e-mosty June 2017: Osman Gazi B. US Suspension. Hålogaland B. e-mosty June 2017: Suspension Bridges | Page 45

interface are prone to fatigue damage at this point. In
addition, experience has shown that no matter how
diligently the suspenders are painted, because of their
construction, water will find a way into the ropes, and
collect at the socket. When dirt and road salts are
added to this mix, the result can be accelerated
corrosion, broken wires and a loss of strength. The
typical end bearing socket detail is usually below deck
level in a confined area as shown in Figure 5, which
can cause water and dirt to be trapped and make
inspection and maintenance difficult. Making sure
these sockets are washed down regularly to remove
dirt and salt is extremely important.
Protective coatings to suspenders have been another
maintenance issue for bridge owners. In the USA,
Noxide is used on a number of bridges. Some owners
have had issues with coatings bulging and water
retention at the bottom of the suspenders and have
used a thinner coating over a short length of the
suspender immediately above the socket. It does
seem somewhat counterintuitive given the
aforementioned problems at the socket level but
allowing trapped water to get out from inside the
rope is more important at this location.
As a consequence of all the concentration of issues at
the socket level of suspenders it is recommended that
owners consider removing a number of short
suspenders for examination and testing if the
suspenders have been in service for more than 25
years, even if there are no external signs of damage.
A typical suspender replacement frame used in the US
is shown in Figure 6.
Figure 5: Typical suspender socket detail
on a US suspension bridge
It is unfortunate that there appears to be no effective
method of testing suspenders for wire breaks at the
most critical area - the socket interface. Removal and
testing or unwrapping of this type of rope appears to
be the only sure way of determining whether failure
has occurred within the inner wire core.
Figure 6: Typical suspender replacement temporary
jacking frame
2/2017