DETAIL DESIGN OF O/D CABLE TRENCH SECTIONS AS PER INDIAN STANDARD CODE OF PRACTICE
INPUT PARAMETERS: Self-weight of concrete of grade M20 = Self-weight of cable over the tray Wide of tray excluding earth bus weld portion, L1 = Self weight of the angle 50x50x6 =
3
kN/m kg/Rm mm kg/Rm
[SP:6(1) pp pp. 15 155]
3
Unit weight of MS steel = Unit weight of soil, γ = Φ=
Bearing capacity of the soil, SBC = Depth of water table from top of the cover slab, Dw = EGL to top of cover plate height =
PRELIMINARY DIMENSION CHOSEN: Thickness of the base slab = Thickness of the side wall = Thickness of the cover slab = Rows of tray (MS angle), nr = Total width of tray = Clearance between the two tray = Internal width of the trench = Internal clear height of the trench = =((nr-1)x250)+250+100 Spacing of Insert Plate = Number of 25mm diameter diameter cables placed in two tiers on a 500mm wide tray = DESIGN OF CABLE TRAY:
25.00 1.15 450.00 4.50
78.50 kN/m 18.00 kN/m3 20.00 deg. 2
120.00 kN/m 0.50 meter 0.20 meter
150 100 100 3 500.00 600 1600 850
mm mm mm rows mm mm mm mm mm
1500 mm 40 nos.
0.349066 rad.
Properties of section (unit mm) ISA50506
area 568
Cx =Cy
Ix=Iy
rx = ry
Zx = Zy
14.5
1.29E+05
15.1
3.60E+03
Weight of Cable at each angle support point = 0.690 kN Weight of 3mm thick cable tray = 0.177 kN kN Weight of support angle ISA50506 = 0.023 kN kN Total = 0.889 kN kN this load acts at 250mm from face of Insert plate (c. g.) Total moment due to this load at Insert plate= FACTORED MOMENT = Resisting moment of tray =
0.667 kNm 1.000 kNm 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 concrete The bottom half portion of the plate shall be checked against Bearing Stress of Steel Provide 65 650mmx100mmx6mm thick M.S .S.. pl plate, so so total are reaa = 65000 sq.mm The tension at upper half portion = 1333.688 N 2
Actual bond stress at upper half =
0.041 N/mm
Permissible stress in bond (table21, IS:456-2000) =
0.800 N/mm
2
2
Yield stress of the M.S. Plate =
250.000 N/mm
Bearing Stress of plate at lower half =
187.500 N/mm
Bearing Stress of concrete at lower half =
HENCE, SAFE
2
HENCE, SAFE
2
HENCE, SAFE
5.000 N/mm
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 slab Span of the slab = Width of the slab taken =
1700 mm 1000 mm
Load per meter due to self weight = Load per meter due to Live Load = Total UDL = Factored UDL =
2.5 10 12.5 18.75
kN kN/m kN kN/m kN/m kN/m
Maximum Bending Moment (M u) =
6.773 kNm
Maximum Shear Force, (Vu) = 15.938 kN Provide, 100mm thick slab and effective depth (d) =80 mm 2
Mu /bd
=
Vu /bd = Percentage of reinforcement as per Table 2, SP:16 = Provide 8 tor bars @225 mm c/c as main steel Provide 8 tor bars @300 mm c/c as distribution steel
1.06 0.20 0.32
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 = Load from the cover slab including live load = Total load = Factored load =
2.125 6.25 8.375 12.5625
Active earth-pressure: earth-pressure: Coefficient of active earth pressure, K a =
0.490
Total area of pressure diagram, Pa = C.G. of pressure diagram above base of wall = Moment at base of the wall due to earth pressure = Factored moment =
3.188 0.283 0.903 1.355
kN kN kN kN
kN m kNm kNm
Force on wall from cable tray: Factored moment per meter length of wall due to cable tr ay as calculated above in the design of various parts of cable tray = 1.000 kNm Total factored moment at base of vertical wall per meter length = Total factored vertical load at base of wall per meter length = Considering per meter length of wall to act as Column Pu /f ck bD = 2
Mu /f ck bD = Percentage of reinforcement as per Chart 34, SP:16 =
2.35 2.355 5 kNm kNm 12.5 12.563 63 kN
0.006281 0.011776 0% Steel
Provide 8 tor bars @150 mm c/c as main steel Provide 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
3.20 3.204 4 kN/m kN/m 180 1800 mm Factored self weight of the base slab = Factored downward udl due to self weight = Height of the water table above bottom of base slab = Uplift pressure on base slab = Factored upward udl due buoyant force =
10.125 kN 5.625 kN/m 0.6 meter 5.886 kN kN/m 8 829 kN/m
Net Factored upward force on base slab = Maximum base pressure on soil = Net maximum bending moment at mid-span, M u= Net maximum shear force, V u = 2
Mu /bd
=
Vu /bd = Percentage of reinforcement as per Table 2, SP:16 = Provide 8 tor bars @150 mm c/c as main steel Provide 8 tor bars @250 mm c/c as distribution steel
3.204 kN/m 25.125 kN kN/m 1.29762 kNm 2.8836 kN 0.076782 0.022182 0
HENCE, SAFE
PROJECT: CONSTRUCTION OF 400KV G.S.S. LOCATION: TITLE: CLIENT:
JAISALMER SWYAD CABLE TRENCH TYPE-C RAJ. RAJYA VIDYUT NIGAM.
