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Re: Building Natural Frequency

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Title: Building Natural Frequency
Simpler but no right at all is the sum of each  column stifness  by story.
Please see formula for multistory buildings with modal participation factors.
Or You can try with simplified formula :
T=0,09 .  [ (  H  /  L ^ 0.50 ) ] ^0.50    for concrete frames
T=0.10   H  / (L^ 0.50)   steel frames
H: total height of building
L= lenght of building in the considered direction
Fabio Zárate
Civil Structural Engineer
ZYZ Consultores
----- Original Message -----
Sent: Monday, July 08, 2002 12:35 PM
Subject: Building Natural Frequency

I am curious how everybody comes up with the natural frequency of a building.
Does everybody have to input every building into a structural software
package to get this? All of the new codes I have seen require frequency in
order to calculate wind and seismic loads.  Even the simplified methods
require this.  How does everybody handle this for small buildings, or where
an existing building needs to be modified?

I know the equations and theory behind finding the natural frequency.  I
am just looking for how this is found practically.  Since the natural frequency
is (k/m)^1/2, I can find the mass of the building fairly easily, but the stiffness
of the whole building is much harder.  You almost need to input it into some
sort of structural package to get this.  How do others handle this?

Zachary Goswick, P.E.
Structural Engineer
Angus-Young Associates, Inc.
555 South River Street
Janesville, WI  53545-4827
Phone: (608)756-2326
Fax: (608)756-0464
Email: zachg(--nospam--at)