I have a Validation > Analysis > General > Supports > "No supports defined in model" validation error. Why do I get this and how do I resolve it?

Question

I have a Validation > Analysis > General > Supports  > "No supports defined in model" validation error. Why do I get this and how do I resolve it?
 

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Answer

This message is self explanatory. No supports exist in the model (i.e. under columns), and hence the structure is unsupported. Applied loads cannot go to ground and hence the structure is not in equilibrium.

We have seen this appear after a mat foundation has been modelled. In this scenario, the supports that are automatically placed under columns are manually deleted to ensure the columns are supported on the mat foundation (with a specified ground stiffness). 

The error may then be triggered later in the modelling process if the Engineer decides to delete the mat foundation (as they no longer wish to model it), but forget to reinstate the supports.
To reinstate the supports, use the Model ribbon tab > Support command. Define the degrees of freedom required in the Properties window and then place the supports by either clicking at the base of each column, or by boxing a window in a 2D plan view.

Alternatively, the error may also be triggered if the Engineer unselects Use Ground Bearing Springs in the mat properties. Because the springs are removed, the model is once again unsupported.
To reinstate the supports in this case, reselect Use Ground Bearing Springs, then define the spring type and set the spring stiffness accordingly.