Civil Engineering Reference
In-Depth Information
(ii) Design actions:
To consider the effects of the buoyant uplift, we can either use the submerged weight
of the whole footing, or use the total weight and subtract the uplift force due to water
pressure under foundation.
Design value of self weight of concrete and soil (unfavourable, permanent action):
W
=
(
W
+
W
)×
γ
,
d
concrete
soil
G unfav
=
(
54 0
.
+
76 8
.
)
×
1 35
.
=
176 6
.
kN
Design value of the vertical structural (unfavourable) actions:
V
= ×
V
γ
+ ×
V
γ
=
(
800 1 35
×
.
)
+
(
350 1 5
×
.
)
=
1605
kN
d
G
G unfav
,
Q
Q unfav
,
Design value of water pressure under the base (unfavourable (negative) action - from
Single Source Principal):
U
= ×
U
γ
,
= − ×
(
1 5 2 0 2 0 9 81 1 35
.
.
×
.
×
.
)
×
.
=−
79 5
.
kN
d
G unfav
Design effect of actions (i.e. sum of vertical forces):
F W V
=
+ + =
U
176 6 1605 79 5
.
+
−
.
=
1702 1
.
kN
d
d
d
d
Overburden pressure q
:
=
γ
z
=
(
20 9 81 1 5
−
.
)
×
.
=
15 29
.
kPa
soil
(iii)
Design material properties:
′
tan
φ
tan
.
28
1 0
°
=
=
′
=
Design angle of shearing resistance:
φ
tan
−
1
tan
−
1
28
.
0
°
d
γ
φ
′
=
γ
γ
γ
20
1
=
k
Design weight density of soil
:
γ
=
20 N m
k
/
3
d
(iv)
Design geometry:
No eccentric loading,
⇒
A'
=
B
×
L
=
2.0
×
2.0
=
4.0 m
2
No inclined loading,
⇒
i
c
=
1.0
Foundation base horizontal,
⇒
b
c
=
1.0
From EN 1997-1:
2004
, Annex D:
′
φ
=
′
N
q
=
e
π
⋅
tan
φ
tan
2
45
+
14 72
.
2
N
=
2
(
N
q
−
1
)
tan
φ
′ =
14 59
.
γ
d
′
=
s
q
= +
1
sin
φ
1 47
.
s
γ
=
0 7
.
(v)
Bearing resistance:
′
=
′
+
′
′
R/A
c N b s i
q N b s i
+
0 .
γ
B N b s i
c
c c c
q q q q
γ
γ γ γ
R
k
=
4 0
.
× +
[
0
(
15 29 14 72 1 0 1 47 1 0
.
×
.
× ×
.
.
×
.
)
+
(
0 5
.
×
(
20 9 81
−
.
)
×
2 0 14
.
×
.
59 1 0 0 7 1 0
× × ×
.
.
.
)]
=
1738 8
.
kN
R
1738 8
1 0
.
k
R
=
=
=
1738 8
.
kN
d
γ
.
Rv
