10 April 2019

London Bridges series: 53. Holborn Viaduct

I suspect that for many people, Holborn Viaduct in London is known mainly as a street name rather than as a bridge: the street extends for around 425 metres (1400 feet) between Holborn and Newgate Street, but only a relatively short length of bridge is visible where the street passes above Farringdon Street. Elsewhere, most the street is hemmed in by buildings either side.

What can be seen today bears little resemblance to how this site looked in the past. What is now Farringdon Street was once the River Fleet, running north to south through a valley before spilling into the River Thames. The Fleet can be seen on the mid-16th century "copperplate map" of London, which also shows the old Holborn Bridge which then spanned the river.

Fleet Ditch was used as an open sewer, and was eventually covered over, section by section, and converted into a buried sewer. Today it remains there, running below the roadway down to the Thames.

Between 1863 and 1869, the entire valley was improved in a scheme designed by city surveyor William Haywood. The southern end of the scheme included the reconstruction of Blackfriars Bridge, while at Holborn, the old bridge was removed and replaced with what is now Holborn Viaduct. Haywood worked with engineer Rowland Mason Ordish on the viaduct's design.

Source: Grace's Guide

A contemporary drawing (above) shows the full extent of the Holborn Viaduct construction. Most of its length consists of brick arch spans, enclosed on their ends to form chambers, and in addition to the Farringdon Street structure, there are special spans over other roadways and railways. A drawing made in 1941 reveals the structure, exposed by bomb damage to adjacent buildings (below).

Source: drawing by Louisa Puller, via Wikipedia

Work on the new bridge started in 1867 and was completed in two years. The spans over Farringdon Street use paired cast-iron arched members supported on granite piers. The decking was originally constructed from cast-iron troughing topped in mass concrete.

On all four corners of the bridge, a large building was constructed to house a staircase connecting the upper and lower roadways. The one shown in my photograph is a post-war reconstruction, as the two north buildings were damaged by bombs during the Second World War.

The visible bridge is spectacular and ornate, and does make me wonder quite how its construction was funded. It is adorned with ornamental lighting, four statues (representing commerce, agriculture, science and fine art), and the ironwork on the main elevations is finely detailed and highly decorative.

From below, entrances into the masonry vaults can be seen, and perhaps income from letting these spaces and the staircase buildings helped contribute towards the cost of construction.

It can also be seen that the bridge has been extensively altered. By the end of the 1980s, the deck was found to be in poor condition due to water penetration, and calculations suggested the bridge to be seriously under-strength for modern heavy goods vehicle loads. DHV Burrow-Crocker Consulting (since merged into the Waterman group) were appointed to examine, assess and design improvements to the bridge.

The altered arrangement is visible in the photographs and explained in a diagram below taken from a 1993 technical paper. The existing decking was completely removed, and new steel-concrete composite decks inserted in between the cast-iron arch girders. The existing piers were extended upwards in reinforced concrete to encase the ends of the cast iron members, and the new bridge deck was supported via bearings onto the concrete extensions.

It's an exemplary piece of engineering, leaving the historic structure seeming largely unaltered from most point of views, and retaining most of the original fabric. The extensions to the piers are especially well-detailed, and I would not have noted them if I hadn't read the paper.

Further information:

07 April 2019

Bridge competition debris part 29: Network Rail Footbridge Design Ideas Competition

I posted last July when Network Rail announced this contest, but what with one thing and another, I've neglected to write about the result.

Quick recap: Network Rail were looking for ideas which were "innovative, challenge presumptions and raise expectations for the quality of future designs". The contest ran alongside a more conventional commission for a consultant team to refresh the organisation's station footbridge designs, which led to the appointment in October of Arup and Knight Architects.

The ideas competition was open to pretty much any entrant, offering a £20,000 prize fund but no commitment to use the winning idea or to commission any further work.

The winner was announced in December as Gottlieb Paludan Architects, Denmark, with Strasky, Husty and Partners Ltd, Czech Republic (above). The judges also highly commended a design from Hawkins\Brown with WSP (below).

There were a further 18 entries on the judges' longlist. In total, 121 entries were submitted, so clearly something about this contest struck a chord amongst the creative professions. Given the very low probability of actually getting any significant reward, it's interesting how many well-known names took part, but perhaps also unsurprising that many entries look like they were dashed off in a spare lunch-break.

One thing that strikes me about the entries is the proportion which adopt a modern or futuristic approach. I believe the competition identified the need for station footbridges which would link railway platforms in both a new-build context, and also upgrades to existing stations, some of them heritage settings. Network Rail included examples of historic lattice-truss bridges in the material they supplied to entrants, but very few designers submitted ideas which appear adaptable to different settings. There were quite a few entries with a latticework theme, but hardly any which looked adaptable to many situations.

