Reply To: Why my modal frequency are same?

[peteroznewman]

It looks like your structure has 4 almost identical trusses along the top. In the mode shown, the trusses are vibrating: down,up,up,down. That is one of 16 modes starting with: down, down, down, down and ending with: up, up, up, up.  All 16 modes have similar frequencies. This is normal and is no trouble.