31 October 2017

Canadian Bridges: 3. Granville Bridge, Vancouver

Granville Bridge is the next bridge east along False Creek in Vancouver after the Burrard Street Bridge.

Completed in 1954, the 1.1 km long bridge carries eight lanes of highway traffic and two footways between Downtown Vancouver and Granville Island (and beyond).

It is the third bridge on this site, with a timber trestle bridge erected in 1889, replaced by a steel truss bridge in 1909. Both structures incorporated swing spans.

The current bridge was designed by engineer John Robert Grant to sit at a significantly higher level than its predecessors, eliminating the opening span and thus accommodating much higher traffic levels. Pressure for change had no doubt been partially addressed when the Burrard Street Bridge was completed in 1932 (also designed by Grant).

Granville Street Bridge lacks the architectural attention that was devoted to its Burrard street neighbour. The main span is a conventional steel cantilever truss, notable only for the main span truss being significantly less deep than the approach span trusses, which didn't have to respect the same shipping clearance. This looks more than a little odd, but it's understandable given the need to reduce the overall length of the structure. The side spans are seen less clearly, with a background of buildings, so I imagine the odd relationship simply isn't apparent to any casual observer.

Although the design is pretty much entirely engineering-led, it's not unattractive or inappropriate to its setting. It is rational, orderly and from most viewpoints, uncomplicated.

Proposals have recently been made to add an elevator where the bridge passes above Granville Island.

Further information:

30 October 2017

Canadian Bridges: 2. Burrard Street Bridge, Vancouver

The next two bridges that I'll feature from Vancouver both span False Creek, a significant water inlet which separates Downtown Vancouver from parts of the city to the south and south west.

I saw both bridges on an evening dinner cruise, so my photos are quite limited.

Burrard Street Bridge (a.k.a. Burrard Bridge) is the oldest surviving bridge across False Creek, completed in 1932 to a design by architect George Lister Thornton Sharp and engineer John Robert Grant. Grant was a structural engineer with experience in both the USA and Canada, who had first proposed a bridge at this site in 1910, and who later went on to design the nearby Granville Street Bridge. Sculptor Charles Marega also worked on the bridge, and would later design the lion sculptures that gave Lion's Gate Bridge its name.

The bridge supports a five-lane highway, a cycleway and a pedestrian walkway. The centre truss span is 90m long. The most prominent feature is the towers, designed in an art deco style in exposed concrete.

These have an architectural significance well beyond their simple role in holding up the main span. They act as giant bookends, distracting the eye from the very different span forms on either side: a curved truss above deck in the centre, and deep, flat trusses below deck on the approaches. See also Sydney Harbour Bridge, completed in the same year, for a similar solution.

It isn't clear from the river view, but the towers also form wide portals, with windowed internal galleries. As well as acting as gateways, the architect specifically intended these to block views of the overhead truss bracing, clearly considering it unsightly.

An extensive programme of repairs, strengthening, modifications to the non-vehicle lanes, and installation of anti-suicide fencing has just been completed in October 2017. From my photographs, you barely see the fencing, so it hasn't marred the bridge's appearance too much.

It's a nice bridge. The art deco style has generally worn well, with a degree of regularity and restraint that doesn't look too ridiculous even in the modern day.

Further information:

29 October 2017

Canadian Bridges: 1. Lion's Gate Bridge, Vancouver

September was a busy month for the Pontist. As well as a trip to the Footbridge 2017 conference in Berlin, I attended the IABSE Symposium in Vancouver. As you might expect, I found time to visit a few bridges while there.

The single most unmissable bridge in Vancouver is the Lion's Gate Bridge, which spans 472m across the First Narrows, connecting North Vancouver and West Vancouver to the main city centre. It was built in 1938 to a design by Philip Louis Pratley, who also designed the very similar Angus L. MacDonald Bridge in Halifax, Nova Scotia.

Lion's Gate Bridge was completed two years ahead of the ill-fated Tacoma Narrows Bridge, escaping that bridge's unfortunate fate by virtue of very different deck construction, with open trusses supporting the deck rather than plate girders.

