Subject:

PIPE SUPPORT FOUNDATION

DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
Output
DESIGN OF ISOLATED FOOTING FOOTING/COLUMN DESIGNATION:
Density Of Concrete w = 24 kN/m³ FOOTING NO. F1
Density Of Soil g = 18 kN/m³ PEDESTAL NO. C1
Depth Of Foundation h = 1 m
Soil Bearing Capacity r = 200 kN/m² REFER STAAD ANALYSIS FILE
SUPPORT REACTION.
(Foundation design basis)
Gross SBC rg = 218 kN/m² #ADDIN?

(Increase in SBC is not allowed.)

Gross SBC rg = 268 kN/m² #ADDIN?

(Increase in SBC is allowed.)

fc'= 28 N/mm²
fy = 414 N/mm²
Length Of Footing L = 1.20 m
Width Of Footing W = 1.20 m
Thickness of Fdtn. t = 0.40 m
Width Of Pedestal cw = 0.50 m
Length Of Pedestal cL = 0.50 m
Height Of Pedestal hp = 1.40 m
Coefficient Of Friction m = 0.5
Ground Water Table Ht. hw = 0.00 m

0.35

W
Wp

0.35
Z

0.35 Lp 0.35

1.0 Load Calculation for Footing & Soil:-

Self Wt. Of Footing wf = 13.82 kN #ADDIN?

Weight of Soil ws = 12.85 kN #ADDIN?

Self Wt. Of Pedestal wp = 8.40 kN #ADDIN?

(Not considered here since it is modelled in STAAD)

Weight of Footing + Soil W = 35.08 kN = wf + ws + wp

 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18

INPUT:- INPUT STAAD SUPPORT REACTION (Units, kN, kN-m)

JOINT LOAD CASE FORCE-X FORCE-Y FORCE-Z MOM-X MOM-Y MOM Z
1 4 0 3.26 0 0 0 0.47
F1-C1 5 -0.21 4.83 -0.42 -0.6 0.07 1.02
6 -0.16 4.83 -0.31 -0.45 0.05 0.88
7 0 3.26 -0.47 -0.46 0.04 0.47
8 -0.16 4.43 -0.67 -0.79 0.08 0.88
9 0 1.95 -0.47 -0.46 0.04 0.28
10 0 1.95 0 0 0 0.28

2.0 Check Maximum and Minimum Pressure at Footing Base:

Area of Footing A = 1.44 m² #ADDIN?

Section Modulus Zxx = 0.29 m³ #ADDIN?

Section Modulus Zzz = 0.29 m³ #ADDIN?

Total Vertical Load Pu = 38.34 kN = W + Fy

P/A = 26.63 kN/m²

Mxx/Zxx = 0 / 0.288
Mxx/Zxx = 0.000 kN/m2

Mzz/Zzz = 0.47 / 0.288

Mzz/Zzz = 1.632 kN/m2

Maxi.Soil Pressure pmax = 26.63 + 0 + 1.632

r max = 28.27 kN/m2 < 218 kN/m²

Less Than Allowable Hence O.K.

Mini.Soil Pressure pmin = 26.63 - 0 - 1.632

pmin = 25.00 kN/m2 > 0

No Tension @ Footing Base

 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
3.0 Check for Overturning:

Overturning Moment Mo = 0.47 kN-m = √(Mx2 + Mz2)

Calculation of Stabilizing Moment

Due to External Load Mel = 1.96 kN-m = Fy * L/2

Due to wt. of Pedestal Mp = 5.04 kN-m = Wp ([L - cL ]/2 + cL/2

Due to Self Wt. of Fdn Mf = 8.29 kN-m = Wf * L/2

Due to Wt. of Soil Ms = 7.72 kN-m = Ws * L/2

Total Stabilizing Moment Msm = 23.0 kN-m

F.O.S. against Overturning FOS = 48.96 #ADDIN?

FOS = 48.96 > 1.2 Safe!

