Civil Engineering Reference
In-Depth Information
Figure 14.11
AREA contract: washboard shear keys (Photo: Robert Benaim)
14.3.10 The reinforcing cage
The reinforcing cage, Figure 14.12, is generally produced in a jig, which ensures that
it is geometrically accurate, and may be placed in the casting cell without the need
for adjustment. Usually it is necessary for each casting cell to be served by two jigs to
ensure that a cage is produced on a daily cycle.
The production of segments is more an industrial activity than typical cast-in-situ
construction, and the preparation of the reinforcing cage needs to refl ect this changed
emphasis. For instance there are reinforcing bars that must respect cover at each end,
such as the transverse bars in the bottom slab, and shear links in the webs; in a long
bridge deck there will be many thousand such bars. The conventional bending tolerance
on the overall length of the bars would make it impossible to respect the correct cover
at each of their ends and in cast-in-situ construction it is normal practice to design
them with a lap. In the industrial process, there is no reason why such 'dead length'
