Converting 5% damped response spectrum to 2% damping

[Jwiggins]

The USGS spectral response graphs are all based off of 5% damping, however IEEE-693 and ASCE 113 for electrical substation design both state that a maximum damping value of 2% must be assumed for all structures.

Is there a good way to convert the USGS 5% damped response spectrum into a 2% damped one?

I have found Figure 2-1 of Fema273 which shows how to build a generalized response spectrum.
(

http://files.engineering.com/getfil...4064-4889-b043-5950ad553287&file=fema273.pdf)

These factors are the same as ASCE 7-10 (and ASCE 7-05) table 18.6-1

But this paper here indicates that there is a very large scatter to the data which produced these damping modification factors
(

http://files.engineering.com/getfil...c58-810f24d461f9&file=Naeim-Kircher-2001.pdf)

Does anyone have any comments? Why doesn't the USGS tool allow you to specify the damping ratio? It seems like they would have the capability if they already have all of the earthquake data to create 5% spectra.

 

[SAIL3]

The OP may have more valuable feedback by posting on the seismology forum....there was a good disscussion on the 5% V's 2% damping ratio for steel structures.....basically, the consensus was to use 5% for steel in a seismic event as there is more damping involved(stresses going pst yield) compared to wind where a 2% value was recommended....

 

[Jwiggins]

Ok, I will try re-posting

Thanks

 

[delagina]

intredasting

 

[GregLocock]

That's an interesting line of argument, but is it not more likely that a steel frame structure will have less damping than a typical building?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?