Supporting Live Load an a Mechanical Duct 1

[tdstructural]

I have to design gravity and seismic support for a small platform approximately 4’ wide x 17’ long. The platform is along the side of a boiler and will be used by employees to maintain some small mechanical units.

We are having problems fitting the platform into the structure because of the numerous ducting/insulation/mech units around it. We are considering using a large steel duct to transfer the platform forces to the structural steel columns. The steel duct will be fabricated out of ASTM A36 flat plate and it is about 3’ deep and 5.5’ wide.

I know I can design the duct to be able to carry the loads (it might need stiffeners) but is there anything in the code that does NOT allow this. The duct will be transferring heated air at about 0.25 psi pressure. My concern is carrying live load on a mechanical duct. I’ve never heard of anyone doing this.

Thanks

 

[JStephen]

In tank and vessel work, it is fairly common to support access platforms off the tanks and vessels- usually just for access on the item itself, as opposed to access for other items. And fairly common to hang piping or whatever from them, too. There are provisions in the vessel codes for local loading due to attachments. I don't know what code ductwork like that would fall under, if any.

You might check into deflection of the duct due to pressure or thermal movement and also possible vibration.

 

[msquared48]

It's mice to be re-assured that something mechanical can support something structural.

Mike McCann
MMC Engineering

 

[racookpe1978]

Hey! I'd never use mice to support something up high! (Rats, maybe. Raccoons? Sure. Opossums? Nah - They're too squirrelly.) 8<)

 

[csd72]

Mike,

yeah, its about time that the ME's 'gave something back'

 

[a2mfk]

I know this is not really related, but is it possible there are any ducts in a typical office building that could support someone's weight? IE, TV and movies often show someone crawling through ductwork, like in Diehard I think, and I always think that is complete BS since most ducts I have seen are hung with very light gauge straps and maybe a couple of screws to the roof/floor structure.

I know, the original OP was not about this, and the ductwork is for some heavy duty stuff, not typical building ductwork.....