Transformer Foundation Design

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i i o o n n t t h h e e r r e e i i n n . . R R e e p p r r o o d d u u c c t t i i o o n n

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CONTRAC

CONTRACT N

T N O.

O. : P

: PG

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B / D A

D AN I

N I D A

D A// 1

1 DES

DESII GN-BUI

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SII O N L I

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PROJECT

T I

T I T L E

T L E :

:

EMPLOYER

::

POWER

POWER GR

GRII D CO

D COMPANY OF BANGLADE

MPANY OF BANGLADESH LI

SH LI MI

MI TE

TED (

D ( PG

PGC

CB )

B )

Paper Size

A

A 4

4

W W e e r r e e s s e e r r v v e e a a l l l l r r i i g g h h t t s s i i n n t t h h i i s s d d o o c c u u m m e e n n t t a a n n d d t t h h e e i i n n f f o o r r m m a a d d i i s s c c l l o o s s u u r r e e t t o o t t h h i i r r d d p p a a r r t t i i e e s s

w w i i t t h h o o u u t t e e x x p p r r e e s s s s a a u u t t h h o o r r i i t t y y i i s s : :

D e s

D e si g n C

i g n Ca l c u l a

a l c u l at i o n

t i o n f o r

f o r F

Fo u n d a t i o n

o u n d a t i o n o f A u t

o f A u t o T r a n s f o r m e r

o T r a n s f o r m e r

D DOOCCUUMM EENN T T NN OO. . :: SUSUBBMM II TTTTAA L L NN OO. . : : JDP/A26/001 JDP/A26/001 S ES ECCT IT I O N : 1O N : 1 2 ,2 , B u i l d iB u i l d in g a n d n g a n d c i v ic i v il e n g i n e e r i n g w o rl e n g i n e e r i n g w o r k sk s DES

DESII GNED BY :GNED BY : Md. GiasuddinMd. Giasuddin CCHH EECCKKEED D BB Y Y :: AA PPPPRROOVV EED D BBY Y : :

CONTRACTOR

CONTRACTOR : M: M THTH G AG AA R D AA R D A// S - LS - LII N D P RN D P RO A /O A / S JS JVV

DATE : DATE :

19 Nov '05

19 Nov '05 RREEVV. . NN OO. . :: MM AA NN UUFFAA CCTTUURREER R : :

E:\PROJECTS

E:\PROJECTS FOR EXECUTION\Joydevpur FOR EXECUTION\Joydevpur - Kabirpur - Kabirpur --Tangail OHL\Joydevpur Substation\Design

Tangail OHL\Joydevpur Substation\Design Calculation\Static Cal of Foundation For Auto Calculation\Static Cal of Foundation For Auto Transformer

Transformer

II D D : :

J

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i o n t h e r e i n . R e p r o d u c t i o n t r i c t l y f o r b i d d e n .

CONTRACT N O.

: PGCB / D AN I D A/ 1

DESI GN-BUI LD AN D TURNKEY CONTRACT FOR CONSTRUCTI ON OF

1 3 2 k V J OY D EV P UR - K A B I R PU R - T A N GA I L T RA N SM I SSI O N L I N E

PROJECT

T I T L E :

Paper Size

A 4

W e r e s e r v e a l l r i g h t s i n t h i s d o c u m e n t a n d t h e i n f o r m a d i s c l o s u r e t o t h i r d p a r t i e s w i t h o u t e x p r e s s a u t h o r i t y i s :

D e si g n Ca l c u l at i o n f o r Fo u n d a t i o n o f A u t o T r a n s f o r m e r

DOCUM EN T N O. : SUBM I TTA L N O. :

JDP/A26/001 S ECT I O N : 1 2 , B u i l d in g a n d c i v il e n g i n e e r i n g w o r k s

DESI GNED BY : Md. Giasuddin CH ECKED B Y : A PPROV ED BY :

