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definition of embedded element stiffness in COMSOL

Posted 06.04.2025, 21:50 GMT-4 1 Reply

Ghufranullah Khan
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Hello everyone, I am using the solid mechanics and truss module in comsol to model the GFRP bars reinforced concrete beam behaviour under three point bendind load. And when I use the multiphysics section to insert my bars in concrete, it ask for the spring stifnesses in axial and transverse directions. By default comsol have different it itself as shown in the figure I have attached. I am curious why they are using 10^3 with these stiffnesses and what if we manually define the stiffnesses, will it be correct? Thanks Regards Khan

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1 Reply Last Post 08.04.2025, 05:21 GMT-4
Henrik Sönnerlind COMSOL Employee

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Posted: 6 months ago 08.04.2025, 05:21 GMT-4

First: You only need to enter these parameters when you do not assume a perfect connection (Connection type = Rigid).

Basically, the default coefficient 10^3 can be interpreted as a penalty parameter. That is, the connection constraint is implemented using a very stiff spring.

If you want to use the non-rigid option to actually simulate a physical flexibility of the connection, you must enter some completely different numbers. Then the dependency on the other variables in the default expression are probably not relevant either.

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Henrik Sönnerlind
COMSOL
First: You only need to enter these parameters when you do not assume a perfect connection (Connection type = Rigid). Basically, the default coefficient 10^3 can be interpreted as a penalty parameter. That is, the connection constraint is implemented using a very stiff spring. If you want to use the non-rigid option to actually simulate a physical flexibility of the connection, you must enter some completely different numbers. Then the dependency on the other variables in the default expression are probably not relevant either.

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