Civil Engineering Reference
In-Depth Information
the abutment. The abutment segment can then be cast on shuttering carried by the
abutment itself, Figure 15.18 (a).
There are several strategies that allow longer end spans to be built. As the stability
falsework is designed to resist the effects of one segment out of balance, it is usually
possible to complete the cantilever construction with one additional segment in the end
span. If the end span needs to be still longer, falsework may be cantilevered forwards
from the abutment foundation, Figure 15.18 (b).
It is also possible to build the unbalanced end of the end span using the end span
traveller. Once the point of balance with the main span has been reached, a prop
is installed and the traveller continues building, Figure 15.18 (c). Generally, two or
three segments may be built before another prop is needed. If the ground is subject
to settlement, the props should be equipped with levelling jacks. As permanent top
fi bre tendons are not required at this section, the construction bending moments can
be carried in reinforced concrete action, or by using temporary prestressing bars.
Although this is probably an economical way to build a long end span, frequently the
programme precludes it, as the traveller is needed elsewhere on the bridge.
The last resort is to build a substantial length of the end span on independently
founded falsework, Figure 15.18 (d). In order to control its settlement relative to the
abutment, it should consist of beams resting on a few towers equipped with levelling
jacks. The one advantage of this method, when the construction programme is of the
Figure 15.18
Construction of end spans
