# Frequently Asked Questions (FAQ)

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• ### A single-span beam consisting of several apparently straight members receives small torsional moments in the load case of "dead load." Why?

#### Answer

There is very likely an inaccuracy in the modeling, which has to be checked as follows:

• Set the view in the member direction, then zoom in.

• Select all existing nodes that should lie on the same line: If the respective coordinates in the transverse direction do not correspond to the member axis, the corresponding field of the coordinate is empty and there is a deviation.

• ### In the RF-/DYNAM Pro - Equivalent Loads module, it is possible to take accidental torsional effects into account.. Which calculation approach is behind the calculation? Which values have to be entered for the eccentricities eX and eY?

#### Answer

Accidental torsion is regulated in EN 1998-1, section 4.3.2. The eccentricities are to be determined manually, in EN 1998-1, they are given as 5% of the building length. In other international seismic standards, the principle of accidental torsion is regulated similarly, but the determination of the eccentricities may differ.

For each equivalent load (at each FE node/internal node), a torsional moment is determined according to the following formula:

$\mathrm M\;=\;\left|{\mathrm F}_{\mathrm x}\;\ast\;{\mathrm e}_{\mathrm y}\right|\;+\;\left|{\mathrm F}_{\mathrm y}\;\ast\;{\mathrm e}_{\mathrm x}\right|$

The exported load cases are then output in duplicate number - with the torsional moment M rotating around the vertical axis, once in the positive and once in the negative direction of rotation.

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#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### Wind Simulation & Wind Load Generation

With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.

The generated wind loads acting on these objects can be imported to RFEM or RSTAB.

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