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Vertical Earthquake Modal Response Spectrum Analysis per ASCE 7-16 with ideCAD

How does ideCAD vertical earthquake analysis with Local Vertical Vibration Modes according to ASCE 7-16?

  • The vertical seismic load effect is determined automatically.

  • Mode numbers should include vertical modes. The user defines the number of modes.


D = Dead load
Sav = Design vertical response spectral acceleration
Ev = Vertical seismic load effect

Vertical response spectrum should only apply structures in Seismic Design Categories C, D, E, and F. Determining of the vertical response spectrum, Vertical Response Spectrum is expressed in ASCE 7-16 Section 11.9.

According to ASCE 7-16 11.9.3, the design vertical response spectral acceleration, Sav, is determined as two-thirds of the value of SaMv determined in Section 11.9.2.

The vertical seismic load effect, Ev, is determined in accordance with Eq. (12.4-4b).

It has been determined that the vertical earthquake effect has an effect on the building behavior as a certain proportion of the horizontal earthquake effect, as a result of the experiments and monitoring the movements of the buildings under earthquakes. According to the regulation, it is calculated in 2 different ways. It is calculated by using the spectrum only for structures in Seismic Design Categories C, D, E, and F.

In cases where the vertical earthquake effect is calculated with the spectrum, the mode representing the vertical movement on the relevant element should be calculated. Even if the number of modes is sufficient for the horizontal earthquake effect, if the relevant mode is not available, the targeted mode number should be increased, and the relevant mode should be included in the calculation. Otherwise, internal forces and displacements for vertical earthquakes affecting the element cannot be calculated correctly.

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