17 February 2017

"Bridges of Dublin" by Annette Black & Michael B Barry

Dublin City Council seem to have done a good job recognising the importance to the City (and tourists) of the city's River Liffey, and not only the river but the many bridges which cross it. They maintain an excellent website devoted to these structures, which includes not just informative material, but plenty of bridge-related stories and a substantial insight into bridge history and engineering generally.

The City Council has also published a series of books on the city's engineering history (in cooperation with Four Courts Press). "Bridges of Dublin: the remarkable story of Dublin's Liffey Bridges" (Dublin City Council / Four Courts Press, 256pp, 2015) [amazon.co.uk] is to some extent the in-print companion to the Bridges of Dublin website, and also owes a debt to Michael Phillips and Albert Hamilton's paper Project history of Dublin's River Liffey Bridges, published in the ICE's Bridge Engineering journal.

The book covers 24 structures in detail, every span across the Liffey from Lucan Bridge to the sea.

Each bridge is documented with a large 2-page photo (generally of excellent quality), often an aerial image, a location map, and a range of other images including drawings, historical paintings and etchings, and old photographs. More recent structures are often accompanied by photographs taken during construction.

The associated text provides not just a history of each bridge, or the stories associated with it, but something of a history of Dublin and wider Ireland. Most of Dublin's bridges were built in the 18th and 19th centuries, the period starting with the Acts of Union of 1801, and including the Irish War of Independence and Civil War of the 1920s.

Emblematic of the role of the various bridges as political symbols, many of the spans have been renamed at key points in history. An example is the Rory O'More Bridge, renamed in 1939 after a 17th century Irish rebel leader. The bridge had previously been renamed the Emancipation Bridge in 1929 (the centenary of Catholic Emancipation), having originally been named the Victoria and Albert Bridge when first opened in 1861. This repeated renaming recurs throughout the book, and makes an interesting contrasts to other cities, such as London, where the need to mark major political change has been absent.

The bridges also encapsulate a history of engineering, as in many major and historic cities. The oldest surviving bridge is Mellows Bridge, a three-span masonry arch structure completed in 1768 to a design by military surveyor Charles Vallancey. However, older bridges crossed the Liffey in both timber and stone, and more recent structures include spans in cast iron, wrought iron, early steel, reinforced concrete, prestressed concrete, and modern steel. The most recent spans include highly contemporary structures such as the James Joyce Bridge, Samuel Beckett Bridge, and Seán O'Casey Bridge.

Much of the interest in Bridges of Dublin is in the ability to see so clearly the many historical, technical and architectural differences between the many structures, as well as their close similarities and relationships.

The text is generally good at providing some structural engineering detail for those with a more technological interest, and at crediting designers and builders. The text is not critical in nature, but is highly informative.

In addition to the sections on each bridge, there is an introduction by City Engineer Michael Phillips, which primarily relates the history of bridge engineering, and a useful chapter which sites the history of the bridges more clearly in context with the history of the city and its river (again accompanied by some very well reproduced historical images). Guides are given to two possible walking tours for the main city bridges, and a series of technical drawings are included covering key bridges, although these are reproduced too small to be of much value.

Overall, this is a very impressive book, not only for students of Dublin's architectural and engineering history, but for anyone with an interest in bridges. There are few books which bring so much well-researched information together with such an excellent range of imagery, and I can definitely recommend it to interested pontists.

06 February 2017

Calatrava in Greenwich

Plans have been announced for Santiago Calatrava's second bridge in the UK (the first being 1995's Trinity Footbridge). Yes, there's a whole load of other stuff as well, some yuppie flats and a super-sized greenhouse, but that's not what you read the Happy Pontist for, is it?

Ok, a little context. Calatrava's "Peninsula Place" is just part of a huge £8.4bn redevelopment of London's Greenwich Peninsula, albeit a key part as it includes the gateway underground station. The development is somewhat controversial, largely because of the very small proportion of "affordable" housing which is to be included, following pressure from the developers.

Calatrava's scheme is as grandiose as you would expect. The bridge is intended to link his part of the site, with station and apartment blocks, to the riverside.

