Electrical Duct-Bank Concrete Encasement Volume
Concrete for an electrical duct bank - the encasement around a bundle of conduits.
Example
You enter
- Duct-bank envelope width (ft) 2
- Duct-bank envelope height (ft) 1.5
- Run length (ft) 100
- Number of conduits in the bank 6
- Conduit actual outside diameter (in) 4.5
- Waste allowance (percent) 5
You get
- Net area (ft²) 2.337
- Volume (cy) 8.66
- Concrete to order 9.09 cy (with waste)
Details, formula, and sources
Net area = bank width x height - conduits x pi/4 x OD^2; volume = net area x length / 27. A 24 x 18 in bank around six 4.5 in-OD conduits over 100 ft is 8.66 cy (9.1 cy with 5% waste); a bigger 30 x 24 in bank is 16 cy - the envelope, not the conduits, drives the pour. Order right so it finishes in one continuous lift with no cold joint; the engineer sets the encasement.
net_area_ft2 = bank_width_ft x bank_height_ft - num_conduits x (PI/4) x (conduit_od_in/12)^2; volume_cy = net_area_ft2 x length_ft / 27; ordered_cy = volume_cy x (1 + waste_pct/100).
Duct-bank encasement identity by name (bank cross-section minus conduits, times the run); first-principles volume arithmetic.
The encasement geometry is public quantity-survey arithmetic; the mix and encasement dimensions come from the engineer and AHJ.
Estimate. AHJ and licensed professional govern.
Field names used by the API: bank_width_ft, bank_height_ft, length_ft, num_conduits, conduit_od_in, waste_pct, net_area_ft2, volume_cy, ordered_cy
- Conduit OD the actual outside diameter, not the trade size (a 4-in conduit is ~4.5 in OD)conduit manufacturer
- Encasement the bank envelope and mix (often red-dyed concrete or flowable fill) come from the engineer and AHJengineer / AHJ