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003510
2021-06-22

Question

What method is applied in the RF‑/DYNAM Pro - Equivalent Loads add-on module?


Answer:

Just as in the "Forced Vibrations" add-on module, the "Equivalent Loads" add-on module performs the multimodal response spectrum analysis.

Although the name may suggest otherwise, the simplified response spectrum method is not carried out here, as explained in EN 1998‑1, for example.

The equivalent loads are determined separately for each direction of excitation according to the following formula:

$\begin{Bmatrix}{\mathrm F}_{\mathrm X}\\{\mathrm F}_{\mathrm Y}\\{\mathrm F}_{\mathrm Z}\end{Bmatrix}\;=\;\mathrm\Gamma\;\ast\;\begin{Bmatrix}{\mathrm u}_{\mathrm X}\\{\mathrm u}_{\mathrm Y}\\{\mathrm u}_{\mathrm Z}\end{Bmatrix}\;\ast\;{\mathrm S}_{\mathrm a}(\mathrm T)\;\ast\;\begin{Bmatrix}{\mathrm M}_{\mathrm X}\\{\mathrm M}_{\mathrm Y}\\{\mathrm M}_{\mathrm Z}\end{Bmatrix}\;$

The differences between both add-on modules are described in this FAQ.