• Select nothing and open the Data table .
• Go to the tab page “Bars”.
• Scroll through the list until you reach the relevant bar, in this example: 348.
• You’ll see that the bar has a zero length.

• Remember the start and end node of the bar. In this example numbers 238 and 30.

• Close the Data table.
• Go to the menu Select > Points Numbers….
• Enter on of the numbers, for example 238.

• Hit OK to perform the search. Hit immediately after that to isolate the point.
  This will make it easier for you to locate the point in the structure.
  If you can’t retrieve the point, repeat the steps with the other point number. “30” in this example.
• Run the Projection function in the X and Z direction on that point. This will remove the zero length bar from the model.

Or send your model (*.bsf-file) to support@buildsoft.eu