Scotland’s Oldest Bridges.

A map-based catalogue of the oldest masonry bridges in Scotland. 

Arch shapes on early bridges.

In 1675, Robert Hooke provided the principles of catenary theory, but the practice of arch building had long preceded him.  The Etruscans, the Romans, the Persians and the Chinese Dynasties all built masonry arched bridges. Many Roman bridges remain intact in Europe, today, but in Scotland nothing remains.  In Europe, arch building became a lost art for 600 years but re-emerged in the 11th century. Vaulted stone bridges appeared in Britain for the first time.  The Romanesque semicircular arch was the fundamental solution for Norman ecclesiastical architecture as well as for bridges. A semi-circle had been the Roman mainstay for arches, and it was this that they copied. Some Romanesque vaulted bridges can be seen in Europe, but in Britain most were made of wood, perhaps with masonry piers.  Fountains Abbey Infirmary Bridge in Yorkshire and Clattern Bridge in Kingston are rare examples of  English  Norman (Romanesque) vaulted arched bridges.   Exeter Bridge (above) was recently uncovered. There are no Norman bridges in Scotland.    

Romanesque architecture gave way to Gothic in the 12th and 13th centuries. (The oldest known 

pointed arch is in ancient  Byzantium and dates from the 6th century.)   An ogive or gothic arch has a geometry that is closer in shape to a catenary/parabola.  Consequently, cathedral arches and rib-vaults could be given slimline voussoirs, and bridges built in the Gothic shape could be slimmer yet strong. They need less buttressing.   There is an odd additional stratagem here for pointed arches:  a weight on the tip (crown) of the arch alters the geometry of the thrust line,  bringing it more into line with an ogive shape, which confers stability.  This additional stability was known about in medieval times, often seen on domes,  but seldom seen on bridges.   

However, above is the Puente del Diablo near Barcelona, a 13th century 37m arch on the River Liobregat . Note the remarkably slim voussoirs. 

Not all medieval bridge arches from this period are of ogive shape; there are some semicircular and segmental arches, possibly remnants of a bygone style; perhaps precursors of things to come.  Around 1500, the Renaissance brought an end to the building of pointed bridge arches,  and rounded shapes predominated thereafter.

From the mid-eighteenth century onwards, segmental shapes became the most common.   Although this shape has a flattened profile, a  parabola or a catenary can still be drawn within the thickness of the arch, particularly if it is wide enough.  Interestingly, the flatter the arch the more a parabola coincides with a circle-segment. But substantial lateral abutments are are always needed.  This has been known for centuries,  as in France, Italy, Spain and England there are many medieval segmental bridges.  In Scotland, there are only a few.   

‍ Next: Early Bridge Building.  Previous: Arches    Force-lines

Page last updated Oct.2020