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:

29 September 2019

Iceland Bridges: 4. Jökulsá á Dal Canyon Bridge

There are many arch bridges in Iceland, but this is probably one of the more unusual ones.

Built in 1994, this bridge is 125.5m long, with a main span of 70m. The steel-concrete composite road deck is supported on the arch via slender piers at 14m spacing.

The bridge was designed by Línuhönnun Consulting Engineers, who became part of EFLA Consulting Engineers in 2008. Swiss engineer Christian Menn was involved as a consultant.

The bridge is unusual for the arch being of composite construction, with a concrete slab supported on two steel box girders, and for its angular form. In the UK, we'd describe it as a "thrupenny-bit" profile. This solution was chosen over girder and framed options for aesthetic reasons, although studies showed a steel frame bridge to be slightly less expensive.

The composite form was chosen to eliminate the need for falsework as far as possible. The steel girders were erected first, and used to support 150mm thick prefabricated concrete panels. A further layer of in-situ concrete was then poured to create an arch 300mm thick in total. The width of the arch varies from 4.4m at the crown to 6.4m at its springings.

The bending stiffness of the arch and deck are similar, so in the finished bridge, they both resist asymmetrical bending equally.

The construction sequence had to be considered very carefully to ensure that the very slender arch remained stable at all stages - the construction photo below (taken from a technical paper describing the bridge's design and construction) shows quite how slender it appeared.

Further information:

26 September 2019

Iceland bridges: 3. Suspension bridge over Jökulsá á Fjöllum on Route 1

My journey took me east from the previous two bridges, following the Route 1 highway.

Iceland is well-supplied with large rivers, carrying meltwater from icecaps and glaciers. The Jökulsá á Fjöllum river appears wide but relatively unspectacular. However, the volume of water is substantial, as can be seen around 20 km to the north where the river spills over the enormous Dettifoss, reportedly Europe's largest waterfall.

Before there was a bridge here, the river could only be crossed by a ferry. The bridge was built in 1947, one of a number of suspension bridges completed within a 12 year period from 1945 to 1957, following Iceland's independence from Denmark.

The bridge is 171m long, with a main span 102m long and 3.7m wide. The steel ropes were supplied by British Ropes Ltd, and the steelwork was supplied and erected by Dorman Long.

The Icelandic roads authority have been planning a new bridge a little to the south of the existing structure, on the grounds that the existing bridge requires both speed and weight restrictions (lorries are forbidden by signs from travelling in convoy across the bridge). The new structure is proposed as a 5-span concrete box girder bridge, 230m long. Construction was due to start in 2015, but evidently it has been delayed.

Further information:

24 September 2019

Iceland Bridges: 2. Road bridge over Skjálfandafljót at Fosshóll on Route 1

This bridge was built across the Skjálfandafljót river in 1972, replacing an older truss bridge dating from 1930. The older bridge (and the remains of its 19th-century predecessor) can be seen in the photo at the end of this post.

Today, this structure carries Route 1, the main Icelandic ring road. Like many bridges in the country, it is only a single lane wide, although reportedly the national highway authority is considering building a new 2-lane bridge immediately to the north of this span.

As with many bridges in Iceland, it can best be described as pragmatic. The ladder-like inclined legs allow the main bridge girders to be more economical in size.

Further information: