FOOTING DESIGN CALCULATIONS
Project Name : Footing Design
Client Name : ABC
Engineer Name : XYZ
Analysis File : D:\Needhi (F Drive)\Working\SCUBE Standard Models (STAAD, ETABS, RAM)\RCDC STD Models\Standard model for Demo - With SW (Latest)\Staad\RCDC-Staad-Demo -with RCC wall.std
Analysis Last Modified : 5/17/2018 2:28:47 PM


Definitions:
1. A = Plan area of footing base in 'sqmm'
2. Ast Prv = Area of tensile reinforcement provided in 'sqmm'
3. Ast Rqd = Area of longitudinal reinforcement from bearing moment and minimum % steel provided by user and as per code in 'sqmm'
4. Asv = Area of shear reinforcement required in 'sqmm/m'
5. AsvPrv = Area of shear reinforcement provided in 'sqmm/m'
6. A1 = Bearing area of footing at slope of 1:2 in 'sqmm'
7. A2 = C/s Area of column in 'sqmm'
8. ax = Length of Edge of Punching Perimeter parallel to Dc (Column Depth)
9. ay = Length of Edge of Punching Perimeter parallel to Bc (Column Width)
10. B = Width of footing base in 'mm'
11. Beff = Effective width of footing in 'mm'
12. Boff = Footing offset along B in 'mm'
13. BoffB = Footing offset along B below column in plan in 'mm'
14. BoffT = Footing offset along B above column in plan in 'mm'
15. Bv = Effective width for One-way Shear Design in 'mm'
16. B1 = Width of sloped footing at top in 'mm'
17. c = Maximum crack spacing in 'mm'
18. ColOff = Column offset in sloped footing in 'mm'
19. D = Depth of footing in 'mm'
20. Deff = Effective Depth of footing in 'mm'
21. Df = Depth of founding layer in 'm'
22. Do = Distance from Extreme Compressive fibre to Centroid of Tensile Force in 'mm'
23. Dv = Effective depth for shear design in 'mm'
24. dom = Average Effective Depth of footing for Punching Shear Check in 'mm'
25. Dn = Depth to Neutral Axis in 'mm'
26. Dw = Ground water level in 'm'
27. Ec = Modulus of elasticity of concrete due to creep in 'N/sqmm'
28. Es = Modulus of elasticity of steel in 'N/sqmm'
29. f'c = Characteristic Cylinder strength of concrete in 'N/sqmm'
30. f'ctf = Characteristic Flexural Tensile strength of concrete in 'N/sqmm'
31. fcv = Concrete Shear Strength in 'N/sqmm'
32. Fd.ef = Effective Design Service Load per Unit Area in 'N/sqmm'
33. Foss = Safety factor against sliding
34. Fosu = Safety factor against uplift
35. Fst = Stress in steel in 'N/sqmm'
36. Fsy = Yield Stress of Steel in 'N/sqmm'
37. k1 = Coefficient that accounts for bond properties of the bonded reinforcement
38. k2 = Coefficient used for the creep calculation
39. k2 = Coefficient that accounts for the longitudinal strain distribution
40. k3 = Coefficient depend on the age of concrete at loadings used for the creep
41. k4 = Coefficient depend on the enviromental condition used for the creep calculation
42. k5 = A modification factor for high strength concrete used for creep calculation
43. k6 = Coefficient accounts for the non-linear creep that develops at sustained stress level of 0.45 fcmi
44. Kcs = Factors Used in Serviceability Design to Take Account of the Long-Term Effects of Creep and Shrinkage.
45. kd = The depth of the neutral axis on the cracked section in 'mm'
46. Ku = Neutral Axis Parameter being the Ratio, at Ultimate Strength Under any Combination of Bending and Compression, of the Depth to the Neutral Axis from Extreme Compression fibre to D.
47. Kuo = Ratio of Depth to Neutral Axis from extreme Compressive fibre; at ultimate strength
48. Kv = Coefficient used for Allowable Shear
49. L = Length of footing base in 'mm'
50. L1 = Length of sloped footing at top in 'mm'
51. Leff = Effective length of footing in 'mm'
