Weird bridge in Eastern Maine (Eastern Maine RR / NBSR)

I have the same question the photographer has. What are the arches for? http://photos.nerail.org/showpic/?photo ... ge=61&key=

The arches seem substantial enough to have supported a metal canopy. Maybe such a canopy was snow-and-ice footing protection on the bridge for diverging-route CP crews way back when?

I have seen many photos of this bridge and never one with a cover. Could just be the design of the bridge. The Through Truss has braces across the top to keep things together, this could serve the same function.

Mike

an arch like that offers no structural support. there must have been a cover at some point. and those orange things on the power lines are weights, not aircraft markers

my vote is they supported some sort of canopy.

I would think that the orange balls on the wires are flotation devices for the cable to be easier seen if they fell in the water.

The balls are for marking the lines for low flying aircraft, many pilots follow rivers as when they fly visualy and the wires across water or ones that are higher than the tree line are hard to see.
The attached link is a statement from a guy that makes them.

http://www.answerbag.com/q_view/89403

peter

arcadia terminal wrote:The balls are for marking the lines for low flying aircraft, many pilots follow rivers as when they fly visualy and the wires across water or ones that are higher than the tree line are hard to see.
The attached link is a statement from a guy that makes them.

http://www.answerbag.com/q_view/89403

peter

Yep. You see them often on power lines that are on approaches to small municipal airports. Not so much near airports that take higher-flying jets and fixed-route commercial flight paths.

HI

I take a guesss, how about this , the arches were used as snow and ice breakers , for when the cars passed under the arches . Pat

My guess is they *are* structural, to tie the two sides of the truss together. Perhaps they were installed at some point after the bridge was built in order to cure some deficiency?

Feel like if there were some other reason- a canopy, snow-scraper, etc.- there'd be other bridges with such a structure: but I've never seen anything else like it.

Anyone know when the bridge was built?

My guess, the bridge originally had braces for stability across the top that were replaced by the arches in order to facilitate higher load dimensions and/or to provide greater stability to the structure. Either that, or the bridge was open across the two (and yes, there are two truss-spans with braces, each having 4 braces apiece) spans, and the braces were simply added later s a means of stabilization and to reduce vibrations that most likely came with an increase in load size/weights after the bridge was built.

I also think they are structural, they look way too beefy to hold up a tin roof.

Cosmo wrote:My guess, the bridge originally had braces for stability across the top that were replaced by the arches in order to facilitate higher load dimensions and/or to provide greater stability to the structure. Either that, or the bridge was open across the two (and yes, there are two truss-spans with braces, each having 4 braces apiece) spans, and the braces were simply added later s a means of stabilization and to reduce vibrations that most likely came with an increase in load size/weights after the bridge was built.

Could be structural but I am not a bridge designer. A shape like that isn't going to offer a whole heck of a lot of support to tie the top of the trusses together but they may not need much. I think a better picture to show just how massive they may be might help us answer this question. IMO the look to big to hold up a canopy but small to brace the top of the truss. Arches are a very effective shape when they are loaded in compression and the legs are prevented from spreading but they have very little resistance on their own to keeping the bottoms a fixed distance apart.

Well, they wouldn't need to hold so much weight themselves. I think they're there for stabilization. If you look at other bridges, the top-braces aren't much larger. I believe the unique shape is for greater clearance.

I posed the question to a bridge engineer... he believes it was most likely built as a "pony" truss, but later modified to handle greater loading. This prompted my memory... a quick search in Lavalle's"Canadian Pacific to the East" comes up with this possible modification time: In 1931, Ship Pond and Wilson's Stream bridges were replaced to accomodate heavier locomotives and doubleheading. According to the book, "many other lesser structures were brought up to the same standard at this time." Brownville Junction's 70-ft turntable was also replaced with a 100-footer. BTW, there's a 1953 color pic of the bridge on page 129 of the book.