p

1. Combine Footing Design
Given Data:
At exterior column:
Pu at exterior column= 515.2 KN
Mux at exterior column =2.5 KN-m
Muy at exterior column =24.4 KN-m
Exterior Column Dimension=375x375 mm
Structure Design of RCC Building Manual and Excel

2. Combine Footing Design
Given Data:
At interior column:
Pu at interior column= 713.7 KN
Mux at interior column =4.5 KN-m
Muy at interior column =19.2 KN-m
Interior Column Dimension=375x375 mm
Fc’=28 MPa
Fy =420 MPa
Allowable Bearing Capacity = 1 tsf (95) KPa
Depth of Footing = 4 ft (1.2m)
Structure Design of RCC Building Manual and Excel

3. Combine Footing Design
Solution:
Pu at exterior footing = 1.1x 515.2 = 566.5 KN
Pu at interior footing = 1.1x 713.7 = 785.4 KN
Service Load = (566.5+785.4)/1.3 = 1039.92 KN
x ’ = 𝑃2𝑥𝑆
=785.4/1.3𝑥3.277
= 1.903 m
𝑅 1039.92
x1 = 0.1875
Length of footing = 2x(x’+x1) ≅ 4.2 m
Width of footing =
𝑅
= 1039.92
≅ 2.6 m
𝑞𝑥𝐿 95𝑥4.2
FinalArea of footing = 4.21x2.6=10.95 m²
Structure Design of RCC Building Manual and Excel

4. Combine Footing Design
Solution:
Center of Gravity = 3.277 / 2 = 1.6385 m
Center of Rigidity= (515.2x0+713.7x3.277)/(515.2+713.7)
= 1.9032 m
Structure Design of RCC Building Manual and Excel

5. Combine Footing Design
Pu = 1229x1.1= 1351.9 KN
qu= Pu/Af = 1351.9/(10.95)
= 123.80 KPa
Approximate depth of footing for exterior, H =
𝑃 + 1.5𝑀𝑥 + 1.5𝑀𝑦
+60 mm
/(0.01α𝑓𝑓𝑐′)
H =
/(0.01x30x28)
566.5/1.3 + 2.5𝑥𝑥/1.3 + 1.5𝑥𝑥𝑥.𝑥/1.3
+60 mm = 286 mm ≥ 250mm
Structure Design of RCC Building Manual and Excel

6. Combine Footing Design
Approximate depth of footing for interior, H =
𝑃 + 1.5𝑀𝑥 + 1.5𝑀𝑦
+60 mm
/(0.01α𝑓𝑓𝑐′)
H = 1.3
785.4
+ 1.5𝑥4.5
+ 1.5𝑥19.2/1.3
1.3
/(0.01x𝑥0x28)
+60 mm=298 mm ≥ 250mm
Take H=300 mm
Structure Design of RCC Building Manual and Excel

7. Combine Footing Design
SFD & BMD
At Point B:
• 321.88x0.187= 60.2 KN
• -566.5+60.2 = - 506.3 KN
At Point C:
• 321.88x3.277= 1054.8 KN
1054.8-506.3 = 548.5 KN
• 548.5-785.4 = - 237 KN
Structure Design of RCC Building Manual and Excel

8. Combine Footing Design
SFD & BMD
At Point D:
• 321.88x.736= 237 KN
Structure Design of RCC Building Manual and Excel

9. Combine Footing Design
SFD & BMD
At Point B:
• 60.2x0.187/2 = 5.63 KN-m
At Point C:
• 506.3 x X/2= ?
X=?
-566.5+60.2 + 321.88X=0
X=1.573 m
506.3 x 1.573/2= 398.2 KN-m
398.2 – 5.63 = 392.6 KN-m
Structure Design of RCC Building Manual and Excel

10. Combine Footing Design
SFD & BMD
• 548.5x1.704/2 = 467.3 KN-m
• 467.3-392.6= 74.722 KN-m
At Point D:
• 237x0.736/2 = 87.216 KN-m
• Diff = 87.216-69.12= 12.5 KN-m
Structure Design of RCC Building Manual and Excel

