I have a Validation > Model > Loads > “Temperature load defined on rigid diaphragm” warning. Why do I get this and how do I resolve it?

Question

I have a Validation > Model > Loads > “Temperature load defined on rigid diaphragm” warning. Why do I get this and how do I resolve it?
 

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Answer

A Temperature load defined on rigid diaphragm validation warning occurs when you have applied a temperature load to a slab panel but the slab panel is defined as a diaphragm with the Diaphragm option set to “Rigid”.

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If you hover over the Temperature load defined on rigid diaphragm validation warning or an item within the folder branch a tooltip advises “A temperature loading is applied to an area of rigid diaphragm - no effect will be seen in model”.

A rigid diaphragm induces infinite in-plane stiffness, meaning any relative translation of nodes within the panel is prevented. The panel can translate/rotate as a rigid in-plane body.

In this scenario, Tekla Structural Designer does not apply a temperature load to the rigid diaphragm slab, hence no effect will be seen.

It should be noted that this validation warning is about temperature loads applied to slabs. If you were to apply a temperature load to the beams where a rigid diaphragm exists you will see the temperature effect as the strain builds up but elastic extension is prevented.

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You can double click the Temperature load defined on rigid diaphragm or individual temperature load to locate it in the active scene view. If the load is not in the active scene view then the Structural 3D view is opened and set active.

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To resolve the issue, select the slab panels under the temperature load and change the Diaphragm option to either None (in which case some other form of bracing system may be required) or to Semi-rigid. A semi-rigid diaphragm allows for in-plane stiffness properties to be modelled and hence in-plane deformation effects can occur.  Temperature induced forces will then be more realistic - both the semi-rigid diaphragm and beams will experience temperature induced strain.  Where full expansion (or contraction for a -ve temperature change) is inhibited - by connection to other members and/or supports - temperature strain induced forces will develop.

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After making one of the above changes then the validation warning is no longer displayed.

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You will probably also encounter another validation warning “Temperature load defined to non-meshed slab” which will need to be addressed.

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