5 - 25M

10M @ 400mm c/c

10M @ 400mm c/c

545

730

5 - 25M

Duct bank reinforcement Details for 6- 125mm duct:

Reinforcement for duct bank shall be provided as the figure below:

Plan showing location for 6-125mm duct bank.

Maximum settlement or deflection calculation:

Sc= Settlement of clay soil

Cc= Compression Index

eo= initial void ratio

H= Thickness of clay layer

σo= Initial Over burden pressure

Δσ= Extra pressure due to new construction.

Wl= Liquid limit = 60% (assumed)

W= water content =50% [assumed]

S= Saturated condition=1.0 [assumed]

G= Specific Gravity of soil= 2.7 [assumed]

Live load Calculation:

The pressure transmitted to the pipe from highway load, WL= 8600 N/m (Considering AASHTO

HS20 Loading.

This load has been considered for depth 2.3m.

Impact load:

Impact load factor is considered 1.0. (For more than 3 ft depth for Highway road as per AASHTO)

Self weight of the duct bank:

Duct bank self weight= 23.55x (0.730x0.550-6x0.781x.1252) =7.73 kN/m

Initial Over burden pressure, σo

σo=ɣsatxH/2=16.9x2.3/2=19.43 kN/m2

Extra pressure due to new construction:

545

730d1

d1

Settlement of soil/ deflection of duct bank:

Moment calculation for duct bank:

Δmax=17mm,

=20163 MPa

Moment of inertia for duct bank section,

=9.13x10-3 m4

Length of the deflection l=12m

Longitudinal reinforcement Calculation for duct bank:

Provide 5 nos 25M for both top and bottom

Shear Force for duct bank:

5 - 25M

10M @ 400mm c/c

10M @ 400mm c/c

545

730

5 - 25M

Shear streess on the section,

Shear resistance by the concrete,

Compressive strength of the concrete 21 MPa.

So transverse reinforceemnt is not required.

Mimimum transverse reinforceemnt ,

Yield strength of transverse reinforcement= 400 MPa

Spacing of transeverse reinforceemnt = 400mm

Withd of the section, bw= 730mm

Summary of the duct bank design:

Compressive strength of concrete, =21 MPa

Yield strength of longitudinal and transverse reinforcement= 400 MPa

Longitudinal Reinforcement= 5 Nos 25 M on top and bottom of the duct bank section

Transverse reinforceemnt 10M @400mm c/c both top and bottom.