26 October 2019

"Tower Bridge: 1894 to date. Operations Manual"

Haynes Publishing must be best known for their car and motorcycle maintenance manuals, but they have increasingly branched out into other territories, with recent publications including "The Human DNA Manual" and the "Milky Way Owner's Workshop Manual". In the areas of architecture and infrastructure they have published Manuals for "London Underground", "The Great Pyramid", "Hadrian's Wall" and now "Tower Bridge" (188pp, 2019, ISBN 978-1-78521-649-7).

It is, of course, Tower Bridge's 125th anniversary this year, and this new book by engineer John Smith joins books by Kenneth Powell and Harry Cory Wright published to mark the occasion. A comparison against the Powell book is inevitable, and although there is plenty of overlap between the two, there are some very clear differences.

Powell's book has, on the whole, the better photographs, and is a much easier read for a non-engineer, with much more detail on the context and a strong narrative surrounding those who designed and built the structure. As befits its publication by Haynes, Smith's book has far more detail on the construction work, the bridge components, and its operating technology.

The early sections of the book give a fairly comprehensive account of the somewhat tortuous process by which the bridge was eventually conceived, including the sometimes ingenious and sometimes monstrous alternative designs put forward.

The real dive into detail begins in the third chapter, documenting the eight separate contracts which were let for construction of the bridge, dividing up the works required for the piers and abutments, approach structures, metal superstructure, masonry superstructure, hydraulic machinery, paving and lighting. No client today would take this approach, retaining the entire liability for integrating a complex construction process on their own, but when the bridge was built there would have been no single contractor with the capability to do it all.

It's interesting here to see the extent to which the contract conditions used in the 1890s are very similar to those still in widespread use at the end of the 20th century. Extracts from the very first contract (for the piers and abutments) make this clear: the power of the resident engineer, payment retention, liquidated damages etc. The unrealistic timescales demanded by the client, and unrealistic prices submitted to win the work, also remain familiar today.

The core of the book consists of four chapters which itemise every single element of the bridge, describing them in exquisite detail and explaining just how every piece fits together. At times, the level of detail presented, with dimensions, plate thicknesses, etc, is numbing rather than interesting. For the engineering reader, there are several interesting extracts from drawings included, and the comprehensive nature of the text does mean that there appear to be no significant details left unmentioned.

There are many aspects of the bridge explained here which are essentially absent from the account in Powell's book. One example is the presence of stiffening girders concealed within the balustrades of the southern span, which ensure that water pipes carried across this span were protected against excessive movement. Another is the explanation of the arrangement of the high-level footways, the suspension bridge ties which pass through these, and the additional suspension cable added in 1960 to relieve the footway girders of the weight of those ties. These elements of the bridge are not immediately apparent to the casual visitor, but Smith's text, photographs and drawings make everything clear.

The book contains one excellent cutaway diagram showing how the components of the bridge fit together, and it's a shame there weren't more. My over-riding impression, after reading this book, is quite how complex Tower Bridge really is, and how well it merits this wealth of information. It really is an engineering masterpiece, whatever anyone may think of its architectural merits.

The book concludes with biographies of the main participants in the bridge's design and construction, and a detailed timeline of alterations and maintenance work in the period from 1894 to date. One of three appendices gives a detailed breakdown of the author's calculations of loads and forces in the bridge's key structural elements.

I couldn't, with any honesty, recommend this book to anyone who is not an engineer, but it is so detailed that it will probably remain a key reference work for Tower Bridge for the indefinite future. It is clear, thorough (sometimes too much so!) and well-illustrated throughout.

13 October 2019

Lancashire Bridges: 8. Seven-arch Bridge, Rivington

This is an interesting bridge that I stumbled across on a visit to Rivington Terraced Gardens, near Bolton in Lancashire.

The Gardens were built over a two decade-period starting in 1905, for industrialist William Hesketh Lever, also known as Viscount Leverhulme. Lever made his fortune with his family firm Lever Bros (later to become Unilever), selling Sunlight Soap. He had made a home, the Bungalow, at Rivington, and the surrounding estate was landscaped by Thomas Mawson, who later became the first President of the Institute of Landscape Architects.

Most of the Gardens then fell into ruin, but a Heritage Trust has been busy in recent years clearing vegetation and conserving the site's historic structures (there are eleven Grade II Listed Buildings within the site).

The Seven Arched Bridge carries a footpath over an access track, and was reportedly inspired by a bridge that Lever had seen while visiting Africa.

Historic England lists the bridge as part of a group of structures including a staircase, walls and a summer house, all of which proceed up the hill from the bridge. All these structures are built in a common style using thin slabs of gritstone.

Historic England's listing suggests that the design for the bridge was based on a bridge in Nigeria. Lever did source palm oil for his soap from the British colonies of West Africa, but he is also known to have visited Belgian Congo (now the Democratic Republic of Congo) in 1911 to set up palm oil plantations.

There is an image of a bridge in Albertville (now Kalemie, in the D.R.C.) from circa 1930 which might be relevant - I've certainly not found anything else online (there are further images of the same bridge on these pages).

In any event, this is not an elegant bridge, but it is interesting for its unusual architectural style, and the way its robust mass is built up from fine detail.

