Monorail beams

xdan0920 · Feb 18, 2015

RedDad said:
Post-tensioned beams are not "unreinforced until they are tensioned." The tensioning causes "pre-loading" of compressive forces in the beam section's tension zones, thus increasing the overall bending strength of the beam over a long span. But the tensioning cables are not a form of reinforcement, per se. In fact, the beam section would have had quite a bit of other standard reinforcement cast into it during manufacturing off site.

Post-tensioning tendons are passed thru hollow conduits that are cast into the beam section, so that they do not bond with the concrete, thus allowing the tendons to be tensioned after the beam is installed. These beams were both pre-stressed and post-tensioned after installation, and were hollow in cross section. Post-tensioning thru multiple spans is fairly common. Whether WDW's were done in such fashion - I can only quote other sources that claim this is the case:
View attachment 83482
View attachment 83483

Honestly, who do you think you are? I think Fordlover might be a structural engineerer. What are you? A dad, I guess. Stick to changing diapers!

Master Yoda · Feb 18, 2015

xdan0920 said:
Honestly, who do you think you are? I think Fordlover might be a structural engineerer. What are you? A dad, I guess. Stick to changing diapers!

He is a "Red" dad, that means he is a commie to boot!

Bob · Feb 18, 2015

Master Yoda said:
He is a "Red" dad, that means he is a commie to boot!

And we all know how good commie engineering is when it comes to trains....see China:

MichWolv · Feb 18, 2015

Bob said:
And we all know how good commie engineering is when it comes to trains....see China:

Well this thread has certainly gone off the rails.

sjhym333 · Feb 18, 2015

MichWolv said:
Well this thread has certainly gone off the rails.

Or more appropriately off the beams

Tom · Feb 18, 2015

RedDad said:
Post-tensioned beams are not "unreinforced until they are tensioned." The tensioning causes "pre-loading" of compressive forces in the beam section's tension zones, thus increasing the overall bending strength of the beam over a long span. But the tensioning cables are not a form of reinforcement, per se. In fact, the beam section would have had quite a bit of other standard reinforcement cast into it during manufacturing off site.

Post-tensioning tendons are passed thru hollow conduits that are cast into the beam section, so that they do not bond with the concrete, thus allowing the tendons to be tensioned after the beam is installed. These beams were both pre-stressed and post-tensioned after installation, and were hollow in cross section. Post-tensioning thru multiple spans is fairly common. Whether WDW's were done in such fashion - I can only quote other sources that claim this is the case:
View attachment 83482
View attachment 83483

100% correct, of course.

Vegas used the same design when they started building their system in the early 2000's. In fact, they used the old WDW monorails when they launched the first leg of the system.

During a college trip to the Association of General Contractors convention, we were given a tour of the site where they were casting the beams. We got an up close and personal view of the beams in each stage of production.

Relatively speaking, there's very little concrete in them. Lots of styrofoam, a rebar cage, tubes for the post-tension cables, and a shell of concrete.

danlb_2000 · Feb 18, 2015

Tom said:
100% correct, of course.

Vegas used the same design when they started building their system in the early 2000's. In fact, they used the old WDW monorails when they launched the first leg of the system.

During a college trip to the Association of General Contractors convention, we were given a tour of the site where they were casting the beams. We got an up close and personal view of the beams in each stage of production.

Relatively speaking, there's very little concrete in them. Lots of styrofoam, a rebar cage, tubes for the post-tension cables, and a shell of concrete.

Then there was that guy who tried to cheat a casino, I hear he got a REALLY up close and personal view of the concrete work.

Fordlover · Feb 19, 2015

Tom said:
100% correct, of course.

Vegas used the same design when they started building their system in the early 2000's. In fact, they used the old WDW monorails when they launched the first leg of the system.

During a college trip to the Association of General Contractors convention, we were given a tour of the site where they were casting the beams. We got an up close and personal view of the beams in each stage of production.

Relatively speaking, there's very little concrete in them. Lots of styrofoam, a rebar cage, tubes for the post-tension cables, and a shell of concrete.

I'd love to see how they tension (elongate) the last set of cables with all the beams in place. Perhaps their machine is compact and can fit in the gap between the beams.

I'd love to see a cross section of Monorail beam, clearly they are constructed much differently from highway overpass beams.

Fordlover · Feb 19, 2015

RedDad said:
Post-tensioned beams are not "unreinforced until they are tensioned." The tensioning causes "pre-loading" of compressive forces in the beam section's tension zones, thus increasing the overall bending strength of the beam over a long span. But the tensioning cables are not a form of reinforcement, per se. In fact, the beam section would have had quite a bit of other standard reinforcement cast into it during manufacturing off site.

Post-tensioning tendons are passed thru hollow conduits that are cast into the beam section, so that they do not bond with the concrete, thus allowing the tendons to be tensioned after the beam is installed. These beams were both pre-stressed and post-tensioned after installation, and were hollow in cross section. Post-tensioning thru multiple spans is fairly common. Whether WDW's were done in such fashion - I can only quote other sources that claim this is the case:

Thanks for the article.
It clearly refers to the beams as prestressed, which means they are reinforced with cables, either before or after concrete is placed, but prior to being transported on site (correct?). They may further connect the beams with additional cables, but I've never seen that process. I would love to see what kind of elongation they would get on 600 feet of cable. That's gotta be one big jack!

I guess you can learn something new every day if you pay attention. Thanks again for the info.

Tom · Feb 19, 2015

Fordlover said:
I'd love to see how they tension (elongate) the last set of cables with all the beams in place. Perhaps their machine is compact and can fit in the gap between the beams.

I'd love to see a cross section of Monorail beam, clearly they are constructed much differently from highway overpass beams.

Fordlover said:
Thanks for the article.
It clearly refers to the beams as prestressed, which means they are reinforced with cables, either before or after concrete is placed, but prior to being transported on site (correct?). They may further connect the beams with additional cables, but I've never seen that process. I would love to see what kind of elongation they would get on 600 feet of cable. That's gotta be one big jack!

I guess you can learn something new every day if you pay attention. Thanks again for the info.

I guess the part I can't really comment on is whether they post-tension a run of beams once they're set in place. It was my impression that they post-tensioned each beam, after the concrete cured...not that they strung multiple beams together.

JoeCamel · Feb 19, 2015

Tom said:
I guess the part I can't really comment on is whether they post-tension a run of beams once they're set in place. It was my impression that they post-tensioned each beam, after the concrete cured...not that they strung multiple beams together.

In the linked article they said they "post tensioned a string of six at a time" of the prestressed beams.

Tom · Feb 19, 2015

JoeCamel said:
In the linked article they said they "post tensioned a string of six at a time" of the prestressed beams.

I don't not reed so good.

RedDad · Feb 20, 2015

Fordlover said:
Thanks for the article.
It clearly refers to the beams as prestressed, which means they are reinforced with cables, either before or after concrete is placed, but prior to being transported on site (correct?). They may further connect the beams with additional cables, but I've never seen that process. I would love to see what kind of elongation they would get on 600 feet of cable. That's gotta be one big jack!

I guess you can learn something new every day if you pay attention. Thanks again for the info.

From what I understand, most of the strength was obtained from the prestressing, and the post-tensioning was more to allow additional alignment, etc. See the link below from the company that designed them - it shows some conceptual images of the connections and beam forms, etc.

This is definitely not your usual bridge/DOT construction. Most of the beams I see in those structures are just prestressed, particularly in FL.

http://www.abam.com/sites/default/files/attachments/tpr-MONORAILEX2011.pdf

Monorail beams

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