Civil Engineering Reference
In-Depth Information
Figure 8.19
Variation of minimum shear reinforcement with
a/d
ratio
The UH minimum stirrup requirement at the chosen sections can be checked in terms of the
maximum stirrup spacing
s
max
as follows:
A
v
f
y
A
v
f
y
s
max
=
0625
f
c
(MPa)
b
w
75
f
c
(psi)
b
w
/
M
u
≤
.
or
V
u
d
0
25
(8.28a)
0
.
0
.
V
u
d
/
M
u
≥
0
.
5
A
v
f
y
A
v
f
y
s
max
=
125
f
c
(MPa)
b
w
or
5
f
c
(psi)
b
w
0
.
25
<
V
u
d
/
M
u
<
0
.
5
(8.28b)
0
.
1
.
8.3.6 Comparisons of Shear Design Methods with Tests
8.3.6.1 UH Shear Design Method
The analytical shear strengths
V
cal
calculated from Equations (8.18), (8.24) and (8.28a or b)
are compared with the experimental shear strengths
V
exp
for 148 prestressed I-beams tested
by 14 groups of researchers available in the literature. The
V
exp
/
V
cal
ratios for the UH method
are plotted against the span-to-depth ratio
a/d
in Figure. 8.20. It can be seen that the
V
exp
/
V
cal
ratios for all 148 beams vary from 1.0 to about 2.0.
Closer examination of the
V
exp
/
V
cal
ratios in Figure 8.20 reveals that this strength ratio is
strongly influenced by the sizes of the test specimens. Let's define beams with a height greater