Another thing that jumps out is that this competition probably created a significant learning opportunity - assuming (from the quality of the design images) that many of the entries will have been prepared by younger professionals, it must have been a marvellous opportunity to test out their design and illustration skills.

Many of the entries are impractical, even amongst those where an engineer is named as well as an architect. However, I think it's clear that a good proportion of entrants did understand that this was a contest about ideas - the more pragmatic looking entries generally didn't make the longlist.

I can strongly recommend spending a few minutes checking out the competition website. I'm only going to include the winning, highly commended and long-listed designs here, but although there's a fair bit of dross, there are also quite a number of thought-provoking concepts, and one or two interesting styles of illustration.

Winner: Gottlieb Paludan Architects / Strasky, Husty and Partners Ltd
The winning design is beautifully presented and highly minimalist in its conception: a staple-shaped deck below a staple-shaped roof, modular and suitable for a variety of spatial arrangements.

Highly Commended: Hawkins\Brown / WSP
Like the winner, this is a modular, adaptable design, but with the structure and architecture secondary to the potential for a bridge as a social and commercial space. It's a smart, enticing idea, perhaps well-suited to some urban locations but over-ambitious for most other sites.

Long list (selected images only: see competition website for more)

Luca Poian Forms, UK with Soluxn Ltd

Weston Williamson + Partners, UK with AKT II Ltd

Atkins Architecture, UK

 PHASE3 Architecture + Design, UK with AKT II Ltd

Miguel Costa, Andy Fisher, Melanie Davison, Priscille Rodriguez & Jan Verhagen

CF.Architects, UK with Cake Industries

Softroom, UK with Eckersley O'Callaghan and Inverse Lighting

[Y/N] Studio, UK

 Xing Design Studio, People's Republic of China

 Pelizziarchitettura, Italy

 Squire and Partners, UK

 Marks Barfield Architects, UK with COWI

 Sweco Architects, Sweden with Sweco Civil and Sweco Structures

 Method Architecture, UK

 Kashdan Brown Architects Ltd, UK

 AWW, UK with Mott MacDonald

 Metropolitan Studio of Architecture, Pakistan

 Fereday Pollard Architects, UK

03 April 2019

"Tower Bridge" by Harry Cory Wright

This lovely new book is part of a series of "pocket photo books", and is published alongside books on the Barbican Centre and Trinity College Library, Dublin. Harry Cory Wright is a photographer better known for his landscape photographs, who applies his sensibility to buildings for these small-but-sweet volumes.

Tower Bridge (Thames and Hudson, 176pp, 2019, amazon.co.uk) measures 17cm x 12cm and features 120 images of this iconic London bridge. There are some similar photographs in Tower Bridge: History - Engineering - Design, which I reviewed recently, displayed there at larger size, but I don't think the pocket format detracts from Wright's images at all.

Unsurprisingly, the pictures have something of a landscape sensibility. Very few show the bridge in its surroundings, but several show the surroundings viewed from within the bridge towers or walkways. Most of the photos show details of various sorts, viewed in a way which emphasises shape, colour and texture.

People are notable by their complete absence, even in images of the control cabin and visitor areas.

This makes an opening interview with Chief Technical Officer Glen Ellis feel like a stray presence from another book, some kind of ghost in the machine (although not in the Cartesian sense). Other than this interview, Wright's book is all machine and no ghost.

There are relatively few photos of the exterior of the bridge, and especially few of the stonework cladding, which is perhaps a shame as many parts of it are exquisitely detailed. However, Tower Bridge makes up for it with everything else that is included.

There are some fascinating images of the interior of the towers, glimpses of steel framework peeking out between stone and staircases. Rivets appear, and then reappear repeatedly.

There are some great images of well-preserved control gear within the bridge operator's cabin, and of the bridge machinery, both operational parts as well as the preserved but now motionless steam engines. The epic bascule chambers appear, but so also does the inside of the accumulator tower, which is not something I've often seen photos of.

Towards the end, there are some particularly nice photographs of small machinery parts, valves, cogs, regulators and the like, as well as workers' tools and shelves full of spare nuts and bolts.

The reader is left to make of it all what they will. Some brief information is given for each photograph in a section at the end, for the curious to pursue.

What stood out for me is the extent to which Tower Bridge really is one of our greatest surviving examples of Victorian engineering, notable for assembling in one place such a variety of interesting parts. It is extremely well cared for, and if it has been substantially altered then that is generally very well hidden.

Obviously, this is a book which should appeal to anyone interested in architecture and engineering, but also admirers of fine photography. The price and size also make it an affordable gift. I very much enjoyed it.