# FAQ 003505 EN-US

### In RF‑/DYNAM Pro, the Rayleigh damping is available. How do I determine and use these factors?

For some solving methods, the Rayleigh coefficients are absolutely necessary. Since the Lehr's damping values are only given in the literature, it is necessary to convert them.

The following formula is used for converting the Lehr's damping values into the Rayleigh coefficients:

${\mathrm D}_{\mathrm r}\:=\:\frac12\;\left(\frac{\mathrm\alpha}{{\mathrm\omega}_{\mathrm r}}\;+\;\mathrm\beta\;{\mathrm\omega}_{\mathrm r}\right)$

Where α and β are the Rayleigh coefficients. It is necessary to set up a system of equations that always contains the angular frequencies of the two most dominant mode shapes. For both of these mode shapes, the structure will then be damped with the specified Lehr's damping value. All other mode shapes of the structure will have different damping values. These result from the curve displayed in Image 01. The curve shows an example of two angular frequencies of 10 and 20 rad/s and Lehr's damping of 0.015.

It is also possible to use the "Calculate from Lehr's Damping..." button to activate the corresponding conversion tool.

#### Reference

 [1] Manual RF-DYNAM Pro. (2020). Tiefenbach: Dlubal Software.

Write Comment...

Write Comment...

• Views 2039x
• Updated 10/27/2021

Submit Individual Question

NCSEA Structural Engineering Summit

Conference 02/15/2022 - 02/16/2022

RFEM 6 | Dynamic Analysis and Seismic Design According to EC 8

Online Training 03/10/2022 8:30 AM - 12:30 PM CET

2022 NASCC: The Steel Conference

Conference 03/23/2022 - 03/25/2022

International Mass Timber Conference

Conference 04/12/2022 - 04/14/2022

Structures Congress 2022

Conference 04/21/2022 - 04/22/2022

Glass Design with Dlubal Software

Webinar 06/08/2021 2:00 PM - 2:45 PM

Blast Time History Analysis in RFEM

Webinar 05/13/2021 2:00 PM - 3:00 PM EST

Timber Beam and Surface Structures | Part 2: Design

Webinar 05/11/2021 2:00 PM - 3:00 PM

Plate and Shell Buckling Utilizing Dlubal Software

Webinar 03/30/2021 2:00 PM - 2:45 PM

Webinar 03/10/2021 2:00 PM - 3:00 PM EST

The Most Common User Errors With RFEM and RSTAB

Webinar 02/04/2021 2:00 PM - 3:00 PM CET

Webinar 01/19/2021 2:00 PM - 3:00 PM EST

Dlubal Info Day Online | December 15, 2020

Webinar 12/15/2020 9:00 AM - 4:00 PM CET

FEA Troubleshooting and Optimization in RFEM

Webinar 11/11/2020 2:00 PM - 3:00 PM EST

Soil-Structure Interaction in RFEM

Webinar 10/27/2020 2:00 PM - 2:45 PM CET

NBC 2015 Modal Response Spectrum Analysis in RFEM

Webinar 09/30/2020 2:00 PM - 3:00 PM EST

Documenting Results in the RFEM Printout Report

Webinar 08/25/2020 2:00 PM - 2:45 PM

Length 0:50 min

Length 1:01 min

Length 49:44 min

Length 1:26 min

Length 6:32 min

Length 14:48 min

Length 1:01:38 min

Length 2:37 min

Length 7:43 min

Length 9:17 min

Length 1:22 min

Length 1:21 min

Length 5:34 min

Length 10:05 min

Length 1:20 min