Cause (in general)

This error is always related to an inconsistency in the dimensions of the used cross-section(s). Resulting in cross-section classifications, imperfection factors, effective properties, … not being calculated automatically.

Example 1:

An RHS-section is used to create an elliptical cross-section. But because r0 (=25mm) equals B/2 (=50mm/2), the cross-section classification in the weak direction cannot be performed.
Solution: set B= 51mm or set r0 to 24mm.

Example 2:

Some cross-section shapes are associated with cold-formed sections, like these in the list below:

When the option ‘Automatic calculation’ is selected, Diamonds calculates the general, elastic (except T_wm) and the plastic properties of the cross-section.
But Diamonds cannot calculate the effective and design properties for these cross-section shapes. These shapes are in Diamonds because manufacturers (Joris Ide, Brausa, Sadef, …) provided us with lists of common cross-sections with their dimensions and effective properties. So although you can play around with the dimensions, Diamonds is not capable of calculating the effective properties!

So if you want to perform a steel verification on these cross-section shapes, you should:

• Check the option ‘Automatic Calculation’. This way the general, elastic and plastic properties are calculated.
• Uncheck the option ‘Automatic calculation’. This way you can adjust the value of T_wm in the tab page ‘Elastic’.
• Define all the properties in the tab page ‘Effective’.
• Define all the properties in the tab page ‘Design’.

• Schematising the construction
• Determining the internal forces and moments (= global analysis)
• Checking the cross-sections (= design):
  • Strength
  • Stability 
  • Stiffness

The explanation below covers the design of steel.

In Diamonds

• Calculate the internal forces (syn. global analysis) F9 or .
• Set the buckling lengths.
  Don’t skip this step! Without the correct buckling lengths the stability results have no meaning.
• Define the lateral torsional buckling supports (if relevant).
• Select the correct steel standard using the menu Analysis > Steel standard.
  A list with all available standards in Diamonds can be found here.
• Click on F3 or  to start the verification (more info).
• Decide whether global imperfections are necessary or not.
• View the results with . For the results of the strength check click , for those of the stability check click .
  The results of the strength and stability check are displayed as a percentage of the total capacity (= 100%) of the section.
  • A structure is sufficient for strength, if the percentage is less than 100% for all bars.
  • A structure is sufficient for stability, if the percentage is less than 100% for all bars.

  Based on the percentage no judgment can be made on the extent to which a section is sufficient or not. This is because the used formulas are not always linear.

• Optionally, optimize the cross-sections.
  You can use the Optimization-function for this , but it might take a few iterations (and thus time).
  We recommend that you change the cross-sections manually to one (or more) size(s) bigger/smaller depending on the result you had then recalculating the model. Exspecially for experienced engineer, this works faster than the Optimization function.
• Don’t forget to verify the stiffness! Thus the vertical and horizontal deformation.
  Diamonds can calculate the relative deformation, but it’s still up to you to verify it.
  A structure is sufficient if the strength, stability and stiffness are sufficient.

The verification/ unity check of user defined cross-sections (using the tool Section Utility) is only supported for steel cross-sections according to Eurocode.