It's a cable-stayed structure, so tall that they couldn't even fit all of it into one of the publicity images. In much of Calatrava's recent career the designer seems to have been largely rehashing all his older ideas, while making his designs steadily bigger and steadily more illogical. In line with this principal, he has chosen to stitch together two previous designs to make this new one: Calgary's Peace Bridge, and Valencia's Serreria Bridge.

Frankenstein would have been proud.

The bridge somewhat resembles a giant white snake shedding its skin, rearing up like some kind of super-sized horror-film monstrosity. It's far from clear what it actually spans (only a cycleway is shown in the visualisations), but it seems unlikely that it needs to be this big for functional reasons: like many of Calatrava's recent bridges, its giganticism seems purely symbolic.

The mast is restrained by a single vertical cable, necessitating enormous foundations to counter-balance the main span. (Perhaps it's also symbolic: look, the success of this enterprise is hanging by a thread.)

The curvature of the mast is to some extent structurally rational, as it reduced bending moments and hence should in theory slightly reduce the amount of steelwork required.

The main span is a tubular truss, with metalwork arranged in an intersecting helix, which evokes a futuristic sensibility without actually being structurally sensible in any way: there's a Jane Austen joke in there somewhere, I'm sure.

From the images, it seems as if the mast is on the riverside, which feels the wrong way round to me: the more visually and physically massive part of the bridge should be anchored further inland, I think.

Assuming this entire project doesn't go belly-up following an Brexit or Trump-related economic meltdown, I'm confident this will be a very interesting scheme to watch over the next few years.

04 February 2017

Deux livres sur les passerelles à Paris

I'll conclude my series of posts on the bridges of Paris with mentions for a couple more relevant books.

"Passerelle Simone-de-Beauvour, Paris" (Archives d'Achitecture Moderne, 128pp, 2006) is written by Armelle Lavalou, Francoise Lamarre and Jean-Paul Robert, and credited to the bridge's architect, Feichtinger Architectes.

It's a well-illustrated volume with text in both English and French throughout. It's filled with images of the completed bridge as well as its construction, but sadly the book is not large, measuring only 24cm by 16cm, which leaves some of the imagery and diagrams a little small.

The bridge is explained both in terms of its architecture and its engineering, although the explanation of the engineering is aimed squarely at non-technical readers: I was left with plenty of questions. A number of somewhat diagrammatic drawings are included, which are very interesting but without dimensions and again missing some of the details that would better explain how the bridge works.

There are some lovely pictures of competition-stage physical models and design-stage wind-tunnel test, which I'd like to have seen reproduced at much larger size. For me, the best section covers the construction of the bridge, including its static and dynamic load testing.

The book acknowledges the participation of RFR, the structural engineers, without giving them detailed credit, very much giving the impression that they were the subsidiary partner. I don't know whether this is a fair reflection or not.

Overall, it's an essential book for anyone wanting to learn more about this spectacular bridge, but it could have been much better.

"Passerelle Solferino Paris / Solferino Bridge Paris" (Birkhauser, 128pp, 2001) by Francoise Fromonot has the same page count but a larger format (30cm by 23cm). It is also well-illustrated, with shared French and English text. I didn't visit this bridge during my recent trip to Paris, but I thought it was worth featuring the book here anyway.

The core of the book has less text, giving more space to images of the design competition, the bridge under construction, and the completed span. The larger format works well for these.

The key attraction, for me at least, is the inclusion of a lengthy section covering the engineering design and construction issues, which gives extensive and numerical detail on key points such as foundation loads, vibration modes, steel grades etc. While I'm sure this is of limited interest to some readers, it opens up the opportunity for specialists to much better understand the merits of the design.

The book also features a number of detailed design drawings, which are fascinating because of the bridge's extensive geometric complexity. Indeed, perhaps the only thing missing here is a more critical voice, as this is a bridge which was criticised from several quarters, both for the complexity of its fabrication as well as its dynamic behaviour and initial lack of slip resistance.

Nonetheless, it's a thorough and well-presented book, and I can recommend it to anyone interested in this bridge.