Talk:Bollman Truss Railroad Bridge

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Article name[edit]

I found several variations for the name of this bridge. I ended up using the one in the National Historic Landmark program -- "Bollman Truss Railroad Bridge". I made redirects of the others. — Eoghanacht talk 02:50, 1 April 2006 (UTC)[reply]

Suspension bridge[edit]

Occasionally this bridge is referenced as being a suspension bridge as well as a truss, but not consistently. The bridge is always refered to as a truss, however. It has been too long since I took my static structures classes to confirm if it should be classified as just a truss or a combination suspension system. So I just removed the reference to the suspension bridge from the main article as being unverified. — Eoghanacht talk 14:27, 4 April 2006 (UTC)[reply]

It's definitely a truss bridge, though this is not as obvious for the deck version. The key is the presence of the compression members; it's composed of the same sort of force triangles as other truss systems, and the through version clearly relies on the upper chord of the bridge to keep the pylons apart. A true suspension bridge relies on symmetry of forces to eliminate the tortional forces on the pylons.
Bollman's patent drawing is a bit confusing because it doesn't show any members across the bottom. If I recall correctly, actual examples did include those members (providing stiffening). In any case the compressional elements of the deck are crucial in the deck version. Mangoe 18:05, 30 June 2006 (UTC)[reply]

Analysis showed it to be a combination. Contributions From the (Smithsonian) Museum of History and Technology, The Engineering Contributions of Wendel Bollman (1964) by Robert M. Vogel:

  • Bollman received a patent for his truss in January 1852, and in the same year published a booklet describing his system in general and the Harpers Ferry span in particular. Here, he first calls it a “suspension and trussed bridge,” which is indeed an accurate designation for a system which is not strictly a truss because it has no active lower chord. (The analogy to a suspension bridge is quite clear, each pair of primary rods being comparable to a suspension cable.) Thereafter, Bollman’s invention was generally termed a suspension truss.
The paper is a valuable reference for the works of Bollman.Palmeira (talk) 03:45, 12 October 2020 (UTC)[reply]
Cheers Palmeira, and thanks for your work on this article. Unfortunately, Vogel's paper isn't correct on this item. Suspension bridges need an anchor to counterbalance the tension from the main cable supporting the bridge deck. (See this Youtube video -(jV7zQ55O-P4) entitled "Suspension Bridge Cable" design by Nasser Yari PhD, PE for a schematic look at force loadings on a suspension bridge.) Trusses, even the Bollman bridges, don't need an anchor. See this Youtube video- (Hn_iozUo9m4) entitle "Understanding and Analysing Trusses". A truss is like laying a beam on the abutments. The pictures in this article show that there are pin connections on the base. There are no suspension cables on the back sides of the towers to anchor the Bollman bridge. Like a beam, the Bollman bridge lays on the abutments. (See Structural Systems of the Bollman Truss Bridge at Savage, Maryland, Association for Preservation Technology International (APT), Vol. 37, No. 1, 2006. for a more technical discussion.) Many thanks, Risk Engineer (talk) 18:14, 13 October 2020 (UTC)[reply]
Perhaps you can present that in the article citing reliable sources. That does not nullify the view of Bollman himself nor several experts cited in other sources that the design is a "suspension truss" or sometimes "semi suspension" type. Vogel notes "The analogy to a suspension bridge is quite clear, each pair of primary rods being comparable to a suspension cable." As for anchors, several have noted the upper chord ends are the anchors. Each rod is anchored at the end of that member and the rod pairs "suspending" a part of the lower deck are anchored at opposite ends of that member. The forces act against that member, not an anchor point distant from those ends as in the pure suspension bridge. I found this simplified diagram helpful in visualizing that — even if the text goes further than the sources I've seen and claims "Properly speaking, it is not a truss, but a multiple suspension system." In any case, there is fairly wide support in multiple references for an element of suspension in this design. Palmeira (talk) 00:25, 14 October 2020 (UTC)[reply]
Cheers Palmeira. I gave you the 2006 APT article reference as a credible source. The youtube materials are from engineering design classes. I don't dispute that there is some lack of clarity (from our 21st-century perspective) on 19th-century usage. The suspension elements in Bollman's bridge were diagonals, redundant diagonals. Suspension elements in structures require a counterforce to take the tension of the cabling, or in this case, the diagonal in tension. In Bollman's bridge and in other trusses, this is resisted, not by an external abutment or anchor, but by a top chord in compression. The Wikipedia article on trusses supports (no pun intended) this argument. There is no mention of the word "suspension" in the article. Vogel misses the point about the counterbalancing force of the gravity anchors for suspension bridges such as the golden gate bridge. Doing some research on this topic, I found that the newer cable-stayed bridges are self-anchored (Think the new Bay Bridge span) and the older bridges are "Earth anchored". But the point remains the same. To my mind, the strongest argument against suspension is the lack of external anchoring abutments. I would be pleased to work with you to develop language that clarifies this ambivalence in usage. Cheers Risk Engineer (talk) 14:58, 14 October 2020 (UTC)[reply]
Sources exist and are clear on suspension aspects. You are free to, as is standard here, offer other credible sources with different views as contrast in a discussion of differing scientific, technical or historical opinions. I also note that sources using "suspension" are not just 19th century. There can be no doubt that some modern sources, regardless of what some others may now state, state the design is a form of "suspension" — that is simple fact. Vogel, regardless of your view, has published in peer reviewed, well cited very credible form his view (as have others). Work within those to explain that some other experts have a different view is acceptable. Deleting or otherwise removing is not. As with my expert views in other areas "to my mind" counts not at all. We as individuals, regardless of expertise, are not credible (an unfortunate thing in some rare cases I've found here where "incredible" but published authors have corrupted a "popular" subject) and we may be entering into the Wikipedia prohibited original research. Cite recognized experts in recognized credible sources with their arguments and we have a pro/con discussion of the design that can fit. I do not believe YouTube videos are generally credible sources here, but may be mistaken if their producer is clearly an authoritative and recognized one. Palmeira (talk) 15:36, 14 October 2020 (UTC)[reply]
PS: I noted that the article you mentioned does not have a link to the full text so here it is so other interested readers can see the interesting result: Structural Systems of the Bollman Truss Bridge at Savage, Maryland. Some of those "suspension" references are cited in that paper, including Vogel. It is interesting in revealing a fairly complex redundancy system (that "suspension" aspect) which could mitigate failure of other structural members. The interactions are interesting as is the comment that "Bollman understood that his design did not result in classic truss behavior" and is not simply a classic truss. Palmeira (talk) 16:27, 14 October 2020 (UTC)[reply]