CONTRACTOR : M TH G AA R D A/ S - LI N D P RO A / S JV

DATE :

19 Nov '05 REV. N O. : M A N UFA CTURER :

E:\PROJECTS FOR EXECUTION\Joydevpur Kabirpur -Tangail OHL\Joydevpur Substation\Design

Calculation\Static Cal of Foundation For Auto Transformer

I D :

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MT H JGAARD A/S - LINDPRO A/S JV

1. GENERAL 1.1 Considerations :

a) Raft foundation is considered for a 132kV Transformer.

b) The bottom of the r aft is at a depth of 1.0m from existing ground surface.

c) Soil bearing capacity is considered 90.04 kN/m2minimum value from BH-4, BH-5 & BH-7. d) The Top of bund wall is 200mm above the finished switchyard surface level.

1.2 Soil Data:

Allowable bearing capacity of soil is considered : 90.04 kN/sqm Unit weight of soil : 17.94 kN/cum.

Frustum angle : 15.00 Deg. Water Table from EGL : 2.50 m

1.3 Material Properties :

Concrete………...…fc'= 20 N/mm2 Reinforcing Steel…………..f y= 415 N/mm2

Concrete Clear Cover……….= 60 mm Unit Weight of Concrete…….= 24.0 kN/cum.

2. DESIGN DATA AND FOUNDATION GEOMETRY :

( Reference Dwg no. 56.20.3-03-3537)

Transformer's Length = 6.80 m Transformer's Width = 5.10 m Height of Transformer = 5.00 m Total Weight of Tx. ( with Oil ) = 72,000 Kg

Weight of Oil = 19,000 Kg Density of Oil = 840 Kg/cum.

Design of Transformer Foundation ; Joydevpur 132/33kV Sub-station

Total volume of oil = 22.62 Cum Pit volume reqd. below the stone ( 125% of oil vol. ) = 28.27 Cum

Inside length of pit considered = 7.80 m Inside width of pit considered = 5.80 m

Surface area of the pit = 41.47 sqm. Width of Tx. Supporting Pedestal = 2.68 m Length of Tx. Supporting Pedestal = 3.89 m

Area of Tx. Supporting Pedestal = 10.4 sqm. Net surface area of the pit = 31.0 sqm.

Average Depth required = 0.9 m

Provided depth below Grating = 0.90 m Thickness of grating = 0.05 m Thickness of gravel layer on top of grating = 0.225 m

Free height above gravel top = 0.05 m Max. height of pit wall above base slab = 1.225 m

Ce n t e r o f F o u n d a t i o n C e n t e r o f

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3. LOAD CALCULATION

Transformer Length, L = 6.80 m Transformer Width, B = 5.10 m Transformer Height above top of Pedestal, H = 5.00 m

Total weight of Transformer ( with oil ) = 720.00 kN

3.1 Wind load calculation - as per BNBC

Maximum wind velocity , Vb= 160.0 km/hr ( Specified in the Contract specification) Height of top of transformer from FSYL = 5.20 m

For exposure B , Czat Top = 0.85 For exposure B , Czat Bottom = 0.801 Velocity to Pressure conversion coefficient, Cc= 4.72E-05

Structure Importance Factor CI= 1.25

1.284 kN/m2 ; at Top = 1.210 kN/m2 ; at Bottom

L/B = 1.33 H/B = 0.98

( Ref. Bangladesh National Building Code 1993, Chapter 2;Page 6-33)

( Ref. Bangladesh National Building Code 1993, Chapter 2;Page 6-34) Ce n t e r o f F o u n d a t i o n z

q =

2 z c I z b

q = c c c v

z G p z

Design Wind Pressure, p = c c q

- , p . Gust Co-efficient, CG= 1 .30

1.335 kN/m2 _{; at Top} = 1.258 kN/m2 ; at Bottom Average Pressure , Pz= 1.29671 kN/m2

