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-   -   CHICAGO: Transit Developments (https://skyscraperpage.com/forum/showthread.php?t=101657)

Busy Bee Feb 25, 2022 3:01 PM

I smell a scandal...

ardecila Feb 25, 2022 3:55 PM

Quote:

Originally Posted by Rizzo (Post 9549093)
I was on a SB brown line train this AM and witnessed chunks of concrete missing on the flyover exposing the rebar mesh. In maybe 8-10 areas. It didn’t look intentional because the 1 - 2 sqft areas were all organic in geometry. It was like a few inches of the outer layer was missing.

Interesting. I can't imagine any kind of concrete structure could fail this quickly after construction though. It takes years for rebar to rust and cause spalling.

Was it on the parapet/sound wall, or the columns?

Rizzo Feb 25, 2022 5:25 PM

No it was on the concrete deck fascia, not the columns or sound wall panels. It had the appearance of what you see on deteriorating overpass piers. Except the rebar was still intact with a green coating. Like occasionally you’ll see after-the-fact alterations in walls and parking decks, but the disturbed areas will be lightly saw cut so they are square or angular. These had pot hole like appearances, only disturbed to the first layer of rebar.

Busy Bee Feb 25, 2022 7:18 PM

Thats really really really bad if true. That would seem to point to a major bond failure between the concrete and the epoxy coated rebar. If the stresses and vibrations of the viaduct are causing this spalling this is major. Major.

ardecila Feb 25, 2022 7:31 PM

Interesting, like this area you mean? Might have been a problem with the concrete mix or not vibrated correctly in the forms. Or the connection detail for those sound panels may have caused some stress in the concrete leading to damage. If the rebar was green then it was coated, so it's definitely not a corrosion problem.

https://i.ibb.co/1JRpK76/flyover.jpg

Here's hoping the concrete was removed intentionally for a positive reason, and not as the result of (or investigation into) quality issues...

Rizzo Feb 25, 2022 8:38 PM

The red area is where it is, just further up (north)

Rizzo Feb 25, 2022 11:31 PM

Walked by it a moment ago. Ardecila, I think you’re right. The panel mounts are breaking through the fascia. The damage is worse than I saw this morning. I took pictures but have no way of posting.

Randomguy34 Feb 26, 2022 1:26 AM

Try using imgur.com to upload the photos.

This sounds pretty concerning

left of center Feb 26, 2022 6:37 PM

Wow, that's scary. I wonder if the CTA is aware of this issue?

Rizzo Feb 27, 2022 1:30 AM

I searched twitter “CTA flyover” and found this.

https://twitter.com/srboisvert/statu...798417926?s=21

Busy Bee Feb 27, 2022 1:37 AM

They're gonna have to rebuild the whole wall. Hopefully the contractor eats the cost and not the taxpayer.

Randomguy34 Feb 27, 2022 2:12 AM

Quote:

Originally Posted by Rizzo (Post 9550538)
I searched twitter “CTA flyover” and found this.

https://twitter.com/srboisvert/statu...798417926?s=21

The 100 year old concrete walls being replaced on the Red & Purple Lines looked better than this

galleyfox Mar 3, 2022 8:23 PM

Quote:

But the CTA said the missing sections of concrete — which leave steel rebar and PVC drainage pipes exposed — are only cosmetic and were knocked off safely by the contractor to remove a danger.

The concrete structure supporting the bypass started “spalling,” a condition in which concrete fragments break off their larger body, according to CTA spokesperson Tammy Chase. The transit authority discovered the spalling while conducting regular inspections of the structure
———

The CTA immediately asked Walsh-Fluor to perform daily inspections of the structure and remove any loose concrete immediately after discovering the spalling, Chase said. The areas of the structure that are missing concrete are a result of Walsh-Fluor workers cleaning out any loose debris before it has a chance to fall.

“The visible recessed areas are the result of proactive mitigations to protect the public and our employees from any falling debris, ahead of the contractor completing the repairs,” Chase said.

Walsh-Fluor will repair the spalls this spring at no cost to CTA, Chase said.

https://blockclubchicago.org/2022/03...-from-falling/

Busy Bee Mar 3, 2022 10:11 PM

Was the concrete soundwall even necessary? They should have just have used a galvanized railing.

Mr Downtown Mar 3, 2022 10:37 PM

The tracks curve as they ascend the flyover. Leaving the sides open to the noise from squealing wheels 30 feet above a residential neighborhood would have been quite a "screw you" to Wrigleyville.

ardecila Mar 4, 2022 12:07 AM

Quote:

Originally Posted by Busy Bee (Post 9556027)
Was the concrete soundwall even necessary? They should have just have used a galvanized railing.

I'm pretty sure this is required, yes. This is how Environmental Impact is supposed to work - you identify impacts like increased noise pollution, and propose design solutions like a sound wall.

It looks like they tried to do too much, though. To keep the flyover structure as slender and sleek as possible, they specified a concealed panel connection that looks really nice and clean in a section drawing, but isn't rigid enough. Looks like the concrete spalling is caused by flex in the connection.

Rizzo Mar 4, 2022 1:34 AM

Quote:

Originally Posted by Busy Bee (Post 9556027)
Was the concrete soundwall even necessary? They should have just have used a galvanized railing.

In the overall result from what was there to now, it seems more of a thoughtful gesture. Residents have endured much louder track noise on the existing steel structure and constant track switch clatter. I speak from experience. Ultimately, the sound walls will reduce certain noise, but to a limit. But imagine showing plans with no visible sound mitigation techniques. The problem with concrete, is unless there’s very specific acoustical treatments, it can bounce sound all around instead of absorbing it. The curve on the flyover is gentle enough that you don’t get that squealing wheel noise, but you’d hear sounds at the rail joints, and there’s a knocking noise, where the train “shudders” at the very top before descending. So it’s best to do all that you can to dampen that.

Randomguy34 Mar 5, 2022 3:56 PM

Oil has reach $5 a gallon in the city, and prices will continue to climb. Alongside offices requiring employees to return to work, this could jumpstart transit ridership post-COVID

twister244 Mar 5, 2022 9:32 PM

Quote:

Originally Posted by Randomguy34 (Post 9557735)
Oil has reach $5 a gallon in the city, and prices will continue to climb. Alongside offices requiring employees to return to work, this could jumpstart transit ridership post-COVID

Agreed. I was driving by a gas station the other day and saw $4.96 and had to do a double take. Even way out in the post-Cook exburbs, prices are north of $4 there too.

The Blue line outbound from downtown on Friday afternoon was PACKED. I have no pre-Covid exposure, so I don't know how that compares, but it was the busiest I have seen the trains in all of the time I have spent in the city over the last year.

the urban politician Mar 6, 2022 2:41 PM

Wow, well I guess that’s good for transit. However, many will probably choose WFH over riding the train so I’m not sure how much gas prices will really boost transit ridership


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