DETAIL DESIGN OF O/D CABLE TRENCH SECTIONS AS PER INDIAN STANDARD CODE OF PRACTICE

INPUT PARAMETERS:

Self-weight of concrete of grade M20 = 25.00Self-weight of cable over the tray 1.15 kg/RmWide of tray excluding earth bus weld portion, L1 = 450.00 mmSelf weight of the angle 50x50x6 = 4.50 kg/Rm [SP:6(1) pp. 155]

Unit weight of MS steel = 78.5018.00 kN/m320.00 deg. 0.3490659 rad.

Bearing capacity of the soil, SBC = 120.00Depth of water table from top of the cover slab, Dw = 0.50 meterEGL to top of cover plate height = 0.20 meter

PRELIMINARY DIMENSION CHOSEN:Thickness of the base slab = 150 mmThickness of the side wall = 100 mmThickness of the cover slab = 100 mm

3 rowsTotal width of tray = 500.00 mmClearance between the two tray = 600 mmInternal width of the trench = 1600 mmInternal clear height of the trench = 850 mm

Spacing of Insert Plate = 1500 mm

kN/m3

kN/m3

Unit weight of soil, γ =Φ =

kN/m2

Rows of tray (MS angle), nr =

=((nr-1)x250)+250+100

Number of 25mm diameter cables placed in two tierson a 500mm wide tray = 40 nos.

DESIGN OF CABLE TRAY:

Properties of section (unit mm) areaISA50506 568 14.5 1.29E+05 15.1 3.60E+03

Weight of Cable at each angle support point = 0.690 kNWeight of 3mm thick cable tray = 0.177 kNWeight of support angle ISA50506 = 0.023 kN

Total = 0.889 kNthis load acts at 250mm from face of Insert plate (c.g.)

Total moment due to this load at Insert plate= 0.667 kNmFACTORED MOMENT = 1.000 kNmResisting moment of tray = 1.782 kNm HENCE, SAFE

The Insert Plate is to be checked against the following two philosophies :The top half portion of the plate shall be checked against Bond Stress with concreteThe bottom half portion of the plate shall be checked against Bearing Stress of SteelProvide 650mmx100mmx6mm thick M.S. plate, so total area = 65000 sq.mmThe tension at upper half portion = 1333.688 N

Actual bond stress at upper half = 0.041

Permissible stress in bond (table21, IS:456-2000) = 0.800 HENCE, SAFE

Yield stress of the M.S. Plate = 250.000

Bearing Stress of plate at lower half = 187.500 HENCE, SAFE

Bearing Stress of concrete at lower half = 5.000 HENCE, SAFE

Since the plate is bonded throughout with concrete, there will be no bending of plate and hence thickness of plate need not be designed.

ANALYSIS AND DESIGN OF COVER SLAB:For simplification, we take one meter strip of the slabSpan of the slab = 1700 mmWidth of the slab taken = 1000 mm

Load per meter due to self weight = 2.5 kN/mLoad per meter due to Live Load = 10 kN/m

Total UDL = 12.5 kN/mFactored UDL = 18.75 kN/m

6.773 kNm

15.938 kNProvide, 100mm thick slab and effective depth (d) =80 mm

Cx =Cy Ix=Iy rx = ry Zx = Zy

N/mm2

N/mm2

N/mm2

N/mm2

N/mm2

Maximum Bending Moment (Mu) =

Maximum Shear Force, (Vu) =

= 1.06

= 0.20Percentage of reinforcement as per Table 2, SP:16 = 0.32

Provide 8 tor bars @225 mm c/c as main steelProvide 8 tor bars @300 mm c/c as distribution steel

ANALYSIS AND DESIGN OF VERTICAL WALL:Calculations are for one meter length of wall

Computation of vetical load per meter length of wall:Self weight of the side wall = 2.125 kNLoad from the cover slab including live load = 6.25 kN

Total load = 8.375 kNFactored load = 12.5625 kN

Active earth-pressure:

0.490

3.188 kNC.G. of pressure diagram above base of wall = 0.283 m Moment at base of the wall due to earth pressure = 0.903 kNm

Factored moment = 1.355 kNm

Force on wall from cable tray:Factored moment per meter length of wall due to cable tray as calculated above in the designof various parts of cable tray = 1.000 kNm

Total factored moment at base of vertical wall per meter length = 2.355 kNmTotal factored vertical load at base of wall per meter length = 12.563 kN

Considering per meter length of wall to act as Column

0.0062813

0.0117761Percentage of reinforcement as per Chart 34, SP:16 = 0% Steel

Provide 8 tor bars @150 mm c/c as main steelProvide 8 tor bars @250 mm c/c as distribution steel

ANALYSIS AND DESIGN OF BASE SLAB:Calculations are for one meter length of wall

12.5625 kN 12.5625 kN

2.355 kNm 2.355 kNm

Mu/bd2

Vu/bd

Coefficient of active earth pressure, Ka =

Total area of pressure diagram, Pa =

Pu/fckbD =

Mu/fckbD2 =

3.204 kN/m1800 mm

Factored self weight of the base slab = 10.125 kNFactored downward udl due to self weight = 5.625 kN/m

Height of the water table above bottom of base slab = 0.6 meterUplift pressure on base slab = 5.886 kN/mFactored upward udl due buoyant force = 8.829 kN/m

Net Factored upward force on base slab = 3.204 kN/mMaximum base pressure on soil = 25.125 kN/m HENCE, SAFE

1.29762 kNm

2.8836 kN

= 0.0767822

= 0.0221815Percentage of reinforcement as per Table 2, SP:16 = 0

Provide 8 tor bars @150 mm c/c as main steelProvide 8 tor bars @250 mm c/c as distribution steel

Net maximum bending moment at mid-span, Mu=

Net maximum shear force, Vu =

Mu/bd2

Vu/bd

PROJECT:CONSTRUCTION OF 400KV G.S.S.

LOCATION: JAISALMERTITLE: SWYAD CABLE TRENCH

TYPE-CCLIENT: RAJ. RAJYA VIDYUT

NIGAM.

INPUT PARAMETERS:

Self-weight of concrete of grade M20 = 25.000Self-weight of cable over the tray 1.150 kg/RmWide of tray excluding earth bus weld portion, L1 = 300.000 mmSelf weight of the angle 50x50x6 = 4.500 kg/Rm [SP:6(1) pp. 155]

Unit weight of MS steel = 78.50018.000 kN/m320.000 deg.

Bearing capacity of the soil, SBC = 120.000Depth of water table from top of the cover slab, Dw = 1.000 meterEGL to top of cover plate height = 0.275 meter

PRELIMINARY DIMENSION CHOSEN:Thickness of the base slab = 150 mmThickness of the side wall = 100 mmThickness of the cover slab = 60 mm

6 rowsTotal width of tray = (300+50)= 350.00 mmClearance between the tray & wall= 350 mmInternal width of the trench = (350+350)= 700.00 mmInternal clear height of the trench = 1300 mm

Spacing of Insert Plate = 1500 mmNumber of 25mm diameter cables placed in two tiersona350mmwidetray= 28 nos.

DESIGN OF CABLE TRAY:

Properties of section (unit mm) areaISA50506 568 14.5 1.29E+05 15.1 3.60E+03

kN/m3

kN/m3

Unit weight of soil, γ =Φ =

kN/m2

Rows of tray (MS angle), nr =

=((nr-1)x200)+150+150

Cx =Cy Ix=Iy rx = ry Zx = Zy

Weight of Cable at each angle support point = 0.483 kNWeight of 3mm thick cable tray = 0.124 kNWeight of support angle ISA50506 = 0.016 kN

Total = 0.622 kNthis load acts at 175 mm from face of Insert plate (c.g.)

Total moment due to this load at Insert plate= 0.654 kNmFACTORED MOMENT = 0.980 kNmResisting moment of tray = 1.782 kNm HENCE, SAFE

The Insert Plate is to be checked against the following two philosophies :The top half portion of the plate shall be checked against Bond Stress with concreteThe bottom half portion of the plate shall be checked against Bearing Stress of SteelProvide 1100mmx100mmx6mm thick M.S. plate, so total area = 110000 sq.mmThe tension at upper half portion = 1867.162 N

Actual bond stress at upper half = 0.034

Permissible stress in bond (table21, IS:456-2000) = 0.800 HENCE, SAFE

Yield stress of the M.S. Plate = 250.000

Bearing Stress of plate at lower half = 187.500 HENCE, SAFE

Bearing Stress of concrete at lower half = 5.000 HENCE, SAFE

Since the plate is bonded throughout with concrete, there will be no bending of plate and hence thickness of plate need not be designed.

