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RE: Old Seismic Values

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Jason W. Kilgore wrote:  "But I'm still stuck on the 'peak velocities of 1.5
inches per 
second' part. Where does this come in?" 


I'll take a stab at it: 

spectral acceleration = w*(spectral velocity) = (w^2)*(spectral
displacement) 

where: w = 2*pi*f = 2*pi/T 		(in radians) 
f= natural frequency of structure 
T = natural period of structure 

A tripartite response spectrum has a "constant velocity" range in the
mid-range of natural frequencies, at the peak velocity response. So the peak
velocity and natural period should be able to be used with the above formula
to determine effective acceleration: 

w*V = 2*pi*V/T 

where V = spectral velocity 

If you divide this quantity by 386 in/s^2, you get the result in terms of
"g's":

2*pi*1.5/(386*T) = 0.024g/T

The value 0.024g should roughly correspond to BOCA's "effective peak
velocity-related acceleration", Av.  


William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 


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