CHICAGO: Transit Developments

[J_M_Tungsten]

Plus, it's a very visually interesting bridge. I can't wait to see the refresh of it once completed. Are there plans for improving the lighting for the lower deck? Possibly the same kind they put in for lower Wacker?

[Mr Downtown]

Another consideration is the trains pounding across every few minutes. That puts a lot of stress on the cantilevered leaves, and particularly the sliding lock mechanism in the center. Double-leaf bascule bridges proved so unsuitable for steam railroad bridges at the turn of the 20th century that there are none left (in Chicago at least). So a stiff, heavy design that's overbuilt for the expected loading helps to solve other problems with the operating mechanisms.

[ardecila]

That's true. The former Metropolitan 'L' bridge between Jackson/Van Buren was really beefy too, and it had no lower deck.

[pilsenarch]

I was under the impression that most, if not all, of the draw bridges in the loop have been landmarked, so any replacement must replicate the existing...

[Mr Downtown]

^Michigan Avenue, Cermak Road, and Cortland Street are the only landmarked road bridges. (Eleven railroad bridges are landmarked).

[Rizzo]

Originally Posted by emathias

It's moveable, made of metal that's exposed to the elements, has carried just about every possible form of land transportation every single day of its existence, and yet lasted 90 years even with what might be called inconsistent maintenance. I think that's called an engineering success, so the risks involved with changing the design seem a lot higher than simply re-using the same design.

Totally agree. Meanwhile we have other examples of newer bridges that are already falling apart. They are designed to last 50 years with anticipation of maintenance that will never happen. Anyone check how busted up the North Ave bridge is? And take a look at the deck conditions. yikes.

The benefit of really thick steel materials is they can go on with decades of rusting and still perform within their design parameters.

I think we'll see alot of the other crossings on the Chicago river stick around simply because they are so well built and great design ingenuity.

[denizen467]

Well it is really not convincing to suppose, in a field of construction, engineering, or materials science, that a 90 year technology/approach is better than what exists today. Think of how concrete PSI has evolved in just the last two decades - or, as far as steel, welding, riveting goes, watch any documentary about how the Titanic was built versus techniques used to build ocean liners many decades later. Here would be an interesting image search - can one find any example, anywhere, of a very old bridge being replaced with an exact replica?

I think Mr Downtown's explanation makes sense, plus a desire to retain exactly the same look and not tinker with a popular look-and-feel. But I wonder, from a design perspective, was this a lost opportunity to have one incredibly unique, sleek, modern bridge on the River? Or have we all subconsciously decided that all downtown bridges need to maintain a unified husky, big-shoulders look for at least the next half century? I feel the latter probably is the case, and we've just never really talked about it much explicitly here or in the local papers.

[Mr Downtown]

When road bridges are replaced, as at Randolph, they are replaced by new designs. When Columbus Drive bridge opened it was one of the longest bascule spans in the world, and used welded box girders instead of riveted built-up plates.

But what kind of double-deck bascule design could be conceived that wouldn't look essentially the same as the existing bridge? Maybe the trusses could have members that are two inches thinner, or be smooth instead of riveted, but any design meeting the functional requirements would still look almost identical.

[ardecila]

You could go with a Vierendeel truss to eliminate diagonal bracing, and use welded joints for a really sleek look. But yeah, it'd still have the same overall profile.

There is an opportunity to create an upper-level pedestrian walkway as an overlook for the river canyon. The ADA requirements might get in the way, though.

[Mr Downtown]

A Vierendeel truss? On a movable cantilevered leaf that tilts through 80 degrees, has a counterweight on one end, and has heavy trains running along the top chord? Can you imagine how stiff those connections would have to be? I wouldn't want to do the analysis.

Here's a photo showing the replacement work from above. It's pretty large, so I'm posting a link:

http://i.imgur.com/eA4Yg3G.jpg

[ardecila]

The challenges don't seem insurmountable with computer analysis. If the new bridge wasn't an engineering challenge, it wouldn't be worth replacing the old design. Not necessarily a Vierendeel, but it would be great to get something bold, somewhere, and continue the groundbreaking traditions of last century's engineers. I'm tired of arch bridges in primary colors.

[nomarandlee]

http://www.chicagotribune.com/news/l...,4447327.story

Stevenson to shoulder more Pace express buses

By Richard Wronski, Chicago Tribune reporter
7:26 a.m. CST, March 8, 2013

Running express buses on the shoulders of the chronically jammed Stevenson Expressway — a congestion-fighting strategy introduced 15 months ago — has proved so successful that Pace plans to add more than a dozen daily trips.

Starting May 6, the number of inbound and outbound trips will increase to 32 a day on two routes between the far southwest suburbs, the Near West Side and downtown Chicago, Pace officials said.......


The strategy is so viable that the suburban bus agency and the Illinois Tollway are partnering to expand express bus routes on the Jane Addams Memorial Tollway (Interstate 90) when the road is rebuilt and widened over the next several years..........

