NTPC DOCUMENT NO - 9396-001-PVC-740

BHEL DOCUMENT NO - 4-726-25-33-108

BARAUNI THERMAL POWER STATION - R&M 2x110MW (BIHAR)

Bharat Heavy Electricals Limited

BHOPAL

Scope of this Design Document Covers Design of CABLE TRENCH for Unit No -7 For Barauni

Revision

R1Revised as per revise E.S.P. cable trench layout

drawing

Scope of this Design Document Covers Design of CABLE TRENCH for Unit No -7 For Barauni

Thermal Power Station Bihar - (R&M)

CONSULTANT STEAG ENERGY SERVICES (INDIA) PVT. LTD.

DESCRIPTION

OWNER BIHAR STATE ELECTRICITY BOARD

OWNER CONSULTANT NTPC LIMITED

CLIENT BHARAT HEAVY ELECTRICALS LIMITED, BHOPAL

Design of Compressor Foundations and Strengthening Beams for Unit No -6 7For Barauni Thermal Power Station Bihar

1.0.1 Units of Measurement

S.no.

1

S.no.

1

2

3

4

3.0 Loads

Reinforced Concrete 25 kn/m^3

Soil 16 kn/m^3

Geo-technical Investigation Report of M/S Ground Geotechnics Pvt Ltd Submitted by Bhel Bhopal.

3.0.1 Dead Load

Dead load includes the weight of all structural components and other permanently applied external loads. Self-wt. of materials is

calculated on the basis of unit weights given below.

IS : 456 -2000 Plain and Reinforced concret code of practice

SP : 16 - 1980 Design aids for reinforced concrete to IS: 456-1978

IS :800 -1984 Code of Practice for General construction in steel

2.0.2 Codes, Standards and References

Reference Document No Document description

Input Drawing no Input Drawing name

BHEL input drawing no - A3 -726 - 19 - 33 -142 Control room layout for E.S.P.

1.0 INTRODUCTION

Scope of this Design Document Covers Design of E.S.P. CONTROL ROOM Cable trench foundation & structure

Units of measurement used in design shall be of SI or Metric system.

2.0 REFERENCE DRAWING & DOCUMENT

For the arrangement and design of cable trench foundation, following standards and documents have been refered : -

2.0.1 Reference Drawing

Page 1

Soil 16 kn/m^3

The steel reinforcement shall be deformed high yield strength bars of Fy = 415 N/mm2 conforming to IS: 1786

4.0.2 Concrete

Grade M 25 (having concrete cube compressive strength at 28 days of 30 N/mm2) conforming to IS: 456).

4.0 Material

4.0.1 Reinforcement

Page 1

a.negi

Typewritten Text

INPUT DRAWING

M 25

Fe 415

25 kn/m^3

25 kn/m^2

18 kn/m^3

9.81 kn/m^3

8.19 kn/m^3

0.5

20 kn/m^2

1.5 m

2 m

0.3 m

1.575 m

(a)

1 m

1.5

DESIGN OF CABLE TRENCH R.C.C. WALL

DESIGN DATA

Grade of concrete =

Grade of reinforcement steel =

Unit weight of concrete =

Allowable compressive strength of concrete =

For earth pressure

Clear height of cable trench (h) =

Clear width of cable trench =

Thickness of base slab =

Height of wall from top of bottom slab =

Bending moment Calculation

Case -1 ANALYSIS AND DESIGN OF TRENCH WALL FOR SATURATED CONDITION

Dry density of soil =

Density of water =

Submerged density of soil =

Coefficient of earth pressure at rest Ko =

Surcharge on back fill conisdered Fs =

Detail of cable trench

1

Pe = 10.125 kn

0.5 m

0.3 13.50 kn/m^2

13.50 kn/m^2

10.13 kn

5.06 kn-m

(b)