Relative to its span, the bridge is notable for its height above water. The steel towers are cross-braced above and below deck level, with a Vierendeel portal directly above the highway and an arched crown element which is as much decorative as structural. The vertical taper to the towers, the open appearance, and the slenderness of the bracing are all quite attractive in appearance, although the ornamental portal and crown are very much "of their time".

The anchorages are well hidden for a bridge of such height, allowing the northern approach viaduct to share the main towers' open appearance.

The bridge was extensively altered in 2000-2001 to accommodate modern traffic loads, with the complete replacement of the three-lane deck, and moving the pedestrian and cycle walkways to the outside of the cable hangers.

Options were considered for complete replacement of the structure, but deck renewal was the preferred option. The concrete deck was replaced with a steel orthotropic deck, while the original edge trusses (above deck level) were replaced with new trusses below deck level.

Triangular bracing can be seen connecting the main cables to the deck near the anchorages and at midspan. This looks like it was added in the refurbishment rather than being original, and by restraining the longitudinal sway of the cables relative to the deck, it significantly enhances overall stiffness of the structure.

Many North American suspension bridges have a liking for a kind of "ornamental" style that I think has not aged very well. Lion's Gate definitely has some of this quality to its towers, but I think generally its clean lines are attractive, and the designers did well to keep such a tall bridge so elegant.

Further information:

25 October 2017

London Bridges: 51. Blackfriars Railway Bridge

I've got a backlog of bridges visited over the last couple of months to write up and cover here, and I'll start with a bridge in London.

Railways first came to London in 1836, but it was 1860 before a railway bridge was built across the River Thames, Grosvenor Bridge. Others rapidly followed, Battersea Bridge (1863), Hungerford Bridge (1864), Blackfriars Bridge (1864) and Cannon Street Bridge (1866). Each bridge sought to bring travellers from south of the river closer to the key destinations of the north bank.

The bridge at Blackfriars was no exception, carrying the London, Chatham and Dover Railway (LCDR) across the river to Ludgate Hill station, and within a year or two of completion, further north along what is now the route of the Thameslink railway. The bridge was a five-span wrought iron lattice truss viaduct, supported on tall cast iron piers, and designed by the LCDR's chief engineer, Joseph Cubitt. This original bridge was dismantled in 1985, leaving only its piers and part of the south abutment behind. The remnant of the abutment still displays the lavish crest of the LCDR.

In 1886, a second bridge was completed immediately to the east, named St Paul's Railway Bridge and connecting to the new St Paul's Railway Station on the north bank. This was a wrought iron arch viaduct, designed by Henry Marc Brunel and John Wolfe-Barry, the latter best known for the Tower Bridge, which commenced construction in the same year St Paul's Bridge was completed.

This bridge continues to carry the railway today, although it has been through considerable change. Originally, there was a railway station at the south end, although this was used by passengers for only two decades before a new station was built at the north side. This station remains in use, and was extended between 2009 and 2012 with longer platforms. A photovoltaic roof was added, making it reportedly the largest photovoltaic installation on a bridge in the world.

To accommodate the extended station, the bridge was widened, strengthened, and largely reconstructed, to a design by Tony Gee and Partners. The arch members remain those from the 1886 structure, but the original deck and spandrel columns were removed and replaced with steel elements, acting as Vierendeel trusses rather than as simple arches.

The bridge was widened to the east with one steel arch supported on the original masonry piers. These had their end elevations rebuilt.

On the west side, one of the three rows of cast iron columns from 1864 was taken down, and the 1886 bridge piers were extended laterally, supported on the original 1864 foundations. The widened piers support three new lines of steel arch ribs.

The work has been artfully done, and although the difference between steel and wrought iron arches is immediately apparent to a professional, I doubt that any casual visitors see this as anything other than a historic railway bridge. The shaping and disposition of the new arches sits happily with the old, even replicating the end hinges on each span.

The treatment of the western extension at foundation level is less visually successful, but clearly far less expensive than building new foundations would have been. The extension stonework doesn't match the detail on the east face, and the horseshoe collar which sits on the old foundation (precast concrete, masonry clad) feels a little awkward to me.

The detailing of the new spandrels is very well done, it matches the historic appearance very well. Overall, the reconstruction is a very impressive piece of engineering, and I think all involved must be very proud of what was achieved. The attention to detail both for permanent and temporary works must have been considerable.