I understand the argument from the Bollman and Vogel side but show me where the anchorages are for the Bollman bridge? Cheers Risk Engineer (talk) 20:52, 15 October 2020 (UTC)[reply]

It is not up to me to show you the anchorages as you specify. The references stand by themselves. You can perhaps find other reliable sources that discuss how there is a different opinion — how those that have found the design to be a “suspension and trussed bridge”, "suspension truss" or "semi suspension" in articles published in established sources are in error. You seem fixated on a single, modern view of what a suspension must be, focused on Golden Gate type cable systems with cables anchored at each end. The articles are clear. They are discussing suspension aspects and elements mixed with truss elements and not a cable suspension system. Other engineers may disagree and insist on "suspension" being only one thing. If you can find other experts that demonstrate the specific "suspension" aspects within the Bollman design are in no way suspension elements then cite them in a discussion of why an established view is wrong. Still, you must not remove cited text regardless of your opinion. The cites and "reliability" of the sources stand. In quite a few science or history articles one finds such discussions. There is no point in us discussing this further. Find published, reliable counter views specifically dealing with the "suspension" aspects in the Bollman design, not some "it is not because suspension only applies to a pure suspension cable design" type argument and work that into a discussion without removing the Bollman/Vogel and other's cited viewpoints. Palmeira (talk) 11:08, 17 October 2020 (UTC)[reply]

Reconcile (type vs. example)[edit]

This article should be about the truss it's titled for, not about any specific example. From the Truss bridge article, there are at least two of these truss bridges still around, and there may be more. I suggest that a partisan of the Savage, Maryland bridge create a separate article for it, and point to it as an example of such a bridge here, or make the references to that bridge be a subset of this article instead of the whole thing. Meanwhile, this article should be revised to explain what this truss is. - Denimadept 20:44, 17 October 2007 (UTC)[reply]

The historical markers near the bridge, and the American Society of Civil Engineers states it is the only surviving Bollman Truss bridge. The only other Bollman-designed bridge I know of (Wells Creek Bollman Bridge) is a Warren Truss system. Where is the other Bollman Truss bridge? — Eoghanacht talk 16:50, 26 November 2007 (UTC)[reply]
Truss_bridge#Bollman_truss says the other is located in Meyersdale, Pennsylvania. - Denimadept (talk) 17:27, 26 November 2007 (UTC)[reply]
The Meyersdale bridge is the Warren-type bridge that used to span Wells Creek. It would be wonderful if there were more Bollman-truss bridges around, but that does not appear to be the case. — Eoghanacht talk 18:19, 26 November 2007 (UTC)[reply]
I still say that the article should refer to an example, even if it may be the only remaining one, as an example, and not be only about the one bridge. The article is supposed to be about a bridge type. If it's about a particular bridge, it should have the bridge infobox and be treated as a specific bridge. - Denimadept (talk) 21:01, 26 November 2007 (UTC)[reply]
To expand on that, this article should explain what a Bollman truss is, not talk about what a particular instance of it is. - Denimadept (talk) 21:02, 26 November 2007 (UTC)[reply]
I would normally agree that a type should have a separate article from an example -- but given that there is only one example, it seems hard to justify two articles (IMHO). An analogy would be if there were a famous ancient Japanese sword that were also the only surviving example of its type, would the sword and the type each have an article? If you think there is a better way to format this article, or to illustrate the type (maybe with a structural diagram?) then go ahead and Be BOLD! Another alternative to two articles is to beef up the Bollman section in the truss bridge article to better explain the structural type.— Eoghanacht talk 14:01, 27 November 2007 (UTC)[reply]
If we knew more about the structural type, I think that'd be best. Then we could revamp the separate article to be just about the specific bridge and point to it from the truss bridge article. - Denimadept (talk) 14:26, 27 November 2007 (UTC)[reply]

"sole surviving"[edit]

Regarding the description of the Savage Mill bridge as being the "sole surviving": there is a Bollman Bridge on the Great Allegheny Passage bicycle trail. See this page: http://www.meyersdalepa.org/railroad/bollman.html or this page: http://en.wikipedia.org/wiki/Wells_Creek_Bollman_Bridge

Perhaps the Savage Mill bridge is the "sole surviving", if there is an additional description such as "sole surviving Bollman Bridge crossing a river" or whatever.

Hank Moore

This article is about a Bollman truss bridge. The bridge you mention is a Warren truss. - Denimadept (talk) 17:16, 27 September 2011 (UTC)[reply]

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