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.

Keywords

Multimodal Response spectrum analysis Equivalent loads Calculation

Reference

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RFEM Main Program
RFEM 5.xx

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Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

Price of First License
3,540.00 USD
RSTAB Main Program
RSTAB 8.xx

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The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

Price of First License
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RSTAB Dynamic Analysis
DYNAM Pro - Equivalent Loads 8.xx

Add-on Module

Seismic and static load analysis using the multi-modal response spectrum analysis

Price of First License
580.00 USD
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RF-DYNAM Pro - Equivalent Loads 5.xx

Add-on Module

Seismic and static load analysis using the multi-modal response spectrum analysis

Price of First License
760.00 USD