How the software calculate effective depth, d to satisfy
punching shear in pad footing?
To explain this, let us explain from basic diagonal tension block checking.
Elevation of pad
pd
b
a
pd
Diagonal tension
block
C
Plan view of pad
d
A
B
q
Where,
A or B
=
pad dimension
a or b
=
stump dimension
p
=
multiplier for d for distance from stump to punching edge
d
=
effective depth of pad footing
q
=
soil bearing capacity
cp
=
critical perimeter of tension block
Ashaded
=
Shaded area
V
=
Total shear force
Vc
=
Shear capacity of concrete
c
c
shaded
shaded
V
pd
b
d
pd
a
d
pd
b
pd
a
AB
q
V
d
cp
V
pd
b
pd
a
AB
q
A
q
V
pd
b
pd
a
AB
A
pd
b
pd
a
cp
<
+
+
+
+
+
−
×
<
+
+
−
×
=
×
=
+
+
−
=
+
+
+
=
)
2
(
2
)
2
(
2
)]
2
)(
2
(
[
*
)]
2
)(
2
(
[
)
2
)(
2
(
)
2
(
2
)
2
(
2
The software will automatic calculate the Vc base on the rebar provided and :-
2
2
2
2
2
2
2
2
2
2
2
2
4
2
4
2
4
2
2
4
2
4
2
4
2
2
4
2
4
2
)
4
2
2
(
pd
V
bdV
pd
V
adV
d
qp
bpqd
apqd
qab
qAB
pd
V
bdV
pd
V
adV
d
qp
bpqd
apqd
qab
qAB
V
pd
bd
pd
ad
d
p
bpd
apd
ab
q
AB
q
c
c
c
c
c
c
c
c
c
+
+
+
+
+
+
+
=
+
+
+
=
−
−
−
−
=
+
+
+
+
+
+
−
the software will differentiate effective depth d w.r.t. p , and look for the minimum effective depth.
Once it obtain the depth it will shown both the effective depth (d) and the critical perimeter
distance from stump (p) in the textual output.
Critical perimeter
distance measure
from stump.
Minimum effective
depth w.r.t. p.