What have the Romans ever done for us?

Posted on 15/06/2012 by dougaj4

Maybe the Romans can  fairly claim the credit for spreading the aqueduct from Portugal to the Middle East, but the voussoir arch, typical of Roman aqueduct construction, did not originate with them.

The first known voussoir arches were constructed by the Etruscans who occupied the regions north of Rome (including Tuscany, western Umbria and northern Latium) from before 700 BC to 264 BC, when they were absorbed in the Roman Empire.

There are at least two surviving Etruscan arches in Perugia, the most well known being the Augustus or Etruscan Arch, dating from the 3rd century BC.

Arch of Augustas, Perugia

Arch of Augustus, Etruscan Arch

The other is the Porta Marzia, also dating from the 3rd Century BC.

Porta Marzia

Porta Marzia

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Return of Excel – Evaluating commas

Posted on 14/06/2012 by dougaj4

The Newton/Galileo posts here will continue with their Italian theme for some time yet, but since I am now back in Australia it’s time to give Excel a look in again.

I recently (well a couple of months ago) had a query about using the Eval User Defined Function (UDF) when the decimal separator was set to a comma, rather than a decimal point.  In response to that I added an option to the code for Eval and Evala that would replace all occurrences of “,” with “.” and “;” with “,”.  This allows the Excel Evaluate command to operate correctly, regardless of how the values are entered.

The revised spreadsheets using these functions may be downloaded from:

Note that the modification has as yet only been made in the Eval and EvalA functions, and not the integration functions.

After modifying the code I discovered that there is an Excel option that allows the original functions to work, without substituting commas for decimal points.  In Excel 2010, under File-Options-Advanced, deselect “Use System Separators” and enter a “,” for Decimal Separator, and a space for Thousands Separator.

System separators options

The spreadsheet will now display decimal numbers with a comma separator, and will only accept a comma as the separator for new numbers, but the Eval functions will work correctly.

However – this (strangely) only seems to work if the region language is set to English.  If the region is set to French (or presumably any other region that uses the comma separator) the original Eval functions no longer work.  I have only given this limited testing (since I normally use the decimal point), so if anyone else has any comment on how the regional separator options work in Excel, please leave a comment below.

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Seven Florence Bridges

Posted on 08/06/2012 by dougaj4

There are seven bridges over the River Arno in the central area of Florence, of which only one (The Ponte Vecchio) is an original old structure, the remainder of the old bridges having been destroyed by the retreating German army at the end of World War 2.  Of the new bridges, 2 are replicas of the original structure and 4 are of new design, but all are of interest.

5 bridges over the Arno, looking downstream with the Ponte Vecchio in the foreground.

The first and last of the seven structures are reinforced concrete arch bridges:

The Ponte di San Niccolo is an elegant single span designed by Riccardo Morandi and constructed between 1947 and 1949.  It replaced a steel suspension bridge built between 1836 and 1837.

Ponte di San Niccolo

The structure has wide vertical cracks in the spandrel walls at both abutments, possibly due to thermal movements:

Crack as northern abutment

The Ponte Alla Vittoria is a 3 span bridge with flat concrete arches. The original bridge on this site was also a steel suspension bridge.  The new bridge has an unusual strongly shaped  deck, merging smoothly into the concrete piers:

Ponte Alla Vittoria

Ponte Alla Vittoria

The next bridge from the East is the Ponte alle Grazie, completed in 1953, replacing a 9 span arch bridge originally built in 1227 and rebuilt in 1345.  The new structure is a 5 span reinforced concrete arch structure, but its form is clearly based on that of the adjacent Ponte Vecchio, especially in the relationship of the deck and piers:

Ponte alle Grazie

The design of this bridge was subject to a competition, with some controversy about the use of reinforced concrete rather than traditional materials, described (in Italian) at: Ponte alla Grazie.

