Structural modification and consideration of factors

Product Support
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1

As part of my master's thesis, I am using the student version of Dlubal RFEM 6. I have noticed that the stiffness modification does not appear to work as expected.
When I multiply the stiffness by a factor of 0.5 using the stiffness modification, it is actually multiplied by a factor of 0.25.
A simple comparison calculation for a fixed-ended bar confirmed this behavior: reducing the stiffness by a factor of 0.5 results in four times the deformation instead of the expected double the deformation.
Could you please look into this and let me know whether it might be a bug, or whether I may be overlooking something in how I enter or apply the stiffness modification?

Thank you in advance.

3

Hi Andreas1705,

Thanks for your message!

To analyze the problem more closely, the model file would be very helpful:

:right_arrow: Click File → Save As and choose the following settings to reduce the file size:

image
image467×393 8.19 KB

:right_arrow: Then upload the file here (e.g. *.rf6, *.rs9) so the community can help find a solution too.

:owl: Would you rather not share the file publicly? No problem — send it to me in a direct message: click my profile picture or username → Message.

Best,
Marco Nikoleizig

4

Test Structure Modification.rf6 (1.1 MB)

5

Hi Andreas1705,

The effect you describe is exactly right. In the structural modification, the checkbox for Gamma_M1 is selected. This gamma value is read from the material properties. You had also set k = 0.50 here, as shown in the image:

image
image1282×848 77 KB

Solution: Either disable Gamma_M1 in the structural modification or set k = 1.0 in the material.

Best regards,
Marco Nikoleizig