Civil Engineering Reference
In-Depth Information
ratios
a/h
and transverse reinforcement indices . For all six cases, the
shear strength ratio increases with the increase of longitudinal reinforcement
index. This means that the longitudinal steel is effective for
a/h
ratios from 0.5
to 2 and with transverse reinforcement indices from 0.05 to 0.55. The
effectiveness is relatively large when the longitudinal reinforcement index
varies from 0.1 to 0.3 but becomes gradually smaller at higher range.
7.4.3
Transverse reinforcement
The variation of shear strength ratio as a function of the transverse
reinforcement index is shown in Figure 7.11 for six combinations of shear
span ratios and longitudinal reinforcement indices. For large
a/h
ratios of 1.0
and 2.0 (cases 2,3,5 and 6), increases with the increase of
especially in the low range. For small
a/h
ratio of 0.5 (cases 1 and 4),
however, decreases slightly with the increase of . This is
because under large effective transverse compression, (i.e. small
a/h
ratio) more
transverse reinforcement leads to relatively less compressive strain
e
d
and this in
turn leads to more softening of the concrete according to Eqn (7.8c)
Figure 7.11
Effect of transverse reinforcement index on shear strength
The ineffectiveness of the transverse reinforcement in the range of
low
a/h
ratios can also be observed from the tests of Kong
et al.
(1970).
Three pairs of their test specimens with
a/h
ratios less than 0.5 are listed
in
Table 7.3.
In each pair of beams (1-30 versus 2-30; 1-25 versus 2-25, and 1-20
versus 2-20), the
a/h
ratio and the longitudinal steel percentage are
identical, but the transverse steel percentage
r
t
differs greatly, 0.0245 versus
0.0086. It can be seen that the three beams with lower
r
t
(0.0086) all have
