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Author Topic: Unique bridge support structures  (Read 800 times)

MCRoads

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Unique bridge support structures
« on: May 24, 2022, 10:59:07 PM »

Found this very unique structure in Mane of all places, not where I would expect any kind of unique bridges.

I could also swear there is a bridge suspended from another bridge via cables somewhere in NYC, or maybe Philly, but I cannot for the life of me find it.
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Dirt Roads

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Re: Unique bridge support structures
« Reply #1 on: May 25, 2022, 09:14:06 AM »

Found this very unique structure in Mane of all places, not where I would expect any kind of unique bridges.

This is an example of something I've always been fascinated with about bridges and certain building structures.  It looks like one of the old steel support structures has been removed and replaced with this new concrete catch structure.  In order to build such a contraption, that entire section of bridge would have needed a temporary support structures (similar to shoring structures).  After the shoring is in place, the old structure can be removed and the new structure can be constructed (around the shoring structure).  Then the shoring structure can be removed.  It's not completely obvious how this was done on this bridge, as the [right side] crossbeam has been placed directly beneath the old bridge bearing.  The [left side] crossbeam may also be under an old bridge bearing, but I can't see it from this angle.  [Note the very close spacing of the old steel support structures to the [right side] of the bridge as you approach the abutment.
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Tom958

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Re: Unique bridge support structures
« Reply #2 on: May 25, 2022, 01:19:28 PM »

Found this very unique structure in Mane of all places, not where I would expect any kind of unique bridges.

An awesome find. Thanks! That's called a straddle bent.

This is an example of something I've always been fascinated with about bridges and certain building structures.  It looks like one of the old steel support structures has been removed and replaced with this new concrete catch structure.  In order to build such a contraption, that entire section of bridge would have needed a temporary support structures (similar to shoring structures).  After the shoring is in place, the old structure can be removed and the new structure can be constructed (around the shoring structure).  Then the shoring structure can be removed.  It's not completely obvious how this was done on this bridge, as the [right side] crossbeam has been placed directly beneath the old bridge bearing.  The [left side] crossbeam may also be under an old bridge bearing, but I can't see it from this angle.  [Note the very close spacing of the old steel support structures to the [right side] of the bridge as you approach the abutment.

The auto bridge was only built in 2000 per https://bridgehunter.com/me/sagadahoc/sagadahoc/. I'm gonna guess that the road below it was either built along with it or was once narrow enough to fit between the original steel bents.

Wait: that road was visible in the 1997 aerial, but not in the 1985 one. Most likely, then, the road beneath the bridge was closed while the straddle bent was under construction. That being the case, it ought to have been possible to place the falsework pretty much wherever.
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Dirt Roads

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Re: Unique bridge support structures
« Reply #3 on: May 25, 2022, 04:13:36 PM »

Found this very unique structure in Mane of all places, not where I would expect any kind of unique bridges.

An awesome find. Thanks! That's called a straddle bent.

There's a better term than straddle bent, but I'm still word seeking.  A column (pier) is one-dimensional, and a straddle bent is two-dimensional.  This structure is three-dimensional.  When we build them to support rail transit over top of a building, we use a simple word: bridge.  But a bridge that supports another bridge gets another term.  Still word seeking.
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roadman65

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Re: Unique bridge support structures
« Reply #4 on: August 13, 2022, 11:17:30 AM »

Not so unique unless you consider elevated rail lines over an already elevated overhead freeway to be such.

However to have the subway piers in the middle of the freeway extend below deck, is rare. 

https://goo.gl/maps/dHitAdcfj9wXHgxC6

Anyway, I find this interesting with the three wrought iron piers all together.  You don’t often see this.
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