Talk:Response spectrum

I haven't found yet any external refs that I like. --Zeizmic 15:42, 25 Apr 2005 (UTC)

I have largely replaced this section because for transient input, such as seismic, there will always be a finite peak response, even with no damping. Infinite response occurs with periodic input and then only after an infinite time.--Muchado 11:27, 4 February 2006 (UTC)


 * Although this is a great tool for building codes, and seismic hazard analysis, there are limitations. The fundamental assumption is that these are linear oscillators, which have been exposed to a sufficient amount of shaking, as to have achieved a steady state in the equations of motion.  Of course, the oscillators only register a finite peak acceleration because of the damping that is assumed, normally 5% of critical for structures. (Undamped oscillators would fling those blocks into orbit!)
 * Actually response spectra do not assume steady-state. They are made up of "peak responses" to any transient input. This is a common confusion due to the superficial similarity to plots of simple harmonic response to simple harmonic excitation (transfer functions). Or perhaps "response spectra" mean something else in other fields? My apologies if that is the case. Muchado 01:27, 25 May 2006 (UTC)

Need to organize the uses of Response Spectrum
Time history analysis for a structure gives us the Action/Displacement with respect to time.

So, in this respect how the Response Spectrum Analysis for a structure is different from Time History Analysis.

i.e, what more or less is done when we perform Response analysis for a structure? —Preceding unsigned comment added by 121.52.146.226 (talk) 10:52, 23 July 2008 (UTC)

Time history analysis generally refers to time domain analysis of multi-degree-of-freedom systems to earthquake ground motions. Response spectra are created by plotting the maximum response of "single-degree-of-freedom" systems with a range of different natural frequencies to a ground motion. Response spectrum analysis is the decomposition of a multi-degree-of-freedom system into "single-degree-of-freedom" systems (typically by modal analysis), and then reading the response of those systems off the response spectrum, and combining the results (typically using some form of SRSS combination) to approximate the response of the structure to ground motion. The advantage is that you don't need to do a time history analysis, and also that you can define a "design response spectrum" which is an idealised form that envelopes the effects of many different earthquakes. Since we don't know what earthquake ground motion is going to occur, we would have to choose appropriate ground motions or generate artificial ones and then perform multiple analyses. Response spectrum analysis reduces the analysis time significantly. I will see if I can find time to rewrite the article at some point, but am currently too busy doing design. --Muchado (talk) 06:27, 4 August 2008 (UTC)
 * There is something new called Uniform Hazard Spectrum (UHS). Can anyone tell me how to use it in a modal response analysis and in a time history analysis? Thanks. Zymogen (talk) 17:00, 16 February 2009 (UTC)

Predominant period and frequency
Hi,

We need to add why it is important to estimate the predominant period and frequency and how to do it.

RB — Preceding unsigned comment added by 132.177.81.47 (talk) 23:46, 2 May 2013 (UTC)

Damping
Need a discussion on what damping is, is not well defined here or on other pages it seems Jtyler277 (talk) 17:31, 7 December 2017 (UTC)

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Presence of damping required for steady state?
The following statement:

"If the input used in calculating a response spectrum is steady-state periodic, then the steady-state result is recorded. Damping must be present, or else the response will be infinite."

Should only be true if the response spectrum contains the natural frequency of the oscillating mass, correct? 208.181.64.249 (talk) 16:39, 29 December 2022 (UTC)