∴ Force results from Wind = 1.297*6.8*5.1 = 44.97 kN

3.2 Seismic load calculation - as per BNBC

Design Base Shear is given by :

Where, Z = Seismic Zone Co-efficient = 0.15 ( for Zone 2 )

I = Structure Importance Factor = 1.25 ( with essential Facilities ) R = Response Modification Coefficient = 6 ( For RCC wall System ) C = Numerical coefficien t system is given by :

S = Site coefficient for soil characteristics = 1.5 T = Fundamental period of vibration is given by :

Ct= 0.049 hn= 5.00 m

T = 0.164 Sec C = 6.262 W = Total Seismic dead load =Transformer Weight = 720.00 kN

Design base shear V = 140.90 kN

4. SOIL STABILITY CHECK 4.1 Check for Soil Bearing Capacity :

Weight of each Transformer with 15% impact =828.00 kN

Weight of Transformer supporting Pedestal = 306.50 kN

Length of foundation pad = 8.800 m Width of foundation pad = 6.800 m Thickness of foundation pad = 0.300 m

( For all type of non braced RCC structure )

( Ref. Bangladesh National Building Code 1993, Chapter 2;Page 6-53)

z

Design Wind Pressure, p =

= ZICW V R 2 3 1.25 = S C T

( )

34 t n

T C h

= 8 2 8 . 0 k N 1 4 0 . 0 k N CL of Foundation L o a d A p p l i c a t i o n o n F o u n d a t i o n

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MT H JGAARD A/S - LINDPRO A/S JV

Design of Transformer Foundation ; Joydevpur 132/33kV Sub-station

Weight of Pad = 430.85 kN

Width of Bund Wall = 0.200 m Total Length of Bund wall = 28.540 m

Height of Bund wall = 1.225 m Weight of Bund wall = 167.82 kN

Total area of the Yard within bundwall = 41.47 m2 Area of Tx. supporting Pedestal = 10.43 m2 Net area to be filled with gravel = 31.04 m2 Thickness of Gravel = 0.225 m

Weight of gravel = 111.76 kN

Total Vertical Load = 828+306.5 +430.85+167.82+111.76 = 1844. 93 kN

Maximum Moment at base due to Max. Horizontal Load =140.9*1.525 = 214.87 kN.m Eccentricity for Horizontal load = 214.87/1844.93 = 0.116 m

Net Eccentricity = 0.116+0.600 = 0.716 m Q = Fzb= 1844.93 kN kNs A = LxB = 59.84 m2

e = e

l= 0.716m m L /6 = 1.467

>e

q

_max

=

43.54 kN/m2

Gross allowable soil pressure = 90.04 +

γ

sDf = 107.98 kN/m2 So it's OK.

max min Q 6e So;q = (1+ ) A L Q 6e and;q = (1- ) A L CL of Found a t i o n L o a d A p p l i c a t i o n o n F o u n d a t i o n

Net Upward Pressure = 43.54-γ'sDf = 35.60 kN/m2

4.2 Check for Settlement :

Settlement of a Soil layer is given by :

Where, Cc= Compression Index = 0.258 From soil test report of BH-4.

e

0= Initial Void ratio = 0.989 From soil test report of BH-4. H = Thickness of the Soil Layer = 5.00 m From soil test report of BH-4.

p

0= The original Soil Pressure at the mid point of the

layer = γ∗H/2 = 45.00 kN/m2 Δ p = Change In Pressure =

q

max- γDf = 25.60 kN/m2

S =

0.1269 ft. = 1.524 inch. Which is less than 2.0" , so OK.

