I had duplicate posts for the 1931 and 2006 US-1 highway bridges. So this one is now the 2006 bridge. The 1931 suspension bridge is here.
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| By Bruce C. Cooper (uploader) - Uploader's work and collection, CC BY-SA 4.0, Link |
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| Tim Berry posted The Penosbscott Narrows Bridge in Prospect Maine contains the highest public bridge observatory in the world. It's 420 feet (128m) above the river atop the tower in the foreground. Denny Baughman: I’ve been to the observatory at the top of the tower…great views of the bay area as well as Fort Knox from there. |
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| Highway Engineering Discoveries posted Penobscot Narrows Bridge |
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| Deschaine Digital posted Penobscot Narrows Bridge and Fort Knox 🏰 📍 Prospect, Maine |
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| WaldoHancockBridge |
In 2003, when MaineDOT was partway through a major rehabilitation of the main suspension cables of the 71-year-old bridge, engineers unexpectedly discovered the severe corrosion of the cables which had been hidden by protective sheathing. Engineers agreed the cables were too corroded to save and the bridge would need to be replaced as soon as possible. For safety, the Waldo-Hancock Bridge load was reduced overnight from 100,000 to 24,000 pounds.The Bridge Hunter post for the old bridge had:
Over the next 16 weeks, 16 new strengthening cables were designed, fabricated, and installed, a feat never before accomplished on a standing suspension bridge. Half the bridge’s weight was transferred to these new cables. This engineering and construction innovation assured the safety of the Waldo-Hancock Bridge while its replacement was built.
[MDOT-history]
Link to article regarding new bridge constructionBut that link is now broke. I spent some time looking and found a new link for the Mar 2007, issue, https://ascelibrary.org/toc/ciegag/77/3, but they want serious money to read anything. And it looks like it focuses on a measuring technique.
Submitted by Craig Philpott
http://www.pubs.asce.org/magazines/CEMag/2007/Issue_03-07/ar...
Fortunately, the AspireBridge article is probably more interesting anyhow.
The replacement was designed by FIGG. I recognize FIGG as the designers of the FIU truss that collapsed a few days after it was moved into position because of a design error! (They did not use enough rebar in a joint between a truss member and the deck to withstand the lateral forces in that joint.) I'm glad I'll never have to drive over this bridge. Especially since they designed a "unique" cable-stay system. However, since MDOT, FIGG and the two joint contractors "united to create a mission statement for the project" and since they formed a Public Advisory Committee, maybe it is a good design. "Designers also included an innovative nitrogen gas protection and monitoring system... A gauge within the system will record any fluctuations in pressure, allowing MDOT to monitor the system’s status and take necessary corrective action." [AspireBridge]
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| AspireBridge, p28 |
These construction photos also give us additional views of the Waldo-Hancock Bridge.
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| AspireBridge, p29 |
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| AspireBridge, p30 [The fact that they could build that many deck segments without having to add cable stays is a testament to the strength of the box girder design for the deck.] |
The patented cable-stayed "system carries the stay cable through a stainless-steel sleeve, creating a continuous cable and eliminating the need for anchorages in the pylon....The concept of cradle
saddles is not new, notes Rohleder [senior vice president and project director for FIGG], but in the past, they have created a “bundling” effect caused by the top strands squeezing the lower strands as cables got larger, reducing their ability to withstand impact. In the new Penobscot Narrows Bridge, each strand has its own pipe, eliminating this concern. Another impressive benefit of the system is that at any time, it will be simple to inspect, and, if necessary, pull out and replace an individual strand. This ability is expected to extend the bridge’s life, which is predicted to be at least 100 years, says Rohleder." [AspireBridge, p30]
So MDOT joins the Midwest DOTs in letting a big bridge rot until it had to be replaced. To be fair, unlike the Midwest truss bridges, MDOT could not easily see the rot until they dug into the cables during rehabilitation. Does that mean that no one has yet invented a way to inspect the inside of suspension cables for corrosion? Ultrasound? X-ray? Changes in diameter? Changes in electrical conductivity? ??? If not, then we now have a bunch of cable-stay bridges in America that are going to be big questions marks in a few decades. Especially if it proves that you do need a monitored pressurized nitrogen environment to avoid corrosion.
saddles is not new, notes Rohleder [senior vice president and project director for FIGG], but in the past, they have created a “bundling” effect caused by the top strands squeezing the lower strands as cables got larger, reducing their ability to withstand impact. In the new Penobscot Narrows Bridge, each strand has its own pipe, eliminating this concern. Another impressive benefit of the system is that at any time, it will be simple to inspect, and, if necessary, pull out and replace an individual strand. This ability is expected to extend the bridge’s life, which is predicted to be at least 100 years, says Rohleder." [AspireBridge, p30]
So MDOT joins the Midwest DOTs in letting a big bridge rot until it had to be replaced. To be fair, unlike the Midwest truss bridges, MDOT could not easily see the rot until they dug into the cables during rehabilitation. Does that mean that no one has yet invented a way to inspect the inside of suspension cables for corrosion? Ultrasound? X-ray? Changes in diameter? Changes in electrical conductivity? ??? If not, then we now have a bunch of cable-stay bridges in America that are going to be big questions marks in a few decades. Especially if it proves that you do need a monitored pressurized nitrogen environment to avoid corrosion.
(new window) You can tell this is a modern video because it has bad "music," and it uses the current fad of having just a bunch of closeups. It finally has an overview at 4:24 so that I could see what kind of cranes were being used. When I read photography books, they would talk about starting your presentation with "establishing context" photos and then take shots of your subject. But I would normally dive right into photos and/or videos of my subject. Especially if they are doing something interesting. But I would remember before I left an area to walk away and get some context shots. Fortunately, I don't have to use the photos in the order that I took them, and I'll use some of my last shots at the beginning of a blog post. In the case of video, I take advantage of the boring scenes such as lowering something to the barge to zoom out and pan around and then zoom back in for the end of the movement. I want to record things like the angle of the boom. Nonetheless, this video is interesting.
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| This photo has been moved to "1939-2013 US-1 Waldo-Hancock Bridge." |
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| This photo has been moved to "1939-2013 US-1 Waldo-Hancock Bridge." |
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| John Weber posted Traveling in Maine I was fortunate to take this photo of these two bridges. Now the old bridge is gone. Taken at the Penobscot River crossing. Called the Historic Waldo-Hancock Bridge. |
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| Sandi O'Neill posted The Penobscott Bridge in Maine that someone posted earlier which is one of my favorites! This photo shows the older bridge on the left that this one replaced and has since been taken down. Going to the top is so awesome! |
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| Mike Reynolds commented on Sandi's post I live 20 minutes away |
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| Nick Souza commented on Sandi's post New to the group and just went to this bridge for the first time, this past weekend. I got lots of pics from the observatory and of Fort Knox, which is right beside it. |
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| Stephanie Andy commented on Sandi's post Beautiful |
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| Matt Baggs commented on Sandi's post August, 2018 |
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| MainDOT posted You have five days left to see fall foliage from the tallest bridge observatory in the world! The Penobscot Narrows Observatory & Fort Knox State Historic Site will close for the season on October 31st. Thanks to everyone involved for another great year! The observatory will re-open next season on May 1st, 2025. Bridges Now and Then posted |
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