INPUT PARAMETERS: Self-weight of concrete of grade M20 = Self-weight of cable over the tray Wide of tray excluding earth bus weld portion, L1 = Self weight of the angle 50x50x6 =
25.000 1.150 300.000 4.500
3
kN/m kg/Rm mm kg/Rm
[SP:6(1) pp pp. 15 155]
3
Unit weight of MS steel = Unit weight of soil, γ = Φ=
Bearing capacity of the soil, SBC = Depth of water table from top of the cover slab, Dw = EGL to top of cover plate height =
PRELIMINARY DIMENSION CHOSEN: Thickness of the base slab = Thickness of the side wall = Thickness of the cover slab = Rows of tray (MS angle), nr = Total width of tray = (300+50)= Clearance between the tray & wall= Internal width of the trench = (350+350)= Internal clear height of the trench = =((nr-1)x200)+150+150 Spacing of Insert Plate = Number of 25mm diameter diameter cables placed in two tiers ona350mmwidetray=
78.500 kN/m 18.000 kN/m3 20.000 deg. 2
120.000 kN/m 1.000 meter 0.275 meter
150 100 60 6 350.00 350 700.00 1300
mm mm mm rows mm mm mm mm mm mm
1500 mm 28 nos.
DESIGN OF CABLE TRAY: Properties of section (unit mm) ISA50506
area 568
Weight of Cable at each angle support point = Weight of 3mm thick cable tray = Weight of support angle ISA50506 =
Cx =Cy
Ix=Iy
rx = ry
Zx = Zy
14.5
1.29E+05
15.1
3.60E+03
0.483 kN 0.124 kN kN 0.016 kN kN
this load acts at
Total = 0.622 kN kN 175 mm from face of Insert plate (c.g.)
Total moment due to this load at Insert plate= FACTORED MOMENT = Resisting moment of tray =
0.654 kNm 0.980 kNm 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 concrete The bottom half portion of the plate shall be checked against Bearing Stress of Steel Prov Pr ovid idee 110 1100m 0mm mx1 x100 00m mmx6 x6m mm th thic ick k M. M.S. S. pl plat ate, e, so to tota tall are areaa = 1100 11 0000 00 sq.mm The tension at upper half portion = 1867.163 N 2
Actual bond stress at upper half =
0.034 N/mm
Permissible stress in bond (table21, IS:456-2000) =
0.800 N/mm
2
2
Yield stress of the M.S. Plate =
250.000 N/mm
Bearing Stress of plate at lower half =
187.500 N/mm
Bearing Stress of concrete at lower half =
HENCE, SAFE
2
HENCE, SAFE
2
HENCE, SAFE
5.000 N/mm
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 slab Span of the slab = Width of the slab taken =
800 mm 1000 mm
Load per meter due to self weight = Load per meter due to Live Load = Total UDL = Factored UDL =
1.5 10 11.5 17.25
Maximum Bending Moment (M u) =
1.380 kNm
Maximum Shear Force, (Vu) = Assume effective depth of the cover slab (d)=
6.900 kN 40 mm
2
Mu /bd
=
kN kN/m kN kN/m kN/m kN/m
0.86
Vu /bd = 0.17 0.099 Percentage of reinforcement as per Table 2, SP:16 = Provide c/c mai main n 0.37 0.372 2148 148 (per (perce cen nt pro prov vided ided)) 8 tor bars @ 225 c/c 8 tor bars @ 300 c/c distribution steel Provide
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 = Load from the cover slab including live load = Total load = Factored load =
3.25 5.75 9 13.5
Active earth-pressure: earth-pressure: Coefficient of active earth pressure, K a =
0.490
Total area of pressure diagram, Pa = C.G. of pressure diagram above base of wall = Moment at base of the wall due to earth pressure = Factored moment =
7.457 0.433 3.232 4.847
kN kN kN kN
kN m kNm kNm
