Gsgeorge Member Username: Gsgeorge
Post Number: 249 Registered: 08-2006
| Posted on Wednesday, October 17, 2007 - 12:26 am: | |
Anyone else notice this? Every time I drive underneath I think it's gonna fall on top of me. The steel beams appear to slouch and warp. The bridge is very wide and goes over five lanes of freeway on each side of the median. If you look closely, the center supports are not attached to the joints in the center of the bridge. Something seems off, it's just wonky... |
Burnsie Member Username: Burnsie
Post Number: 1177 Registered: 11-2003
| Posted on Wednesday, October 17, 2007 - 12:33 am: | |
It seems as if the center pier wasn't attached to the bridge, the bridge would fall down. If there are beams connected towards the center, often the point of meeting isn't actually on top of the pier. |
Eriedearie Member Username: Eriedearie
Post Number: 10 Registered: 08-2007
| Posted on Wednesday, October 17, 2007 - 2:32 am: | |
Gsgeorge - yes I noticed that when I was driving through 2 weeks ago. Thought it was my imagination. |
Wolverine Member Username: Wolverine
Post Number: 370 Registered: 04-2004
| Posted on Wednesday, October 17, 2007 - 3:06 am: | |
No worries as long as its reached its maximum deflection. |
Gannon Member Username: Gannon
Post Number: 10748 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 6:00 am: | |
Wolverine, What?! Just because it has sagged as far as it is designed to go before breaking, there are NO worries? I'd say then we're at the beginning of worries for it. You don't bend metal, hold it with mass, then load it periodically with VIBRATION, much less rolling humming vibration-inducing random traffic...it is exactly the definition of an impending problem. Now, if we were in the MIDDLE of the deflection range, without the attendant sag from mass, then the bridge would be able to handle this periodic vibratory nuisance easily...especially if the lossy joints were all functioning properly! Now that it is at its maximum, if we're guessing, then the vibrations will all be transmitted directly to the stuff we'd rather NOT find a resonant fault with...we just might find that a line etched by pidgeon shit has become a galvanic fault line just awaiting that next periodic vibration to become a CRACK. We saw in Minneapolis what happens then...only this time the bridge won't just fall into a river. Oddly, the Grand River would be falling into the freeway this time...h-m-m-n-n. That would be Murphy Poetry. |
Gannon Member Username: Gannon
Post Number: 10749 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 6:02 am: | |
pigeon |
Gannon Member Username: Gannon
Post Number: 10750 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 6:03 am: | |
shit |
Charlottepaul Member Username: Charlottepaul
Post Number: 1832 Registered: 10-2006
| Posted on Wednesday, October 17, 2007 - 8:40 am: | |
Like this? http://www.fhwa.dot.gov/bridge /lrfd/images/us_ds3_img22785.g if This is lateral torsional buckling. It can be easily fixed with cross-bracing between each steal member. Grand River crosses I-96 several times. What other cross street is nearby? |
Gannon Member Username: Gannon
Post Number: 10755 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 9:04 am: | |
NOT fixed, rather 'band-aided'...and I'm not talking rock band groupies. Adding mass might exacerbate the resonance issues...and enable a more severe break should one of those crack potentials propagate. |
Gsgeorge Member Username: Gsgeorge
Post Number: 250 Registered: 08-2006
| Posted on Wednesday, October 17, 2007 - 9:35 am: | |
I'm talking about this one, between Oakman and Livernois. The last Grand River exit before the express lanes (if you were going westbound). |
Danindc Member Username: Danindc
Post Number: 3477 Registered: 10-2003
| Posted on Wednesday, October 17, 2007 - 10:52 am: | |
Any photos? Deflection (and vibration) is a serviceability concern. Deflection is proportional to supporting member stiffness, and is not directly related to flexural or shear capacity. While I'm not a bridge engineer, I'd be happy to look at photos and give an opinion. |
Gannon Member Username: Gannon
Post Number: 10758 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 11:15 am: | |
I'll do what I can, Dan. Thanks for the input. As with the previous discussion, somewhat related, my gut instinct goes to dynamic resonance issues...while most engineering is focussed on static load issues, and lossy connections AVOIDING said resonances. I still say that now that the planet is resonating higher, from the one hundred year 'standard' of 7.83 Hz to now somewhere between 11-12 Hz, we might see some issues creeping up with any concrete-shrouded and -clad steel structures...at least the ones built before significant seismic decoupling applied engineering. I've little proof of it at the moment, so every issue becomes suspect data. Please forgive my immediate jumping to those guesses!! (I know a little bit how tough it is for linear-thinking engineers to tolerate us holistic-types! We appear too much like outlaws to you, but so did the Einsteins to everyone thoroughly studied in Newton's subset of physics...doesn't limit anyone's genius, just shows their perspectives and open-ness to new data.) |
Gannon Member Username: Gannon
Post Number: 10768 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 3:09 pm: | |
I don't think there is any problem whatsoever with this bridge. This half is largely on solid ground on the other side of the street, due to the angle of the intersection, so they must've had to make this side of the span flat. If you compare it with the whole span, it certainly looks like it is sagging...but from the other side looking straight down the edge you can see it is merely an optical illusion...the side we think is sagging seems perfectly straight. There is NO evidence of cracked concrete from any bend stresses, although that fencing looks suspicious! Cheers.
