Modal analysis

[ShanJY]

Hello everyone:
When I perform a modal analysis of the structure, the eigenvalue results of the first few orders of modalities appear negative, so does anyone know where the error is. There is no error in the gravity analysis.
Thank you!

[mhscott]

Your model is unstable somehow. Check the boundary conditions and apply other loads, not just gravity, to see if the analysis converges.

[ShanJY]

Thanks for your help, I will make adjustments to my model based on your suggestions.