Force on wall from cable tray: Factored moment per meter length of wall due to cable tr ay as calculated above in the design of various parts of cable tray = 0.980 kNm Total factored moment at base of vertical wall per meter length = Total factored vertical load at base of wall per meter length = Considering per meter length of wall to act as Column Pu /f ck bD =
5.82 5.828 8 kNm kNm 13.5 13.500 00 kN
0.00675
2
Mu /f ck bD = 0.029138 Percentage of reinforcement as per Chart 34, SP:16 = 0.02 % Steel Provide 8 tor bars @ 150 c/c c/c mai main n 0.33 0.334 4933 933 (per (perce cen nt pro prov vided ided)) 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 5.828 kNm
13.5 kN 4.847 kNm
1.8796 1.87965 5 kN/m kN/m 800. 800.00 00 mm Factored self weight of the base slab = Factored downward udl due to self weight =
4.5 kN kN 5.625 kN/m
Height of the wa water ta table above bottom of ba base slab = Uplift pressure on base slab = Factored upward udl due buoyant force =
0.51 meter 5.0031 kN kN/m 7.50465 kN/m
Net Factored upward force on base slab =
1.87965 kN/m
Maximum base pressure on soil =
34.97533 kN/m
Net maximum bending moment at mid-span, M u=
0.150372 kN kNm
Net maximum shear force, V u = 2
Mu /bd
=
HENCE, SAFE
0.75186 kN 0.008898
Vu /bd = 0.005784 Percentage of reinforcement as per Table 2, SP:16 = 0.02 Provide 8 tor bars @ 150 c/c c/c mai main n 0.22 0.223 3289 289 (per (perce cen nt pro prov vided ided)) Provide 8 tor bars @ 250 c/c distribution steel WELD DESIGN FOR TRAY TO INSERT PLATE: thickness of the weld for 6mm plate = 3 mm Throat, t = 3x0.75= 2.25 mm length of the weld, d = 73.33933 mm mm Using cleat angle of 50x50x6 we provide welding length = DESIGN FOR BONDING: Design anchorage length of 10mm bars assumed = Design bond strength as per clause 26.2.1.1 for M20 = Resisting bond strength of the insert plate = Calculated bond strength required =
100 1.2 11309.73 1867.163
100 mm
mm Mpa N N
HENCE, SAFE
60 350
150 200 200 200 200
150 150
100
PROJECT: CONSTRUCTION OF 400KV G.S.S. LOCATION: TITLE: CLIENT:
JAISALMER SWYAD CABLE TRENCH TYPE-D RAJ. RAJYA VIDYUT NIGAM.
INPUT PARAMETERS: Self-weight of concrete of grade M20 = Self-weight of cable over the tray Wide of tray excluding earth bus weld portion, L1 = Self weight of the angle 50x50x6 =
25.000 1.150 150.000 4.500
3
kN/m kg/Rm mm kg/Rm
[SP:6(1) pp. 155]
3
Unit weight of MS steel = Unit weight of soil, γ = Φ=
Bearing capacity of the soil, SBC = Depth of water table from top of the cover slab, Dw = EGL to top of cover plate height =
PRELIMINARY DIMENSION CHOSEN: Thickness of the base slab = Thickness of the side wall = Thickness of the cover slab = Rows of tray (MS angle), nr = Rows of tray (MS angle) continuous, n r1 = Total width of tray = Clearance between the tray & wall = Internal width of the trench = Internal clear height of the trench = =((nr1+nr-1)x200)+100+100 Spacing of Insert Plate = Number of 25mm diameter diameter cables placed in two tiers on a 200mm wide tray = Number of 25mm diameter diameter cables placed in two tiers on continuous tray =
78.500 kN/m 18.000 kN/m3 20.000 deg. 2
120.000 kN/m 1.000 meter 0.275 meter
150 100 100 1
mm mm mm rows
1 200.00 200 400.00 400
rows mm mm mm mm mm mm
1500 mm 16 nos. 32 nos.