ANALYSIS AND DESIGN OF COVER SLAB:For simplification, we take one meter strip of the slabSpan of the slab = 800 mmWidth of the slab taken = 1000 mm

Load per meter due to self weight = 1.5 kN/mLoad per meter due to Live Load = 10 kN/m

Total UDL = 11.5 kN/mFactored UDL = 17.25 kN/m

1.380 kNm

6.900 kNAssume effective depth of the cover slab (d)= 40 mm

= 0.86

= 0.17Percentage of reinforcement as per Table 2, SP:16 = 0.099Provide 8 tor bars @ 225 c/c main 0.372148 (percent provided)Provide 8 tor bars @ 300 c/c distribution steel

N/mm2

N/mm2

N/mm2

N/mm2

N/mm2

Maximum Bending Moment (Mu) =

Maximum Shear Force, (Vu) =

Mu/bd2

Vu/bd

ANALYSIS AND DESIGN OF VERTICAL WALL:Calculations are for one meter length of wall

Computation of vetical load per meter length of wall:Self weight of the side wall = 3.25 kNLoad from the cover slab including live load = 5.75 kN

Total load = 9 kNFactored load = 13.5 kN

Active earth-pressure:

0.490

7.457 kNC.G. of pressure diagram above base of wall = 0.433 m Moment at base of the wall due to earth pressure = 3.232 kNm

Factored moment = 4.847 kNm

Force on wall from cable tray:Factored moment per meter length of wall due to cable tray as calculated above in the designof various parts of cable tray = 0.980 kNm

Total factored moment at base of vertical wall per meter length = 5.828 kNmTotal factored vertical load at base of wall per meter length = 13.500 kN

Considering per meter length of wall to act as Column

0.00675

0.029138Percentage of reinforcement as per Chart 34, SP:16 = 0.02 % SteelProvide 8 tor bars @ 150 c/c main 0.334933 (percent provided)Provide 8 tor bars @ 250 c/c distribution steel

ANALYSIS AND DESIGN OF BASE SLAB:Calculations are for one meter length of wall

13.5 kN 13.5 kN

5.828 kNm 4.847 kNm

1.87965 kN/m

Coefficient of active earth pressure, Ka =

Total area of pressure diagram, Pa =

Pu/fckbD =

Mu/fckbD2 =

800.00 mm

Factored self weight of the base slab = 4.5 kNFactored downward udl due to self weight = 5.625 kN/m

Height of the water table above bottom of base slab = 0.51 meterUplift pressure on base slab = 5.0031 kN/mFactored upward udl due buoyant force = 7.50465 kN/m

Net Factored upward force on base slab = 1.87965 kN/mMaximum base pressure on soil = 34.97533 kN/m HENCE, SAFE

0.150372 kNm

0.75186 kN

= 0.008898

= 0.005784Percentage of reinforcement as per Table 2, SP:16 = 0.02Provide 8 tor bars @ 150 c/c main 0.223289 (percent provided)Provide 8 tor bars @ 250 c/c distribution steel

WELD DESIGN FOR TRAY TO INSERT PLATE:thickness of the weld for 6mm plate = 3 mmThroat, t = 3x0.75= 2.25 mmlength of the weld, d = 73.33933 mmUsing cleat angle of 50x50x6 we provide welding length = 100 mm

DESIGN FOR BONDING:Design anchorage length of 10mm bars assumed = 100 mmDesign bond strength as per clause 26.2.1.1 for M20 = 1.2 MpaResisting bond strength of the insert plate = 11309.73 NCalculated bond strength required = 1867.162 N HENCE, SAFE

Net maximum bending moment at mid-span, Mu=

Net maximum shear force, Vu =

Mu/bd2

Vu/bd

60350 150

200

200

200 100

200

150150

PROJECT:CONSTRUCTION OF 400KV G.S.S.

LOCATION: JAISALMERTITLE: SWYAD CABLE TRENCH

TYPE-DCLIENT: RAJ. RAJYA VIDYUT

NIGAM.

INPUT PARAMETERS:

Self-weight of concrete of grade M20 = 25.000Self-weight of cable over the tray 1.150 kg/RmWide of tray excluding earth bus weld portion, L1 = 150.000 mmSelf weight of the angle 50x50x6 = 4.500 kg/Rm [SP:6(1) pp. 155]

Unit weight of MS steel = 78.50018.000 kN/m320.000 deg.

Bearing capacity of the soil, SBC = 120.000Depth of water table from top of the cover slab, Dw = 1.000 meterEGL to top of cover plate height = 0.275 meter

PRELIMINARY DIMENSION CHOSEN:Thickness of the base slab = 150 mmThickness of the side wall = 100 mmThickness of the cover slab = 100 mm

1 rows

1 rowsTotal width of tray = 200.00 mmClearance between the tray & wall = 200 mmInternal width of the trench = 400.00 mmInternal clear height of the trench = 400 mm

Spacing of Insert Plate = 1500 mmNumber of 25mm diameter cables placed in two tierson a 200mm wide tray = 16 nos.Number of 25mm diameter cables placed in two tierson continuous tray = 32 nos.

