Posted on 11/28/2017 10:57:12 AM PST by Tolerance Sucks Rocks
After two successful efforts to replace small bridges in 55 hours over one weekend, the Pennsylvania Turnpike says it is looking for more opportunities to use the fast-replacement approach.
In late September, the turnpike was closed for a weekend between Cranberry and Beaver Valley to replace a bridge in New Sewickley Township. Crews built the new bridge directly beside the existing structure, demolished the old bridge and used paraffin to slide the new bridge across beams into place.
Earlier this month, it replaced another bridge on the Northeast Extension in Lehigh County. In that case, sections of the new bridge were built on each side of the old one and rolled together after the old bridge was demolished.
In both instances, the work went smoothly and crews were done about two hours before the road was scheduled to reopen, said Wally Wimer, the turnpike’s engineering project manager.
In Lehigh, crews had to work around a 1-inch gap when they used hydraulic jacks to force the bridge in place, something that can be avoided in the future by more extensive use of on-site laser surveying equipment during construction, Mr. Wimer said.
(Excerpt) Read more at post-gazette.com ...
Always thought that there was a better way to replace small bridges at least.
Prefab sections certainly should speed up the work.
The union wire lathers don’t like them though. Small towns simply can’t afford to go that route over prefabs.
Do you use the existing support beams?
Do you use the existing support beams?
What’s their bottom line here ?
We’ve seen bridge collapses. It’s a nightmare of mine that is shared by literally everyone in America.
We can do fast, but can we do good for a change ? Why is it older bridges throughout the Northeast lasted for over a century, but these newer Eisenhower bridges can’t seem to live up to that legacy ?
It seems like they are using the same abutments while replacing all the structural members on the bridge.
Interesting! Unfortunately anything that results in “substantial savings” will never happen in New Jersey.
In Rhode Island a decade ago, a new interstate bridge was fabricated at a shoreside facility about fifteen miles away, whilst the new abutments were being prepared. The completed bridge fabrication was then loaded on a barge, moved into place at high tide, then as the tide receded the bridge eased into the new abutments.
Brilliant cost saving engineering!
They just used that method to replace part of the Sarah Mildred Long Bridge (U.S. 1) between Maine and New Hampshire.
Speaking just generally, the older bridges that you refer to were designed in the day when slide rules, logarithm tables and various engineering tables were used. Lumped in with this, material specifications for steel and concrete were not as precisely uniform. To compensate for the lower precision of design, materials and construction techniques, safety factors were greater. In other words, the bridges were way over built.
This does not imply at all though that there is anything inherently deficient with modern designs that can use computer optimization and graphical tools achieve performance targets more efficiently with regards to materials and constructability.
No matter if an older design or modern, the keys to longevity are inspection, maintenance and repair. Short on any of these and you loose service life at the least and catastrophic failure at the worst.
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