Baseplates...Typical Detail for Highway Sign 1

[asixth]

Hi guys,

I have quite a large highway sign that is behaving like a massive sail in the wind, picking up a large base shear and overturning moment.

The steel post is approximatley 300 dia (1' dia circular). A typical highway post is detailed such that there are four (4) hold down anchors. I need to increase this so I can get it to work and was wondering whether anyone has some typical baseplate designs for highway posts, in terms of stiffener plate and bolt locations etc.

Any help would be appreciated.

 

[JedClampett]

If you look at some of the state DOT websites, they have typical details for their cantilever signs. For instance, Texas has a monotube detail (ftp://ftp.dot.state.tx.us/pub/txdot-info/cmd/cserve/standard/traffic/mc.pdf). Of course, you'll have to check it for your conditions, but it gives you an idea of what's possible. And if anyone complains, you can point them at the detail.
A 12 inch post will be very difficult to anchor.

 

[hogan666]

Washington state has a link to every states DOT standard plans. I have found this to be a very useful resource. You can go over the different designs for overhead signs. As you can see there are many variations on this design.

http://www.wsdot.wa.gov/Design/Standards/OtherStates.htm

 

[asixth]

Thanks guys,

I will need to get a copy of AASHTO, does that have any standard designs or is it just a code.

 

[msquared48]

Primarily just a code.

Mike McCann
MMC Engineering

 

[asixth]

I have a highway sign very similar to that of the New Jersey standard design. I am going to design the baseplate like Texas above.

Just a question with the truss. They are fabricated out of Circular Hollow Sections, how are these connected. I assume they need to be welded but how would you provide vent holes for galvanising.

Secondly, is the higway sign connected to the steel frame or or brackets connected to the frame which can then support the signage.

Thanks for the standard DOT designs. My department of transport doesn't have a highway sign of this size.

 

[csd72]

I would suggest levelling nuts under that baseplate to ease construction.

 

[JedClampett]

As far as fabrication, the fabricators have techniques to fit up the ends. If you have a copy of Blodgett, "Design of Welded Structures", Chapter 5 goes into more detail than you'll ever need, unless you're opening a shop.
For venting the members, if you have a sign, you'll probably want power for lights. So a continuous path for cables is desirable. If you have a hole at every tube-to-tube connection and an access hole at the base (see the TX details) that might do the job. Anyway, the galvanizer is cognizent of venting and will be on the lookout for improperly vented members. They don't like explosions in their vats of 800 degrees molten zinc.