I have a Validation > Model > General > “Supports exist within area of Mat Foundation” warning. Why do I get this and how do I resolve it?
Not version-specific
Tekla Structural Designer
Environment
Not environment-specific
Question
I have a Validation > Model > General > “Supports exist within area of Mat Foundation” warning. Why do I get this and how do I resolve it?
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Answer
If you hover over one of the problem items a tooltip is displayed “Delete supports unless they are intended to assist the Mat”.
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You can double click the “Supports exist within area of Mat Foundation” warning or items listed under the branch to highlight the selected items with the warning. Alternatively, you can right click and choose Highlight Items from the context menu. The view will automatically switch to the Structure 3D scene view with the selected items highlighted if they are not available in the currently active scene view.
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When columns are defined in the model a support is automatically placed below them if a supporting element is not determined. You control the support degrees of freedom via the Properties window. In the screenshot below a pinned support (default) has been defined.
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You may decide at a later stage of the design process to introduce a Mat foundation via the Foundations ribbon tab.
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You can specify Soil Parameters that allow the ground stiffness to be modelled as a series of linear or non-linear springs by defining the Type, Stiffness and Horizontal Support options.
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Existing supports within the boundary of the mat foundation are not automatically deleted when a mat foundation is created. For this reason the Validation warning is presented to you.
Your resolution depends upon what you wish to achieve:
- If you intend the column(s) to be supported solely by the mat foundation then you can select the support(s) under the columns and use the Delete key. Alternatively you could use the Delete command on the Quick access toolbar or Edit ribbon tab. Since no mat foundation and column support exist - the validation warning would be removed.
- If you intend the existing support(s) underneath the column to assist the mat foundation then you would keep the support(s). In this situation, the validation warning will still be reported to you.
Example
The implication of modelling localised supports and the mat foundation are best explained by way of a simple example. We will review the analysis results that come about from considering the following support arrangements:
- local supports only,
- local supports with a ground bearing mat foundation,
- just a ground bearing mat foundation,
1. Local support only.
Support reactions (Fz only) for gravity combination.
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2. Local supports with a ground bearing mat foundation. (Note. An area load has been applied to the mat foundation).
Support reactions (Fz only) for gravity combination.
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Close up where a localised support exists.
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Bearing pressures under the mat foundation. Zero where local support exists.
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3. Ground bearing mat foundation only. (Local supports under columns removed)
Support reactions (Fz only) for gravity combination.
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Close up where a localised support has been removed.
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Bearing pressures under the mat foundation. The localised support no longer exists resulting in an increase in the bearing pressure where the column is now resisted by the soil interaction under the mat foundation.
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Summary
When the local support is retained, the mat bearing pressure will be zero at that point. If the local support is deleted then the intensity of the bearing pressure increases locally. Your construction details will determine which of these is more appropriate e.g is there a separate pad base for the column, is the mat isolated from the pad base or is the column supported directly off the mat?