5. STRUCTURAL DESIGN 5.1 Design of Pit Wall :

Angle of repose for backfilled soil, φ = 0.00 Deg

Coefficient of earth pressure , Ka = ( 1-sin φ ) / ( 1-sin φ ) = 1.00 Unit weight of soil = 17.94 kN/cum

Height of soil at toe side above base = 0.000 m Height of soil at heel side above slab = 0.700 m PL above heel side soil = 0.200 m Thickness of stem = 0.200 m Thickness of base slab = 0.300 m Superimposed live load at heel side = 10.00 kN/sqm

Applied Loading :

Unit Weight of Gravel Fill = 16 kN/cum. Unit Weight of Brick = 19 kN/cum. Unit Weight of Sand Fill = 15 kN/cum.

Pressure due to Backfill P1= 1/2*K pγh 2

*1.0 = 4.40 kN ( Per meter of width )

0 10 0 0

log

1

c

p

S

H

e

p

+ Δ

=

+

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K a= ( 1-Sinφ )/( 1+Sinφ ) =1.0 ( For Backfill φ is considered 0 Degree ) 13.75 kN ( Per meter of width ) So Moment about point A = 4.41*0.233+13.75*0.35 = 5.835 kN.m ( Per meter of width )

Factored Moment = 5.838*1.5 = 8.752 kN.m "

Let us check with minimum reinforcement. As per ACI code, Ratio of minimum reinforcement ( in SI unit) is given by =1.4/fy

ρ

min= 0.003373494

85mm 95mm;OK

5.1.1 - Reinforcement Calculation : Vertical Reinforcement

Mdes=Mu/0.9 = 9.725 kN.m Assuming depth of stress block, a = 6.94 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) = 284.47 mm2 (Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed. )

Check for a

a = As*fy/(.85*fc'*b) = 6.94 mm Consideration is OK, So As = 284.47 mm2/m As per Code Min Rebar Required = 0.004bt = 400.00 mm2/m

Consider bar Size = 10.0 mm So Nos. of Bars = 5 Nos

; d Provided =200-100-10/2= Pressure due Surcharge load P2 =10.0+ ( 0.175*16+0.075*19+0.075*15)*0.7 =

y 2 u y c ρ

f

M =

φρ

f bd

1-0.59

...;Where

φ

= 0.9

f'

⎛

⎞

⎜

⎟

⎝

⎠

u y y c M d= = ρf φρf b(1-0.59 ) f ' ∴ Spacing = 200.00 mm Provide φ 10mm @ 200mm at both face of the wall.

Horizontal Reinforcement :

As per Code Min Rebar Required = 0.002bt = 400.00 mm2/m Consider bar Size = 10.0 mm

So Nos. of Bars = 5 Nos Spacing = 1000/5 = 200.00 mm Provide φ 10mm @ 200mm at both face of the wall.

Check for shear :

Shear force , V = 18.14 kN Factored shear , Vu = 27.21 kN Where, b= 1000 mm

d = 95 mm So, vc= Vc/bd = 0.286 N/mm2

AS per ACI Shear Stress applied to concrete should be less than N/mm2; In present case which is coming 0.76 Mpa. This is much greater than applied stress so consideration is quiteOk.

5.2 Design of Transformer Supporting Pedestal : ( Reference Dwg no. 56.20.3-03-3537)

Length of Pedestal = 3.890 m Width of Pedestal = 2.680 m Hight of Pedestal = 1.225 m Weight of Pedestal = 306.50 kN Total Weight of Tx. ( with Oil ) = 720.00 kN

Design Loads:

Compression =720.0+306.5 = 1026.50 kN MomentM= 172.6025

Max. or Min. stress on the section =

I = bh3/12 = 6.24E+12 mm4 Maximum stress on the section = 0.06 Mpa, Compressive Stresse is within acceptable limit, so no rebar is r equired from structural point of view.

0.17 _c'

max/min

P Mc

A I

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MT H JGAARD A/S - LINDPRO A/S JV

Design of Transformer Foundation ; Joydevpur 132/33kV Sub-station

But as per code Minimun Rebar = 0.0018*Ag = 0.0018*3890*2680 mm2. = 18766 mm2. So Use 94 nos. of dia 16mm Bar for Vertical Reinforcement.

