Folks, Can someone explain in simple terms what MDAMP does? I'm running ANTYPE,MODAL followed by ANTYPE,SPECTR. If the curve used in the spectrum analysis already has a damping ratio baked into it, does MDAMP add more damping? If yes, and I intend to use MDAMP, should my applied spectrum curve have 0% damping so as to not apply damping twice? Matt Ridzon, PE, MSME Sr. Engineering Analyst Email matt@prime-engineer.com<mailto:matt@prime-engineer.com> Mail 266 Main St, Burlington, VT 05401 Web www.prime-engineer.com<http://www.prime-engineer.com/> [A blue hexagon with white letters Description automatically generated] PRIME ENGINEERING LLC This message (including any attachments) may contain confidential, proprietary, privileged and/or private information. The information is intended to be for the use of the individual or entity designated above. If you are not the intended recipient of this message, please notify the sender immediately, and delete the message and any attachments. Any disclosure, reproduction, distribution or other use of this message or any attachments by an individual or entity other than the intended recipient is prohibited.

MDAMP is for defining modal damping. In vibrations of MDOF systems, each mode has an individual damping ratio (called modal damping ratios in some books). This commands defines the damping ratio for each mode you intend to solve for. Another damping command available is DMPRAT which defines a constant damping ratio across all frequencies. Good Luck! ===================================== Mohammad A Gharaibeh, Ph.D. Associate Professor Department of Mechanical Engineering The Hashemite University P.O. Box 330127 Zarqa, 13133, Jordan Tel: +962 - 5 - 390 3333 Ext. 4771 Fax: +962 - 5 - 382 6348 ===================================== On Fri, Feb 27, 2026 at 1:40 AM Matthew Ridzon, PE via Xansys < xansys-temp@list.xansys.org> wrote: > Folks, > > Can someone explain in simple terms what MDAMP does? I'm running > ANTYPE,MODAL followed by ANTYPE,SPECTR. If the curve used in the spectrum > analysis already has a damping ratio baked into it, does MDAMP add more > damping? If yes, and I intend to use MDAMP, should my applied spectrum > curve have 0% damping so as to not apply damping twice? > > > > Matt Ridzon, PE, MSME > Sr. Engineering Analyst > > Email matt@prime-engineer.com<mailto:matt@prime-engineer.com> > Mail 266 Main St, Burlington, VT 05401 > Web www.prime-engineer.com<http://www.prime-engineer.com/> > [A blue hexagon with white letters Description automatically generated] > PRIME ENGINEERING LLC > > > This message (including any attachments) may contain confidential, > proprietary, privileged and/or private information. The information is > intended to be for the use of the individual or entity designated above. If > you are not the intended recipient of this message, please notify the > sender immediately, and delete the message and any attachments. Any > disclosure, reproduction, distribution or other use of this message or any > attachments by an individual or entity other than the intended recipient is > prohibited. > > > _______________________________________________ > Xansys mailing list -- xansys-temp@list.xansys.org > To unsubscribe send an email to xansys-temp-leave@list.xansys.org > If you are receiving too many emails from XANSYS please consider changing > account settings to Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list

Okay thanks for this feedback. For my next question, let's assume a few things: • I use MDAMP and apply it to every mode in the analysis • The customer gave me several spectra at various damping values: 2%, 3%, 5%. If I run the spectrum analysis for the customer's 2% curve and apply MDAMP to every mode for 3%, will I get identical results if I had just run the customer's 5% curve? —Matt -----Original Message----- From: Mohammad Gharaibeh via Xansys <xansys-temp@list.xansys.org> Sent: Friday, February 27, 2026 7:06 AM To: XANSYS Mailing List Home <xansys-temp@list.xansys.org> Cc: Mohammad Gharaibeh <mgharai1@binghamton.edu> Subject: [Xansys] Re: [External Email] MDAMP for the Damping Ratio MDAMP is for defining modal damping. In vibrations of MDOF systems, each mode has an individual damping ratio (called modal damping ratios in some books). This commands defines the damping ratio for each mode you intend to solve for. Another damping command available is DMPRAT which defines a constant damping ratio across all frequencies. Good Luck! ===================================== Mohammad A Gharaibeh, Ph.D. Associate Professor Department of Mechanical Engineering The Hashemite University P.O. Box 330127 Zarqa, 13133, Jordan Tel: +962 - 5 - 390 3333 Ext. 4771 Fax: +962 - 5 - 382 6348 ===================================== On Fri, Feb 27, 2026 at 1:40 AM Matthew Ridzon, PE via Xansys < xansys-temp@list.xansys.org> wrote: > Folks, > > Can someone explain in simple terms what MDAMP does? I'm running > ANTYPE,MODAL followed by ANTYPE,SPECTR. If the curve used in the > spectrum analysis already has a damping ratio baked into it, does > MDAMP add more damping? If yes, and I intend to use MDAMP, should my > applied spectrum curve have 0% damping so as to not apply damping twice? > > > > Matt Ridzon, PE, MSME > Sr. Engineering Analyst > > Email matt@prime-engineer.com<mailto:matt@prime-engineer.com> > Mail 266 Main St, Burlington, VT 05401 > Web www.prime-engineer.com<http://www.prime-engineer.com/> > [A blue hexagon with white letters Description automatically > generated] PRIME ENGINEERING LLC > > > This message (including any attachments) may contain confidential, > proprietary, privileged and/or private information. The information is > intended to be for the use of the individual or entity designated > above. If you are not the intended recipient of this message, please > notify the sender immediately, and delete the message and any > attachments. Any disclosure, reproduction, distribution or other use > of this message or any attachments by an individual or entity other > than the intended recipient is prohibited. > > > _______________________________________________ > Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send > an email to xansys-temp-leave@list.xansys.org If you are receiving too > many emails from XANSYS please consider changing account settings to > Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list _______________________________________________ Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send an email to xansys-temp-leave@list.xansys.org If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day. Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list

