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trainfan22

Mantthan Bridge flexing

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You think thats bad, On the J train elevated line, everytime a train comes to a stop in the station or leaves the station the whole station jerks back and forth ALOT.

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all suspension bridges are designed to do that within a safe margin.

Correct. The towers are designed to be stiff with the rest of the bridge being flexible. Now if you had seen the towers moving or the bridge not moving at all then you should worry.

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I think using the Manhattan Bridge for rail use is a bad idea, who knows if the one day the Bridge can collapse. Plus with too much maintenance, one day the the (:)(D)(N)(Q) will be affected which could lead to suspending service on North or South ends. Similar to past reconstructions. Same for the G/Os on the (M)(R)(W)

 

Does the Williamsberg suffer thru this with the Jamaica-Nassau Street Lines passing thru?

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I think using the Manhattan Bridge for rail use is a bad idea, who knows if the one day the Bridge can collapse. Plus with too much maintenance, one day the the (:)(D)(N)(Q) will be affected which could lead to suspending service on North or South ends. Similar to past reconstructions. Same for the G/Os on the (M)(R)(W)

 

Does the Williamsberg suffer thru this with the Jamaica-Nassau Street Lines passing thru?

There is nothing wrong with the bridge. No need to get paranoid. All bridges do the same. They move with the flow of traffic and the winds.

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I think using the Manhattan Bridge for rail use is a bad idea, who knows if the one day the Bridge can collapse. Plus with too much maintenance, one day the the (:)(D)(N)(Q) will be affected which could lead to suspending service on North or South ends. Similar to past reconstructions. Same for the G/Os on the (M)(R)(W)

 

Does the Williamsberg suffer thru this with the Jamaica-Nassau Street Lines passing thru?

 

 

 

No,I don't think the Willy'B flexes.the trackway is in thr middle of the bridge.

while the Manhattan Bridges 2 trackway are on the sides,hence the flexing.

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No,I don't think the Willy'B flexes.the trackway is in thr middle of the bridge.

while the Manhattan Bridges 2 trackway are on the sides,hence the flexing.

All suspension bridges flex. It's a suspension bridge, it's supposed to do that, if it didn't "give" and flex it would collapse. Those cables are there to support and spread out the weight so it doesn't collapse, that weight is transferred and it "gives". All suspension bridges work in a similar way.

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All suspension bridges flex. It's a suspension bridge, it's supposed to do that, if it didn't "give" and flex it would collapse. Those cables are there to support and spread out the weight so it doesn't collapse, that weight is transferred and it "gives". All suspension bridges work in a similar way.

 

Exactly. Heat causes metal to expand and contract also, so there needs to be flexibility built in otherwise the structure would warp. This is the same reason rail has to have joints (and I'm not just talking about the insulated kind that relate to signaling). If it didn't, and the rail tried to expand, it would warp and bend slightly each time and after a few temperature changes, wouldn't be safe to run on.

 

A rigid bridge would not be safe either. The structure would deform. Allowing for flexibility keeps the structure in the intended "shape"

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Everything sways and flexes, even buildings. The Twin towers swayed 10" from it's center. If it didn't do that, the winds would have brought the towers down from the buildings being rigid.

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While all suspension bridges are suspoosed to flex within a certain degree, this seems pretty excessive.
No. It seems excessive because it's in time lapse of hours condensed to a few minutes. The sway and flex in real time is not noticeable. Everyone needs to stop being paranoid. My uncle is an engineer and he said that he sees nothing wrong. The bridge is flexing within it's designed specification.

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No. It seems excessive because it's in time lapse of hours condensed to a few minutes.

 

Its not the time lapse that makes it seem excessive, its the train. When the cars are built up during certain points of traffic you can see the bridge flex also but it is not nearly as drastic as when the train passes. Thats when it flexes alot and you can see the way the traffic lamps are moving up and down that at certain points it looks like close to a foot of flex which is pretty alarming. It causes roadway damage all of the time to the asphalt and concrete. That is why they are constantly doing repairs on this bridge more than any other bridge. I used to work in Brooklyn and would take the train over that bridge every day, I have never seen so much maintenance and construction on any other bridge.

