Civil Engineering Reference
In-Depth Information
Figure 3.21
Shear fi elds
then represents the resultant of a number of sub-trusses. At the end of simply supported
beams, this version of the analogy leads to a possible arrangement of the truss as shown
in Figure 3.21 (b).
At intermediate supports, where the shear force either side of the support is equal,
the arrangement shown in Figure 3.21 (c) is appropriate. If the shear force is unequal
either side of the support, the equal portion may be considered as in Figure 3.21 (c),
while the unbalanced portion would be as in Figure 3.21 (b). In particular, this concept
is used in the design of bridge deck diaphragms (
9.6
) and in other cases when one beam
frames into another and it is helpful to consider that the end reaction is distributed up
the end face of the beam.
Clearly, the simple logic leading to the rules on curtailment of reinforcement over
the piers of continuous beams, described in
3.10.6
, is upset by this concept of a shear
fi eld. It would be interesting to see the results of tests of beams where the reinforcement
is curtailed in accordance with the logic of shear fi elds.