52. LoffL = Footing offset along L on left side of column in 'mm'
53. LoffR = Footing offset along L on right side of column in 'mm'
54. M*ex = Eccentricity moment along column D 'kNm'
55. M*ey = Eccentricity moment along column B 'kNm'
56. M*x = Bending Moment along column D in 'kNm'
57. M*x' = Bending Moment along column D due to odd shaped column 'kNm'
58. M*xx = Total Bending Moment along column D (M*x + M*x' + M*ex) in kNm'
59. M*y = Bending Moment along column B in 'kNm'
60. M*y' = Bending Moment along column B due to odd shaped column in 'kNm'
61. M*yy = Total Bending Moment along column D (M*y + M*y' + M*ey) in 'kNm'
62. N* = Axial load for footing sizing in 'kN'
63. N*comb = Axial load from Load Combination in 'kN'
64. OB = Maximum permissible offset on bottom side of column in plan in 'mm'
65. OL = Maximum permissible offset on left side of column in plan in 'mm'
66. OR = Maximum permissible offset on right side of column in plan in 'mm'
67. OT = Maximum permissible offset on top side of column in plan in 'mm'
68. P1 = Soil pressure at corner 1 in 'kN/sqm'
69. P2 = Soil pressure at corner 2 in 'kN/sqm'
70. P3 = Soil pressure at corner 3 in 'kN/sqm'
71. P4 = Soil pressure at corner 4 in 'kN/sqm'
72. Pdelta = Column Load to be transferred by reinforcement
73. Pt = Calculated percentage tensile reinforcement
74. q = Surcharge Load In 'kN/sqm'
75. sp = Spacing Between bars at outer most layer in 'mm'
76. SPu = Upward Soil Pressure in 'kN/sqm'
77. SPuB = Upward Soil Pressure from bottom 'kN/sqm'
78. SPuL = Upward Soil Pressure from left 'kN/sqm'
79. SPuR = Upward Soil Pressure from right 'kN/sqm'
80. SPuT = Upward Soil Pressure from top 'kN/sqm'
81. V* = Design shear force in'kN'
82. V*x = Shear along major axis (along Column D) in'kN'
83. V*y = Shear along minor axis (along Column B) in 'kN'
84. Vps = Design Shear Force for Punching Shear Check in 'kN'
85. Vu = Ultimate Shear Strength of Footing with Effect of Moment in 'kN'
86. Vuc = Permissible Shear Capacity in concrete 'kN'
87. Vuo = Ultimate Shear Strength of Footing without Effect of Moment in
88. Vus = Design shear force to be resisted by Fitment in 'kN'
89. Vumax = Maximum Shear Capacity for one-way shear force in 'kN'
90. w = Calculated maximum crackwidth in the concrete member in 'mm'
91. Waterpr = Upward water pressure in 'kN/sqm'
92. Waterup = Upward force due to water in 'kN'
93. Wcr = Surface Crack Width in 'mm'
94. Zx = Section modulus of footing base along L in 'mm3'
95. Zy = Section modulus of footing base along B in 'mm3'
96. α2 = Coefficient for Compressive Stress Block
97. α2 = Constant used for calculation of stress in concrete for rectangular stress block
98. α2 = Constant used for crackwidth calculation based on Hypothetical thickness of section (th)
99. α3 = Coefficient used for creep calculation, 0.7x (k4 x α2)
100. γ = Ratio of Depth of the assumed rectangular stress block to kud
101. γ = The ratio, under design bending or design combined bending and compression, of the depth of the assumed rectangular compressive stress block to kud
102. εcc = The creep strain in the concrete
103. εx = Longitudinal Strain in the Concrete at the Mid Depth Of The Section
104. σo = The compressive stress in concrete assuming a cracked section in 'N/sqmm'
105. σ o, Perm = Permissible compressive stress in concrete assuming a cracked section in 'N/sqmm'
106. σ scr, Perm = Permissible stress in the tensile reinforcement assuming a cracked section in 'N/sqmm'
107. Φ = Capacity Reduction Factor
108. Φcc = Design creep coefficient for concrete
109. Φcc.b = Basic creep co-efficient
 
