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denizen467 Dec 19, 2012 7:21 AM

Regarding river crossings around Chicago Ave, have people noticed that the River North spur of the Kennedy has a rather outsized bridge -- it is a truss that almost looks double-decked, like the LSD bridge or the Michigan/DuSable Bridge. I assume it's just for strength and that there isn't really a lower level for vehicles (there might be for service workers), but does anyone know for sure? If it were capable of 2 levels, you could have an Ontario Street crossing and with a little work could tie it right into Halsted and via Erie Street right into Milwaukee Ave.

ardecila Dec 19, 2012 7:53 AM

No, there's no lower level at Ohio St. The truss isn't actually any deeper than the other ones, really - but it's a deck truss, so no members extend above the bridge deck. The other river bridges are pony trusses, so they appear to be skinnier - the members rise above the bridge deck and the deck visually slices them in half.

If you look closely at the double-deck LSD and Michigan bridges, you'll see that the steel sections are very beefy relative to the distance they span, much moreso than the Ohio and Congress bridges. This is because the double-decker bridges were designed to carry twice the load.

Retrofitting the bridge to carry a lower level would be significant; you'd have to somehow thread a roadway through the bridge anchorages, exactly where the counterweights (solid, thousand-ton concrete blocks) and hinge mechanisms are located. Then you'd have to beef up the bridge members to carry the extra load and remove the diagonal sway bracing that crosses through the space inside the truss.

obligatory cool construction image

fun fact: the bridge leaves are staggered, so when it's raised, the bridge looks like this.

http://www.historicbridges.org/truss...e_42708_10.jpg
source

Mr Downtown Dec 19, 2012 2:59 PM

Quote:

Originally Posted by denizen467 (Post 5943792)
If it were capable of 2 levels, you could have an Ontario Street crossing

For Big Wheels,™ maybe. The trusses are only about six feet deep at the end of the leaves.

http://buffetoblog.files.wordpress.c...l-tricycle.jpg

Source

denizen467 Dec 20, 2012 7:59 AM

^ In that case, how about a bikeway for recumbent bicycles!

Quote:

Originally Posted by ardecila (Post 5943805)
The truss isn't actually any deeper than the other ones, really - but it's a deck truss, so no members extend above the bridge deck. The other river bridges are pony trusses, so they appear to be skinnier - the members rise above the bridge deck and the deck visually slices them in half.

Why wouldn't they have just built it in the "pony" configuration - which would have resulted in a slightly lower deck elevation, and therefore permitted approach ramps without such great inclines?

OhioGuy Dec 20, 2012 2:54 PM

I thought this was a nice look at the CTA from long ago:

Keeping Everyone in the Loop: 50 Years of Chicago "L" Graphics

I love the art of the 20's, 30's, and 40's! (oh how I wish the Humboldt Park branch still existed!)

ardecila Dec 21, 2012 12:34 AM

I can't say for sure. Maybe the designers realized what an awesome view would eventually take shape there, and didn't want to block it with steel girders? They probably tried to make the clearance pretty damn high so that openings would be infrequent (far more industrial traffic in the 50s). Remember that this was intended to form part of a full expressway loop around the Loop, and it would have connected to Lake Shore Drive somehow. Any stoplights or operable bridges would have been frowned upon.

The Dan Ryan bridge over the South Branch was also planned to be operable, but it was eventually moved even higher so that sailing ships could pass beneath it freely.

Mr Downtown Dec 21, 2012 3:00 AM

Remember that there are railroads on both banks, so the Ohio-Ontario Feeder had to climb up to 30 feet above the river in any case.

I don't think any Chicago River bridge has been built with pony trusses since the 1940s.

The Dan Ryan bridge is a compromise. Remembering World War II, when the Western canal bridges had to be refitted as lift bridges, the Defense Department wanted the expressway bridge to be a full 180 feet, like the Skyway, or a draw span. FHWA and the city objected, and a compromise 70-foot clearance was approved.

denizen467 Dec 21, 2012 10:40 AM

^ 180 feet?? What were they thinking, what on earth could be that tall (that might need to traverse our measly inland canal of a river)? Were they going to use barges to hide the Statue of Liberty in Peoria during wartime?

Mr Downtown Dec 21, 2012 8:50 PM

Sorry; I'm traveling and typed from memory. I should have said 125 feet.

Storytime, kids: In the 1930s, several of the bridges over the Sanitary & Ship Canal were built as drawbridges, but motors were not installed because traffic was restricted to barges. In the late 1930s, side-by-side bridges for Western Avenue and Western Boulevard were built as fixed spans. But almost immediately, drumbeats of war were heard from Europe, and about 1941 the War Department paid for towers and lift machinery to be installed on those bridges, and for motors, etc., for Cicero and the other bridges. They were concerned that Great Lakes shipbuilders be able to participate in the defense/war effort. As it happens, I'm told the bridges were only lifted once for real, and the subs built in Manitowoc had too deep a draft and had to go through in floating drydocks.

http://i.imgur.com/Kz5Fx.jpg
Source

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

Anyway, memories of this issue were not so distant in 1958, when the decision was made about the clearance the new Dan Ryan bridge would have.

jc5680 Jan 12, 2013 9:26 PM

How many people does it take to re-deck a platform? (12 if you count the other 3 just out of frame) I am not a carpenter, but it seems like it would be hard to do anything very efficiently with that many people in such a small area.


Rizzo Jan 13, 2013 6:13 AM

Anyone who wants to get weekly and 3-day passes before the price hike better get them now. Places all over are running out. I got the last of the 3-day passes at Walgreens. Don't know how fast businesses will keep up with restocking before Jan 14

Rizzo Jan 13, 2013 6:21 AM

Quote:

Originally Posted by Mr Downtown (Post 5947199)
Sorry; I'm traveling and typed from memory. I should have said 125 feet.

Storytime, kids: In the 1930s, several of the bridges over the Sanitary & Ship Canal were built as drawbridges, but motors were not installed because traffic was restricted to barges. In the late 1930s, side-by-side bridges for Western Avenue and Western Boulevard were built as fixed spans. But almost immediately, drumbeats of war were heard from Europe, and about 1941 the War Department paid for towers and lift machinery to be installed on those bridges, and for motors, etc., for Cicero and the other bridges. They were concerned that Great Lakes shipbuilders be able to participate in the defense/war effort. As it happens, I'm told the bridges were only lifted once for real, and the subs built in Manitowoc had too deep a draft and had to go through in floating drydocks.

http://i.imgur.com/Kz5Fx.jpg
Source

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

Anyway, memories of this issue were not so distant in 1958, when the decision was made about the clearance the new Dan Ryan bridge would have.

Are any of the bridges on the Sanitary Canal typically operating? I know most of the barges and tugs can get beneath them without problems. The rail lift and swing bridges seems to operate regularly,

Mr Downtown Jan 13, 2013 4:42 PM

Quote:

Originally Posted by Hayward (Post 5971300)
Are any of the bridges on the Sanitary Canal typically operating?

No, the "Eight-Track Bridge" at Campbell Avenue, frozen in the down position at 17 feet vertical clearance, sets the clearance for the entire Sanitary & Ship Canal. Nothing between Damen Ave. and Joliet still opens.

I don't think any swing bridges are still operable anywhere in the Chicago area, except the one just south of Armitage on the North Branch.

Busy Bee Jan 13, 2013 6:00 PM

Quote:

Originally Posted by jc5680 (Post 5970920)
How many people does it take to re-deck a platform? (12 if you count the other 3 just out of frame) I am not a carpenter, but it seems like it would be hard to do anything very efficiently with that many people in such a small area.


Here's a better question... How many years does it take to move on from using wood decking on platforms? You cannot tell me that radiant heated precast architectural (torched surface) concrete could not have been used on the Brown rehab. The CTA really cheapened out... this, the godawful galvanized railings...

ardecila Jan 13, 2013 9:18 PM

The new Red Line stations have concrete platforms, because the embankment could bear the weight. The Brown Line stations would have needed costly strengthening work on the steel structure to install concrete. They did this at Morgan but that was expensive.

Rizzo Jan 14, 2013 8:08 AM

Quote:

Originally Posted by Mr Downtown (Post 5971500)
No, the "Eight-Track Bridge" at Campbell Avenue, frozen in the down position at 17 feet vertical clearance, sets the clearance for the entire Sanitary & Ship Canal. Nothing between Damen Ave. and Joliet still opens.

I don't think any swing bridges are still operable anywhere in the Chicago area, except the one just south of Armitage on the North Branch.

Well I do know the lift bridge at Ping Tom park operates. I've gone over there a few times to photograph it in action.

So I take it the rail swing bridge at kedzie no longer works.

Mr Downtown Jan 15, 2013 4:01 AM

Yes, the Amtrak bridge (my personal favorite) is lifted several times a day in summer. It's even lower than the Eight-Track because they didn't want grades on the approach to Union Station, so it has to be lifted even for large cabin cruisers and gravel barges. It was designed to someday be set to a higher grade (and to have a twin), but that never happened.

ardecila Jan 16, 2013 12:01 AM

Preferred Design for the Circle Interchange

Aesthetic and Landscape treatments have yet to be decided, but the initial concepts are pretty fussy and not very promising. This is the stuff they should be considering.

There's also a concept to triple the width of the Peoria bridge to make a proper landscape connection between UIC and the West Loop, with a signature CTA headhouse.

http://farm9.staticflickr.com/8095/8...aefbdfb5_b.jpg

J_M_Tungsten Jan 20, 2013 8:06 PM

Today
Wells Bridge
http://i592.photobucket.com/albums/t...e7fc61c13c.jpg

Clark/Division Red Line Renovation
http://i592.photobucket.com/albums/t...45a35acaa4.jpg

http://i592.photobucket.com/albums/t...440a50c8a7.jpg

http://i592.photobucket.com/albums/t...54ae07b3ae.jpg

http://i592.photobucket.com/albums/t...6b5ccf5d67.jpg

http://i592.photobucket.com/albums/t...206f1101a5.jpg

http://i592.photobucket.com/albums/t...42873b7672.jpg

http://i592.photobucket.com/albums/t...49e0f86064.jpg

CTA Gray Line Jan 24, 2013 8:13 AM

2nd Congressional District Candidates Debate
 
Please attend if you can the 2nd Congressional District Candidates Debate:
Wednesday January 30, 2013 4:30pm to 9:00pm
Rich Central High School 3600 203rd St.
Olympia Fields, IL 60461

http://www.facebook.com/events/487324314642723/?ref=22

I will be there to submit ideas for Jobs, and Economic Development,
and to distribute CTA Gray Line information and literature; there may
also be coverage by Fox32 TV:

http://www.myfoxchicago.com/story/17...-electric-line

Mike Payne


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