In ETABS, I defined Response Spectrum Functions in UBC97, ASCE 7-10 and Eurocode 8-2004 types, howerver these Response Spectrum Functions use only 5% damping ratio. When I change the damping ratio value, the Response Spectrum is still unchanged.
How do we define Response Spectrum Functions in different damping ratios in ETABS?
Thanks for your response!
According to EC8-2004, I got your answer.
However, in ASCE 7-10 and UBC 97, I have not found out that. Further more, there is no formula to convert Spectral Acceleration to Spectral Displacement. Do you know what American standard document which I can see that answer?
You should first generate Response Spectrum Function with Seismosignal software based on each code and your damping , the save the fine in notepad and use the spectrum in Etabs.
Design spectra is calculated using a fixed damping ratio, 5% is common value, in most, if not all Codes. Changing damping ratio in ETABS input won't change its ordinate. Calculating RS curves for different damping is tedious but we have empirical formulas of Damping Modification Factor (DMF), proposed by a number of researchers and/or incorporated in Codes. The following paper, available online, is a good source:
http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2994&context=eispapers
If you input damping ratio equal to 5 (not 0.05) in the formula, it will produce 1.
Design spectra is calculated using a fixed damping ratio, 5% is common value, in most, if not all Codes. Changing damping ratio in ETABS input won't change its ordinate. Calculating RS curves for different damping is tedious but we have empirical formulas of Damping Modification Factor (DMF), proposed by a number of researchers and/or incorporated in Codes. The following paper, available online, is a good source:
http://ro.uow.edu.au/cgi/viewcontent.cgi?article=2994&context=eispapers
If you input damping ratio equal to 5 (not 0.05) in the formula, it will produce 1.
Linh, for ASCE 7-10, take a look at Chapter 18... B_1D is defined based on the effective critical damping. Take a look also at the commentary for 18.4 for developing your displacement-response spectra. There's a slightly different approach, with a little more in-depth commentary, offered in ASCE 41-13. Hope that helps.
Sa = omega2x SdThe relation between the Spectral accelleration and Spectral displacement through omega, the natural frequency of vibration (may be computed through natural period) of dynamic system may be used to convert spectral displacement into spectral accelleration or vice versa.
Dear Linh,
first of all, I think you should generate a new response spectrum with your desired damping ratio. for this propose, you can use SeismoSignal software.
after this, you can import generated spectrum into the Etabs and analyze the structure.
I wish bests for you
Good question.. Please share me the best answer might you trust...
Regards…
Check the following reference Please.. it might's assist you in your question … Regards…
https://nptel.ac.in/courses/105101004/downloads/04%20Chapter.pdf
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