Code References:
AS 3600 : 2018
Sr.No. Item   Clause / Table
1. Capacity reduction factor : Table 2.2.2
2. F'ctf : 3.1.1.3
3. α2 : 8.1.3 (1)
4. γ : 8.1.3 (2)
5. Ast min : 21.3.1
6. Allowable Shear (for One Way Shear Check) : 8.2.4.1
7. Shear Coefficient Factor : 6.10.2.4
8. Ultimate Strength in Bending : 8.1.6.1
9. Effective Shear Depth, Dv : 8.2.1.9
10. Kv, θv : 8.2.4.3
11. εx : 8.2.4.2.2
12. Vu-max : 8.2.3.3
13. Check for Vu-max : 8.2.3.4
14. βh : 9.3.3 (Figure 9.3 (A))
15. Dimension of Critical Shear Perimeter (a) : 9.3.3 (Figure 9.3 (A))
16. Shear Strength of footing Vuo (for Punching Shear Check) : 9.3.3
17. Shear Strength of footing Vu (for Punching Shear Check) : 9.3.4
18. Load Transfer : 12.6
 

       
Design Code : AS 3600 : 2018
Footing No : FC1  
Column No : C1 ( 700mm X 600mm)
Analysis No : 1  
       
Concrete Grade : N30  
Steel Grade : 500N  
Clear Cover : 40 mm  
Dfd : 4 m  
Dw : 1 m  
 
Density of Soil = 18 kN/cum
Soil Bearing Capacity = 150 kN/sqm
Gross Bearing Capacity = 222 kN/sqm
Permissible SBC Increase for EQ = 0 %
Permissible SBC Increase for Wind = 0 %
Live Load Reduction = 0 %
Permissible area of loss of contact = 0 %
α2 = 0.8    
γ = 0.9    
 
Design cross section by : Average pressure
Consider overburden pressure : Yes
Surcharge Load = 10 kN/sqm
 
Footing Type : Pad  
Footing Size (L x B x D) : 3400mm X 3300mm X 675mm
Surcharge Load = 112.2 kN
Without considering Effect of Water Table
Footing Self Wt., F1 = 189.34 kN
Soil Weight, S1 = 646.38 kN
Total Weight, W1 = F1 + S1 + Surcharge Load
= 947.92 kN
Considering Effect of Water Table
Footing Self Wt., F2 = 113.6 kN
Soil Weight, S2 = 395.28 kN
Weight of Water (Submerged column), Wc = 9.76 kN
Total Weight, W2 = F2 + S2 - Wc + Surcharge Load
= 611.32 kN
Offset Along L (Loff) = 1350 mm    
Offset Along B (Boff) = 1350 mm    
           
Check For Maximum Soil Pressure:          
Critical Load Combination = [14] : (LOAD 1: LOAD CASE 1) +(LOAD 2: LOAD CASE 2) -(LOAD 4: LOAD CASE 4 EQ-Y)      
N*comb = 1195.83 kN          
N* = N*comb + W1
N* = 2143.74 kN          
M*x = -16.82 kNm          
M*y = -164.8 kNm          
N* / A = 191.06 kN/sqm
M*x / Zx = -2.65 kN/sqm
M*y / Zy = -26.71 kN/sqm
Maximum Soil Pressure = 220.42 kN/sqm
Allowable Soil Pressure = (1 X 150) + 72 kN/sqm
= 222 kN/sqm
 
Check For Minimum Soil Pressure:
Critical Load Combination = [6] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) +(LOAD 4: LOAD CASE 4 EQ-Y)
N*comb = 822.09 kN        
N* = N*comb + W2            
N* = 1433.4 kN          
M*x = -25.97 kNm          
M*y = 132.98 kNm          
N* / A = 127.75 kN/sqm          
M*x / Zx = -4.08 kN/sqm          
M*y / Zy = 21.55 kN/sqm          
Minimum Soil Pressure = 102.12 kN/sqm  
> 0    
 
Check For Buoyancy:
Critical Load Combination = [1] : 0.9 (LOAD 1: LOAD CASE 1)    
N*comb = 830.19 kN          
Factor of safety = 1.4    
Depth of Founding Layer = 4 m  
Ground Water Level = 1 m
Water Pressure = 30 kN/sqm
 