1.5 m

Ps = 15 kn

0.3 m Ko x Fs = 10 kn/m^2

Ko x γsub soil x h =

Earth Pressure at Rest = (Ko x γsub soil x h) =

Lateral force due to eart pressure ( 0.5 x h x Ko x γsub soil x h) =

Bending moment at base due to earth pressure Mep = Pe x 0.50 =

For surcharge

0.75 m

0.75 m

1

10 kn/m^2

15 kn

11.25 kn-m

(c )

3.96 Kn-m

3.96 Kn-m

3.97 Kn-m

11.88 Kn-m

28.20

28.20 kn-m (unfactored bending moment)

110.72 mm

165.72 mm

142 mm

0.2 %

284 sqmm

28.195 kn-m (unfactored bending moment)

2.10

0.653

927.26 sqmm

Check for minimum steel requirement

Calculate Area of Steel (Main Steel near soil face)

Pt Required for Ku 2.097 =

Area of steel required =

Minimum pt =

Ast = (0.2 x 1000 x 105)/100 =

Bending moment at bottom of wall =

Ku = (1.5 x B.M)/(b x d2) =

Wall shall be design per m width

Bending moment at bottom of wall =

Teff = SQRT( 1.5 X B.M.X)/(0.138 x Fck x b) =

Total thickness = (110.72 + 50 + 5) =

Provided thickness of wall 200 mm is more then the reqiuired

Provided effective thickness of wall = (200-50-8) =

Bending moment due to cable tray-1 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Bending moment due to cable tray-2 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Bending moment due to cable tray-3 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Total Bending Moment due to cable tray & cable dead load (Mc) =

Check for thickness of wall

Total bending moment at bottom of wall = (Me+Ms+Mc) = (5.86+11.25+11.88) =

Earth Pressure due to surcharge (Ko x Fs) =

Lateral force due to surcharge ( hxKoxFs ) =

Bending moment at base due to surcharge Ms = Ps x 0.75 =

Bending moment due to cable tray load

2

927.26 sqmm

0.2 %

284 sqmm

(a)

1.5 m

Pe = 4.6069 kn

6.14 kn/m^2

6.14 kn/m^2

4.607 kn

2.30 kn-m

Earth Pressure at Rest

Earth Pressure at Rest (Ko x γsub soil x h) =

Bending moment at base due to earth pressure Mep = Pe x 0.50 =

Lateral force due to eart pressure ( 0.5 x h x Ko x γsub soil x h) =

PROVIDED REINF. STEEL AT 10T @ 170 MM C/C (Provided Ast = 462 > 310.0 sqmm )

Case -2 ANALYSIS AND DESIGN OF TRENCH WALL FOR SUBMERGE CONDITION

For earth pressure

1.0 m

0.50 m

0.3 m Ko x γsub soil x h =

Area of steel required =

PROVIDED REINF. STEEL AT 16T @ 170 + 10t @ 170 Upto height 0.8m from top of base

slab MM C/C (Provided Ast =1644 >927.26sqmm )

Distribution steel on wall face away from soil

Minimum pt =

Ast = (0.2 x 1000 x 105)/100 =

2

(b)

0.75 m

1.5 mPs = 15 kn

0.75

Ko x Fs = 10 kn/m^2Surcharge

10 kn/m^2

15 kn

11.25 kn-m

(C)

1 m

Lateral force due to surcharge ( hxKoxFs ) =

Bending moment at base due to surcharge Ms = Ps x 0.75 =

For water pressure

For surcharge

0.3 m

Earth Pressure due to surcharge (Ko x Fs) =

3

1 m

1.5 m

Pw = 11.036 kn

0.5 m

h x γw0.3 m

14.72 kn/m^2

11.04 kn

5.79 kn-m

(c )

3.96 Kn-m

3.96 Kn-m

3.96 Kn-m

11.87 Kn-m

31.212

31.21 kn-m (unfactored bending moment)

116.49 mm

174.49 mm

142 mm

Provided thickness of wall 200 mm is more then the reqiuired

Provided effective thickness of wall = (200-50-8) =

Check for thickness of wall

Total bending moment at bottom of wall=(Mep+Msp+Msw+Mc)= (2.30+11.25+ 5.79+11.87) =

