* Design of Combined footings
* Project :
INPUT
40 cm
Fcu
Fy
qall
t (R.C) =
250
3600
kg/cm
1.2
60
kg/cm
40
cm
kg/cm2
2
cm
40
40
cm
cm
200 t
2.5
100 t
(C.G) OF "R"
OUT PUT
R=P1+P2
300.00
L=2*A+a+2*C=
543.33
cm
1.67 m
Resultant of 2 loads is at:
P.C
Dims. of P.C :
INPUT
qn(Stress on Soil)=Rt/(L*B)=
R.C
GET
A=
qall=R/(L*B)
GET
B= 458.72
from center of small load col
B (cm)
L (cm)
t (cm)
minimum
460
545
25
CHOSEN
DIM design
460
545
11.97
t/m2
Dims. of R.C :
INPUT
1.67
R*A=P2*S
B (cm)
L (cm)
t (cm)
minimum
CHOSEN
410
495
60
DIM design
410
495
210
SKETCH
145cm
210cm
60cm
25cm
65cm
143.333
83.3333
500cm
550cm
143
83.3
(CHECK SHEAR & MOMENT )
fn=(Rt/(A*B)=
14.78
t/m2
Q0=fn*x0*B=
39.39
Q1=P1-fn*x1*B=
36.36
Q2=P2-fn*x2*B=
87.88
Q3=fn*x3*B=
87.88
Qmax=
87.88
(Qmax-fn*B*d)/(0.87*B*d)
27.80
t/m2
q(sh)=
27.80
t/m2
q(allw) =
63.26
t/m2
get
36.36 t
87.88 t
39.39 t
105 cm
65 cm
185 cm
145 cm
t/m2
87.88 t
from eq:
fn*B*X-P2=0.0
X (at Zero Shear)=
3.30
from eq:
100
14.78
SAFE SHEAR
fn*B*X /2-P2*(X-b/2)
M(0,1) (POSITSVE MOM.)=
M(2,3) (POSITSVE MOM.)=
21.89
82.50
t.m
t.m
M(NEGAT) (at Zero Shear)=
0.00
t.m
M(max)=
d = C1 (Mu/(Fcu*b))
82.50
get C1 =
t.m
5.01
330
cm
0.00 m.t
82.50 m.t
SAFE MOMENT
(CHECK PUNNCHING )
200 t
21.89 m.t
dp1=(p1-Ac*fn/10)/(*qallp)=
0.51
m
p1= 200
2.78 FALSE
were
4
Ac=
1
dp2=(p2-Ac*fn/10)/(*qallp)=
0.24
m
p2= 100
Ac=
SAFE PUNCHING UNDER P1
SAFE PUNCHING UNDER P2
4
1
qallp=
fn=
9
14.78
kg/cm2
t/m2
qallp=
fn=
9
14.78
kg/cm2
t/m2
(A)
Top Rft. :
M(NEGAT) (at Zero Shear)=
from table
0.00
SH(401)
t.m
get J =
As=Mu*1.5/(Fy*j*d)
#####
Asmin=0.15*b*d
33.21
Asmin=11*b*d/Fy
67.65
0.826
#DIV/0!
33.21
Asmin=
0.00
33.21
0.00
33.21 cm2
TAKE As/(B)=
Top Rft. :
(B)
J<0.826
get C1 = ####
#DIV/0!
Asmin=1.33*Asreq
( Longitudinal direction )
d = C1 (Mu/(Fcu*b))
no.
12
total no/(B)
/m
34
7.17
Bottom Rft. :
1- COLUMN C1 WERE P1= 200 t
M(2,3) (POSITSVE MOM.)=
from table
82.50
SH(401)
t.m
get J =
As=Mu*1.5/(Fy*j*d)
0.826
J<0.826
get C1 = 5.01
0.826
0.829
77.1
Asmin=0.15*b*d
33.21
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
33.21
67.65
Asmin=
102.50
67.65
67.65
77.07 cm2
TAKE As/(B)=
no.