11. Combine Footing Design
One way Shear Check :
Max Shear, V = 548.5 KN
Max One way shear on right of int col, V =
548.5 – (.375-.240)x321.88 KN =411 KN
One Way Shear Capacity, φVc=0.75x0.17x√𝑓𝑓𝑐𝑓 x bxd = 411
0.75x0.17x √28x1000x d /1000 = 411 KN
d =234mm.
Again H remains same
Structure Design of RCC Building Manual and Excel

12. Combine Footing Design
Two way Shear / Punching Check :
Take H as 425mm because 300mm fails in Two way later.
Effective depth of footing , d = 425x– 60 = 365mm
Perimeter, bo = 2x(c1+d/2)+(c2+d)
Perimeter, bo =2x(375+365/2)+(375+365)
=1855 mm
Β = 375/375 = 1
Structure Design of RCC Building Manual and Excel

13. Combine Footing Design
φVc = lesser of
1) = 0.75x0.33 x λ x √𝑓𝑓𝑐𝑓 x bo x d
= 0.75x0.33 x 1 x √28 x 1855 x 365 = 886.72 KN
Β
2) = 0.75x0.17 x (1+2
)λ x √𝑓𝑓𝑐𝑓 x bo x d
1
= 0.75x0.17 x (1+2
) x 1 x √28 x 1855 x 365 = 1370 KN
b𝑜
3) = 0.75x0.083 x (αxd +2)x λ x √𝑓𝑓𝑐𝑓 x bo x d
1605
= 0.75x0.083 x (30x240
+2)x 1 x √28 x 1855 x 365 =1762kN
Structure Design of RCC Building Manual and Excel

14. Combine Footing Design
So,
φVc = 886 KN
Actual Shear , Vu = Col load - qu x {Af- (c1+d/2)(c2+d)}
= 512-123.8x {10.95-(375+365/2)/1000
x(375+365)/1000}
= 477.6 KN
So,
φVc > Vu (Depth is Ok)
Structure Design of RCC Building Manual and Excel

15. Combine Footing Design
Two way Shear / Punching Check :
Effective depth of footing , d = 425x– 60 = 365mm
Perimeter, bo = 2x(c1+d)+2x(c2+d)
Perimeter, bo =2x(375+365)+2x(375+365)
=2960 mm
Β = 375/375 = 1
Structure Design of RCC Building Manual and Excel

16. Combine Footing Design
φVc = lesser of
1) = 0.75x0.33 x λ x √𝑓𝑓𝑐𝑓 x bo x d
= 0.75x0.33 x 1 x √28 x 2960 x 365 = 1415 KN
Β
2) = 0.75x0.17 x (1+2
)λ x √𝑓𝑓𝑐𝑓 x bo x d
1
= 0.75x0.17 x (1+2
) x 1 x √28 x 2960 x 365 = 2187 KN
b𝑜
3) = 0.75x0.083 x (αxd +2)x λ x √𝑓𝑓𝑐𝑓 x bo x d
1605
= 0.75x0.083 x (𝑥0x240
+2)x 1 x √28 x 2960 x365 =2467 kN
Structure Design of RCC Building Manual and Excel

17. Combine Footing Design
So,
φVc = 1415 KN
Actual Shear , Vu = Col load - qu x {Af- (c1+d)(c2+d)}
= 714-123.8x {10.95-(375+365)/1000
x(375+365)/1000}
= 646 KN
So,
φVc > Vu (Depth is Ok)
Structure Design of RCC Building Manual and Excel

18. Combine Footing Design
Area of Steel :
Top Longer Steel:
Bending Moment, Mu = 392.6 KN-m
𝑏𝑑2
R= 𝑀𝑢
= 1.1158
W=0.85𝑓𝑓𝑐′
= 0.85𝑥28
= 0.056667
𝑓𝑓𝑦 420
Ro = Wx(1- 1 − 2.614𝑥𝑅
) = 0.00307 > 0.002 (OK)
𝑓𝑓𝑐𝘍
Area of Steel = Ro x b x d = 0.00303 x 2600 x 365 = 2924 𝑚𝑚2
#19 @ 230 c/c
Structure Design of RCC Building Manual and Excel