Wall shall be design per m width

Bending moment at bottom of wall =

Teff = SQRT( 1.5 X B.M.X)/(0.138 x Fck x b) =

Total thickness = (116.49 + 50 + 8) =

Bending moment at base due to water pressure Mw = Pw x 0.50 =

Bending moment due to cable tray load

Bending moment due to cable tray-1 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Bending moment due to cable tray-2 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Bending moment due to cable tray-1 = ((3.5 x 0.820) + (3.5 x 0.310)) =

Total Bending Moment due to cable tray & cable dead load (Mc) =

Water pressure

Water Pressure (h x γw) =

Lateral force due to water ( 0.5 x Ko x γw x h) =

3

Minimum pt = 0.20 %

Ast = (0.2 x 1000 x 105)/100 =284.00 sqmm

31.21 kn-m (unfactored bending moment)

2.32

0.743

1055.06 sqmm

Minimum pt = 0.20 %

Ast = (0.2 x 1000 x 105)/100 =284.00 sqmm

82.50 Kn

75.00 Kn

81.00 Kn

70.00 Kn

21.00 Kn

329.50 Kn

29.95 Kn/sqm

Distribution steel on wall face away from soil

(b) For 1700 mm wide cable

Bending moment at bottom of wall =

Ku = (1.5 x B.M)/(b x d2) =

Pt Required for Ku 2.32 =

Area of steel required =

PROVIDED REINF. STEEL AT 16T @ 170 + 10t @ 170 Upto height 0.8m from top of base

slab MM C/C (Provided Ast =1644 > 601.4 sqmm )

Calculate Area of Steel

Check for minimum steel requirement

BEARING PRESSURE CHECK

(a) For 1200 mm wide cable

(i) Self weight of base slab = (25 x 2.2 x 5 x 0.3) =

(ii) Self weight of wall = (25 x 0.2 x 1.5 x 5 x 2) =

(iii) Back fill weight = (18 x 0.3 x1.5 x 5 x 2) =

(iv) cable tray weight = (3.5 x 5 x 4) =

(v) EC Panel load = (7 x 3) =

Total Weight =

Bearing Pressure = (329.50/(2.2 x 5) =

PROVIDED REINF. STEEL AT 10T @ 170 MM C/C (Provided Ast =461.95 sqmm > 310.0 sqmm )