Matt, You’re not double-counting. What's basically happening for spectral response analysis is that you're doing a tabular lookup of the acceleration to be applied to each mode based on its damping value. You *could* enter all three curves with their corresponding spectral accelerations with the SV command and ANSYS would use the damping value for each mode (as Mohammad notes, you can apply different damping values to each mode) and ANSYS would interpolate between these curves to apply the right acceleration. For a uniform damping level for all modes, you could get away with using an arbitrary MDAMP value as long as you use that same for the single SV curve you enter. Regards, David J. Gross, P.E., ASME Fellow | Dominion Engineering, Inc. Director, Federal Services 12100 Sunrise Valley Drive, Suite 220 | Reston, VA 20191 office 703.657.7300 | desk 703.657.7311 | mobile 301.580.3066 dgross@domeng.com | domeng.com -----Original Message----- From: Matthew Ridzon, PE via Xansys <xansys-temp@list.xansys.org> Sent: Friday, February 27, 2026 8:06 AM To: XANSYS Mailing List Home <xansys-temp@list.xansys.org> Cc: Matthew Ridzon, PE <Matt@prime-engineer.com> Subject: [Xansys] Re: [External Email] MDAMP for the Damping Ratio *** WARNING: This email originated from outside of the organization. Exercise caution when viewing attachments, clicking links, or responding to requests. *** Okay thanks for this feedback. For my next question, let's assume a few things: • I use MDAMP and apply it to every mode in the analysis • The customer gave me several spectra at various damping values: 2%, 3%, 5%. If I run the spectrum analysis for the customer's 2% curve and apply MDAMP to every mode for 3%, will I get identical results if I had just run the customer's 5% curve? —Matt -----Original Message----- From: Mohammad Gharaibeh via Xansys <xansys-temp@list.xansys.org> Sent: Friday, February 27, 2026 7:06 AM To: XANSYS Mailing List Home <xansys-temp@list.xansys.org> Cc: Mohammad Gharaibeh <mgharai1@binghamton.edu> Subject: [Xansys] Re: [External Email] MDAMP for the Damping Ratio MDAMP is for defining modal damping. In vibrations of MDOF systems, each mode has an individual damping ratio (called modal damping ratios in some books). This commands defines the damping ratio for each mode you intend to solve for. Another damping command available is DMPRAT which defines a constant damping ratio across all frequencies. Good Luck! ===================================== Mohammad A Gharaibeh, Ph.D. Associate Professor Department of Mechanical Engineering The Hashemite University P.O. Box 330127 Zarqa, 13133, Jordan Tel: +962 - 5 - 390 3333 Ext. 4771 Fax: +962 - 5 - 382 6348 ===================================== On Fri, Feb 27, 2026 at 1:40 AM Matthew Ridzon, PE via Xansys < xansys-temp@list.xansys.org> wrote: > Folks, > > Can someone explain in simple terms what MDAMP does? I'm running > ANTYPE,MODAL followed by ANTYPE,SPECTR. If the curve used in the > spectrum analysis already has a damping ratio baked into it, does > MDAMP add more damping? If yes, and I intend to use MDAMP, should my > applied spectrum curve have 0% damping so as to not apply damping twice? > > > > Matt Ridzon, PE, MSME > Sr. Engineering Analyst > > Email matt@prime-engineer.com<mailto:matt@prime-engineer.com> > Mail 266 Main St, Burlington, VT 05401 > Web www.prime-engineer.com<http://www.prime-engineer.com/> > [A blue hexagon with white letters Description automatically > generated] PRIME ENGINEERING LLC > > > This message (including any attachments) may contain confidential, > proprietary, privileged and/or private information. The information is > intended to be for the use of the individual or entity designated > above. If you are not the intended recipient of this message, please > notify the sender immediately, and delete the message and any > attachments. Any disclosure, reproduction, distribution or other use > of this message or any attachments by an individual or entity other > than the intended recipient is prohibited. > > > _______________________________________________ > Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send > an email to xansys-temp-leave@list.xansys.org If you are receiving too > many emails from XANSYS please consider changing account settings to > Digest mode which will send a single email per day. > > Please send administrative requests such as deletion from XANSYS to > xansys-mod@tynecomp.co.uk and not to the list _______________________________________________ Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send an email to xansys-temp-leave@list.xansys.org If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day. Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list _______________________________________________ Xansys mailing list -- xansys-temp@list.xansys.org To unsubscribe send an email to xansys-temp-leave@list.xansys.org If you are receiving too many emails from XANSYS please consider changing account settings to Digest mode which will send a single email per day. Please send administrative requests such as deletion from XANSYS to xansys-mod@tynecomp.co.uk and not to the list