19. Combine Footing Design
Area of Steel :
Bottom Longer Steel Under Interior Column:
Bending Moment, Mu = 74.722 KN-m
𝑏𝑑2
R= 𝑀𝑢
= 0.215
W=0.85𝑓𝑓𝑐′
= 0.85𝑥28
= 0.056667
𝑓𝑓𝑦 420
Ro = Wx(1- 1 − 2.614𝑥𝑅
) = 0.00057 < 0.002 (Provide minimum steel)
𝑓𝑓𝑐𝘍
Area of Steel = 0.002x b x h = 0.002 x 2600 x 425 = 2215 𝑚𝑚2
#16 @ 215mm c/c
Structure Design of RCC Building Manual and Excel

20. Combine Footing Design
Area of Steel :
Bottom Longer Steel Under exterior Column:
Bending Moment, Mu = 5.63 KN-m
Here moment is much lesser but for additional safety we ‘ll provide
Minimum area of steel.
Area of Steel = 0.002x b x h = 0.002 x 2600 x 425 = 2215 𝑚𝑚2
#16 @ 215 c/c
Structure Design of RCC Building Manual and Excel

21. Combine Footing Design
Area of Steel :
Design of Transverse Beam Under Exterior Column:
Approximate width of beam = c1+d/2
= 375+365/2 = 557.5 mm
Load on transverse beam = Pu/B = 714/2.6 = 197.69 KN/m
Bending Moment, Mu = Load x 𝑙2 / 2
=197.69x
(2600/2−375/2) 2
2
=123 KN – m
Structure Design of RCC Building Manual and Excel

22. Combine Footing Design
Area of Steel :
Design of Transverse Beam Under Exterior Column:
Bending Moment, Mu = 123 KN-m
𝑏𝑑2
R= 𝑀𝑢
= 1.656
W=0.85𝑓𝑓𝑐′
= 0.85𝑥28
= 0.056667
𝑓𝑓𝑦 420
Ro = Wx(1- 1 − 2.614𝑥𝑅
) = 0.00456 > 0.002 (Ok)
𝑓𝑓𝑐𝘍
Area of Steel = 0.00456x b x d = 0.00456 x 557.5x 365 = 929 𝑚𝑚2
#19 @ 140mm c/c or #25 @ 275mm c/c
Structure Design of RCC Building Manual and Excel

23. Combine Footing Design
Area of Steel :
Design of Transverse Beam Under interior Column:
Approximate width of beam = c1+d
= 375+365 = 740 mm
Load on transverse beam = Pu/B = 714/2.6 = 273.8 KN/m
Bending Moment, Mu = Loadx 𝑙2 / 2
=273.8x
(2600/2−375/2) 2
2
=170.4 KN – m
Structure Design of RCC Building Manual and Excel

24. Combine Footing Design
Area of Steel :
Design of Transverse Beam Under Exterior Column:
Bending Moment, Mu = 170.4 KN-m
𝑏𝑑2
R= 𝑀𝑢
= 1.992
W=0.85𝑓𝑓𝑐′
= 0.85𝑥28
= 0.056667
𝑓𝑓𝑦 420
Ro = Wx(1- 1 − 2.614𝑥𝑅
) = 0.00553 > 0.002 (Ok)
𝑓𝑓𝑐𝘍
Area of Steel = 0.00456x b x d = 0.00553 x 740x 365 = 1394 𝑚𝑚2
#19 @ 145mm c/c or #25 @ 245mm c/c
Structure Design of RCC Building Manual and Excel

25. Combine Footing Design
Area of Steel :
Distribution Steel:
Area of Steel = 0.002x b x h = 0.002 x 1000 x 425 = 850 𝑚𝑚2
#16 @ 200 c/c
Structure Design of RCC Building Manual and Excel