Upward force = Water Pressure X L X B  
= 336.6 kN  
Downward force = N*comb + (F2 + S2 - Wc) x 0.9  
= 1279.4 kN  
Factor of safety available = Downward Force / Upward Force  
= 3.8
  > 1.4
Check For Sliding:
Critical Load Combination = [7] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 4: LOAD CASE 4 EQ-Y)
N*comb = 1152.57 kN          
Coefficient Of Friction = 0.4    
Factor of safety = 1.2    
Shear V*x = 62.09 kN  
shear V*y = 12.99 kN  
Resultant sliding force = 63.43 kN  
Downward force = N*comb + (F2 + S2 - Wc)  
= 1651.68 kN  
Upward water pressure = 336.6 kN  
Net downward force = 1315.08 kN  
Force resisting sliding = Friction Coeff X Net Downward Force  
= 526.03 kN  
Factor of safety available = Resisting Force / Sliding Force  
= 8.29  
> 1.2  
 
Check For Overturning:
Along Width:
Critical Load Combination = (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 3: LOAD CASE 3 EQ-X)    
Factor of safety = 1.50    
N*comb = 1072 kN  
Moment M*x = 140.57 kNm  
N* = N*comb + (F2 + S2 - Wc)  
= 1571.12 kN  
Stabilizing Moment for N* = 2670.91 kNm  
DeStabilizing Moment = 140.57 kNm  
Overturning Factor of safety = 19    
Safe in Overturning > 1.50    
 
Along Length:
Critical Load Combination = (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) +(LOAD 4: LOAD CASE 4 EQ-Y)    
Factor of safety = 1.50    
N*comb = 822.09 kN  
Moment M*y = 132.98 kNm  
N* = N*comb + (F2 + S2 - Wc)  
= 1321.2 kN  
Stabilizing Moment for N* = 2179.99 kNm  
DeStabilizing Moment = 132.98 kNm  
Overturning Factor of safety = 16.39    
Safe in Overturning > 1.50    
 
Design For Bending:
Bottom Reinforcement Along L:
Critical Load Combination = [20] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 3: LOAD CASE 3 EQ-X)
N*comb = 1072 kN          
M*x = -140.57 kNm          
M*y = -14.7 kNm          
N* / A = 95.54 kN/sqm          
M*x / Zx = -22.11 kN/sqm          
M*y / Zy = -2.38 kN/sqm          
 
Deff = 627 mm          
Beff = 3300 mm          
ku = 0.36          
Φ = 0.85          
SPu = 117.65 kN/sqm          
M* = SPu X B X Loff X Loff / 2      
= 353.8 kNm          
Ast Rqd (M*) = 2995 sqmm          
Ast Prv (Distributed Across Total Width) = 27 - N12 @ 130          
  = 3053.7 sqmm  
 
Top Steel Along L:
Ast Prv (Distributed Across Total Width) = 25 - N12 @ 140 c/c  
= 2827.5 sqmm  
 
Bottom Reinforcement Along B:
Critical Load Combination = [22] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 4: LOAD CASE 4 EQ-Y)    
N*comb = 1152.57 kN          
M*x = -16.72 kNm          
M*y = -164.28 kNm          
N* / A = 102.72 kN/sqm          
M*x / Zx = -2.63 kN/sqm          
M*y / Zy = -26.62 kN/sqm          
 
Deff = 611 mm          
Leff = 3400 mm          
ku = 0.36          
Φ = 0.85          
SPu = 129.35 kN/sqm          
M* = SPu X L X Boff X Boff / 2          
= 400.74 kNm          
Ast Rqd (M*) = 3166 sqmm          
Ast Prv (Distributed Across Total Length) = 28 - N12 @ 130          
  = 3166.8 sqmm    
 
Top Steel Along B:
Ast Prv (Distributed Across Total Length) = 35 - N10 @ 100 c/c  
= 2748.9 sqmm  
Design For Shear:
One Way Shear Along L:
Critical Section @ d from Column Face  
  = 627 mm  
Critical Load Combination = [20] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 3: LOAD CASE 3 EQ-X)    
N * comb = 1072 kN          
M*x = -140.57 kNm          
M*y = -14.7 kNm          
N* / A = 95.54 kN/sqm          
M*x / Zx = -22.11 kN/sqm          
M*y / Zy = -2.38 kN/sqm          
 
