Reinforced Concrete Ductbank Under Building Footing

strap89

Member
Is it true that no matter how large a building is that the foundation will be designed for a typical pressure related to a soil type? A footing may be designed around 5000 psf foot for a high rise or a three story office building on the same type of soil, you would just expect larger or more footings on a taller building. Correct?

Related to a concrete encased and rebar enforced conduit ductbank passing 3' or so under a 5000 psf footing, it seems like to me there would be little risk of crushing this ductbank. If my concrete is rated for 3000 psi, I would think compression strength would be more than enough to handle this load. Maybe there are complications with tensile and shear forces? Has anyone seen a ductbank run directly under a large footing before? Obviously not ideal, but I could see certain situations where you have no choice given the location of an equipment room and the conditions of the foundation design.
 

strap89

Member
Yeah, I'm asking in regards to an electrical ductbank, structural engineer says it's ok. Hoping an old timer on the forum maybe had some words of wisdom or first hand experience after a long career of running ductbank.
 

Julius Right

Senior Member
Occupation
Electrical Engineer Power Station Physical Design Retired
The duct bank behaves like a beam standing free on 2 manholes.
No other force except the its weight will exert on it.
The footing has to be provided with a window through which the duct bank
will pass free and never touch neither the top nor the bottom of the window.
 

Attachments

ramsy

Owner/Operator
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
Whats wrong with pipe raceways, especially since pipe would fit thru smaller windows in the building footing?
 
... you would just expect larger or more footings on a taller building. Correct?
Absolutely. Footings are designed to support the planned load in the existing environment, that's why some buildings sit on 150+ foot piles, occasionally driven to bedrock, and some on 3' of concrete resting on dirt.

This is really a civil engineering question.
 
Top