Old pony bent, caps and roller nest on
the east pier of bridge 35.
Performing comparatively minor bridge work is expensive for many of the reasons noted in the last blog post, but also for the cost of mobilizing the specialized equipment to perform the work. Any opportunity to combine two or more tasks into one project generally yields substantial cost savings. So the scope of work was set: change timber caps and girders, replace bearing pads, and replace pony bent. For bridge 35, this should have been four days work but unfortunately not everything goes according to plan.
Work began on a typical spring day in the Northwest: wet and cool. Initially, the bridge lifted without incident and the old roller nests were removed. Timber replacement began and then something started to go wrong: a weld in the steel added to support the jacking arrangement failed and two steel angles near the jacking area began to fail. The bridge slowly descended approximately 6 inches onto the pier. Fortunately no one was hurt and there was no serious damage. However this was another timely reminder about how challenging it can be working with a structure designed and built more than 125 years ago. And because it is "safety first," this minor damage will be repaired before any passenger trains operate over the bridge, even though this will affect the first trains of the year.
Imhoff's 65 ton crane lifts the end of
New copper-treated timbers are in
place and now workers are installing
the new base, soul plate, and bearing
pad on the south side of the east pier.
New soul plate is inserted
on top of the new
Fabreeka pad under bridge
35 in North Bend.
With all the work except installation of the new pony bent complete, repair of the damaged steel angles is now the focus. New angle irons are being drilled to match the existing holes. They will be incorporated into the bridge as soon as their fabrication is complete. After these minor repairs are completed and the bridge is "double checked," train service to North Bend will resume.