Covered Aqueduct (USA)

[magpie patrick]

Took the Stepdaughter to the American Museum in Claverton today. Whilst there I attempted to rectify the shortage of books in my collection 🤭 with several purchases including this one. "Covered Bridges" - I've known of their existence and even driven over a few, but knew nothing about them. 

 

Imagine my delight on finding within a picture of a covered aqueduct! 

 

Apparently its on the Whitewater Canal in Indiana - so I'm off to research that now! 

 

It seems there is always something out there to discover. 

[Mac of Cygnet]

I see that it mentions the bridges of Madison County, the exact title of the acclaimed film starring Clint Eastwood and Meryl Streep.

[robtheplod]

8 hours ago, Mac of Cygnet said:

I see that it mentions the bridges of Madison County, the exact title of the acclaimed film starring Clint Eastwood and Meryl Streep.

its a lovely film......

[Pluto]

14 hours ago, magpie patrick said:

Took the Stepdaughter to the American Museum in Claverton today. Whilst there I attempted to rectify the shortage of books in my collection 🤭 with several purchases including this one. "Covered Bridges" - I've known of their existence and even driven over a few, but knew nothing about them. 

 

Imagine my delight on finding within a picture of a covered aqueduct! t at

 

Apparently its on the Whitewater Canal in Indiana - so I'm off to research that now! 

 

It seems there is always something out there to discover. 

It may reflect on the Germanic origins of many US inhabitants. Wooden bridges were common in the European Germanic area, and some were quite advanced in design. This is the Schwecht Aqueduct on the Wiener Neustadt Kanal, built from Vienna in 1800c. No cover, but the principal is the same. Perhaps Americans did not want to get their canal water wet?

[David Mack]

American road bridges were covered so that the quantity (and hence weight) of snow which could accumulate on the bridge was limited. But that shouldn't be the same issue for an aqueduct (Archimedes and all that).

[magpie patrick]

According to the book they were used because open bridges didn't last more than about twenty years, the rainfall is cited but I guess it would be a combination of rain, wind and sun that would do the damage. I'm not entirely clear whether the open bridges that preceded them were truss bridges and thus the covered bridge was just a truss bridge with cladding. 

 

As for the aqueduct, my thoughts were the same as @Pluto - what's the point in stopping it getting wet! More research needed... 

[matty40s]

The bridges in the USA and Canada are subject to far more extremes of temperatures, frost, ice and heat than anything in this country.

 

This is a very common sign on most roads , warning that even if the road seems dry and safe, the bridge ahead may not be. The road surface, and whole construction will be subject to far more stress, so would an aqueduct, especially if the watercourse froze.

Covering up the bridge would help stop water ingress and perhaps prevent/reduce frost damage.

[David Mack]

37 minutes ago, matty40s said:

The bridges in the USA and Canada are subject to far more extremes of temperatures, frost, ice and heat than anything in this country.

 

This is a very common sign on most roads , warning that even if the road seems dry and safe, the bridge ahead may not be. The road surface, and whole construction will be subject to far more stress, so would an aqueduct, especially if the watercourse froze.

Covering up the bridge would help stop water ingress and perhaps prevent/reduce frost damage.

The temperature of the road surface exposed to cold wind etc. is moderated by the ground underneath. But a bridge deck has cold air above and below, so would get colder quicker when there is a sudden drop in air temperature. I guess an aqueduct would be somewhere between the two.

[Pluto]

Although the low temperatures would have been a problem, the spring floods probably damaged American canals to a greater degree. Canals could easily be drained over the winter period, with boats left 'floating' in winter docks. Watchmen would have remained on board to cut the ice which formed around the boats. I have photos of this on the Oder, and many winter docks  survive on European waterways. There is an excellent German book on ice breaking, with details of how to blow up ice jams around bridges. North American and Easter European conditions are very different to ours.

[StephenA]

2 hours ago, David Mack said:

The temperature of the road surface exposed to cold wind etc. is moderated by the ground underneath. But a bridge deck has cold air above and below, so would get colder quicker when there is a sudden drop in air temperature. I guess an aqueduct would be somewhere between the two.

 

There are bridges in Maine which specifically warn that the bridge deck will freeze before the rest of the road

[magpie patrick]

11 hours ago, Pluto said:

Although the low temperatures would have been a problem, the spring floods probably damaged American canals to a greater degree. 

 

This is very true, the Whitewater Canal being a case in point I find. Apparently it opened in full in 1847 but the same year parts were washed away in floods, some of the damage was never repaired. The canal as a whole lasted only a few months, although some bits traded for many years before the canal was completed and after the floods closed part of it. 

 

I'm only one page ahead at the moment, so the above is almost all I know... 

[Derek R.]

That bridges of any kind are subject to cold winds both from above - and below, it is natural that care need be taken when negotiating same. Likewise with a road lined with hedges or walls, where a gateway is present in the hedge or wall more cooling/freezing wind will reduce the road temperature by the gateway.

 

I think the roof over American bridges is more intended to increase longevity of the bridge deck. An umbrella reduces the chance of a soaking. Snow, not so much. Snow on a bridge roof will bring the same amount of weight applied to the roof, thereby the bridge as a whole.

[magpie patrick]

18 minutes ago, Derek R. said:

 

I think the roof over American bridges is more intended to increase longevity of the bridge deck. An umbrella reduces the chance of a soaking. Snow, not so much. Snow on a bridge roof will bring the same amount of weight applied to the roof, thereby the bridge as a whole.

 

Thanks Derek, the book clearly states the idea developed to increase bridge longevity by protecting the main elements from the weather. The book refers to the number of  joints involved in a wooden bridge of any significant span, and I believe joints are where rot sets in first.

 

Although it's a slim volume I haven't finished the book yet as I bought four more the same day and I keep reading those too! As well as doing Internet searches to add to what I'm learning. I now understand the difference beyond King trusses and Queen trusses for example.