Enerpac JS125 - Page 45

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Document number: ED.03783.00.001.ENG rev 4 Page 45 of 153
Example how to calculate the ground bearing pressure of the foundation (JS250):
Data
depending
on the
operation
force on one unit
F
unit
1000
kN
number of applied barrels
Nr_barrels
17
side_load
p
1.5
%
swivel_height
Swivel
height
8000
mm
Height of foundation
h
0.25
m
Fixed data
own mass
one unit
Unit
mass
75
kN
one barrel
Barrel
mass
4
top barrel
Top_barrel
mass
24
measures of the bearing area
L
jack-up
B
jack-up
0.37
0.27
m
m
safety factor s
S
1.65
reaction-width of the barrel
Reaction_width
1070
mm
1. The force on one bearing area caused by the load and the side load is:
F
load and side load
= F
unit
(
1
/
4
+
1
/
2
p * Swivel
height
/ Reaction_width)
F
load and side load
= 1000 (
1
/
4
+
1
/
2
0.015 * 8000 / 1070) = 306 kN
2. The force on one bearing area caused by the own mass of the system:
F
own mass
= (Unit
mass
+ Top_barrel
mass
+ Nr_barrels * Barrel
mass
) / 4
F
own mass
= (75 + 24 + 17 * 4) / 4 = 42 kN
3. Total force on one bearing area is
F
total
= F
load and side load
+ F
own mass
F
total
= 306 + 42 = 348 kN
4. Take the safety factor into account:
F
total safe
= F
total
* S
F
total safe
=348 * 1.65 = 574 kN
5. The ground bearing pressure without foundation on one bearing area would be:
σ
no foundation
= F
total safe
/ (L
jack-up
* B
jack-up
)
σ
no foundation
= 574 / (0.37 * 0.27) = 5748 kN / m
2
6. The ground bearing pressure with foundation on one bearing area would be:
σ
foundation
= F
total safe
/ (L
tot
* B
tot
)
σ
foundation
= F
total safe
/ ((L
jack-up
+ 2*h) * (B
jack-up
+ 2*h)
σ
foundation
= 574 / ((0.37 +2*0.25) * (0.27+2*0.25)) = 857 kN / m
2

NB
• The actual ground bearing pressure shall not exceed the allowable ground
bearing pressure.
• Complete the checklist of Appendix A with the calculated maximum ground
bearing pressure as well as the height of the foundation