Space Frame Help 1

[2jb]

I was wondering if anyone could help me with estimating the cost of a space frame (ROM ok). Preliminary drawings of the space frame are attached (3 pages). Any help would be greatly appreciated. I work for an organization where I cannot easily pick the brain of a fabricator (gov't, I cannot sole-source or contact potential subcontractors). I don't feel that typical off-shelf estimating will do this justice and was hoping someone might have some experience with a similar structure.

Any thoughts on the design are appreciated too...

Thanks for your time,

Josh Brunson, PE
Structural Engineer
NAVFAC

 

[JedClampett]

I've found that for steel, no matter how complex, that $4000 a ton is always pretty close. For for all the extra welding and cutting a 20% premium is a good idea.
For whatever reason steel is treated as a commodity and you get commodity prices.

 

[2jb]

Thank you for the response.

 

[Larryhd2]

I agree with the $2/lb rule for a general buildings.... but I think these trusses with all the cutting and welding would probably double this, at least for the custom truss portion. You also need to add in all the inspection time for all the welding which isn't in the $2/lb rule and varies widely with location. Inspections aren't normally paid for by the contractor, especially in gov't work, and aren't included in the bid price.

Your drawings are conceptual and the connections will not be easy. If you plan to just attach web tube to the chord tube you need to evaluate bending in the wall of the chord tube to distribute the load. I'm guessing the 1/2" wall thickness won't be adequate in some areas necessitating a cover plate. You might look at pipes for the chords rather than tubes and/or using knife plates for the connections that distribute the load over a larger length of the wall of the chord.

I'm assuming NAVFAC is naval facilities and this looks to be an aircraft hanger. I'm sure there are plenty of these types of facilities in your library. Maybe you could look at the cost breakdown of some of those facilities to get a better sense of cost? You would need to break out the steel cost and adjust based on steel price as that number varies widely. Other costs you might just do an inflation adjustment...... this would be my approach, but I'm not an estimator....

Looks to be a fun project....