Unexpected Natural Vibrations

Hello.
I’m seeing very high natural vibrations for a model in Karamba and I’m hoping that someone can please help me understand why they are so large. I have a 40-story tower that I have modeled in both SAP2000 and Karamba. The fundamental period for this tower in SAP2000 is around 4 to 5 seconds (ballpark), which is around what I’d expect. The fundamental period in Karamba is more than 70 seconds (see below).


Since the output frequency is in hertz I’m just taking the inverse value to get the period.
Is there something obvious that I’m missing?
I’m attaching my script.
Thanks!
JaredTowerVibes.gh (42.3 KB)

Hello Jared,
I think there is something wrong with the units: The floor slabs have a thickness of 3cm and the diagonal of the bounding box of the tower is 530m.
Do you use SI or Imperial Units?
Best,
Clemens

Hi Clemens.
Thanks for the prompt response!
I am using imperial units. The slabs should be 3" and I am using 26"x26"x3" thick box columns instead of the wide flanges I was using previously (see snip below).


I have also cleaned up some duplicate members and points and played with my mass assumptions, but despite these adjustments I am still getting high natural frequencies (see below).

Is it possible that the output is angular frequency in units of radians/sec rather than in Hertz? The numbers circled in red above are the output from the natural vibrations component given in Hertz, but the values circled in blue have been divided by 2*Pi. I’m uploading my revised model as well.
Jared
TowerVibes_V2.gh (58.5 KB)

Hi Jared,
I think you are not using the latest build of Karamba3d 1.3.2. In Karamba3d 1.3.2 build 190731 there was a bug which resulted in wrong cross section properties of predefined cross-sections when using Imperial Units (see https://www.grasshopper3d.com/group/karamba3d/page/new-features-and-bug-fixes).
When running your definition with the latest build I get these results:


Best,
Clemens

Hi Clemens,
I downloaded the latest build of Karamba and it looks good. Thank you for getting back to me!
Jared