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User Area > Advice

Typical warning message in the Text Ouput window in Modeller: 

Midside Node L of Quadratic edge M does not define BMI21 Element P defined by the edge end nodes

And the typical warning message from LUSAS Solver text output file (*.OUT):


Most common causes & links to solutions 

This warning occurs due to a combination of linear interpolation order elements (a node at each end/corner) and quadratic interpolation order elements (that have a mid-side node).

For example, whilst the end nodes of linear order beam elements can be shared with corner nodes of quadratic order shell elements, the midside node of the shell has no counterpart on the beam.  By default, these ‘free’ midside nodes will be automatically ‘connected’ by using constraint equations.  The message may occur for example, if using a linear order 3D thick beam element (Eg. BMI21) with a quadratic order thick shell element for example (QTS8).  However, since the release of V15 note that there is a quadratic 3D Thick beam element (BMI31) which is compatible for use with QTS8.

It best (where possible) to use the same interpolation order for elements that share an edge in LUSAS and avoid the automatic creation of constraints which can slow the solution and make the edges they are applied to behave as if over-stiff.  Elements that only share end or corner nodes intentionally can be of different interpolation order in the same analysis without any problem or warning message.

Please refer to the Element Reference Manual and the Theory Manual Volume 2 for more detailed information regarding the elements available in LUSAS.  These manuals are available via the Help menu in Modeller:

Help > Help Topics > Contents

Please also see the user area page Rules for connecting elements

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