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Its not the time lapse that makes it seem excessive, its the train. When the cars are built up during certain points of traffic you can see the bridge flex also but it is not nearly as drastic as when the train passes. Thats when it flexes alot and you can see the way the traffic lamps are moving up and down that at certain points it looks like close to a foot of flex which is pretty alarming. It causes roadway damage all of the time to the asphalt and concrete. That is why they are constantly doing repairs on this bridge more than any other bridge. I used to work in Brooklyn and would take the train over that bridge every day, I have never seen so much maintenance and construction on any other bridge.

You keep thinking that. :tup: I'll listen to what my uncle, who is an engineer for more than 10+ years says.

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You keep thinking that. :tup: I'll listen to what my uncle, who is an engineer for more than 10+ years says.

 

Really? what bridges did your uncle build?

 

The bridge was opened to traffic on December 31, 1909 and was designed and built by Polish bridge engineer Ralph Modjeski with the deflection cables designed by Leon Moisseiff, who later designed the infamous original Tacoma Narrows Bridge that opened and collapsed in 1940

 

For 18 years, between 1986 and 2004, one set of tracks was closed to repair structural damage.

 

The four sets of tracks on this bridge causes much stress than it was originally designed for.

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Really? what bridges did your uncle build?

 

The bridge was opened to traffic on December 31, 1909 and was designed and built by Polish bridge engineer Ralph Modjeski with the deflection cables designed by Leon Moisseiff, who later designed the infamous original Tacoma Narrows Bridge that opened and collapsed in 1940

 

For 18 years, between 1986 and 2004, one set of tracks was closed to repair structural damage.

 

The four sets of tracks on this bridge causes much stress than it was originally designed for.

 

My uncle works for AECOM, a fortune 500 company. One of their biggest current projects is something you may have heard about, the Second Avenue Subway. Google that.

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My uncle works for AECOM, a fortune 500 company. One of their biggest current projects is something you may have heard about, the Second Avenue Subway. Google that.

 

No wonder there is another delay in the SAS project. :):tdown:

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Correct. The towers are designed to be stiff with the rest of the bridge being flexible. Now if you had seen the towers moving or the bridge not moving at all then you should worry.

 

The towers that held up the Tacoma bridge didnt move either when the roadbed was swaying and flexing and eventually fell.

 

 

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There is a flaw in the design of the mantthan Bridge, the subway tracks should have been put in the middle of the bridge, not on the outside like it currently is. Back in the day one side of the Bridge saw more rail traffic than the other, causing a lot of wear and tear. I guess the Bridge today sees equal rail service on both sides so the situation isn't as bad as it was in years past.

 

Slightly off topic but if go on the overpass that goes over the Sunnyside Yard in Queens, everytime a bus or truck drives over it you can feel the Bridge flexing and bouncing. Same goes for the overpass that goes over the LIRR hunterpoint station in LIC, these are nice spots to railfan but the constant bouncing can be quite scary.

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The towers that held up the Tacoma bridge didnt move either when the roadbed was swaying and flexing and eventually fell.

 

 

 

The Tacoma Narrows Bridge had extreme flexibility, both vertically and in torsion. This weakness was due to the shallowness of the stiffening girders and the narrowness of the roadway. The winds were as strong as 40MPH. In addition, a support cable at mid-span snapped, resulting in an unbalanced loading condition. That along with the extreme flexibility and high winds caused the demise of the Tacoma Narrows.

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The Tacoma Narrows Bridge had extreme flexibility, both vertically and in torsion. This weakness was due to the shallowness of the stiffening girders and the narrowness of the roadway. The winds were as strong as 40MPH. In addition, a support cable at mid-span snapped, resulting in an unbalanced loading condition. That along with the extreme flexibility and high winds caused the demise of the Tacoma Narrows.

 

Also if I remember correct it had something to with resonance in physics...which is the exact force that will cause an object to keep moving back and forth forever, which is what the wind was providing until the bridge tore itself apart. It was poor design because resonance has to be anticipated and built so that while there is flexibility, resonnance will not be reached

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Also if I remember correct it had something to with resonance in physics...which is the exact force that will cause an object to keep moving back and forth forever, which is what the wind was providing until the bridge tore itself apart. It was poor design because resonance has to be anticipated and built so that while there is flexibility, resonnance will not be reached

Correct. :tup:

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My uncle works for AECOM, a fortune 500 company. One of their biggest current projects is something you may have heard about, the Second Avenue Subway. Google that.

 

A subway tunnel is not a suspension bridge. :)

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