Deff = 627 mm          
Dv = 564.3 mm          
Bv = 3300 mm          
Φ = 0.75          
SPu = 117.65 kN/sqm          
V* = SPu X (Loff - d) X B          
  = 280.71 kN          
Vu-max = 13830.65 kN            
Φ Vu-max = 10372.99 kN            
Max Stress Permissible = Φ Vu-max / (bv x dv)            
= 5.57 N/sqmm            
Stress due to V* = V* / (bv x dv)            
= 0.15 N/sqmm            
Stress due to V* <= Max Stress Permissible            
Hence, Safe            
Vuc = kv X bv X dv X sqrt(f'c)            
εx X 10^-3 = 0.44            
kv = 0.24            
cot θv = 1.59            
Vuc = 2452.78 kN            
ΦVuc = 1839.58 kN            
V* <= ΦVuc            
Shear Reinforcement Not required            
 
One Way Shear Along B:
Critical Section @ d from Column Face
 
  = 611 mm  
Critical Load Combination = [22] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 4: LOAD CASE 4 EQ-Y)    
N * comb = 1152.57 kN          
M*x = -16.72 kNm        
Muy = -164.28 kNm          
N* / A = 102.72 kN/sqm          
M*x / Zx = -2.63 kN/sqm          
M*y / Zy = -26.62 kN/sqm          
 
Deff = 611 mm          
Dv = 549.9 mm          
Bv = 3400 mm          
Φ = 0.75          
SPu = 129.35 kN/sqm          
V* = SPu X (Boff - d) X L          
  = 324.99 kN          
Vu-max = 13967.59 kN            
Φ Vu-max = 10475.69 kN            
Max Stress Permissible = Φ Vu-max / (bv x dv)            
= 5.6 N/sqmm            
Stress due to V* = V* / (bv x dv)            
= 0.17 N/sqmm            
Stress due to V* <= Max Stress Permissible            
Hence, Safe            
Vuc = kv X bv X dv X sqrt(f'c)            
εx X 10^-3 = 0.49            
kv = 0.23            
cot θv = 1.57            
Vuc = 2355.79 kN            
ΦVuc = 1766.85 kN            
V* < φVuc            
Shear Reinforcement Not required            
 
Design For Punching Shear:
Critical Section @ dom/2 from Column Face
  = 309 mm
   
Critical Load Combination = [22] : (LOAD 1: LOAD CASE 1) +0.6 (LOAD 2: LOAD CASE 2) -(LOAD 4: LOAD CASE 4 EQ-Y)    
N*comb = 1152.57 kN          
M*x = -16.72 kNm          
M*y = -164.28 kNm          
V* x = 62.09 kN          
V* y = -12.99 kN          
N* / A = 102.72 kN/sqm          
M*x / Zx = -2.63 kN/sqm          
M*y / Zy = -26.62 kN/sqm          
 
dom = 619 mm          
ax = 1319 mm          
ay = 1219 mm          
Punching Perimeter, u = 5076 mm          
Punching Area = 3142044 sqmm          
Φ = 0.75          
SPu = Average Pressure            
  = 102.72 kN/sqm          
Vps (Design Shear Force ) = { SPu [ (L x B)- (Leff x Beff)]}            
= 987.4 kN          
βh = Dc / Bc = 1.17            
fcv = 1.86 N/sqmm            
Shear Strength of Footing, Vuo = u x dom x fcv            
= 5851.29 kN            
Shear Strength of Footing, Vu = Vuo / ( 1 + [ u M*x / (8 V*y ax dom) ] + [ u M*y / (8 V*x ay dom) ] )            
= 1384.89 kN            
ΦVu = 1038.67 kN            
Vps < ΦVu            
 
Load Transfer Check For Load Transfer From Column To Footing
Critical Load Combination = [16] : 1.2 (LOAD 1: LOAD CASE 1) +1.5 (LOAD 2: LOAD CASE 2)
N*comb = 1269.15 kN
Φ = 0.6
A2 = 0.42 sqm
A1 = 11.22 sqm
Base Area = 11.22 sqm
Allowable Bearing Stress = 32.4 N/sqmm
Allowable Bearing Load = 13608 kN
> N*Comb, Hence Safe.