Hello, I'm looking for how Flac proceeds to obtain the dynamic characteristics of the structure, such as the natural frequencies, what are the conditions to fix to have a structure with a fixed base and what should be the dynamic input. thank you
Perform a free-vibration analysis (without damping). After determine the displacement complete cycle period. You must utilize the representative time displacement history. Then, you can compute the natural frequencies as the reverse of the periods.
Sir Armand Augustin Fondjo thank you for your answer, i understand your response, it's for soil, but i can't do it for structure. the real question is how i perform free vibration analysis for the structure?
Two possible ways:
(1) Perform a free vibration by applying a small INITIAL velocity, then recorded the displacement/velocity history. As A.A. Fondjo said.
(2) If the structure is soil layers, it can be estimated through the transfer function of the ground motion against the input motion.
Hi Sonia,
You may try taking the spectral ratio in the frequency domain by considering the oscillation at the top and at the bottom. The frequencies where you see the amplification result as your natural vibration modes.
Ali Guney Ozcebe Thank you for your answer Ali, I solved the problem last year, I thought it was like the other structural software finally no, you have to go through the spectra.
Thank you again.
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