Portland's Burnside Bridge will soon be closed for three weeks to auto
traffic (open to pedestrians and bikes though) for repairs. Built in the
1920s, the Burnside is a lifting bridge having two hinged spans (photos
Now according to this:
"The closure will allow a contractor to replace parts of a hinge that
attaches the 3.8 million pound counterweight to the lift span. The
original parts have worn and broken so that the hinge cannot turn freely
when the bridge opens for river traffic. If the hinge were to fail, the
east lift span would not be able to open.
Replacement of the pin and bearing that form the hinge is technically
challenging. The contractor will need to detach the counterweight and
lower it to replace the parts. A complex rigging system will support the
counterweight while it is detached. The bridge closure is needed to ensure
the safety of the public, workers and the bridge itself. Vibrations from
traffic could impact drilling operations and other work."
Impressive! I'm sure repairs to a hinge with a 3.8 million pound
counterweight will be "challenging" indeed.