Duct Bank Reinforcing 1

[IsaacStructural]

Question came from an electrical engineer. For a cast in place underground electrical duct bank, that doesn't go underneath a road or other specific load source, are there guidelines for reinforcing/not reinforcing these? I could see adding temperature and shrinkage steel to make the thing stay solid, but I'm wondering, is that industry standard?

Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[SlideRuleEra]

Steel reinforced duct banks is standard practice at electrical generating stations.

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[IsaacStructural]

Yeah I was aware of this in the power industry, I'm wondering about smaller commercial applications, elementary schools, those sort of buildings.

Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[TDIengineer]

From my experience an electrical duct bank requires no reinforcing.

We have provided on limited cases where the duct bank ended up being load bearing from a footing placed over it.
My experience is in healthcare and education design, what you are describing.

 

[IsaacStructural]

Thanks TDI, do you typically get involved in these at all? Do you specify the concrete strength, review mixes, etc?

Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[TDIengineer]

Usually the specification provided by the electrical engineer address this issue. No I steer clear as it is not a structural item. The concrete is simply protection for the conduits. I would have my concrete spec 03300 defer to site concrete for the duct encasement.

I have seen specs include a red dye in the concrete where the ductbank has emergency power. And I have seen notes to provide reinforcement within the ductbank if it will be subject to heavy vehicular loading. Also possibly where the duct bank crosses dissimilar soil types.

2,000 psi concrete is adequate for most cases. Where heavily loaded, provide 3,000 and reinforce.