BRIDGES – Spanning the World

BRIDGES SPANNING THE WORLD

Marcus Binney

BRI DGE S S PANNI NG TH E WORL D / CONTE MP ORARY BRI DGE S

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CONTENTS INTRODUCTION

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THE PRIMITIVE BRIDGE Clapper Bridges

ROMAN BRIDGE-BUILDERS Bridges in Rome • Bridges in Northern Italian Cities • Bridges Carrying Roman Roads • Major City River Crossings • Iberian Aqueducts • Roman Road Bridges in Iberia • Roman Engineering in France • Roman Bridges in the Levant

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THE MIDDLE AGES The Chinese Forerunner • Chapel Bridges • Fortified Bridges • Medieval Chinese Bridges • Thames Bridges • Devil’s Bridges • Long Bridges • German Bridges • High-Arch Bridges • Multi-Arch Marvel • Chinese Canal Bridges

THE SIXTEENTH AND SEVENTEENTH CENTURIES The Inhabited Bridge • A Wooden Bridge • The Monumental Arched Bridge in Italy • Great Bridges of the Islamic World • Isfahan • Graceful Footbridges • A Bridge in Peru • Bridges in Central Europe • From Northumberland to Wales • By Royal Command

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THE EIGHTEENTH CENTURY Le Corps des Ingénieurs des Ponts et Chaussées • Georgian Civil Splendour • Monumentality as an End in Itself • Garden Bridges • Swiss Covered Bridges by the Grubenmann Brothers • Palladian Bridges in Country and Town • Bridges of the Imagination • Revolution and Empire in Paris • A Bridge in Ireland • Fantasy Bridges

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BRIDGES S PAN N I N G T HE WO R LD / contents

THE NINETEENTH CENTURY Thomas Telford • Triumphal Suspension Bridges • The Bridges of Taishung County • Brunel as a Pioneer of Great Spans • Isambard Kingdom Brunel • Bridges in Castle Style • Railway Viaducts in the Roman Manner • Transporter Bridges • Triumphal-Arch Bridges • Double-Decker Bridges • Trestle Bridges • Great Single-Arch Bridges • The Grace of Multiple Arches • Avant-Garde French Railway Viaducts • Aqueducts Live Again • Gustave Eiffel as Bridge-Builder • Bascule Bridges • Fin-de-Siècle Imperialism • Ancient Traditions Live on in China • The Magnificent Three • Wind and Rain Bridges in Rural China

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THE TWENTIETH CENTURY Military Bridges in World War II – The Bailey Bridge • Floating Bridges in Washington State • Truss Bridges • Inhabited Bridges • Giant Cable-Stayed Bridges • The Soaring Lightness of Stilt Bridges • Bridges on the Curve

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CONTEMPORARY BRIDGES Norman Foster • Santiago Calatrava • Alain Spielmann • Wilkinson Eyre • Paris Pioneers the Adventurous Footbridge • Breath-Taking Spans of the Latest Cable-Stayed Bridges • New Rail Bridges • Connector Bridges • Longest Suspension Bridges • The Classical Bridge Revived • Bridges as Sculpture • Garden Bridges Go Cosmic • Mathematics in Bridge Design • Moving Bridges Press the Bounds of Ingenuity • Concrete Still the Wonder Material • Toni Ruttiman – Bridge-Builder to the World’s Poor • Tony Hunt – The Bridge that Floats Away

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PAST TO PRESENT Constantine – A City of Bridges • Living-Root Bridges of India

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GLOSSARY

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INDEX

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BRI DGE S S PANNI NG TH E WORL D / con ten t s

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BRIDGES S PAN N I N G T HE WO R LD / R oma n B r i d g e - B u i l d e rs

ROMAN BRIDGE-BUILDERS Roman bridges rank with temples, theatres and amphitheatres as the great surviving buildings of the ancient world. They are witness to the durability of well-designed, well-built engineering structures, surviving not just as romantic ruins but in some cases as impressively complete structures. The grandest example is the Pont du Gard, built to carry water from a spring at Uzès to Nîmes in France.

