… Drive
Typical bridges are engineered to have a 50 year lifespan… as Ottawa’s main artery, The Queensway (Hwy 417) is approaching it’s semicentennial anniversary, it’s time to replace many of the original bridges. Last time I saw a (major) bridge replaced in Ottawa, it was the G. Dunbar (Bronson) bridge over the Rideau River… it took years of traffic-hell and simultaneous construction/demolition to replace a 6 lane bridge. And while it’s a fairly major thoroughfare, isn’t a 400-series high-way like the 417.
Years aren’t an option for the Queensway. Days aren’t even. A few years ago the Queensway was shutdown for 5 hours due to a bomb-scare, and that was estimated to have a $125 million impact on the city – and that wasn’t even during peak traffic hours..! So – how to replace a bridge with minimal traffic impact? It’s not like you can tear out a few lanes at a time and build a new span while you tear out half of it… nor is reducing lanes and diverting traffic to the other side a real option either – certainly not at 100KMph.
No, no… that won’t work.
Instead, let’s just pick up and pull out the old bridges (East & West) and drop in new, prefabricated spans instead. Yeah. They’re only 650 tons a piece, it’ll be a breeze…
This weekend, they actually pulled it off, in just 17 hours! (2 hours longer than estimated.)
Around midnight, Sean and I went to take pictures, just after they’d finished pulling out the old spans, not that they had anywhere to put the Westbound span yet…
The procedure:
- build 3 scaffolds in the staging yard
- build 2 bridge spans atop scaffolds
- remove westbound span using first transporter, move to far north of worksite
- remove eastbound span using second transporter, put a top 3rd, unused scaffold
- pick up new eastbound span using second transporter
- install eastbound span
- while installing eastbound span, unload old westbound span on to scaffold vacated by new eastbound span
- move second transporter away from the bridge-site
- install westbound span
- pave
- disco
(5 second exposure; I couldn’t figure out why the scaffold was clear, but the bridge was blurred, heh.)
A few minutes after that above photo was taken, the westbound-span transporter was reversing into the staging yard… the creaking and groaning was quite impressive… then came the bang. Everything stopped… And then kept going. I guess they know what they’re doing. It was still freaky to see these massive structures moving overhead.
I was especially amused when Sean asked if I was going to file a noise complaint.
At about 0330, we drove around to the south side, as nothing exciting was visible from the north side (despite being in the grandstands.)
We were able to get much closer, and the lighting was better, we could see the engineers verifying all the footings. Good timing – they were just starting to remove the transporter.
(~1 minute)
Since it was about 4AM at this point, we went home. Fortunately, some people were scraping the webcam feed and have assembled it into a time-lapse video, so you can see some of the action. Unfortunately, there was no stable, wide view, so the operators were moving it around a lot. Hold your tummy.
Curiously, the old spans won’t be disassembled for about a week – “just in case”. And apparently they were delayed on installing the Westbound section due to a hydraulics problems… This I can believe, if you look at the pistons under the spans, they’re easily 2 or 3 feet wide!
Incidentally – Mammoet (not Marmoset, it’s Dutch for mammoth), the company that was responsible for moving the spans around, is the same company that raised the Kursk.