How to prevent/minimize wind moments from reaching the footing/pier 1

[shaukat1]

I have a problem with a footer design. There is a wind moment of about 10000.00 lbf-ft coming from an isolated column (connected to flexible wood frame shallow truss). I do not want the moment transferred to the footer because then the footer size becomes substantial. Is there a way of
accomplishing this ?

I noticed that some light standards(structural tubes or pipe columns about 30 ' to 40 ' high,cantilevers) are supported by a plate. The plate will have typically 4 - 1/2" to 5/8"
anchor bolts that descend into the pier. There is an air space of about 4" to 5" between the bottom of the plate and the top of the pier. I wondered why ! Is this arrangement to stop moment from going down to the pier/footer ?
I will appreciate very much if someone could enlighten/help me on this. A technical reference or actual design example will be very helpful. Thanking you in advance.

 

[JAE]

The air space between the column/pole base plate and the top of a concrete pier is not to avoid moment. You cannot avoid moment in the pier that way.

If the isolated column is the only structural element that is resisting the lateral wind coming in from the truss above, the only way to prevent this is to provide some other load path for the wind to get down to the foundation without bending the column. This is usually done by providing lateral bracing (such as X bracing) between two columns. This re-directs the lateral force at the roof (or whatever level the truss is at) to the lower level using axial loads in the braces. At the foundation, you then have vertical and horizontal forces at the top of the pier/foundation to deal with - and not a moment in the pier.

This is pretty basic structural design. I would suggest you meet with someone personally who can further assist you directly.