"Paul Scott" wrote:

"Bruce" wrote in message
.. .
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.

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.

Presumably this isn't the only structure of this type on the road network
though?

Are many more due to be found before long?


There are plenty of structures of this type (precast segmental
pre-stressed post-tensioned) but I think the Hammersmith flyover was
the first. I don't know of any subsequent structure of this type that
lacks the essential combination of bridge deck waterproofing, proper
drainage, adequate concrete cover to reinforcement/pre-stressing
tendons and grouting of tendon ducts.

So Hammersmith is very much a one-off. That doesn't mean that other
structures don't have problems of their own, but the design and
subsequent operation and maintenance practice related to the
Hammersmith flyover seems to have combined in a way that could only
end in tears.