Interesting bridge on the Kansai Main Line

[Kiha66]

I came across these pictures of an interestingly built bridge today, where it uses a lattice truss bridge in place of a pier for a girder bridge where the pier would otherwise fall in the center of the river.  It could make a neat diorama or module scene.  

http://casco.blog.so-net.ne.jp/2010-06-23

[velotrain]

Neat use of recycling.  It looks like they did something similar on the next segment on the opposite side of the river from the tunnel, where it looks like they could only build a pier on one side of the track - note the angled catenary bridge.

 

In the first photo, it looks like they used old rail as a fencing material.

 

[westfalen]

If I'd seen that on a layout I'd laugh at it but as they used to say in Model Railroader "there's a prototype for everything".

[tsubasa119]

Interesting, wonder why they did it though, the river doesn't look like it would be navigable so why not just build a pier in the river?

[velotrain]

One possible reason I thought of is that this river might be susceptible to seasonal strong current, and if there are frequently large trees in the river during those periods, repeated impacts could over time weaken a centrally placed pier.  Many stone piers were built with up-river facing V's to help prevent trees from getting stuck on a pier, with continual water pressure against the tree possibly impacting the integrity of the pier.  Another - perhaps more likely, reason was the difficulty of diverting the main flow to allow construction of a central pier at this location?  Or, maybe they were removing the truss span from somewhere else and some young engineer had an aha moment . . . .  Clearly, whatever the reason was, they must have thought it was valid, or they wouldn't have built four piers instead of one  ;-)

Edited October 5, 2017 by velotrain
fix typo

[tsubasa119]

Ah of course, didn't think of debris in fast flowing water striking the pier!

[Kiha66]

Thats a very good point, I know in Kyushu last year there was a bridge that was toppled by typhoon flow and debris.  I find it interesting they just didn't make the main span longer to cover that part, perhaps the curve of the bridge made this the preferred alternative.

[velotrain]

Also suggestive that this river is liable to extreme changes in flow, notice how high the markings go on the water level gauge next to the truss section, and the red warning line at roughly the same height as the top of the truss piers.  Of course, this could well represent concerns for downstream locations vs. this particular structure.

 

Too bad it wouldn't align with other modules, as it would make an intriguing (long) T-Trak scene.

 

Someone should start a Fremo-Trak group!

 

 

[katoftw]

Every river in Japan is liable to extreme changes in flow.  So Charles' suggestion makes the most sense.

[katoftw]

https://www.google.com.au/maps/@34.5790244,135.6695528,3a,75y,309.66h,99.67t/data=!3m6!1e1!3m4!1svq7ecBDdUGLjSrnbX8Uvqg!2e0!7i13312!8i6656?dcr=0

 

They have actually done the cross support three time on this same bridge.  the example given.  Once over the road and further away from the tunnel portal side.

Edited October 5, 2017 by katoftw

[Kiha66]

14 minutes ago, velotrain said:

Also suggestive that this river is liable to extreme changes in flow, notice how high the markings go on the water level gauge next to the truss section, and the red warning line at roughly the same height as the top of the truss piers.  Of course, this could well represent concerns for downstream locations vs. this particular structure.

 

Too bad it wouldn't align with other modules, as it would make an intriguing (long) T-Trak scene.

 

I bet you could compress the truss bridge enough to just barely fit a T track model.  Perhaps if you used through girder instead of deck type of the prototype, although another inch or two would greatly add to the scene.  It seems like kato's new tall bridge piers  then a small truss bridge with the normal height piers would work very well.

[Kiha66]

2 minutes ago, katoftw said:

https://www.google.com.au/maps/@34.5790244,135.6695528,3a,75y,309.66h,99.67t/data=!3m6!1e1!3m4!1svq7ecBDdUGLjSrnbX8Uvqg!2e0!7i13312!8i6656?dcr=0

 

They have actually done the cross support three time on this same bridge.  the example given.  Once over the road and further away from the tunnel portal side.

 

Thanks for finding the street view, interesting that the cross supports seem to be later additions halfway between the single tall piers.  I wonder why the change. 

[katoftw]

https://goo.gl/maps/s55bypDFoTR2

 

It flows when it wants to flow.

[cteno4]

33 minutes ago, velotrain said:

Too bad it wouldn't align with other modules, as it would make an intriguing (long) T-Trak scene.

 

Someone should start a Fremo-Trak group!

 

 

You can freemo on modules and the just have end modules that come back to standard and even then you can shift modules in and out some if needed.

 

jeff

[velotrain]

That looks like it's only up to the yellow line on the gauge.

 

 

[velotrain]

Jeff - I was thinking more of the vertical alignment issues.  At the very least it would call for a deeper box.

[cteno4]

Yes 3" would not do it. Although you can do transition modules with gradients on either side! Or do your own freemo loop, not all Ttrak needs to interop you can always have a table with an alternative idea going on.

 

jeff

[Kiha66]

35 minutes ago, katoftw said:

https://goo.gl/maps/s55bypDFoTR2

 

It flows when it wants to flow.

I was wondering about those lower road bridges, I guess just blocking them off a few times a year is a lot cheaper than a proper span.

[katoftw]

2 hours ago, Kiha66 said:

I was wondering about those lower road bridges, I guess just blocking them off a few times a year is a lot cheaper than a proper span.

Well that said bridge is now gone.

 

[bikkuri bahn]

The bridge is officially called the No. 4 Yamato River Bridge [第四大和川橋梁].  The construction method is due to the fact that the line crosses the river at 30 degrees on a 400m radius curve, and the north side has both a rocky outcropping and a national highway running on the valley/cliff face, so conventional piers couldn't be located where they typically would be.  The river flow is also a factor, of course.