Design of pile foundation
Data
1 Diameter of pile 300 mm
Length of the pile as per soil
2 recommendation 6000 mm
3 Grade of Concrete Fck 30 N/mm2
4 Grade of Steel fy 500 N/mm2
5 Pile Above Ground Level 600 mm
6 Total length 6600 mm
7 Axial Load 900 kN
8 Area of pile Ag 70685.835 mm2
9 Ultimate load Pu 1350000 N
Solution
Step1 Longitudinal Reinforcement
0.4xFckxAg+(0.67xfy-
pu = 0.4xFck)Asc
(pu-(0.4xFckxAg))/(0.67xfy-
Asc = 0.4xFck))
= 1553.467 mm2
1.25% for l<30D
Step2 Minimum Reinforcement of steel 883.573 mm 2
1.50% for30D>l<40D
2.00% forL>=40D
Asc = 1553.467 mm2
Diameter of Bar = 16
Area of Rebar Ab = 201.062 mm2 2
No.of Bars Required = Asc/Ab
No.of Bars Required = 7.726 8
Hence Provide 8 No's of 16 mm diameter bar as a main reinforcement
Step3 Lateral Reinforcement (Center portion) π
0.2% of vol.of pile per pitch
I.Center portionof pile vol.of reinforcement = length D2
Tie Rebar d = 8
Vol of One tie vol. of tie = (πD2)/4)xperimeter d 250
perimeter = 2πr r 125
= 785.398
Vol.of tie = 39478.4176043574 mm3
Vol of Pile Per pitch Length = Areax Pitch
70685.8347057704p
0.2% of vol.of pile per pitch length = (0.2/100)x70685.8347057704p
141.3716694115
141.371669411541P
39478.417604 = 141.371669411541P
P 279.2526803191
Maximum per pitch D/2 150
Hence Provide 8mm diameter bar of ties @ 150 mm c/c
Step4 Lateral Reinforcement (Near Pile End/Head)
0.6% of vol.of pile per pitch
I. vol.of tie reinforcement = length
3D
Vol. of Pile upto Length(3D) = 63617251.2351933
0.6% of vol.of pile per pitch length = (0.6/100)x70685.8347057704p
424.1150082346
424.115008234622P
39478.417604 = 424.115008234622P
p = 93.084226773 93
Hence Provide 8mm diameter bar of ties @ 93 mm c/c
Step5 Spiral reinforcement near pile head
For the length of 3d = 900
Vol. of Spiral = 0.6% of vol.of pile per pitch length
Vol.of Spiral = (πD2/4)πD
7.580 50.26548
1263.309
300 25 415
450 30 500
600 35 550
750 40
900 45
1000 50
30D 9000 1.25
for30D>l<40D 40D 12000 1.5
forL>=40D 2
12
16
20
25
32
8
10
12
900