Civil Engineering Reference
In-Depth Information
Table 6.3 compares the ultimate load capacity of top-loaded wall-beams
W1-3 as predicted by the respective equations. In the calculations for the
ACI method Eqn (6.1a) governs for this group of wall-beams and the
Table 6.3
Predicted ultimate loads and test values for top-loaded wall-beams
unmodified value of
V
n
has been used. In evaluating the Schütt Eqn (6.4) the
value of the modulus of rupture of concrete has been assumed to be
2×splitting strength for each specimen. In the CIRIA Eqn (6.6) the
recommended values λ
1
=0.44 for normal concrete and λ
2
=0.85 N/mm2 for
plain bars have been used.
Figure 6.11
Shear reinforcement at support for bottom loads (CIRIA Guide 2).
* Value from Eqn (6.6). However, governing ultimate shear capacity values are W1-L2:513
kN
and W3-L1:546 kN.
The load at which the first diagonal crack was detected in these specimens
is also given in Table 6.3. It can be observed that Schütt's equation is grossly
conservative and that the ACI figures are more conservative than the CIRIA
values. Both CIRIA and ACI design values of ultimate loads are in the same
range as the test values of load at first crack. However, the failure load for
these three specimens is more than twice the shear strength calculated by Eqns
(6.1a) and (6.6). Moreover Eqn (6.6) values for two of the wall-beams exceed
the governing value of Eqn (6.7). In addition, failure of these specimens was
