Talk:Arch bridge

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That old photo sucks. I used the lack of copyright info as justification for removing it, but that fact that #1 it is still an unknown location, #2 the photo is underexposed, #3 it dosent even show the whole main span, much less the entire bridge (read abutments). #4 a rock takes up 1/3 of the photo. Cacophony 18:55, Apr 16, 2005 (UTC)

i'd vote for the old photo to stay for now. Because 2 photos is better than 1, and a photo of older bridge is nice complement to a modern tech version. Xah Lee 21:04, 2005 Apr 17 (UTC)

This is not a good photo for this article as the bridge is a compression arch suspended-deck bridge, a sophisticated variation of the basic arch bridge. Better would be Image:NagasakiMeganebashi.jpg - Leonard G. 04:14, 18 Apr 2005 (UTC)

[edit] Future changes

I'm planning to add the following to this article:

• brief history or timeline, including reference to the extensive history of arch bridges in China, plus key engineers like Perronet
• comments on arch shapes, i.e. semicircular, elliptical, basket-handle, gothic pointed etc.
• more on arch terminology e.g. voussoirs, starlings, intrados and the like
• some notable arch bridges e.g. the largest spans

Any other ideas for what is missing? -- Kvetner 19:48, 26 January 2007 (UTC)

Me. I would be most grateful for including material on the medieval superbridge at Trezzo sull'Adda. Why? Because this bridge must have been amazing as it doubled the longest span of stone bridges then (from 37 to 72). Still, the briidge is almost unknown, as nobody covers the subject.

There is also a claim that the Etruscans build very early on stone arch bridges (earlier than both Greeks and Romans). Two of them are included in Structurae, but I am not sure whether these are still the original structures. Including the Etruscans in a comprehensive history of stone arch bridges would definitely be an almost revolutionary thing.

For the timeline, see also

• Trajan's Bridge - longest span for a 1000 years
• Ponte Santa Trinità - first elliptical arch bridge
• Steinerne Brücke in Regensburg, Germany - model for many medieval bridges to come
• Pont Saint-Bénezet - IMHO this bridge could be the first segmental arch bridge in Europe. What we need is the span-rise-ratio. Regards Gun Powder Ma 15:22, 28 March 2007 (UTC)

I will review all the above against my various reference books when I get a moment. Please note that Trajan's bridge was not the longest span, it just claims to be the longest bridge (total length). -- Kvetner 16:36, 28 March 2007 (UTC)

Fine. But which ancient or medieval bridge had a span of more than 57 meters? Gun Powder Ma 22:04, 28 March 2007 (UTC)

I can't find a reference to substantiate that quoted span of 57 metres, and I note that the main Wikipedia article on Trajan's Bridge only says 52 metres. In Troyano's "Bridge Engineering: A Global Perspective", it refers to spans up to 38 metres, with masonry piers up to 15 metres thick - you'll note that adds up to 53 metres, and I therefore wonder whether Structurae is incorrect. Whitney doesn't mention the bridge at all. There were certainly Roman stone arch bridges up to 32-35 metre span, and it's debated whether they got up to 38 metres (at the Ponte Vella de Ourense, for example). So the best that could be said would be that Trajan's Bridge is probably the longest span for a millennium - unless you can find a better reference.

Yes, the Trezzo bridge was a major advance, and again it is discussed in Troyano - possibly little covered elsewhere as it was destroyed in the 15th century.

On segmental arches, I am fairly sure there are Roman examples. Troyano cites Alconetar bridge over the Tagus, which was Roman and had a fairly low span/rise ratio. Whitney mentions the Pons Fabricus as not being semi-circular, but segmental. There were also a number of low span/rise ratio bridges built in the 14th century, of which the Pont d'Avignon (a.k.a. Saint-Benezet) was only one - Vecchio and Scaliger are from the same century and I don't know which came first - there's nothing in the Wikipedia article on Pont Saint-Bénezet to make this clear (according to Troyano, it was originally built as a timber bridge in the 12th century, with the stone arch bridge being a 14th century rebuild - this contradicts Whitney who reports the stone bridge as dating from the 12th century - any other sources on this one?). -- Kvetner 23:26, 28 March 2007 (UTC)

I think structurae has arrived at their "57 m" by dividing the total length by the number of pillars (1135/20 = 56,7). However, they did not calculate the width of the pillars, as a bridge span is in my understanding defined as the free space between two pillars, so you are correct that they number is strange. Anyway, the bridge's wooden arches are clearly segmental, so assuming a record span is not unrealistic: www.hdg.de/eurovisionen/html/br2_1.html

As for Alconetar, go to Google Images. You can see that the three surviving arches are segmental arches, but

• these look a bit like much later amendments
• these segmental arches had very conventional span/rise ratio, so the advantages of the seg. arch bridge were not fully exploited

The arches of the Pons Fabricius look rather semi-circular to me.

Could you uncover your references? As for Roman bridges there is the classical: Colin O'Connor, Roman Bridges, Cambridge Univ. Press (1994) ISBN 0-521-39326-4 Gun Powder Ma 10:23, 29 March 2007 (UTC)

I'm sure you're right about where Structurae derived the span from, and yes, for a masonry arch the span is the clear distance between springings.

Troyano's book states that two arches at the Alconetar site are original (spans 6m and 7m), although a photo caption confirms that some are later reconstructions on top of the original Roman piers. Troyano doesn't state a span/rise ratio but from his photos it is clearly much higher than the 2:1 of a semi-circular arch.

Charles Whitney's book discusses the Pons Fabricius (page 61 of my copy) and states that it is not semi-circular - his photo and others on the net certainly appear to show that the arch intrados does not become vertical at the visible springings but is still sloping, although Whitney acknowledges that there may be real springings lower down, hidden by the stonework at the base of piers, in which case the arches would indeed be semi-circular.

Now all we need to do is get some of this information onto the relevant pages! -- Kvetner 20:40, 29 March 2007 (UTC)

I've been working for some time on category:Roman bridges, but you certainly provide new infos here. This is what a webpage says about the Alconetar bridge: destroyed in the 13th century, 3 arches left, moved in 1972 - I hope they did not change the arch structure then. Here the most authoritative photo: http://users.servicios.retecal.es/jomicoe/Alconetar.JPG

El puente de Alconétar, sobre el Tajo en Garrovillas (Cáceres) cerca de Alcántara, estaba en la Vía de la Plata. Debió de ser también monumental. Fue destruido por los árabes en el siglo XIII y nunca después reconstruido. Hoy día es un puente sin río. Al construir el pantano de Alcántara hubiera quedado sepultado por las aguas. En el año 1972 se trasladaron sus restos a un nuevo emplazamiento. Apenas quedan tres arcos de los 13 que tuvo. Se aprecia su solidez en sus fuertes machones.

As for the Pons Fabricius, there are some Roman bridges (and even more medieval ones) whose arches are designed somewhere between semi-circular and segmental. This is only natural as a demanding structure the segmental arch bridge could not have been invented in a day, but must have been reasonably the result of a lengthy development process. This means there are certainly transitory forms between the two types, what we need in every single case is the span/rise ratio of the bridge to make qualified judgements on its segmental or semi-circle character. Gun Powder Ma 23:18, 29 March 2007 (UTC)

That photo at retecal.es is similar to the ones in Troyano's book - his text and captions imply that the arch on the left is an original Roman arch and the other two are more recent, but he doesn't state his source for this. On the Pons Fabricius, my understanding is that any circular arc shorter than the boundary of a semi-circle is a segment, and hence Pons Fabricius is segmental - it lacks the higher span/rise ratio of the bridges more normally called segmental, but as you say, it's transitional. Ironically though, I believe it's one of the earlier Roman bridges? There is a drawing of this bridge by Piranesi (not the one on the Pons Fabricius page), reproduced by Whitney, and available online at [1], which suggests the arch is just the top portion of an enormous circular structure, but this is incredibly unlikely and probably just an overactive imagination on Piranesi's part. PS: I've reset the indentation to avoid this discussion getting too hard to follow! -- Kvetner 12:34, 30 March 2007 (UTC)

Wait. You first said that "Troyano's book states that two arches at the Alconetar site are original (spans 6m and 7m)", but now you write that "his text and captions imply that the arch on the left is an original Roman arch and the other two are more recent". In that case, the bridge would not be a Roman segmental arch bridge at all, wouldn't it?

Did Troyano somewhere write that the wooden low span/rise ratio bridges of the Romans also constitute segmental arches (despite their superstructure being out of wood, not stone)? Gun Powder Ma 15:18, 30 March 2007 (UTC)

That's correct; if I read Troyano correctly then the implication is that there is at least one more arch not shown in the photograph you mentioned. But it could just be that he got it wrong, of course. I don't recall if he discusses timber arches (I'm at work right now, the book is at home); it may be a while before I can comment further as I'm travelling quite a bit over the next week. -- Kvetner 15:53, 30 March 2007 (UTC)

Back home, and my reading of Troyano is correct, he reports two surviving arches. He gives the following references: Victor W Von Hagen "Los caminos que conducian a Roma", Barcelona, 1973; and Carlos Fernandez Casado "Tres monumentos salvados de las aguas por la sociedad Hidroelectrica Espanola", Boletin de la Real Academia de Bellas Artes de San Fernando, 1979. Apparently, the Alconetar's designer was Apollodorus of Damascus, also credited with Trajan's Bridge at Orsovo, which we have already discussed! -- Kvetner 19:07, 30 March 2007 (UTC)

Which arches are Roman? The two segmental arches or the semi-circles one(s)? Gun Powder Ma 22:20, 30 March 2007 (UTC)