Civil Engineering Reference
In-Depth Information
SOLUTION
From Table 6.1
1.0 for bottom bars
1.5 for epoxy-coated bars with clear spacing
6
d
b
(1.0)(1.5)
1.5
1.7
1.0
c
side cover of bars
80 mm
c
one-half of c. to c. spacing of bars
40 mm
OK
(a) Using SI Equation 12-1 with
K
tr
0
c
K
tr
d
b
40
0
25.4
1.575
2.5
OK
f
y
c
d
d
b
9
10
K
tr
d
b
c
f
(1.0)(1.5)(1.0)(1.0)
1.575
9
10
4
20
21
78.6 diameters
(b) Using Computed Value of
K
tr
and SI Equation 12-1
K
tr
A
tr
f
y
t
10
sn
(2)(71)(420)
(10)(200)(4)
7.45
c
K
tr
d
b
40
7.45
25.4
1.87
2.5
OK
d
(1.0)(1.5)(1.0)(1.0)
1.87
9
10
4
20
d
b
66.2 diameters
21
7.16 COMPUTER EXAMPLE
EXAMPLE 7.10
Using SABLE32, determine the development length needed for #6 uncoated bottom bars used in a
beam made with lightweight concrete. Assume
c
2 in.,
K
tr
0,
c
f
4000 psi, and
f
y
60,000 psi.
_
. The term
A
st
/
A
sp
repre-
sents the ratio of the flexural steel required to that furnished. If a value is not input, SABLE32 will
use a ratio equal to 1.0.
The necessary data is input into the computer, and an answer of 29.599 diameters
22.199 in.
is provided. No printout is provided.
SOLUTION
Development length is represented on the toolbar with the hook symbol
PROBLEMS
7.1
Why is it very difficult to calculate actual bond
stresses?
7.2
What are top bars? Why are their required develop-
ment lengths greater than they would be if they were not
top bars?
7.3
Why do the cover of bars and the spacing of those
bars affect required development lengths?
7.4
Why isn't the anchorage capacity of a standard hook
increased by extending the bar well beyond the end of the
hook?
