I have set 20% nominal pinned fixity at the base. Why have the deflections not reduced due to this increased base fixity?
Environment
Not environment-specific
Question
I have a small simple goalpost frame that I’m designing. I was trying to utilize the software's function to set the bases to be nominally pinned and assign a 20% rotational stiffness to limit the frame deflection. However, when I run the model its giving me the same deflection values as when I don’t assign the stiffness. Would you be able to explain to me why this isn’t working for me?Image
Answer
Currently you have a release applied to the bottom of the columns. This then connects to the support underneath, so the nominal fixity cannot play any part.The 'Related To' article displayed on the right "(N-1) rule for the number of pins to apply at a node where N members meet." is worth reviewing to gain an understanding of releases.
Solver View
If you switch to the Solver View you can turn On the Scene Content, 1D Elements > Releases to review where releases have been applied in the model.Image
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To resolve you need to alter the fixity at the bottom of the columns to remove the release, by setting them as Fixed.
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Comparing Deflections
Pinned Bases (fixed column releases)Image
Nominally Pinned Bases 20% (fixed column releases)
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