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Author Topic: Possible new bridge type.  (Read 1996 times)

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Offline AP

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Possible new bridge type.
« on: January 19, 2014, 12:31:46 PM »
So i've been researching the way in which the road/rail infrastructure of scotland was built in the c18th/19th, obviouly it is particularly constrained by large mountains and very wide lochs.

This lead me to stumble upon a bridge type never used in the UK but used in several locations in America. in the nineteenth century. As an engineering solution, there is  no reason it couldn't have been used, it just wasn't. 

The Pontoon Railway Bridge:

There were apparently a small number, over wide waterways which precluded intermediate piers, including at Wabasha Missippi, Marquette Iowa, Chamberlain South Dakota, according to the article here (which has photos) [Book: North American Railroad bridges, pp140-1] The longest lived and best documented seems to be:

1874-1961 Prarie du Chien Pontoon Railroad Bridge ( Chicago, Milwaukee & St Pauls Railroad)
Replaced railroad ferry over the Missippi. Closed 1961. Able to deal with large variation in water level too.
Drawings etc in a 1932 article here & here.

It seems that, predictably,the bridges have low maximum loads, and low maximum speeds. And those with opening spans were very expensive to operate because of the manpower it required.

I'm not saying it was a common bridge type, but neither were cantilever bridges or some of the tall metal bridges (Crumlin, Meldon etc). It appears seattle is currently planning to run its light rail system accroas the I90 floating bridge (in due course).

For interest, I did also find this image but I'm not sure how permanent that one was...

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Given the (realistic) in game prohibition of building most bridges over deep water (due to intermediate piers), this is precisely where such a bridge was used. as an alternative to a "forth bridge" style construction. (Forth bridge opened 1890)

I suggest it worth adding to pak-britain because it fills a niche no other bridge type can fill. We often play using maps different than the real UK geography so it may be useful. On a water-heavy map it would be invaluable.


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I'm now off to ponder how to network scotland via floating bridges...
« Last Edit: January 19, 2014, 12:43:22 PM by AP »

Offline jamespetts gb

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Re: Possible new bridge type.
« Reply #1 on: January 19, 2014, 12:45:28 PM »
This is an interesting suggestion, but it raises the somewhat theoretical question of how far, if at all, Pak128.Britain should move into the realms of hypothetical infrastructure (and vehicles) that were not actually represented in the UK but might have been. Consistency in principle is important, so if some hypothetical things are included, others ought to be included, too (or else what hypothetical things are included and what are not become arbitrary).

I should also note that the prohibition on building many bridges over deep water is exclusive to Experimental, and that it is based on whether the bridge has a maximum length, to prevent bridges being built over oceans; even a pontoon bridge should not be able to be built over open ocean (think of the waves).

Offline AP

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Re: Possible new bridge type.
« Reply #2 on: January 19, 2014, 01:34:46 PM »
If you think this worth moving to the experimental form please feel free.

Your point is fair,  but I do think its a debate worth having, because:

  • We can use the map generator to produce geographic scenarios not found in the UK In some cases very different. These may logically call for different strategies than those found in the UK historically.
  • There is a difference between entirely fictional hypothetical technologies, and real technologies which were available but not deployed in the UK (due to engineering choices, based primarily on the above. Contrast pontoon bridges with e.g. the Lartigue Monorail, which did not develop into a mainline express format, so I'd have concern if one were proposed.
The comment about pontoons and open ocean is of course fair, but as the saying goes "still waters run deep", I suspect a pontoon bridge across part of a navigable inland lake would work perfectly well. [The absence of cantilever bridges from simutrans is a slightly-related issue... although they fill a different cost-benefit niche.]


Offline jamespetts gb

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Re: Possible new bridge type.
« Reply #3 on: January 19, 2014, 01:46:45 PM »
Ahh, yes, these things are definitely worth a debate, and I look forward to others' views on this topic. It is best to leave it in this forum for the time being pending comments from the maintainers of the Standard version of the pakset on that issue (and the subject generally).

I should note that it is very unlikely that I shall be in a position myself to produce graphics for this in the foreseeable future even if it were considered a good idea because of how long that it takes to produce bridge graphics (combined with the fact that I have not produced bridge graphics before, so should have to learn how to do it) and because of all the other priorities that I have at present, but if others were to be in a position to produce the graphics, then it would merit at least serious consideration.

As to the question of lakes, this is more interesting. The current release versions of Standard and Experimental do not have any means of distinguishing between open seas and inland lakes, but the current Standard nightlies, which Bernd Gabriel is working towards merging into Experimental - see the 112.5-merge branch on Github) do have a new concept of a lake. Although I have not tested this yet, I strongly suspect that the code as adapted would in any event allow any bridge to cross a lake without the deep water restriction (and, even if not, the could should be changed to give this behaviour). What we do not want to have is any sort of bridge that can cross open oceans; but a pontoon bridge might possibly be a good length unlimited cheap bridge.

One issue that has just occurred to me, however, is that there is no way of requiring bridges to be over water: all bridge types in Simutrans can be built as bridges over valleys or roads or as viaducts, which would obviously not make sense for a pontoon bridge.

Offline kierongreen

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Re: Possible new bridge type.
« Reply #4 on: January 21, 2014, 04:08:41 PM »
Eventually I'd like cantilever bridges to be able to be included - however these really require a more complex graphics system for bridges. Pontoons at sea level seem unrealistic as JamesPetts says due to waves. Also I'm not sure how you would simulate the disadvantages of pontoon crossings over lakes and rivers in simutrans.