I have a Validation > Model > Supports > “Support clashing with member length” warning. Why do I get this and how do I resolve it?

Question

I have a Validation > Model > Supports > “Support clashing with member length” warning. Why do I get this and how do I resolve it?
 

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Answer

If we hover over one of the problem supports a tooltip is displayed “A support has been defined at a position other than the base of a column/wall - review model”

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We can double click the “Support clashing with member length” warning or an individual support listed under the branch to highlight the supports or support in the model. Alternatively, you can right click the item and choose Highlight Items from the context menu. The supports or supports are highlighted in the active scene view and their properties are displayed in the Properties Window to allow review or editing.

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Note. In the screenshot above, the supports cannot be seen due to the member geometry of the beams and columns obscuring the supports. To display the supports we could access Scene Content > Members and ensure that Geometry is unchecked. This ensures that the member wires are displayed and not the physical member.

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The question then is… “Are the supports intended to be modelled at this location?”

If the answer is:

• No - To resolve the validation warning, select the supports and use Delete to remove them from the model.
• Yes - We need to understand the consequence of the warning and perhaps look at correcting the degrees of freedom of the support.

   

A support has six degrees of freedom, Translation F_x, F_y and F_z and Rotation M_x, M_y and M_z. A typical pinned support is defined in the screenshot below.
 

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The F_z = Fixed setting is preventing vertical load at the support from passing through into the column below. In this situation we provide the validation warning “Support clashing with member length” since the support clashes with the column.

There may be logical reasons why a support is required at this location. One example would be that we wish to simulate the lateral restraint provided by an adjacent building - without fully modelling it, but assume that the adjacent building does not provide any vertical support. Raised supports are discussed further in another article which is linked in the right panel.

Assuming that we do require the raised supports for lateral restraint, but the vertical load from the upper level is intended to pass through the columns below, then we can select the supports and set F_z to Free.

In the screenshot below we have set F_z, M_x, M_y and M_z to free to ensure only lateral restraint (in directions F_x and F_y) is provided by the supports. Following a Model Validation the “Support clashing with member length” warning is no longer displayed since the vertical load is passed to the columns.

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If the adjacent building was providing vertical support as well then you could have ignored the warning.

Clearly the engineer is responsible for defining the appropriate support fixity, since all six degrees of freedom need to be considered. The Results view can be used to verify the results following an analysis or design. M_x, M_y and M_z to free to ensure only lateral restraint (in directions F_x and F_y) is provided by the supports. Following a Model Validation the “Support clashing with member length” warning is no longer displayed since the vertical load is passed to the columns.