Civil Engineering Reference
In-Depth Information
Another example is a very long railway viaduct, split up into expansion lengths.
If the piers were fl exible, they could be all pinned to the deck. The acceleration and
braking forces are applied by trains of fi nite length. If the whole viaduct is considerably
longer than one train length for a single track railway, or two train lengths for twin
tracks, such forces may be distributed to all the piers of the viaduct by placing shock
absorbers between each of the expansion lengths. Thus for all slow movements the
expansion lengths behave as separate entities, while for sudden loads the whole viaduct
acts as one, Figure 7.17 (b).
An alternative solution to the above example would be for each expansion length to
have at its centre an anchor pier (or piers) that was stiffer than the others, and strong
enough to carry the acceleration/braking forces on that expansion length. This would
probably have a higher fi rst cost, but would not have the maintenance liability of the
locking devices, Figure 7.17 (c).
Figure 7.17
Use of shock absorbers
