Civil Engineering Reference
In-Depth Information
Steel Area (
d
360 mm) Taking Moments at Face of Wall
Cantilever length
3.00
2
150
1000
1.35 m
1.35
2
M
u
(1.35)(226.7)
206.58 kN/m
M
u
206.58
10
6
(0.9)(1000)(360)
2
1.771
bd
2
0.00442 from Appendix Table B.9
A
s
(0.00442)(1000)(360)
1591 mm
2
/m
Use #22 bars @ 225 mm o.c. (1720 mm
2
)
Development Length
From Table 7.1 in Chapter 7
1.0
Assume
c
cover
90 mm
k
c
one- half c. to c. of bars
112.5 mm
Letting
K
tr
0
c
K
tr
d
b
90
0
22.2
4.05
2.50
Use 2.5
9
f
y
d
d
b
c
K
tr
d
b
c
10
f
(9)(420)(1.0)(1.0)(1.0)(1.0)
(10
30.86 diameters
24)(2.5)
d
b
A
s
,reqd
d
1591
1720
A
s
,furn
(30.86)
28.54 diameters
d
(28.54)(22.2)
634 mm
1350 mm
100 mm
1250 mm available
OK
Use 450 mm footing 3 m wide with #22 bars at 225 mm
12.16
COMPUTER EXAMPLES
EXAMPLE 12.12
Repeat Example 12.1 using SABLE32.
SOLUTION
In applying the program,
P
a
represents the sum of the working loads applied to the footing per foot.
It is 20
35 k in this case. In the “Wall Parameters” section, the fixed value of
b
shown on
the screen represents the length of footing used for calculating shear and moment, while
h
is the
thickness of the wall. SABLE32 computes effective depths in multiples of 1 inch.
15
Design a Spread Footing for a Wall
Properties of the Concrete
f
c
= 3000 psi
E
c
= 3122019 psi
Beta
1
= 0.850
Concrete strain = 0.0030 in/in