DESIGN OF CABLE TRAY:

kN/m3

kN/m3

Unit weight of soil, γ =Φ =

kN/m2

Rows of tray (MS angle), nr =

Rows of tray (MS angle) continuous, nr1 =

=((nr1+nr-1)x200)+100+100

Properties of section (unit mm) areaISA50506 568 14.5 1.29E+05 15.1 3.60E+03

Weight of Cable at each angle support point = 0.276 kNWeight of 3mm thick cable tray = 0.071 kNWeight of support angle ISA50506 = 0.009 kN

Total = 0.356 kNthis load acts at 100mm from face of Insert plate (c.g.)

Total moment due to this load at Insert plate= 0.071 kNmFACTORED MOMENT = 0.107 kNmResisting moment of tray = 1.782 kNm HENCE, SAFE

The Insert Plate is to be checked against the following two philosophies :The top half portion of the plate shall be checked against Bond Stress with concreteThe bottom half portion of the plate shall be checked against Bearing Stress of SteelProvide 300mmx100mmx6mm thick M.S. plate, so total area = 30000 sq.mmThe tension at upper half portion = 177.825 N

Actual bond stress at upper half = 0.012

Permissible stress in bond (table21, IS:456-2000) = 0.800 HENCE, SAFE

Yield stress of the M.S. Plate = 250.000

Bearing Stress of plate at lower half = 187.500 HENCE, SAFE

Bearing Stress of concrete at lower half = 5.000 HENCE, SAFE

Since the plate is bonded throughout with concrete, there will be no bending of plate and hence thickness of plate need not be designed.

ANALYSIS AND DESIGN OF COVER SLAB:For simplification, we take one meter strip of the slabSpan of the slab = 500 mmWidth of the slab taken = 1000 mm

Load per meter due to self weight = 2.5 kN/mLoad per meter due to Live Load = 10 kN/m

Total UDL = 12.5 kN/mFactored UDL = 18.75 kN/m

0.586 kNm

4.688 kNProvide, 100mm thick slab and effective depth (d) =80 mm

= 0.09

= 0.06

Cx =Cy Ix=Iy rx = ry Zx = Zy

N/mm2

N/mm2

N/mm2

N/mm2

N/mm2

Maximum Bending Moment (Mu) =

Maximum Shear Force, (Vu) =

Mu/bd2

Vu/bd

Percentage of reinforcement as per Table 2, SP:16 = 0.075Provide 8 tor bars @ 250 c/c main 0.20096 (percent provided)Provide 8 tor bars @ 300 c/c distribution steel

ANALYSIS AND DESIGN OF VERTICAL WALL:Calculations are for one meter length of wall

Computation of vetical load per meter length of wall:Self weight of the side wall = 1 kNLoad from the cover slab including live load = 6.25 kN

Total load = 7.25 kNFactored load = 10.875 kN

Active earth-pressure:

0.490

0.706 kNC.G. of pressure diagram above base of wall = 0.133 m Moment at base of the wall due to earth pressure = 0.094 kNm

Factored moment = 0.141 kNm

Force on wall from cable tray:Factored moment per meter length of wall due to cable tray as calculated above in the designof various parts of cable tray = 0.107 kNm

Total factored moment at base of vertical wall per meter length = 0.248 kNmTotal factored vertical load at base of wall per meter length = 10.875 kN

Considering per meter length of wall to act as Column

0.005438

0.001239Percentage of reinforcement as per Chart 34, SP:16 = 0.02 % SteelProvide 8 tor bars @ 150 c/c main 0.334933 (percent provided)Provide 8 tor bars @ 250 c/c distribution steel

ANALYSIS AND DESIGN OF BASE SLAB:Calculations are for one meter length of wall

10.875 kN 10.875 kN

0.248 kNm 0.141 kNm

Coefficient of active earth pressure, Ka =

Total area of pressure diagram, Pa =

Pu/fckbD =

Mu/fckbD2 =

-10.77525 kN/m500.00 mm

Factored self weight of the base slab = 2.8125 kNFactored downward udl due to self weight = 5.625 kN/m

Height of the water table above bottom of base slab = -0.35 meterUplift pressure on base slab = -3.4335 kN/mFactored upward udl due buoyant force = -5.15025 kN/m

Net Factored upward force on base slab = -10.77525 kN/mMaximum base pressure on soil = 43.71339 kN/m HENCE, SAFE

-0.336727 kNm

-2.693813 kN

= 0.0199

= 0.0207Percentage of reinforcement as per Table 2, SP:16 = 0.02Provide 8 tor bars @ 150 c/c main 0.223289 (percent provided)Provide 8 tor bars @ 250 c/c distribution steel

Net maximum bending moment at mid-span, Mu=

Net maximum shear force, Vu =

Mu/bd2

Vu/bd