Strap footing calculation:
ColumnID,
Service
Load(DL+LL)
A1 342.622 kN
B1 406.2506 kN
Area of footing
required A1 3.02 m2
Area of footing
required A2 3.58 m2
Square Size Adopted ,L1xB1 1.8 m
Square Size Adopted ,L2xB2 1.905 m
R1= 428.6276 kN
R2= 320.24kN
eccentricity at footing
F1,e= 0.7492 m
Udl under footing F1 357.1897 kN/m
Udl under footing F2 252.1609 kN/m
Thickness of footing:
i)one way shear:
For footing F1:
Let us assume Pt=0.2% so from tble 16 of IS 456:2000,
Tc=0.2 Mpa
Shear=bdTc=qu(0.75-d)
Therefore,d=0.298 m
For footing F2:
Let us assume Pt=0.2% so from table 16 of Is 456:2000,
Tc=0.2 Mpa
Shear=bdTc=qu(0.8025-d)
Therefore,d=0.245 m
ii) Two way shear:
for column A1:
from clause 31.6.3.1 of IS 456-2000
βc=width of column/length =1
ks= βc+0.5=1.5≤1
Tc=ks(0.25)sqrt(fck)
=1.118 Mpa
Critical perimeterxdxTc=Pu-qu*(critical area-dotted area)
Assume d=363 mm
Hence Tc=0.646 Mpa <1.118 Mpa, safe in punching
Reinforcement for flexure for footings:
i)From bending moment diagram
Mmax=114.89*10^6 KN-m=114.89*10^6 N-mm
Mu/bd2 = 0.457
From Table 2 of SP-16, pt=0.106%
Ast required=733 mm2
Let us provide Ast 12 mm @ 150 mm c/c
Hence ,Ast provided=753.33 mm2
Design for bending in beam,
From bending moment diagram,
Max bending moment= 262*10^6 kN-m
Assume beam total depth=600 mm
Beam width= 300 mm
Mu/bd^2 = 2.994
From table 54,
Percentage of steel in tension=0.837 %
Percentage of steel in compression=0.086%
Hence provide 6-20mm dia @ top and 4-16 mm dia @ bottom.
Combined footing calculation:
Grid A-3,B-3, A-2, B-2
Geometry of
MAT:
Area, A = 19.773 m2
CG of Area in X-
Dir, x = 2.017 m
CG of Area in Y-
Dir, y = 1.8312 m
CG of Load in X-
Dir, x' = 1.751 m
CG of Load in Y-
Dir, y' = 1.564 m
ex = -0.266 m
ey = -0.117 m
Ixx = 30.95 m4
Iyy = 34.3 m4
-
Mxx = P*ex = 449.896 kNm
-
Myy = P*ey = 198.322 kNm
P/A = 85.630 kN/m2
Soil Bearing Capacity, SBC = 125 kN/m2
Moment of axial
From origin
load @ axes X co- Y co-
Stress
Joint P Factored ordinate ordinate =
(KN/Sq- CHECK
Name (KN) Load Distance Distance P*x P*y = x-x1 y-y1
m)
Along X Along Y KNm KNm (m) (m)
(x) (m) (y) (m)
2A 216.71 325.07 0.00 0.00 0.00 0.00 -2.02 -1.68 124.67 OK
2B 513.21 769.82 3.73 0.00 1916.23 0.00 1.72 -1.68 70.39 OK
3A 57.90 86.84 0.00 3.99 0.00 230.88 -2.02 2.31 101.61 OK
3B 121.84 182.77 3.73 3.99 454.94 485.89 1.72 2.31 47.34 OK
A62 50.14 75.22 0.00 3.32 0.00 166.64 -2.02 1.64 105.45 OK
A66 67.33 101.00 0.00 2.66 0.00 179.00 -2.02 0.98 109.30 OK
A68 90.33 135.50 0.00 1.99 0.00 180.11 -2.02 0.31 113.14 OK
A70 123.96 185.94 0.00 1.33 0.00 164.78 -2.02 -0.35 116.98 OK
A72 165.90 248.85 0.00 0.66 0.00 108.93 -2.02 -1.02 120.87 OK
3-167 38.16 57.24 0.62 3.99 23.75 152.19 -1.39 2.31 92.57 OK
3-169 47.32 70.99 1.24 3.97 58.90 187.92 -0.77 2.29 83.62 OK
3-171 56.72 85.08 1.87 3.96 105.89 224.74 -0.15 2.28 74.62 OK
3-173 66.71 100.07 2.49 3.95 166.06 263.78 0.47 2.27 65.62 OK
3-175 76.88 115.31 3.11 3.95 239.20 303.31 1.09 2.26 56.63 OK
1693.13 2964.97 2648.16
Maximum Bending moment calculation:
Max positive bending moment=46.93 kN-m/m
Max negative bending moment=143.08 kN-m/m
𝐵𝑀𝑚𝑎𝑥
Positive Moment: √
0.133𝜎𝑐𝑏 𝑏
Required effective depth =
= 231.93 mm
OK
Area of Reinforcement:
𝑓𝑦 ∗ 𝐴𝑠𝑡
𝑀 = 0.87 ∗ 𝑓𝑦 ∗ 𝐴𝑠𝑡 (𝑑 − )
𝑓𝑐𝑘 ∗ 𝑏
Ast required = 748 mm2
Provide 12 mm rebar @ 150 mm c/c
Punching depth check
Central Column, B2
Load on column,
= 769.817 kN
Pu
= 769817 N
Soil Pressure = 146.297 kN/m2
= 0.146297 N/mm2
Assuming, d = 369 mm
X-Dir Side
= 667.8 mm
Length
Y-Dir Side
= 667.8 mm
Length
Perimeter, bo = 2671.2 mm
τv = Vu
bo*d
= 0.73 N/mm2
0.25√𝑓𝑐𝑘
τc
=
= 1.118034 N/mm2
Corner Column,A2
Load on column,
= 391.3612 kN
Pu
= 391361.2 N
Soil Pressure = 169.72 kN/m2
= 0.16972 N/mm2
Assuming, d = 369 mm
X-Dir Side
= 486.3 mm
Length
Y-Dir Side
= 936.3 mm
Length
Perimeter, bo = 1422.6 mm
τv = Vu
bo*d
= 0.61 N/mm2
0.25√𝑓𝑐𝑘
τc
=
= 1.118 N/mm2
