Design of Foundation

Height Of the Tower 16 M Site Location

Width of the Tower Base 2.000 M
Footing Raft Slab

C/C DISTANCE OF LEGS Lc = 2.000 m

ANGLE OF REPOSE OF FILLED SOIL f = 30 deg

DENSITY OF SOIL gs = 16 kN/m3

FACTOR OF SAFTEY FOR DESIGN = 1

S.B.C OF SOIL g = 150 kN/m2

4.5
m

2.000 m

P.L 0.5
m
F.G.L

2.15
Excavated Line m
1
m

0.35
m

4.5 m

Downthrust Hence Safe

Overturning/Uplift Hence Safe 1.190
FACTORED DESIGN FORCES Punching Shear Hence safe

Compressive force D = 459 kN

Uplift force U = 448 kN

Side thrust S = 45 kN

Overturning moment M = 1283 kNm

Net vertical force (External loads) = 22 kN

DESIGN DATA:

Width of raft Br = 4.5 m

Thickness of raft slab Tr = 0.35 m

Depth of foundation Df = 2.5 m

Height of chimney hp = 2.65 m

Cantilever Length lc = 1 m

width of chimney bp = 0.5 m

Number Of Columns Nc = 4 Nos.

Thickness of P.C.C tpcc = 0.1 m

1
Thickness of soling = 0.05 m

2
 e = 0.5 m
Height of pedastal above ground lvl

Top Width of Footing For Excavation Wt = 6.98 m

Density Of Concrete γc = 25 kN/m3

Characterstic Strength of Steel = 500 N/mm2

Characterstic Strength of Concrete = 20 N/mm2

Resistance created by Passive pressure :

Passive pressure coefficient Kp = 3

Passive pressure at bottom of pad lvl P1 = 40 kN/m2

Passive pressure at top of pad lvl P2 = 34.4 kN/m2

Passive force on column face F1 = 221.9 kN

Passive force on pad surface F2 = 175.8 kN

Total moment due to passive soil force due to F1 = 236.67 kNm

Total moment due to passive soil force due to F2 = 30.76 kNm

Total Passive force Fp = 397.7 kN

Total Moment due to Passive force Mp = 267.43 kNm

Check For Down Thrust :

Moment due to down

M = 1282.7 kN - m
thrust&uplift

Overturning Moment at the base of the slab

= 567.00 kN - m
due to shear

Total Moment M = 1582.3 kN - m

Volume Of Raft VR = 7.09 m3

Volume Of Column Vc = 2.65 m3

Total RCC Volume V = 9.74 m3

RCC Volume below GL V = 9.24 m3

Weight Of Concrete Wc = 243.44 kN Apprent wt considered due to complete

submergence, γc = 15kN/m3
Volume Of Excavated Soil Vs = 41.39 m3

Soil Weight Ws = 662.20 kN

Total Weight On Footing wcc = 121.72 kN Only 50% footing wt. considered
Weight of raft is not considered in the structural design
Net vertical force (External loads) Wn = 22.00 kN because it is assumed to be carried directly by the sub
soil. (A.K Jain. )
Total compression force P = 144 kN

Axial Stress P/A = 28.39 kN/m2 Only 50% area considered for bearing area

Bending stress M/Z = 104.18 kN/m2

Max. Stress Sc = 132.58 kN/m2

S.B.C Of Soil Ps = 150 kN/m2

Factor of saftey = 132.58 < 150

Hence Safe
Check For Over turning :

Moment Of Resistance MR = 1883.42 kN - m While in overturing Case, A. prismodial soil

weight will resist. B.90% footing weight
will resist. (As per IS 456 code Cl. 20.1)
Moment Due To Over turning Mo = 1582.3 kN - m

Factor Of Safety F/S = 1.19

3
Hence Safe

4
Design Of Raft slab:

Combined presure on raft Pb = 132.58 kN/sq m

Length of cantilever portion

Diameter of main rein bars

=

=
1

12.0
m

mm
A st =
0. 5 f ck
fy [ √
1− 1−
4.6 Mu
f ck bd ]
2
bd

Effective depth d = 294 mm

Factored Moment in Cantilever Raft Slab = 66.29 kN-m

Factored Span Moment inRaft Slab = 22.10 kN-m

Hence, Ast = = 518 mm2

Min Ast = = 441 mm2

Spacing = = 218 mm

Spacing Provided= = 150 mm

Ast provided = 754 mm2

pt provided = 0.256 %

Provide 12.0 Dia. @ 150 c/c

CHIMNEY DESIGN
Forces (kg) kg N
compre( Pu) 45900 450141 co-effient of passive earth pressure (kp)
uplift 44800 439354 = 3.00
transverse 4500 44132
longitudinal 4500 44132

angle of repose 30 deg

unit wt of soil 1600 (kg/m^3)
size of chimney 0.5 m
Ht of chimney 2.15 m
Ht of chimney above GL 0.5 m