Use dia 10mm bar @ 200 mm c/c for tie.

5.3. Design of Base Slab Foundation Layout

Ce n t e r o f T x .

5.3.1 Check for Punching of the Base :

Base Thickness, t = 300 mm Clear Cover = 60 mm Consider Max Bar size = 20 mm

d = 300-60-20/2 = 230 mm

Punching Perimeter = (2680+3890)*2 = 13140 mm Punching Area = 13140*230 = 3022200 mm2

Vertical Forces = 1026.50 kN

0.340 Mpa AS per ACI Shear Stress applied to concrete should be less than Mpa In present case which is coming 1.48 Mpa. So OK.

5.3.2 Bottom Reinforcement Along Long Direction : For right side

Net Upward Pressure by soil = 35.60 kN/m2

166.147 kN.m/m Design moment = 170.42/0.9 = 184.607 kN.m/m

Base Thickness, t = 300 mm Clear Cover = 60 mm Consider Bar size = 20 mm

d = 300-60-20/2 = 230 mm

Assuming depth of stress block,

a

= 60.39 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) = 2473.73 mm2

Punching stress developed by Tx. = 1026.5*1000/ 3022200 =

Max Moment Developed at Pedestal face at Bottom = 35.6*3.055^2/2 =

0.33 '

c

f

Ce n t e r o f F o u n d a t i o n

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Check for stress block,a

a= As*fy/(0.85*fc'*b) = 60.39 mm Consideration is OK, So As = 2473.73 mm2 Minimum reinforcement = 0.18 % = 540.00 mm2/m

Consider bar Size = 20 mm

So Nos. of Bars = 7.87 Nos

Spacing = 127 mm Say 120mm

For Left Side

d = 300-60-20/2 = 230 mm

a

Max Moment Developed at Pedestal face at Bottom = 35.6*1.855^2/2 =

5.3.3 Bottom Reinforcement Along Short Direction :

Net Upward Pressure by soil = 43.54 -γ'sDf = 35.60 kN/m2

d = 300-60-12/2-20 = 214 mm ( Bars to be placed on top of long Bars)

a

Spacing = 91 mm Say 90 mm

Calculation For Bar Curtailment

d = 300-60-12/2-20 = 214 mm ( Bars to be placed on top of long Bars)

a

Max Moment Developed at 0.75 m far from Pedestal face at Bottom = 35.6*1.41^2/2 = Max Moment Developed at Pedestal face at Bottom = 35.6*2.16^2/2 =

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MT H JGAARD A/S - LINDPRO A/S JV

Design of Transformer Foundation ; Joydevpur 132/33kV Sub-station

Spacing = 209 mm Say 180 mm

Point of curtailment = 750+(12 times dia of bar ; i.e 12*12 = 144mm use 250mm) 250 = 1000mm from face of Padestal.

5.3.4 Top Reinforcement Calculation along both direction :

Max Hogging Moment Developed = 35.6*(

3.055-0.40)^2/8 = 31.368 kN.m/m Design moment = 27.165/0.9 = 34.854 kN.m/m

Base Thickness, t = 300 mm Clear Cover = 60 mm Consider Max Bar size = 12 mm

d = 300-60-12/2 = 234 mm

a

6. DESIGN OF GRATINGS Layout of Gratings :

Steel of Fy 275.0 Mpa shall be used for gratings.

Main bar : 50X6 Flat Spacing of main bar : 30 mm c/c

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Spacing of secondary bar : 100 mm c/c Thickness of gravel paving = 225 mm

Unit weight of gravel = 16.00 kN/cum Max span of main bar = 1.698 m

6.1 Design of main bar :

Self weight of grating : 0.56 kN/sqm Self weight of gravel : 3.60 kN/sqm Assumed live load : 2.00 kN/sqm Total load per unit area = 6.16 kN/sqm Uniform Distributed Load per main bar = 0.185 kN/m

Check for bending stress :

Max bending moment = 0.185*1.6982/8 = 0.067kN.m Zxx of main bar = 6*502/6 = 2500 mm3 Max bending stress = 0.067*10^6/2500 = 26.64 Mpa

Allowable bending stress = 0.6*Fy = 0.6*275 = 165.00 Mpa ; So OK.