Further information:

06 October 2019

"An Encyclopaedia of British Bridges" by David McFetrich

David McFetrich's "An Encyclopaedia of British Bridges" (Pen and Sword Books, ISBN 978-1-52675-295-6, 2019, 444pp) is the 2nd edition (with a very slight change in title) of a volume previously published in 2010.

It updates and expands its predecessor with one-third more structures discussed across 1,600 individual entries (previously 1,350), and a page-count increased by a quarter. Size does matter in an effort like this - it can never possibly be comprehensive, but an already impressive reference work has been made significantly more valuable.

The additions are from all periods of history, bridges both ancient and modern, and many of them are structures I'd never heard of. Picking the letter K at random, the bridges added are Karlsruhe Friendship Bridge, various Kew Gardens bridges, Kildrummy Castle Bridge, Glasgow's Kingston Bridge, and Knostrop Weir Footbridge. One of these is an inexplicable omission from the previous volume, and the others are all worthy inclusions.

The core of the book remains a well-illustrated alphabetised compendium of notable bridges (I should declare an interest here, as some images in the new volume have been provided by the Happy Pontist). Descriptions vary in detail but always convey the core facts and usually offer interesting information or context. Some entries have been expanded from the previous edition. The Encyclopaedia is frequently my first point of reference when investigating British bridges, and helpfully includes cross-references to other sources and a thorough bibliography.

The book is topped-and-tailed with a brief history of Britain's transport infrastructure, details of how bridges work, a fine glossary, lists of record-breaking bridges and a very helpful geographic index. A length "miscellany" puts the bridges in many different contexts, covering not just "timber bridges" or "suspension bridges" but less obvious subjects such as "tea house bridges", "relocated bridges", "finback bridges" and "ugly bridges".

Every time I open the book, I discover something new, and I imagine most readers will find the same. If you already own the first edition, it may be difficult to justify this new one, unless your interest in the subject is serious. If you don't, and you are at all interested in British bridges, I think this book is indispensable. If you are involved in the bridge design or engineering community, you may even find some of your own bridges here - I certainly did!

An Encyclopaedia of British Bridges is currently available at a discounted price of £54 (postage free in the UK) from the publisher, and also on Kindle via Amazon.

03 October 2019

Iceland bridges: 6. Hvítá bridge

This is the last bridge I'm going to feature from my Iceland trip, and it's the best.

When celebrating its 90th anniversary in 2002, the Association of Chartered Engineers in Iceland designated this bridge the most notable achievement of the third decade of the 20th century, the only bridge to make their list.

The bridge was built in 1928 by the national highway authority to a design by their engineer Árni Pálsson - it was one of the first projects in his career there, he went on to become their chief engineer in 1947.

The structure is 106m long, with two 51m span concrete arches spanning the river Hvítá (the "white river"). This structural form was chosen on cost grounds in preference to a two-span steel girder bridge or a one-span suspension bridge.

The structure carries the road Hvítárvallavegur between Hvítárvalla and Ferjukots. As you can see from the photo, this is a fairly rough highway, as with many in the country.

Prior to construction of the bridge, a ferry crossed the river, but this was unreliable when the river flow was high. Efforts to build a bridge began with surveys in 1910, and drawings were prepared in 1922, six years before construction eventually started.

The bridge would remain the main route from south-to-north in western Iceland until a bridge was completed downstream at Bogarnes in 1981.

The structure is instantly impressive, as attractive as many better-known concrete arches built in mainland Europe in this period. The 3m wide bridge was designed to carry a 6-tonne truck, or a uniform load of 400 kg per square metre (roughly 4 kPa), a similar load to what a pedestrian bridge would be designed for today.

The arch is very slender at its thinnest points, but unlike the broadly contemporaneous deck-stiffened arches of Robert Maillart (starting with the Flienglibach Bridge in 1923), it does not take its stiffness from the road deck.

The bridge draws its strength from the shaping of the arch - its connection to the deck at the middle of each span, and the thickening of the arch towards each support. This could have led to an ungainly appearance, but the sinuous profile of the upper arch surface combines well with the elliptical profile of the underside.

The set-back of the vertical support struts from the edges of the arch and deck also contribute to a fine appearance, emphasising the profile of the arch.

There are many more interesting bridges in Iceland, I only had time to visit a handful. Hopefully I'll get the chance to see more on a future trip!

Further information:

01 October 2019

Iceland bridges: 5. Jökulsárlón Bridge

This must be another one of the most-seen bridges in Iceland. It spans the outfall river from the Jökulsárlón glacier lagoon, and carries the island's ring road, route R1. You can't drive along the south coast of Iceland without eventually passing over this bridge.

The hengibrú (suspension bridge) was built in 1966-7, and has a main span of 108m. A ferry operated here from 1932, but before that the river was very difficult to cross.

I believe this was one of the last of a series of suspension bridges built in Iceland starting in 1945, and there are obvious similarities to the bridge over Jökulsá á Fjöllum that I featured previously, even though that is 20 years older.

When the bridge was built, the glacier Breiðamerkurjökull extended much closer to the highway. The glacier lagoon has grown steadily as the glacier has retreated, some 5.6km in the last century. This location, hugely popular with tourists, will at some point likely become the mouth of a new fjord, with the extent depending on how successfully global warming is tackled. Although efforts have been made to protect the foundations of the bridge against scour, it's lifetime may be limited.

Further information: