Bridges
This page is intended to give a brief outline history of bridge design from Prehistory through to the modern day. Please follow the links below to gain more detail on a specific type.
The First Bridges
Bridges are an integral part of our Road Network. They have been since before even the Romans arrived on these shores, with some examples still surviving which are believed to (possibly) date back as far as 1000AD. One of the earliest Bridge Types still in existence in the British Isles is the Clapper Bridge, as seen at Tarr Steps. Other bridges of similar design also survive, although most bridges of this era were probably little more than a few logs slung across a stream.
Whilst many bridge sites may date back to Roman times, not least London Bridge, none of their structures appear to have survived intact. This may be explained by the fact that they tended to build all but their most important bridges from timber, many being very temporary structures constructed after the first invasion which were either subsequently unused, or maintained as timber structures.
Early Bridges in detail.
Medieval Bridges
Packhorse Bridges
Perhaps the simplest of the bridges built in the Medieval period were Packhorse Bridges, rarely wide enough for even a cart to cross, and often hump-backed in profile. Whilst most were single-arched over narrow channels, some such as that on the right at Allerford, were two-arched.
Although the term 'Packhorse Bridge' has come to describe the design outlined above, there were in fact many different types of Packhorse Bridges, some barely changing gradient from the road they carried, and some appearing more as causeways across wide boggy streams.
Major Bridges
Almost every county in England, and many in Scotland, Wales and Ireland, have large and imposing medieval bridges spanning major rivers. Some are grand gestures showing off how rich the town was, others are simply there to carry the traffic across the river without anyone getting wet feet, yet all have survived for at least 400 years, some a lot more. Of course, at the time, there were a great many more such structures around the British Isles. Unfortunately, as the centuries passed, some have been swept away by floodwater, some by a badly steered ship or lorry, and even more by enthusiastic Victorian or modern planners wishing to 'modernise', 'improve' or 'regenerate'.
The earliest bridges retained the round arch that had been in use since Roman times, with narrow roadways and chunky piers. However, during the course of the medieval period bridge design developed and round arches became pointed, piers were reduced in profile, with more finely designed cutwaters to reduce the risk of flood damage and roadways were widened as coaches and carriages became more common.
Bridge Types
Seventeenth and Eighteenth Century
In the beginning of this period, bridge construction changed little from the previous few hundred years. Most were still built of stone and used arches to carry the roadway across the river. However, with the start of the Turnpike era in the 1670s, bridge design was suddenly kickstarted. Admittedly, in the first century it was more about quantity rather than quality, but for all of their failings, the turnpike companies did build a vast number of bridges.
At the end of this period, there was another sudden leap in bridge design, with the first bridge to be constructed of Iron (right). While this bridge may have still used basic carpenters skills to put it together, it was the first of a new breed of bridges which were soon appearing up and down the country.
Bridge Types
Victorian Bridges
It is in the nineteenth century, and particularly the Victorians who really changed the way that we crossed the water. In 1800 there must have been many thousand small fords across streams and rivers, but by 1900 that number had dwindled to a few hundred. Not only that, but some almost unthinkable achievements were made, such as Brunel's Clifton Suspension Bridge, or Telford's Menai Suspension Bridge. These structures made use of the rapidly developing new technologies, particularly the use of Iron to construct Cables and Chains from which a bridge deck could be suspended.
Whilst many of these bridges, indeed most, used the tried and tested stone-arch philosophy, mainly reverting to the round arch first used by the Romans, if not before, a significant number used the 'new' materials of Iron and later Steel. In addition to Iron Arches and Suspension bridges, as the century progressed girder and truss bridges were developed, often by the railway companies, but also used widely for roads.
Bridge Types
The Modern Bridges
Since 1901, Bridge design has changed almost beyond recognition. Whilst many of the older designs persisted in the first half of the twentieth century, the one type which seems to have dropped from favour at the end of the Victorian era is the most traditional of all - the simple stone arch. Iron Arches were perhaps the next to go, as Concrete - the new wonder material - took over.
While many will mourn the passing of the older designs, it is fair to say that Concrete has proved a very versatile material able to carry any type of road across any type of river, from the lengthy Tay Bridge to something as small and insignificant as the Athelney Bridge in Somerset. It has also changed the way that suspension bridges have been built, with most of the major crossings built after the war using this mix of materials. The Humber Bridge, Forth Road Bridge and Severn Bridge are all suspension bridges, using concrete for the towers and deck.
However, as the millennium drew to an end the negative side of Concrete was realised - most notably the drab grey and lack of design flair that characterises so many of the bridges - and many exciting new bridges, such as the Clyde Arc (right) have been designed to revitalise urban river scenes. Lets hope that bridge design remains exciting once more for many years to come!
Bridge Types
- Cable Stayed Bridges
- Concrete Bridges
- Girder Bridges
- Iron Arch Bridges
- Suspension Bridges
- Truss Bridges
Moving Bridges
The first bridges that were designed to move were probably the drawbridges which we generally connect with Medieval Castles, although they are believed to have been in use by the Ancient Greeks, a couple of thousand years earlier! However, as far as roads are concerned it is really the canal builders that started building moving bridges in any great volume, and the Victorians who built them on the larger scale.
Bridge Types
There are, of course, a great many different ways to move or open a bridge, and for a great many reasons. The most obvious reason is to let a tall masted ship through, and this is also the most common.
Links
- Quality Control of Road and Bridge Construction - National Audit Office Report November 1989 (archive.org)