Ponte alle Grazie

The remaining reinforced concrete bridge is the Ponte Amerigo Vespucci, which is described in the Wikipedia article as an arch, but is in fact a three span prestressed concrete structure:

Ponte Amerigo Vespucci

The bridge construction was completed in 1957, replacing a temporary structure completed in 1949. Further details of the bridge design and construction are given (in Italian) at: Ponte Amerigo Vespucci

The two new bridges downstream of the Ponte Vecchio are both replicas of the original structures at their sites.  The Ponte Santa Trinita is described in the Wikipedia article as the oldest elliptic arch bridge in the world, the previous bridge having been constructed in 1567 to 1569, replacing bridges built in 1252, 1333, both of which were destroyed by floods.

Ponte Santa Trinita

The Ponte alla Carraia is a 5 span segmental arch bridge completed in 1948.

Ponte alla Carraia

Finally the sole remaining old bridge structure is the famous Ponte Vecchio.

Ponte Vecchio

Known more for the gold shops that still line the bridge than for any structural innovation, it is nonetheless an early example of a flat segmental arch construction, having been completed in 1345 with a maximum span of 30 m and rise of 4.4 m.

Ponte Vecchio

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A tour of Venice backstreets

Posted on 02/06/2012 by dougaj4

The great majority of the tourists in Venice are concentrated within a stone’s throw of The Grand Canal and St Mark’s Square, but the real charm of the place is in the back streets and canals, where (apart from the occasional gondola jam) the tourists are relatively rare.

Here is a tour featuring (mainly) a  random selection of the many unsung bridges of Venice.

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Bridges over the Grand Canal

Posted on 30/05/2012 by dougaj4

This post was planned to be a description of the four bridges over the Grand Canal in Venice, but I discovered that The Happy Pontist has already done this, so I will just provide links to his site, some photos, and comments on points of interest.

Venice Bridges: 1. Ponte dell’Accademia

Ponte dell’Accadamia

The Ponte dell’Accadamia was originally a steel girder bridge, completed in 1854, replaced with a single span timber arch in 1948.  This was further upgraded between 1963 and 1965 and in 1986.  The final work is often described as further strengthening of the timber structure, but as can be clearly seen in the pictures below the structure is now a steel girder arch with timber trim, rather than a timber arch with steel strengthening:

Ponte dell’Accadamia steel girder acrches

Ponte dell’Accademia timber trim

Ponte dell’Accademia

Venice Bridges: 2. Ponte de Rialto

The Ponte de Rialto is the oldest bridge over the Grand Canal, a pontoon bridge having been completed at this location in 1181, and several other bridges built and collapsed until the construction of the present bridge in 1588; this structure being one of the most recognisable bridges in the World.

Ponte del Rialto

It is recorded that there was considerable controversy about the choice of a single span arch for this location, some claiming that it would be likely to collapse.  This seems surprising given that larger and flatter arch spans had been completed elsewhere at the time of construction, but as we shall see in a later post, this was not the last time that the stability of flat stone arch bridges would be questioned.

Ponte de Rialto

Ponte de Rialto

Venice Bridges: 3. Ponte degli Scalzi

Quoting from the Happy Pontist:

“Today, the bridge may appear at first sight the least distinguished of the four bridges over the Grand Canal. There are, after all, roughly 300 arch bridges in Venice, most of them in stone. However, its attraction is in its simple elegance, especially its slenderness at midspan. It’s both beautiful and durable, an illustration that older technologies are often still of great value.”

and my photos (taken on a cold and showery late spring day) don’t do it justice.  Nonetheless, here they are:

Ponte degli Scalzi

Ponte degli Scalzi, from the station forecourt

Venice Bridges: 4. Ponte della Costituzione

This, the newest of the Grand Canal Bridges (opened in 2008), escaped my attention, which is a shame since, like all bridges by Santiago Calatrava, it is a bold and eye-catching design.  Follow the link above for a detailed description at the Happy Pontist blog.

Also see these links from the City of Venice site:

City of Venice project website

The works for assembling the fourth bridge on the Grand Canal

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