..

[K 22]

Originally Posted by emathias

Yes it will be consolidated with Madison into a Washington station. Current designs call for it to be constructed so that it won't block the Gehry bandshell view corridor.

EDIT: Some reports mentioned an April, 2013 start date for that station but I haven't seen any updated information about it since last spring or summer. Anyone know whether that's still possible, or what the new start date is?


Chicago-L.org

That looks quite awesome actually. I'm guessing the platforms at Madison and Randolph will be gated somehow from the tracks?

[emathias]

Originally Posted by K 22

That looks quite awesome actually. I'm guessing the platforms at Madison and Randolph will be gated somehow from the tracks?

Past new stations have sometimes had the old ones linger for some time, but I would guess that in this case, disassembling the old stations to open up the view and light to a revived Wabash Street will happen shortly after the new station opens. But I could be wrong, that's just a guess/hope on my part.

[CTA Gray Line]

Originally Posted by K 22

That looks quite awesome actually. I'm guessing the platforms at Madison and Randolph will be gated somehow from the tracks?

This is yet another interesting example of how the Transit Agencies (CTA and Metra) do NOT work together.

With this new station - the walk from the Millennium Park station entrance on the SW corner of Michigan & Randolph to the closest Wabash Ave. CTA 'L' station entrance will be a Block and a half instead of the present 400ft (GREAT on a -10 below zero Chicago winter day).

If it had been sited between Washington and Randolph, instead of Washington and Madison - At the Randolph end it could have been connected directly to the Pedway for an All-Enclosed connection between the Blue and Red Lines, the Loop 'L' Lines, and the MED and South Shore. (and Gray Line?)

In Springfield right now they are talking about consolidating all the Transit Operating Agencies into one (along with CMAP and the RTA) -- THIS IS EXACTLY WHY: http://www.chicagotribune.com/news/l...,4979648.story http://www.senatedem.ilga.gov/index....ove-efficiency

They talk about "Attracting" Tourists to our City: http://www.chicagoloopalliance.com/b...he_Loop/ar/98/ - BUT OUR Regional Transit System has to be divided into "Warring Fiefdoms" -- Rather than an Intelligent Fare and Service C O O R D I N A T E D Regional Transit System like other "World Class" Cities that we supposedly hope to emulate -- N O T H I N G Transit Plans is how we LOST the 2016 Olympics.

Mayor Emanuel can go ALL OVER THE WORLD trying to "Privatize" Midway Airport, and find "Public/Private Partnerships" for the Red Line Extension and many many other things, -- BUT HE CAN'T lift up the Phone to call Alex Clifford and arrange a new CTA 'L' Line to serve EVERY large Tourist Attraction south of Downtown -- How do YOU spell P O L I T I C S ?

[ardecila]

Yep, that'd be awesome. It'd also be the only CTA-Metra connection downtown. They haven't bothered to build a connection at Ogilvie, even though the C&NW had one before. A 2-block pedway would connect Union Station to the Blue Line, but we don't have that either.

The only direct connections are all outlying and they occurred because of historical accidents - Jefferson Park, Davis St, Main St.

[denizen467]

Is the "malling" of Wabash in that render (or rather just traffic-calming down to 2 lanes) the designer's exercise of poetic license or has someone involved actually proposed this?

[harryc]

Where the new piece was welded on.


Innovative use for shipping containers - damn they are strong.

[ardecila]

Originally Posted by denizen467

Is the "malling" of Wabash in that render (or rather just traffic-calming down to 2 lanes) the designer's exercise of poetic license or has someone involved actually proposed this?

No I think they will actually build this. Remember that at Morgan, the stationhouses are placed at ground level and extend out into the parking lane. This avoids a mezzanine and keeps clearances high. Chicago on the Brown Line sorta does this too.

Parking spaces may remain mid-block but I don't doubt for a second that parts of the parking lane will be used for station elements like stairs, elevators, and fare control.

[denizen467]

^ How important is it to increase clearances - especially since I see no transfer bridge, so there may be a mezzanine anyway enabling passage between inner and outer platforms?

Also I think incursion into parking lanes would be fine anywhere other than the corners of the block. I know that bumpouts like this normally indeed are at the block's corners, but here this will impede traffic turning onto and off of Wabash. A vehicle on Wabash with a green light but desiring to turn has to wait for pedestrians in the crosswalk parallel to Wabash (all the way until the end of the entire green cycle during congestion periods); currently this vehicle can wait in the parking lane at the corner, which therefore enables 2 lanes of straight flow to continue during the entire green cycle. Take away the parking lane at the corner and you've got only 1 lane, or 0 lanes if this is a bus or truck. A different but related phenomenon occurs for vehicles desiring to turn onto Wabash.

Actually because all streets in question are 1-way, the above only applies to 1 parking lane; the opposite side could be built upon without affecting flow.

Note that both Lake-Morgan and Chicago-Franklin el stations involve only 1 artery; this station sits at intersections of 2 high-volume streets.