10
16
Bottom Rft. :
( DESIGN)
d = C1 (Mu/(Fcu*b))
total no/(B)
/m
43
9.35
2- COLUMN C2 WERE P2= 100 t
M(0,1) (POSITSVE MOM.)=
from table
SH(401)
21.89
t.m
d = C1 (Mu/(Fcu*b))
get J =
0.826
J<0.826
get C1 = 9.72
0.826
0.860
As=Mu*1.5/(Fy*j*d)
20.5
Asmin=0.15*b*d
33.21
Asmin=11*b*d/Fy
67.65
Asmin=1.33*Asreq
33.21
Asmin=
27.20
33.21
27.20
33.21 cm2
TAKE As/(B)=
Bottom Rft. :
no.
16
/m
total no/(B)
22
4.03
(A)
Top Rft. :
Top Rft. :
(B)
no.
12
total no/(B)
/m
26
Bottom Rft. :
1- COLUMN C1 WERE P1= 200 t
BEAM WIDTH = (a+2d)=
TAKE (B.W)=
83.48
M (working)=WL2/2 =
t.m
were
W=P/B=
48.78 t/m
&
L=
d = C1 (Mu/(Fcu*b))
from table
SH(401)
get J =
( Transverse direction)
As=Mu*1.5/(Fy*j*d)
( DESIGN)
148 cm
145 cm
1.85 m
get C1 = 2.85
J<0.826
0.727
0.826
0.727
90.30
Asmin=0.15*b*d
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
11.53
6.60
11.53
120.09
6.60
Asmin=
11.53
90.30 cm2
TAKE As/(B)=
Bottom Rft. :
T.no
80
12
total no/(B.W)
145
cm
79.88
2- COLUMN C2 WERE P2= 100 t
BEAM WIDTH = (a+2d)=
TAKE (B.W)=
M (working)=WL2/2 =
41.74
t.m
were
W=P/B=
24.39 t/m
&
L=
d = C1 (Mu/(Fcu*b))
from table
SH(401)
148 cm
145 cm
get J =
As=Mu*1.5/(Fy*j*d)
J<0.826
0.805
1.85 m
get C1 = 4.03
0.826
0.805
40.74
Asmin=0.15*b*d
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
11.53
23.48
11.53
54.19
23.48
Asmin=
23.48
40.74 cm2
TAKE As/(B)=
Bottom Rft. :
T.no
37
12
total no/(B.W)
145 cm
36.04
/M
DRAWING
5f12/M
8f12/M
5f12/M
10f16/M
80f12/145
145cm
5f12/M
5f16/M
145cm
37f12/145
* Design of Combined footings
* Project :
INPUT
40 cm
Fcu
Fy
=
=
qall
=
t (R.C) =
60
cm
250
3600
kg/cm
1.5
60
kg/cm2
40
60
cm
cm
cm
kg/cm2
100 t
2.5
200 t
P.C
(C.G) OF "R"
OUT PUT
R=P1+P2
300.00
L=2*A+a+2*C=
Lmin=
373.33
385.00
cm
cm
Resultant of 2 loads is at:
1.67 m
GET
A=
1.67
qall=R/(L*B)
GET
B=
512.82
from center of small load col
Dims. of P.C :
B (cm)
L (cm)
t (cm)
minimum
515
390
25
0
515
0
390
INPUT
chosen
DIM design
qn(Stress on Soil)=Rt/(L*B)=
14.94
Dims. of R.C :
R.C
R*A=P2*S
INPUT
chosen
DIM design
INPUT LOGIC.DIM WERE B<L
t/m2
B (cm)
L (cm)
t (cm)
465
365
60
0
465
0
365
(CHECK SHEAR & MOMENT )
fn(Stress on R.C)=Rt/(L*B)=
17.68
t/m2
Q0=fn*x0*B=
53.42
Q1=P1-fn*x1*B=
97.26
Q2=P2-fn*x2*B=
67.12
Qmax=
97.26
(Qmax-fn*B*d)/(0.87*B*d)
23.40
t/m2
q(sh)=
23.40
t/m2
q(allw) =
63.26
