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Fundamental frequency of a single-pole sign structure

Fundamental frequency of a single-pole sign structure

Fundamental frequency of a single-pole sign structure

(OP)
In order to determine wind loads using ASCE 7, there seems to be adequate information available regarding fundamental frequency and damping ratios for flexible buildings.

However, in researching, I have not been able to find a good reference for calculating these factors, nor a table or chart referencing suggested values for single-pole sign structures.

Can anyone point me in the right direction?

RE: Fundamental frequency of a single-pole sign structure

Force on Components and Cladding
ASCE 7-98, Equation 6-20; F=qz*G*Cf*Af

The values of qz  (velocity pressure evaluated at height z of the centroid area of Af) are the same as MWFRS except the value of G = 0.85. The design forces can be determined using appropriate Cf (net force coefficients from tables 6-9 through 6-12) and Af  (area normal to wind) for each component.

tip: divide your sign into height increments such as 0 to 30 ft, 31 to 60 ft., etc., to find total load.

Guide To The Use of The Wind Load Provisions of ASCE 7-98 (also available for 7-02) published by ASCE is an excellent reference for wind load calculations.

RE: Fundamental frequency of a single-pole sign structure

(OP)
Thanks ERV.

However, for designing the main sign structure (pole and foundation), it is not considered components and cladding, and "G" must be determined based upon a flexible or rigid structure (per Section 6.5.8).

Thus, my original question re: where can I find a good source for fundamental frequency and damping ratio, for single pole sign structures.

RE: Fundamental frequency of a single-pole sign structure

Correct. If the structure has a fundamental frequency less than 1 Hz. it is considered a flexible structure, and the gust factor G = Gf, will be calculated per 6.5.8.2 Flexible or Dynamaically Sensitive Structures (ASCE 7-98). Gf = 0.925 (Equation 6-6).

Try this link:

www.geocities.com/lpittack/cae614proj.html

RE: Fundamental frequency of a single-pole sign structure

(OP)
Thank you ERV.
You have been most helpful. And thanks for the quick response.

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