Bruce wrote:
A steady seepage of salt water into the structure, built in the 1960s,
has weakened the structure, but engineers said it was now safe to take
light traffic.


The flyover was equipped with electric heating elements under the road
surface. These were specified in order to eliminate damage to the
pre-stressed concrete structure from de-icing salt.

Apparently the heating elements never worked properly from the outset.
In that case, the best alternative would have been to use urea for
de-icing, as is routine practice in Germany and some other countries.
But no, the cheaper but potentially very damaging rock salt was used,
and this is what has caused the problems with the pre-stressing cables
within the concrete structure.