4.0 Check for Sliding:

Fx2 = -0.21
Fz2 = -0.67

Resultant Shear Force V = 0.71 kN = √(Fx2 + Fz2)

Total Vertical Load PU = 38.34 kN

F.O.S. against Sliding FOS = 27

FOS = 27 > 1.5 Safe!
 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
5.0 Load Case Check:

Check Max. & Mini. Pressure at Footing Base:

Total Mxx/Zxx Mzz/Zzz ρmax ρall ρmin

Joint Load Case P/A Result
Load
1 4 38.34 26.62 0 1.64 28.26 218 24.99 SAFE
F1-C1 5 39.91 27.71 2.09 3.55 33.35 268 22.08 SAFE
6 39.91 27.71 1.57 3.06 32.34 268 23.09 SAFE
7 38.34 26.62 1.6 1.64 29.86 268 23.39 SAFE
8 39.51 27.43 2.75 3.06 33.24 268 21.63 SAFE
9 37.03 25.7125 1.6 0.98 28.29 268 23.14 SAFE
10 37.03 25.7125 0 0.98 26.69 268 24.74 SAFE

Summary of Bearing Pressure

Without Stress Increase:- With Stress Increase:-
ρmax = 28.26 kN/m 2 ρmax = 33.35 kN/m2
ρmin = 24.99 kN/m2 ρmin = 21.63 kN/m2

Mxx/Zxx
Joint Load Case P/A (1) Mzz/Zzz (3) 1+2+3 1-2+3 1-2-3 1+2-3
(2)
1 4 26.62 0 1.64 28.263 28.263 24.983 24.983
F1-C1 5 27.71 2.09 3.55 33.353 29.173 22.073 26.253
6 27.71 1.57 3.06 32.343 29.203 23.083 26.223
7 26.62 1.6 1.64 29.863 26.663 23.383 26.583
8 27.43 2.75 3.06 33.245 27.745 21.625 27.125
9 25.71 1.6 0.98 28.293 25.093 23.133 26.333
10 25.71 0 0.98 26.693 26.693 24.733 24.733
 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18

6.0 Check for Overturning & Sliding:

Check against Overturning Check against Sliding
Stabilize Moment
Joint Load Case Total Total
FOS for
O/T Mmt. (Soil,Pe Load on FOS Result Hz. Vert. Result
Sliding
d, Fdn) Ped Force Load

1 4 0.47 21.05 1.96 48.96 SAFE 0.000 38.336 #DIV/0! #DIV/0!

F1-C1 5 1.18 21.05 2.90 20.24 SAFE 0.470 39.906 42.5 SAFE
6 0.99 21.05 2.90 24.24 SAFE 0.349 39.906 57.2 SAFE
7 0.66 21.05 1.96 34.99 SAFE 0.470 38.336 40.79 SAFE
8 1.18 21.05 2.66 20.05 SAFE 0.689 39.506 28.68 SAFE
9 0.54 21.05 1.17 41.27 SAFE 0.470 37.026 39.39 SAFE
10 0.28 21.05 1.17 79.36 SAFE 0.000 37.026 #DIV/0! #DIV/0!

7.0 Check For Shear

a) Two Way Shear
Limit State Method

d/2

d/2

Critical Section = At distance d/2 from face of column

Concrete Grade fc' = 28 N/mm²
Column Details
Length CL = 500 mm
Width CW = 500 mm

Foundation Details
Length L = 1200 mm
Width W = 1200 mm
Effective Depth def = 325 mm
Percentage Of Steel = 0.25 %

Length of critical section CL+def = 825 mm

Width of critical section CW+def = 825 mm
Perimeter of critical section bo = 3300 mm #ADDIN?

Punching Load
Maximum Load on Column Pu = 39.91 kN

Punching P = 21.044 kN
 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18

βc = Short Side Of Column

Long Side Of Column
fc' = 28 N/mm²
βc = 1 = CW / CL
as = 40 ACI 11.12.2.2

qu = 27.71 kN = Pu/(Lx * Ly)

Vu = 21.04 kN = qu * ((Lx * Ly)-(Cx+d)*(Cy+d))

FVn ≥ Vu , ( Vn = V c ) ACI - Eq. 11-1

Where: Vc shall be smallest of:

Vc = 2894.32 kN #ADDIN? ACI - Eq. 11-33

Vc = 2797.67 kN #ADDIN? ACI - Eq. 11-34

Vc = 1872.80 kN #ADDIN? ACI - Eq. 11-35

Ratio = Vu / FVc = 0.011 < 1 Safe !

