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RE: Building Natural Frequency

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Title: RE: Building Natural Frequency

Wind Loads calculated in accordance with IBC2000 refer to ASCE7-98.
ASCE7-98 has two methods, the Simplified Procedure and the Analytical Method.
In order to use the simplified procedure, the building cannot be classified
as a flexible building (natural frequency less than 1Hz).  To figure out
if you can use the simplified method, you must figure out the natural
frequency.  If you choose to use the Analytical Method, you are still required
to calculate the frequency in order to calculate the Gust Effect Factor.  Either
way you are required to calculate the building natural frequency. 

I should revise my statement.  IBC2000 and ASCE 7-98 require building frequency
to be calculated for wind loads.  I am not sure how UBC handles this.


-----Original Message-----
From: Ron Hill [mailto:ronhill(--nospam--at)]
Sent: Monday, July 08, 2002 3:22 PM
To: seaint(--nospam--at)
Subject: RE: Building Natural Frequency

>I am curious how everybody comes up with the natural frequency of a
>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.

For tall (multi story ) structures I use a software program.  For one story
where the roof loads are normal, I use simple formulas.

Where is the natural frequency required for building wind loads???  I have
determined frequencies for stack design and vortex shedding but never for
building designs.

Ronald Hill, P.E.
HILL Consulting Engineering
PO BOX 26525
Birmingham, Alabama 35260 USA
Phone: 205.823.4784
FAX: 205.823.4145
Email: ronhill(--nospam--at)
Efax: 509.275.8095

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