t/m2
100 t
17.68
t/m2
67.12 t
from eq:
fn*B*X-P2=0.0
X (at Zero Shear)=
1.22
97.26 t
SAFE SHEAR
get
200
53.42 t
125 cm
65 cm
40 cm
m
40.83 m.t
from eq:
fn*B*X /2-P2*(X-b/2)
M(0) (POSITSVE MOM.)=
M(max) (at Zero Shear)=
17.36
40.83
t.m
t.m
d = C1 (Mu/(Fcu*b))
get C1 =
7.58
17.36 m.t
1.22 m
(CHECK PUNNCHING )
SAFE MOMENT
dp1=(p1-Ac*fn/10)/(*qallp)=
0.41
m
p1= 100
2.78 FALSE
were
2.4
Ac=
0.7
dp2=(p2-Ac*fn/10)/(*qallp)=
0.40
m
p2= 200
Ac=
SAFE PUNCHING UNDER P1
SAFE PUNCHING UNDER P2
4.8
1.44
qallp=
fn=
9
17.68
kg/cm2
t/m2
qallp=
fn=
9
17.68
kg/cm2
t/m2
(A)
Top Rft. :
M(max) (working)=
from table
SH(401)
40.83
t.m
d = C1 (Mu/(Fcu*b))
get J =
As=Mu*1.5/(Fy*j*d)
0.826
76.73
50.73
( Longitudinal direction )
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
( DESIGN)
37.67
Asmin=0.15*b*d
37.67
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
76.73
37.67
Asmin=
50.73
50.73
50.73 cm2
TAKE As/(B)=
Top Rft. :
no.
16
total no/(B)
/m
29
5.43
Bottom Rft. :
M(POSITIVE) (working)=
from table
0.826
0.853
38.14
Asmin=0.15*b*d
(B)
J<0.826
get C1 = 7.58
SH(401)
17.36
t.m
d = C1 (Mu/(Fcu*b))
get J =
As=Mu*1.5/(Fy*j*d)
0.826
J<0.826
get C1 = 11.62
0.826
0.863
16.2
37.67
Asmin=
21.57
37.67
21.57
37.67 cm2
TAKE As/(B)=
Bottom Rft. :
no.
16
total no/(B)
/m
4.03
(A)
Top Rft. :
Top Rft. :
(B)
no.
12
total no/(B)
/m
20
Bottom Rft. :
1-INTERIOR COLUMN
M (working)=WL2/2 =
88.19
were
BEAM WIDTH = (a+2d)=
TAKE (B.W)=
t.m
W=P/B= 43.01 t/m
&
L=
d = C1 (Mu/(Fcu*b))
from table
SH(401)
get J =
( DESIGN)
( Transverse direction)
As=Mu*1.5/(Fy*j*d)
get C1 = 2.96
J<0.826
0.739
0.826
0.739
13.12
5.22
13.12
124.72
5.22
Asmin=
Bottom Rft. :
T.no
83
12
2-EXTIRIOR COLUMN
48.56
were
total no/(B.W)
165
cm
BEAM WIDTH = (a+d)=
TAKE (B.W)=
W=P/B= 21.51 t/m
get J =
As=Mu*1.5/(Fy*j*d)
82.96
94 cm
90 cm
t.m
&
L=
d = C1 (Mu/(Fcu*b))
SH(401)
13.12
93.78 cm2
TAKE As/(B)=
from table
2.025 m
93.8
Asmin=0.15*b*d
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
M (working)=WL2/2 =
168 cm
165 cm
J<0.826
0.738
2.125 m
get C1 = 2.95
0.826
0.738
51.7
Asmin=0.15*b*d
Asmin=11*b*d/Fy
Asmin=1.33*Asreq
7.16
14.58
7.16
68.81
14.58
Asmin=
14.58
51.74 cm2
TAKE As/(B)=
Bottom Rft. :
T.no
46
12
total no/(B.W)
90
cm
45.77
DRAWING
/M
5f12/M
6f16/M
5f16/M
46f12/90
90cm
165cm
5f12/M
83f12/165