Check for shear stress :

Max shear force = 0.157 kN Max shear stress = 0.52 Mpa

Allowable Shear stress = 0.346*Fy = 0.346*275 = 95.15 Mpa ; So OK.

Check for max deflection :

Ixx of main bar = 6*50^3/12 = 62500 mm4 Modulus of elasticity of steel = 200000 Mpa

= 4 = .

Allowable Maximum deflection = l/325 = 5.22 mm ; So OK.

6.2 Design of grating supporting channel :

Max span of channel = 2.505 m Load from grating per channel = 6.16*2.505 = 15.431 kN/m

Max bending moment , M = 12.104kN.m Max end shear, V = 19.327 kN Provide : ISMC 200

Check for bending stress :

Total depth, D = 200 mm Sectional Area, A = 2828 mm2 r yy= 22.3 mm Flange thickness, T = 10.40 mm Web thickness, tw= 6.1 mm Zxx= 182500 mm3 Ixx= 18251000 mm4 Leff / r yy= 2700/22.3= 112.33

Consider ends of channel are not to carry any moment so 2nd and 3rd term of the above equation can be ignored. So C b= 1.75

Bending Stress = M/Z = 12.1*10^6/182500 = 66.32 Mpa

∴ Fb = 0.535*275 = 147.13 Mpa > 66.32 Mpa ; So OK.

Check for shear stress :

Shear stress = V/A = 19.327*1000/2828 = 6.83 Mpa

Allowable Shear stress = 0.346*Fy = 0.346*275 = 95.15 Mpa > 6.83 Mpa ; So OK.

( )

3 3 2 3 2 b 703 10 3516 10 When 2 0.60 3 10550 10 Where C 1.75 1 .05 * ( 1 / 2) 0.3( 1 / 2) b b y y y b y y b X C l X C F r F l F r F F F X C M M M M ≤ ≤ ⎡ ⎤ ⎢ ⎥ = _⎢ − _⎥ ≤ ⎢ ⎥ ⎣ ⎦ = + +

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MT H JGAARD A/S - LINDPRO A/S JV

Design of Transformer Foundation ; Joydevpur 132/33kV Sub-station

Check for max deflection :

Max central deflection = 5wl4/384EI = 2.17 mm

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Co n t e n t s

Pa g e

N o .

1 . G e n e r a l

03

1.1 Considerations

:

03

1.2 Soil

Data:

03

1.3 Material

Properties

:

03 2 . D e si g n D a t a Fo u n d a t i o n Ge o m e t r y :

03 3 . L o a d Ca l c u l a t i o n :

04

3.1 Wind

load

calculation

-

as

per

BNBC

04

3.2 Seismic

load

calculation

-

as

per

BNBC

04 4 . S o i l S t a b i l i t y Ch e c k

04

4.1 Check

for

Soil

Bearing

Capacity

:

04 4.2 Check for Settlement :

05 5 . St r u c t u r a l D e si g n :

05

5.1 Design

of

Pit

Wall

:

05

5.1.1 -

Reinforcement

Calculation

:

06 5.2 Design of Transformer Supporting Pedestal :

06

5.3. Design

of

Base

Slab

07

5.3.1 Check

for

Punching

of

the

Base

:

07 5.3.2 Bottom Reinforcement Along Long Direction :

07 5.3.3 Bottom Reinforcement Along Short Direction :

08 5.3.4 Top Reinforcement Calculation along both direction :

09 6 . D e s i g n o f Gr a t i n g :

09

6.1 Design

of

main

bar

:

10

6.2 Design

of

grating

supporting

channel

:

10

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