Wind Load on Solid Signs

[Thawkes]

The firm where I work regularly designs large solid signs. We compute wind load using ASCE 7 - 05 Chapter 6. Do we have to compute a single wind pressure based on the elevation of the top of the sign or can we break up the sign into segments and use variable pressure based on the elevation of each segment? Thanks in advance.

 

[ToadJones]

From the code it appears that the velocity pressure is evaluated at a height equal to the top of the sign.
As for the design of the actual sign panel itself, I am not sure under which part of the code that would fall exactly...maybe components and cladding.
Oddly enough, we are usually complaining that the wind code is too complicated, and here we have a case where it seems to be straight forward and you want to make it more complicated :-D

 

[TTUengr51]

The company I work for has a sign engineering division (

http://www.sign-engineer.com)

and we perform on average over 1500 sign projects in a given year throughout all 50 states. Our design philosophy is to vary the wind pressure as the height increases. We calculate the Kz factor based upon top elevation of each individual section. Each segment also has a different Cf factor based upon geometry.

The Kz factor determination we use may be somewhat conservative since I have seen others use the centroid height of a segment for the Kz determination.

However, I think using the overall height for one Kz value for the entire height is too conservative.

Nick Deal, P.E.
Michael Brady Inc.

http://www.michaelbradyinc.com