Further information:

24 October 2017

"Berliner Brücken" by Thiemann and Desczyk

While putting together my recent run of posts on the bridges of Berlin, I was looking to see if there was any book I could use to supplement internet research.

There doesn't seem to be a good book in English, but there are several in German. I settled on "Berliner Brücken: Gestaltung and Schmuck" by Eckhard Thiemann and Dieter Desczyk (236pp, Lukas Verlag, 2012) [amazon.co.uk]. The title translates roughly as "Berlin Bridges: Form and Ornamentation".

The book starts with a history of bridge design and construction in Berlin, which is very well illustrated with historical drawings, paintings and photographs. Historically, as with most cities, the major challenge for bridges in Berlin was to span waterways, and a number of beautiful, intriguing and often unusual structures are depicted and discussed.

In more recent history, bridge-building has shifted to the spanning of railways and roads, and the book reflects this, although it does not feature bridges which actually carry rail.

The bulk of the book is a structure-by-structure encyclopaedia of the more significant of Berlin's bridges, featuring around 140 different bridges, each with at least one page to itself, with more significant bridges (or groups of bridges) getting two pages.

Where more than one bridge has stood on a particular site, both old and new structures are covered, and also a number of sites where a bridge once stood but no longer does so. Again, this part of the bridge is very well illustrated, the text is informative, and dates and designers are always given appropriate credit.

The book is generally good at picking out details of bridges: sculpture, decoration and the like, and has an entire section devoted just to this, with several pages of images. It also has seven pages of detailed maps to locate the bridges, a detailed timeline, glossary, bibliography and index.

It really is an excellent model for how such a book should be done.

23 October 2017

German Bridges: 9. Oberbaum Bridge, Berlin

This is the last of the bridges I visited in Berlin in September, and it's going to be short and only a little sweet, as I only visited at night, and very briefly. It's Berlin's most notable bridge, so clearly I'll have to cover it more thoroughly next time I get a chance to visit.

I'll let you read about the bridge at the links below, I'll only comment briefly on the photos.

The bridge carries light rail on its upper level and a highway and footways on the lower deck. The upper central span was rebuilt in 1996 to a design by Santiago Calatrava, and I think it's one of Calatrava's best designs: constrained by working so closely with such a historic bridge, he was obliged to deliver something more modest than usual, and it's a beautifully elegant span which sits well amidst the much more lavish architecture of the historic bridge.

The arch itself seems impossibly thin, although this is a trick of the design, which uses triangular cross-sections for the arch ribs and main deck to emphasise slenderness. There are struts at each end of the bridge supporting the upper level (presumably reducing loads on the historic viaducts), but you generally don't notice them.

Seen up close, the new span is a very modern, almost industrial structure, but seen from further away it appears fragile. As with several other bridges over the River Spree, it was built as a result of German reunification, and may be politically symbolic.

Further information:

22 October 2017

"The Mathematical Bridge" from Ponticulus Design

Ponticulus Design have launched a crowdfunded venture via Indiegogo to manufacture and supply models of Cambridge's famous Mathematical Bridge.

The models are designed to appeal to anyone with an interest in bridges, history, architecture and/or model-making, and to parents or teachers of children interested in science or engineering. The recommended age requirement is 14+ (mainly because there are 81 injection-moulded plastic pieces to be carefully assembled, and a craft knife and superglue are required).

I was lucky enough to get hold of one to try out. It's been many long years since I've assembled a model anything like this, but I was keen to give it a go!

It comes in a neat package with a set of instructions which I found easy enough to follow but which I think a child may need some assistance with. The Ponticulus website suggests up to 8 hours to assemble the model, but I took only about half that.

The finished model is attractive and seems fairly meticulous in how well it matches the real bridge.

The rea; Mathematical Bridge was designed by William Etheridge, adopting a radial and tangential timber network which had been used in the larger Walton Bridge, as well as in timber centering for stone arch bridges. It's not a straightforward bridge to understand, but it can perhaps be conceptualised as a set of overlapping king-post trusses arranged radially.

Ponticulus Design are offering a range of crowdfunding options, including generous discounts for early funders. Visit their Indiegogo site for full details.