Western Railroad Discussion > Victorville New Gree Tree Grade Separation /BNSF

Victorville, CA   Green Tree overpass

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Open for traffic?

mapboy

No, not yet.

Heather McGuffin took the photo. She say's, another year before it opens.

I've always wondered what the difference is in the superstructures that hold up these overpasses are?  In some places, especially California, there are no visible seperate concrete beams - it's a smooth, solid looking piece of concrete making up the main structure of the overapass(as in this photo).  Around where I live, they use pre-built concrete "beams" that they set onto the pillars, you can see them individually underneath the overpasses when its finished (much like steel girder beams would look).

Wonder what the crossover looks like from the bridge?

Out 

wyeth Wrote:
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> I've always wondered what the difference is in the
> superstructures that hold up these overpasses
> are?  In some places, especially California,
> there are no visible separate concrete beams -
> it's a smooth, solid looking piece of concrete
> making up the main structure of the overpass(as
> in this photo).  Around where I live, they use
> pre-built concrete "beams" that they set onto the
> pillars, you can see them individually underneath
> the overpasses when its finished (much like steel
> girder beams would look).

It's a box girder, or box section, bridge. Fairly common in some states, particularly in the West in my experience, but not in other states. They are often constructed on site, with the concrete poured over a falsework frame to create the box shape, and the falsework is (or should be) removed. There was a fairly major problem with some bridges of this type in the Denver area back some years ago when I lived there. The interior falsework had not been removed after construction was completed, and decay of the falsework caused subsequent structural issues for the bridges.

But bridges of this type can also be constructed in pre-fabricated sections, with the concrete pour done over the falsework frame in a production yard. The entire box section is then moved to the site by truck, and lifted into place. Just as is the case for steel or precast concrete beams for the more common stringer or girder bridges to which you refer, with exposed girders supporting the roadway deck.

Bridges of this type are also sometimes constructed by an very interesting method known as incremental launching. A traveler assembly moves over the top of completed sections, and then places new sections out ahead over the area to be spanned.

Wikipedia article with illustrations: https://en.wikipedia.org/wiki/Box_girder_bridge
Another article: https://theconstructor.org/structures/construction-box-girder-bridge/2166/

Bridges of this type can be used for railroad track. Perhaps the most famous railroad bridge of this type is the spectacular Latah Creek Bridge in Spokane, Washington, which utilizes fabricated steel box girders: https://en.wikipedia.org/wiki/High_Bridge_(Latah_Creek)

MC

 



Edited 2 time(s). Last edit at 09/24/22 21:47 by ironmtn.

This is also earth Quake country.  We need strong stuff. its not far fro the San Andres fault.

czuleget Wrote:
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> This is also earth Quake country.  We need strong
> stuff. its not far fro the San Andres fault.

Good point, well taken. Here in the Midwest where I live, many girder / stringer bridges located in proximity to the New Madrid Seismic Zone in the Mississippi Valley have been extensively retrofitted for seismic strengthening. Techniques include jacketing support columns with steel or heavy concrete jackets, particularly at possible shear points where computer structural analysis has shown that they could be subject to fracture and collapse. Roadway support girders have heavy steel cables added to tie them better to the caps of the support columns. And the girder ends are also sometimes "boxed in" with heavy poured concrete sections around them to keep them in place atop the caps during an earthquake. Drive around downtown St. Louis or Memphis and you will see many such seismic retrofits.

But back to this bridge, I too wonder what the view of the tracks will be like. And will the fencing along a sidewalk (?) be of a kind that will allow photography? I've had some favorite spots here in the Midwest completely made useless for photography by the very fine grid fencing that was used.

MC



Edited 2 time(s). Last edit at 09/24/22 21:50 by ironmtn.

In California earthquakes, bridges bounced on the columns and shattered, or bounced off the columns and the bridge collapsed.  So a lot of the columns and girders were tied together with cable, as mentioned.

mapboy

Thank you for the info.  Here in Washington State, you see some older overpasses, particularly on the west side of the state, using the box girder style, but throughout most of the state, and newer overpasses, they seem to standardize on the precast concrete beams.  I like the sleek style of the box girder that California uses, but it seems to me that style would be more expensive to build?  I'm curious what the benefits of each are (as speculated here, maybe earthquake damage resistance?)?

ironmtn Wrote:
-------------------------------------------------------
> wyeth Wrote:
> --------------------------------------------------
> -----
> > I've always wondered what the difference is in
> the
> > superstructures that hold up these overpasses
> > are?  In some places, especially California,
> > there are no visible separate concrete beams -
> > it's a smooth, solid looking piece of concrete
> > making up the main structure of the overpass(as
> > in this photo).  Around where I live, they use
> > pre-built concrete "beams" that they set onto
> the
> > pillars, you can see them individually
> underneath
> > the overpasses when its finished (much like
> steel
> > girder beams would look).
>
> It's a box girder, or box section, bridge. Fairly
> common in some states, particularly in the West in
> my experience, but not in other states. They are
> often constructed on site, with the concrete
> poured over a falsework frame to create the box
> shape, and the falsework is (or should be)
> removed. There was a fairly major problem with
> some bridges of this type in the Denver area back
> some years ago when I lived there. The interior
> falsework had not been removed after construction
> was completed, and decay of the falsework caused
> subsequent structural issues for the bridges.
>
> But bridges of this type can also be constructed
> in pre-fabricated sections, with the concrete pour
> done over the falsework frame in a production
> yard. The entire box section is then moved to the
> site by truck, and lifted into place. Just as is
> the case for steel or precast concrete beams for
> the more common stringer or girder bridges to
> which you refer, with exposed girders supporting
> the roadway deck.
>
> Bridges of this type are also sometimes
> constructed by an very interesting method known as
> incremental launching. A traveler assembly moves
> over the top of completed sections, and then
> places new sections out ahead over the area to be
> spanned.
>
> Wikipedia article with illustrations:
> https://en.wikipedia.org/wiki/Box_girder_bridge
> Another article:
> https://theconstructor.org/structures/construction
> -box-girder-bridge/2166/
>
> Bridges of this type can be used for railroad
> track. Perhaps the most famous railroad bridge of
> this type is the spectacular Latah Creek Bridge in
> Spokane, Washington, which utilizes fabricated
> steel box girders:
> https://en.wikipedia.org/wiki/High_Bridge_(Latah_C
> reek)
>
> MC
>
>  

callum_out Wrote:
-------------------------------------------------------
> Wonder what the crossover looks like from the
> bridge?
>
> Out 

Actually, not too bad, although the classic shot is over as the hill on the south side has been lowered.  Expect to see some pretty unique shots from the bridge soon.  

It's hard to believe it will be another year before this opens, but I think that's to get the roadway to the bridge on both ends done.  I'm only guessing here.  

Nick Tharalson,
Marion,IA

What would a transverse cross-section
of the overpass look like?

timz Wrote:
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> What would a transverse cross-section
> of the overpass look like?

Something like this I think:
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Nathan