Required Depth ( d )
Mu f= 0.90
T = d =
f b Ru B= 1200 mm
rb = 0.028914 = 0.85 f'c b 600/[ fy ( 600 + fy )] f'c = 28.00 MPa
r = 0.021686 #ADDIN? fy = 414 MPa
rmin = 1.4 / fy = 0.00338 < 0.02169 b= 0.85
Mu = 23.01 kN-m
Ru = 7.28 MPa = r fy [ 1 - 0.59 ( r fy / f'c ) ]
Required depth, d = 54 mm < 325 mm Safe !!

33.353 kN/m2
B) One Way Shear
25
0 350 33.206 kN/m2
325
Width, W

31.283 kN/m2
d
400 1200
500

Length, L
500
200 26.253 kN/m2
350
325 25

1200

29.173 kN/m2 33.353 kN/m2

 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
32.134 kN/m2 33.266 kN/m2

Case = With Stress Increase

 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
At Length Refer data from above figure:
Maximum Pressure = 33.266 - 24 x 0.4 - 18 x ( 1 - 0.4 )
12.866 kN/m2 -- For without Buoynacy Condition With Stress Increse
Length at critical section LLc = 1200 mm
Width at critical section WLC = 25 mm
Shear Force = 12.866 x 1.2 x 0.025
= 0.38598 kN

At Width Refer data from above figure:

Maximum Pressure = 33.206 - 24 x 0.4 - 18 x ( 1 - 0.4 )
12.806 kN/m2 -- For without Buoynacy Condition With Stress Increse
Length at critical section = LWc = 1200 mm
Width at critical section = WWC = 25 mm
Shear Force = 12.806 x 1.2 x 0.025
= 0.38418 kN

Designed Shear Stress = 0.386 kN

Corresponding Length = 1200 mm

Allowable Shear Stress νa = 0.8996 N/mm² = 0.17 * √fc' ACI-R11.12.2.1

Increaae In Shear Stress = Allowed

Depth Required = 76 mm < 325 mm Safe !

8.0 Design Of Foundation/Footing:

a) Calculation of Reinforcement at Bottom
Maximum Pressure = 33.35 kN/m2 -- Without Buoyancy Load Case
Pressure due to Soil & Fdn wt = ( 13.824 + 12.852 ) / ( 1.2 x 1.2 )
= 18.53 kN/m2
Net causing moment, w = 14.82 kN/m (assuming 1 m strip)
Maximum Projection of fdn = 0.35 m

Bending Moment, M = 14.823 x 0.35 x 0.35 / 2

M = 0.91 kN.m

As = M / ( f d fy [ 1 - 0.59 ( r fy / f'c ) ]) db = 16 mm
Ast = 9.27 mm² f = 0.90
B = 1200 mm
Asmin = 0.0018 B deff. deff = 325.00 mm
= 702.00 mm² > As D = 400.00 mm
f'c = 28 N/mm²
Horizontal bars fy = 414 N/mm²
Ab = 201.06 mm² r = 0.021686
spacing, S = 286.41 mm
Use S: 250 mm on center bothways

Area Provided = 804.25 mm2

Provide 16 mm dia Bars @ 250 mm spacing bothways

 Subject:
PIPE SUPPORT FOUNDATION
DESIGN OF SPREAD FOOTING Design Code: Designed By: Date:
ACI 318-07 Engr. WBL 26-Mar-18
b) Calculation of Reinforcement at Top
Reinforcement at top is checked for overburden load on top of foundation
since 100% of foundation is not in contact with soil.
Wt. Of Soil + Fdn wt. = 26.676 kN

Area Load, w = 26.676 / (1.2 x 1.2)

w = 19 kN/m²

Maxi. Projection of fdn = 0.35 m

Bending Moment = 18.53 x 0.35 x 0.35 / 2

M = 1.13 kN.m

As = M / ( f d fy [ 1 - 0.59 ( r fy / f'c ) ])
Ast = 11.51 mm²

Asmin = 0.0018 B deff.

= 702.00 mm² > As

Ab = 201.06 mm² db = 16 mm
spacing, S = 286.41 mm
Use S: 250 mm on center bothways

Provide 16 mm dia Bars @ 250 mm spacing bothways

Design Summary :-
Length Of Footing :- 1200 mm
WIdth Of Footing :- 1200 mm
Depth Of Footing :- 400 mm
Reinforcement :-
At Top :- Provide 16 mm dia Bars @ 250 mm spacing bothways
At Bottom :- Provide 16 mm dia Bars @ 250 mm spacing bothways