L = Position of max. BM in chimney

Tran Long
F(temp) = 1200.01 1200.01
h (m) = 1.936 1.936
L (m) = 1.936 1.936
Res. Soil force, F(kg) = 4500.0 4500.0
Moment (kg.m) = 9020.3 9020.3
Mux Muy
BM (N.mm) 88461875 88461875

A) Compression with Bending: B) Tension with Bending:

Ac = 250000 sq.mm 250000 sq.mm
dia = 20 mm 20 mm
cover 50 mm 50 mm
fck = 20 N/sq.mm 20 N/sq.mm
fy = 500 N/sq.mm 500 N/sq.mm
Area of Bar provided 314 mm2
Number of bars provided 12 nos
Asc = 3768 mm2 3768 sq.mm
% of steel = 1.507 1.507

Puz = 3663000 N
pu / puz = 0.1229
n= 1.000 n= 1.000
d1= 60 mm 60 mm
d1/D = 0.12 0.12

pu/fckxbxd = 0.090 pu/fckxbxd = -0.088

p/fck = 0.075 p/fck = 0.075
From SP- 16 Chart 48 From SP- 16 Chart 83
Mu/fckxbxd^2 = 0.160 Mu/fckxbxd^2 = 0.12
Mux1= Muy1 = 400000000 N.mm Mux1= Muy1 = 300000000 N.mm

Check for interaction: (Ref: Clause 38.6 of IS-456:1978) Check for interaction:
(Ref: Clause 38.6 of IS-456:1978)
{(Mux/Mux1)^n} + {(Muy/Muy1)^n} < 1.0 {(Mux/Mux1)^n} + {(Muy/Muy1)^n} < 1.0
0.442 < 1.0 Hence safe 0.590 < 1.0 Hence safe.

5
Design of Stirups
Diameter shall be maximum of the following(As per clause 25.5.3.2 of IS:456-1978):
1) One-fourth of the diameter of the largest longitudinal
bar: 5 mm
2) in no case less than: 8 mm
Adopted diameter of transverse reinforcement 8 mm
Spacing shall be min of the following(As per clause 25.5.3.2 of IS:456-1978):
1) Least lateral dimension of compression member: 500 mm
2) Sixteen times the smallest diameter of the longitudinal
reinforcement bar to be tied: 320 mm
3) Forty-eight times the diameter of the transverse
reinforcement: 384 mm
Adopted spacing of transverse reinforcement 200 mm

Hence provide 8 mm dia. bars @ 200mm c/c

Check For Punching shear

Criteria 1
Effective depth of raft d = 294 mm

bo = 3176 mm

Punching shear tv = 0.492 N/mm2

Allowable Shear tc = 1.118 N/mm2 > 0.49

Criteria 2 : For Edge column
bo = 3294 mm

tv = 0.47 N/mm2

tc = 1.118 N/mm2 > 0.47

Hence safe

6
REQUIRED DATA

Height of Tower = 16 m
Type of Tower = Broad Based
C/C of Tower = 2m
Width of Raft = 4.5 m
Thickness of Raft = 0.35 m
Width of Column = 0.5 m
Height of Column = 2.65 m
Width of T.Beam = 0 mm
Heigth of T.Beam = 0 mm

STEEL
Total length Diameter Unit Wt. Spacing
Description Width (m) Depth (m) Nos. Total Nos.
(m) (mm) (kg/m) (mm)
Raft Slab
At Bottom
Main Bars 4.4 0.25 4.9 12 0.89 150 29 58

At Top
Main Bars 4.4 0.25 4.9 12 0.89 150 29 58

Chair 0.3 0.25 1.500 12 0.89 0 9 9

Reinforcement

Column
Longi. Bars 0.674 2.95 3.624 20 2.47 12 48
Lateral Ties 0.42 0.42 1.830 8 0.395 200 16 64
Legged Ties 0.42 0.21 1.41 8 0.39 200 32 128

Total Weight (kg)

PCC BED
Total
Thickness
Description Width (m) Depth (m) Volume (m3) Nos. Volume
(m)
(m3)
Bed 4.65 4.65 0.1 2.16225 1 2.16

EXCAVATION
Total
Thickness
Description Width (m) Depth (m) Volume (m3) Nos. Volume
(m)
(m3)
Total Area 4.65 4.65 2.65 57.30 1 57.30 21.6225

CONCRETE .
Total
Thickness/
Description Width (m) Depth (m) Volume (m3) Nos. Volume
Length (m)
(m3)
Raft Slab 4.5 4.5 0.35 7.09 1 7.0875
Column 0.5 0.5 2.65 0.66 4 2.65
Total Volume (Cu.m) 9.74
Total Weight
(kg)

252.3

252.3

12.0

429.0
46.2
71.2

1063.04