The Capacity Spectrum Method (CSM) in ATC 40

[sanya greek]

Hello!

After my Pushover Analysis i want to use The Capacity Spectrum Method (CSM) in ATC 40. For that i need ADRS and convert Base Shear and Displacement of top floor to the corresponding spectral acceleration ( Sai ) and spectral displacement ( Sdi ) values on the capacity spectrum.

So i need the sum of dead load and the likely live loads, the modal mass coefficient α and the modal participation factor for the first vibration mode respectively PF1. For the modal mass coefficient α and the modal participation factor i want to get amplitude of the first vibration mode shape for each floor. How i can do it?

If i right, we can use displacements of nodes. But what node to take? I belive, that it mast be nodes of Center Mass of each floor.
How can i find Center Mass of each floor? Or what can i do to find the modal mass coefficient α and the modal participation factor PF1?

Thank you so much!!!

[seismosoft]

In SeismoStruct the target displacement is calculated automatically according to the procedures proposed by the supported Standards (ASCE-41, EC8, and the Italian, Greek and Turkish Codes). In some Codes (EC8, Turkish, Greek) the procedures are similar to the CSM.
Regarding the information that you mentioned in your posts can be extracted as follows:
-Sum of dead load and the likely live load: This is not done automatically, you need to add manually the applied forces
- Modal mass coefficient and the modal participation factor: from eigenvalue analysis
- "we can use displacements of nodes. But what node to take? " For the transformations to the ADRS you will need the deformations all the nodes. Note however that such clarifications on the CSM procedure are beyond the scope of this forum, and should better be discussed with your supervisor.

Seismosoft Support

[warcorsario]

Some time ago, I wanted to do the same: get the data to make the capacity spectrum of ATC-40. One possible strategy that occurred to me is to create control nodes in the center of mass of each level, and when the eigenvalues analysis is performed, read the displacements for the first vibration mode in the control nodes, these data would be the amplitudes modal for the first vibration mode, with that information obtain modal mass coefficient α and the modal participation factor for the first vibration mode respectively PF1 using the respective formulas.