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Re: "dynamic analysis" for earthquake ?

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On Jun 7, 2005, at 5:52 PM, Polhemus, Bill wrote:

I would expect not, but do you use the wind tunnel to derive the spectrum?
I truly don't know but I expect you can use instantaneous anemometer data transformed into a velocity pressure power spectral density curve for random response. You'd have to use real world transient wind pressures, not wind tunnel data. Wind tunnels are usually set up to provide constant aerodynamic conditions, but if you're looking at dynamic response, you'd need transient wind pressure measurements.

The way you'd define a response spectrum is to get a loading history and apply the load history to a bunch of single DOF systems (mathematically) to find the maximum response to the transient load as a function of the frequency of the system. The mathematics amounts to doing the time history solution repetitively for different system frequencies and damping ratios. It's not too hard--you can do it with a couple of different routines which have been published.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)

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