DESIGN OF CABLE TRAY: Properties of section (unit mm) ISA50506
area 568
Weight of Cable at each angle support point =
Cx =Cy
Ix=Iy
rx = ry
Zx = Zy
14.5
1.29E+05
15.1
3.60E+03
0.276 kN
Weight of 3mm thick cable tray = Weight of support angle ISA50506 =
0.071 kN kN 0.009 kN kN Total = 0.356 kN kN this load acts at 100mm from face of Insert plate (c. g.)
Total moment due to this load at Insert plate= FACTORED MOMENT = Resisting moment of tray =
0.071 kNm 0.107 kNm 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 concrete The bottom half portion of the plate shall be checked against Bearing Stress of Steel Provide 30 300mmx100mmx6mm thick M.S M.S.. pl plate, so so to total are areaa = 30000 sq.mm The tension at upper half portion = 177.825 N 2
Actual bond stress at upper half =
0.012 N/mm
Permissible stress in bond (table21, IS:456-2000) =
0.800 N/mm
2
2
Yield stress of the M.S. Plate =
250.000 N/mm
Bearing Stress of plate at lower half =
187.500 N/mm
Bearing Stress of concrete at lower half =
HENCE, SAFE
2
HENCE, SAFE
2
HENCE, SAFE
5.000 N/mm
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 slab Span of the slab = Width of the slab taken =
500 mm 1000 mm
Load per meter due to self weight = Load per meter due to Live Load = Total UDL = Factored UDL =
2.5 10 12.5 18.75
Maximum Bending Moment (M u) =
0.586 kNm
Maximum Shear Force, (Vu) = Provide, 100mm thick slab and effective depth (d) =80 mm
4.688 kN
2
Mu /bd
=
kN kN/m kN kN/m kN/m kN/m
0.09
Vu /bd = 0.06 Percentage of reinforcement as per Table 2, SP:16 = 0.075 Provide 8 tor bars @ 250 c/c ma main 0.20096 (percent pr 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 = Load from the cover slab including live load = Total load = Factored load =
1 6.25 7.25 10.875
Active earth-pressure: earth-pressure: Coefficient of active earth pressure, K a =
0.490
Total area of pressure diagram, Pa = C.G. of pressure diagram above base of wall = Moment at base of the wall due to earth pressure = Factored moment =
0.706 0.133 0.094 0.141
kN kN kN kN
kN m kNm kNm
Force on wall from cable tray: Factored moment per meter length of wall due to cable tr ay as calculated above in the design of various parts of cable tray = 0.107 kNm Total factored moment at base of vertical wall per meter length = Total factored vertical load at base of wall per meter length = Considering per meter length of wall to act as Column Pu /f ck bD =
0.24 0.248 8 kNm kNm 10.8 10.875 75 kN
0.005438
2
Mu /f ck bD = 0.001239 Percentage of reinforcement as per Chart 34, SP:16 = 0.02 % Steel Provide 8 tor bars @ 150 c/c c/c main ain 0.334 .3349 933 (per (perce cent nt prov provid ided ed)) 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 0.248 kNm
10.875 kN 0.141 kNm
-10.77 -10.7753 53 kN/m kN/m 500. 500.00 00 mm Factored self weight of the base slab = Factored downward udl due to self weight = Height of the wa water ta table abo above bottom of ba base slab = Uplift pressure on base slab = Factored upward udl due buoyant force =
2.8125 kN 5.625 kN/m -0.35 .35 meter -3.4335 kN kN/m -5.15025 kN/m
Net Factored upward force on base slab = Maximum base pressure on soil =
-10.7753 kN/m 43.71339 kN/m
Net maximum bending moment at mid-span, M u=
-0.33673 kN kNm
Net maximum shear force, V u =
-2.69381 kN
2
Mu /bd
=
HENCE, SAFE
0.0199
Vu /bd = 0.0207 Percentage of reinforcement as per Table 2, SP:16 = 0.02 Provide 8 tor bars @ 150 c/c c/c main ain 0.223 .2232 289 (per (perce cent nt prov provid ided ed)) Provide 8 tor bars @ 250 c/c distribution steel
