Will Austin ever have a cable-stayed bridge downtown?

[ahealy]

Lamar, I-35, S. 1st? If so, what would Austin's style be?




Dallas Margaret Hunt Hill

The Sai Van Bridge, in Macao.

[Jdawgboy]

Aren't both the 360 bridge and 2nd Street Cable-stayed bridges? They both have cables.

[freerover]

Maybe you should read the posts in the transportation thread.

[ahealy]

Originally Posted by freerover

Maybe you should read the posts in the transportation thread.

The transportation thread gives me anxiety

[freerover]

Originally Posted by ahealy

The transportation thread gives me anxiety

Txdot wants to rebuild I-35 over the lake as a "signature" extradosed bridge. It would possibly be 2 levels depending how they separate the managed lanes. This is all if they can possibly find 8 billion dollars to fund it the entire project.

[The ATX]

Originally Posted by ahealy

The transportation thread gives me anxiety

I know what you mean. But a certain poster that caused much of that hasn't posted in a long time.

[Sigaven]

Originally Posted by Jdawgboy

Aren't both the 360 bridge and 2nd Street Cable-stayed bridges? They both have cables.

Those are both through-arch bridges - the main structure is an arch and the bridge is suspended from it with cables. A cable-stayed bridge has one or more towers from which the cables come down to support the bridge.

I don't think the Lamar or Congress bridges will be replaced any time soon since I think they are considered historic (and quite beautiful concrete arch bridges). I wouldn't mind seeing the S. 1st bridge replaced. Or an I-35 signature bridge could be spectacular if those rumors come true.

[freerover]

Originally Posted by Sigaven

Or an I-35 signature bridge could be spectacular if those rumors come true.

If they were rumors then I would have said that. It’s from txdot directly.

[The ATX]

Originally Posted by freerover

If they were rumors then I would have said that. It’s from txdot directly.

A lot of posters may have missed this in the transportation thread. It would be helpful if you linked to the post or to the project at TxDOT.

[427MM]

Fun idea! I hope it wouldn't be I-35. Let's bury/blow up/hide that ugly beast the best we can. I suggest S.1st as tops. Center of the DT scene, great views of Congress and Rainey and Pfluger and Lamar and straight to City Hall.

[the Genral]

I'm all for giving the Congress Ave bridge a falsie.

[drummer]

I think I-35 could be good, and practically the most likely contender unless a new bridge is built downtown. I don't see any of the other current bridges getting replaced (but I don't know the ages or life expectancy of the current ones). If a double bridge, would that make it narrower (i.e., no access roads on separate bridges)? I don't know that a double bridge would preclude the cut and cap hope that many of us hold either...if I recall, that wasn't supposed to happen until farther north on I-35 (Holly or Cesar Chavez?), so it would have room to accommodate the changes.

[Jdawgboy]

Originally Posted by Sigaven

Those are both through-arch bridges - the main structure is an arch and the bridge is suspended from it with cables. A cable-stayed bridge has one or more towers from which the cables come down to support the bridge.

I don't think the Lamar or Congress bridges will be replaced any time soon since I think they are considered historic (and quite beautiful concrete arch bridges). I wouldn't mind seeing the S. 1st bridge replaced. Or an I-35 signature bridge could be spectacular if those rumors come true.

Ah I see, thanks for clarifying.

[freerover]

Originally Posted by The ATX

A lot of posters may have missed this in the transportation thread. It would be helpful if you linked to the post or to the project at TxDOT.

http://ftp.dot.state.tx.us/pub/txdot...pre-rfp-qa.pdf

[urbancore]

Originally Posted by freerover

http://ftp.dot.state.tx.us/pub/txdot...pre-rfp-qa.pdf

wow.

[ahealy]

Originally Posted by freerover

http://ftp.dot.state.tx.us/pub/txdot...pre-rfp-qa.pdf

well well welllllll

[freerover]

Originally Posted by ahealy

well well welllllll

For the record, I don't post rumors. If I said someone plans on doing so there is some backup for it.


This is how I'm guessing the beige will be structured but it's possible it's a little wider and the managed lanes are at the same level. It would take up less space though if the managed lanes and frontage lanes were on 1 level and the highway mainlines were on the upper level.

[drummer]

I don't know bridge engineering terminology beyond the basics, but freeover's link mentioned a "bridge that is described as employing the Extrados approach"...so I looked that up. Here's a link to a Google image search. Engineering-savvy folks, please chime in!

https://www.google.com/search?tbm=is...&bih=821&dpr=1

[Azul]

Originally Posted by drummer

Engineering-savvy folks, please chime in!

So imagine one of our overpasses here in Texas. Generally they're these concrete structures with a sort of "box" underneath the road that supports and stiffens the road way as it spans between massive columns. We've all seen this and maybe haven't thought much of it; they're "Box Girder Bridges".

https://erkrishneelram.files.wordpre...der-bridge.jpg


Now take that but remove many of the columns. Your bridge now spans a long distance without decent support which causes it to sag, twist, and bounce. What few columns you have left, usually just two, you reinforce and elevate them above the roadway into a tower like structure. The cables can be attached from the tower to the roadway. Workers come and typically post-tension, or tighten after installation order to keep the roadway supported and stiff over it's unsupported spans.

From an aesthetic stand point these bridges usually don't have a high tower like the cable-stay bridges, like the Golden Gate. The stiffer concrete "box grider" portion of the bridge takes more of the load from the cables. This means the cables can be at a more horizontal angle and allows the towers to be smaller.

What this means is I'd fully expect this bridge to be relatively disappointing in comparison to the bridges in Dallas. It may end up looking more like the 35 Bridge in Waco.

https://www.beecreekphoto.com/images...t-DSC02172.jpg

[drummer]

^^ Thanks!

And for the record, given that the span over Lady Bird Lake (I still want to say Town Lake) isn't that much, I'd be perfectly fine with something cut from the same cloth as what we see in Waco.