4

101.25 Kn

75.00 Kn

81.00 Kn

105.00 Kn

50.50 Kn

412.75 Kn

30.57 Kn/sqm

112.50 Kn

75.00 Kn

81.00 Kn

105.00 Kn

373.50 Kn

24.90 Kn/sqm

(a) 16.5 KN

(b) 15 KN

(d) 16.2 KN

(e) 6 KN

53.7 KN

39.60 KN

1.36 < 1.2

Cable tray load = ( 2 x 3 ) =

Factor of safety against uplift = (down ward load)/(upward load) =

Uplift Check for 1200 m width cable trench

Weight of base slab = (25 x 2.2 x 0.3 x 1) =

Weight of Trench r.c.c. wall (25x1.50x0.2x1x2) =

Weight of soil back fill = (18x0.3x1.50x1x2) =

Total downward pressure =

Total Upward pressure (10x2.2x1.80x1) =

CHECK FOR UPLIFT

TOTAL UPWARD LOAD / M WIDTH

Total Weight =

Bearing Pressure = (373.50/(3.0 x 5) =

(i) Self weight of base slab = (25 x 3.0x 5 x 0.3) =

(ii) Self weight of wall = (25 x 0.2 x 1.5 x 5 x 2) =

(iii) Back fill weight = (18 x 0.3 x1.5 x 5 x 2) =

(iv) cable tray weight = (3.5 x 5 x 6) =

(b) For 1700 mm wide cable

(i) Self weight of base slab = (25 x 2.7 x 5 x 0.3) =

(ii) Self weight of wall = (25 x 0.2 x 1.5 x 5 x 2) =

(iii) Back fill weight = (18 x 0.3 x1.5 x 5 x 2) =

(iv) cable tray weight = (3.5 x 5 x 6) =

(v) LTMSB Panel load = (50.5 kn as per E.S.P. trench

layout drawing) =

Total Weight =

Bearing Pressure = (412.75/(2.7 x 5) =

(c) For 2000 mm wide cable

4

(a) 20.25 KN

(b) 15 KN

(d) 16.20 KN

(e) 8.00 KN

59.45 KN

48.60 KN

1.22 < 1.2

22.5 KN

15 KN

16.20 KN

12.00 KN

65.70 KN

54.00 KN

1.22 < 1.2

300 mm

50 mm

5 mm

245 mm

Rb Rd

Cable tray load = (2 x 4) =

Weight of Trench r.c.c. wall (25x1.50x0.2x1x2) =

Weight of soil back fill = (18x0.3x1.5x1x2) =

Total downward pressure =

Total Upward pressure (10x3.0x1.80x1) =

Factor of safety against uplift = (down ward load)/(upward load) =

Cable tray Load = (2.0 x 6) =

Total downward pressure =

Total Upward pressure (10x2.7x1.80x1) =

Factor of safety against uplift = (down ward load)/(upward load) =

Weight of base slab = (25 x 3.0 x 0.3 x 1) =

Uplift Check for 2000 m width cable trench

Uplift Check for 1700 m width cable trench

Weight of base slab = (25 x 2.7 x 0.3 x 1) =

Weight of Trench r.c.c. wall (25x1.50x0.2x1x2) =

Weight of soil back fill = (18x0.3x1.50x1x2) =

Overall depth of base slab =

Clear cover =

Dia of bar =

Effective depth of base slab =

Design of base slab

5

B D E

A

C

50 kn/m

0.4 2.2 0.4

150.00 Kn

75 Kn

4 Kn-m

-26.25 Kn-m

At support

4.00 kn-m

0.10

0.08 % < Minimum pt 0.12%

0.12 %

294.00 sqmm

26.25 kn-m

0.66

0.186% < Minimum pt 0.12%

0.186 %

455.7 sqmm

0.19 %

Reinforcement calculation

Bending moment at support =

Pt required for Ku (0.84) =

Reaction calculation

Bending moment at span =

Ku = (Mu/bd^2) =

Pt Provided =

Ast required =

Ast Provided 10 @170c/c both way at top (Provided ast = 461.95 sqmm > 294 sqmm)

Ku = (Mu/bd^2) =

Pt required for Ku (0.06) =

Ast Provided 10 @170c/c both way at bottom (Provided ast = 461.95 sqmm > 455.7 sqmm)

Provided Pt =

Rb = Rd = ( 50 x 3.0)/2 =

Bending moment calculation

B.M. at B = (50 x 0.4 x 0.4 x 0.5) =

B.M. at C = (50x1.5x1.5x0.5)-(75x1.1) =

Pt Provided =

Ast required =

Rb + Rd = ( 50 x 3.0) =

At Mid span

5

(A.3) Check for shear

(A.3.1)

15.00 kn

15.00 kn

0.09 N/sqmm

0.29 N/sqmm

τv < τc (Hence provided depth is ok in shear)

(A.3.2)

-37.75 kn

0.23 N/sqmm

0.29 N/sqmm

At cantilever face

τv < τc (Hence provided depth is ok in shear)

τc (Permissable shear stress of concrete for Pt (0.09%)

At a distance 0.3381 m from point A

(Unfactored shear force at support)Shear force at A = (50 x 0.30) =

Maximum design shear force at Support A (V) =

τv (Design shear stress) = (V/bd) =

Maximum design shear force at distance of (0.3+0.2+0.245) = 0.745 m from point A (V) =

τv (Design shear stress) = (V/bd) =

τc (Permissable shear stress of concrete for Pt (0.19%) =

66