|
Danindc Member Username: Danindc
Post Number: 3480 Registered: 10-2003
| Posted on Wednesday, October 17, 2007 - 3:18 pm: | |
Looks pretty normal--nothing I'd lose sleep over. Lateral-torsional buckling only governs design when the compression flange of a beam is not continuously braced. In this case, the compression (top) flanges of the plate girders are continuously braced by the roadway decking. |
The_ed Member Username: The_ed
Post Number: 143 Registered: 10-2007
| Posted on Wednesday, October 17, 2007 - 3:22 pm: | |
That's what I was going to say |
Gannon Member Username: Gannon
Post Number: 10770 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 3:27 pm: | |
There WERE an awful lot of tire tracks on the grass...that one we can clearly see from the west looks like fun. It is a pretty tight radius, so it could've been the lawn tractors, but the ones on the west grass were certainly done by people evading some collisions. I always consider the stories people have to tell when I see things like this and/or those tire tracks up the guardrails on sweeping exits, like that I-75 to the north (where you can go I-375 southbound) just east of the stadia. I hope they survived to tell their stories... |
Johnlodge Member Username: Johnlodge
Post Number: 3129 Registered: 10-2003
| Posted on Wednesday, October 17, 2007 - 3:30 pm: | |
Travelling Eastbound on 696, if you take the exit to I-75 North, the exit ramp makes a sharp curving left so you are facing north parrelel with I-75, for merging. The wall on that curve is COVERED with black marks, it must be a regular occurance there. |
Gsgeorge Member Username: Gsgeorge
Post Number: 251 Registered: 08-2006
| Posted on Wednesday, October 17, 2007 - 3:36 pm: | |
That's what i'm talking about. It just looked a bit disconcerting for someone not particularly an expert on bridge design... unlike those of you who responded. Thanks for the pics Gannon! Johnlodge, my favorite exit ramp is definitely SB Lodge to EB Davison. Man, that's a tight turn, right out of the left lane. Before they did all the repair work on the lodge the concrete wall was just TORN APART from cars coming too fast around the curve. That's what you get when you have the oldest freeways in the world--tight turns made for cars 50 years old and 25mph slower. |
Gannon Member Username: Gannon
Post Number: 10774 Registered: 12-2003
| Posted on Wednesday, October 17, 2007 - 3:47 pm: | |
Gsgeorge, Kudos to YOU for noticing anything suspect. That is exactly the sort of awareness we need to hopefully avoid another Minneapolis disaster. I'm just happy the manual focus is still working on my old Olympus E-10... Didj'all know that those guardrails were designed by a student at the (then) General Motors Institute (now Mott something or other)?! Cheers! |
Dnvn522 Member Username: Dnvn522
Post Number: 293 Registered: 11-2004
| Posted on Wednesday, October 17, 2007 - 4:02 pm: | |
http://www.michigan.gov/docume nts/mdot/MDOT_bridge_ratings_r eportbyroute1_205193_7.pdf The bridge report says that while the deck is poor (4), the superstructure is still in fair condition (6). Visually it looks a little funny (sagging), since that is a suspended span. The other span is the supporting span, so it looks different. They have completely different forces and moments working on them. PS. Lateral-torsional buckling is not a concern on this bridge, since any forces that might cause that are VERY minor. Curved bridges sometimes have that concern though. |
Mikeg Member Username: Mikeg
Post Number: 1217 Registered: 12-2005
| Posted on Wednesday, October 17, 2007 - 6:19 pm: | |
quote:Didj'all know that those guardrails were designed by a student at the (then) General Motors Institute (now Mott something or other)
Actually, there are six different types of concrete barrier designs in use on highways in the USA. The most common design is called the New Jersey Barrier and the image above shows its cross section. The somewhat similar, but now obsolete, GM Barrier design was designed at the General Motors Proving Grounds back in the late 1950s. Here is an article with more information, but don't believe their 1970s date for the GM Barrier development - I have read an article about the development of the GM Barrier that appeared in an old internal GM publication that included photos of a 1958 Buick alongside the barrier. It would not be surprising to hear that the designer of the GM Barrier was a graduate of my alma mater, the General Motors Institute (GMI), in Flint, MI. From 1919 through 1982, GMI was owned and operated by GM. At that time, they divested themselves of the Institute and they renamed themselves the GMI Engineering and Management Institute. About 10 years ago, they changed their name to Kettering University, in honor of Charles "Boss" Kettering. |
Dnvn522 Member Username: Dnvn522
Post Number: 294 Registered: 11-2004
| Posted on Thursday, October 18, 2007 - 10:21 am: | |
The GM barrier shape was discontinued in the '70s, so it must of been developed well before that. The New Jersey shape (or a slightly modified version of it) is the most common type used now, with other aesthetic barriers becoming more and more common. (Message edited by dnvn522 on October 18, 2007) |
Mikeydbn Member Username: Mikeydbn
Post Number: 351 Registered: 04-2004
| Posted on Thursday, October 18, 2007 - 11:17 am: | |
Look at that nice I-96 shield (using the new clearview typeface) in Gannons first photo. |