Is Modal Analyisis really needed for UBC97 (or other) Seismic Equivalent Static Methods?

T2ioTD · Feb 24, 2023

I watched a video performing a preliminary check for the general building deformation for the UBC97 seismic equivalent static method, then he goes on, in the next video, and adds the modal load, and proceeds with his equivalent static method study, as we all know.

I am confused here: How could Etabs calculate the deformation due to the seismic load without knowing the frequency of the building (before defining the modal case).

Thanks.

JoshPlumSE · Feb 24, 2023

Well, the modal analysis can be helpful in establishing what the fundamental period is for each direction. And, that information is used in the equivalent static analysis. Right?

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Is Modal Analyisis really needed for UBC97 (or other) Seismic Equivalent Static Methods?

T2ioTD

Civil/Environmental

JoshPlumSE

Structural

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