In engineering terms the Romans made three great innovations. First was the perfection and widespread use of the semi-circular masonry arch with its constructional strength and durability. Second was the introduction of natural cement. This was pozzolana, a material found near the town of Pozzuoli, close to Vesuvius. Mixed with lime, sand and water, it formed a mortar that did not disintegrate when exposed to damp. It could be used as a binding agent in piers, arches and spandrels as well as in foundations. The third innovation was the use of coffer dams – temporary enclosures in riverbeds to keep water out while foundations were being laid. This was done by driving timber piles into the riverbed, removing water and excavating the soft ground within the dam. Most of the Roman bridges which survive, however, were built on solid rock such as the Pont du Gard of c AD 14 and the Puente de Alcántara of AD 98, and the aqueduct at Segovia dating from AD 98.

Aqueducts, bringing fresh water to towns and cities, are to be found all over Rome’s far flung empire, from the aqueduct a mile (1.6km) long at Caesarea on the eastern shore of the Mediterranean to the soaring arched aqueducts at Segovia and Tarragona in Spain.

In Rome itself the ancient bridges across the Tiber are reminders of the grandeur and pomp of the Romans, celebrating their prowess as builders as much as did the great triumphal arches around the city. In cities such as Salamanca and Seville Roman bridges have survived in use as major river crossings for 2,000 years. Other Roman bridges survive as features in an Arcadian landscape recalling paintings by Claude Lorrain. Examples are the Pont Julien in Provence dating from 3 BC and the Pont Flavien of c 12 BC, or the mighty single surviving arch of the Ponte d’Augusto at Narni on the Via Flaminia dating from 27 BC.

L E F T Roman Aqueduct, Caesarea, Israel

BRI DGE S S PANNI NG TH E WORL D / Roma n Bridge Bu il ders

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Roman Bridges in The Levant

Roman Bridge AFRIN, ALEPPO, SYRIA

The three-arch bridge built of pale buff masonry has been weathered by time. Set in a broad, fertile valley east of Cyrrhus, the ends rise quite steeply to carry the roadway and the arches above the level of floodwaters.

The half-rounded cutwaters are massively constructed, shallow niches above them creating an alternative rhythm with the main arches. The three-arch bridge built of pale buff masonry has been weathered by time. Set in a broad, fertile valley east of Cyrrhus, the ends rise quite steeply to carry the roadway and the arches above the level of floodwaters. The halfrounded cutwaters are massively constructed, shallow niches above them creating an alternative rhythm with the main arches.

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BRIDGES S PAN N I N G T HE WO R LD / R oma n B r i d g e s i n T h e L evan t

Roman Aqueduct CAESAREA, ISRAEL

Long sections of this low-level stone aqueduct survive along picturesque sandy beaches. The first aqueduct was built by Herod, Roman king of Judea, when the new city of Caesarea was founded and dedicated to the emperor Augustus. It brought water from the southern side of Mount Carmel, about 6 miles (10 km) north of the city. The water flowed along a conduit in places cut into the solid rock and in others carried on

arches. As the city grew in size a second aqueduct was built in the second century by the legions of the emperor Hadrian, with a tunnel section 3ž miles (6 km) long joining the earlier aqueduct, which was doubled in width. These continued to supply water for 1,200 years. A Roman milestone is located under one of the arches, marking 4 miles (6½ km), presumably from Caesarea.

BRI DGE S S PANNI NG TH E WORL D / Roma n Bridges in Th e L eva n t

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OPPOSITE Pont d’Avignon, Vaucluse, France

THE MIDDLE AGES Medieval bridges, mainly dating from the tenth century onwards, survive in impressive numbers in Europe, the Middle East and China. Almost all the bridges of that era which remain are of stone, massively built to resist floodwaters, with some raised on high arches so floodwaters would pass beneath them.

In Asia medieval bridges often served major caravan routes such as the Silk Road. In Europe bridge-building was encouraged by the Church. Old London Bridge, begun in 1176, was commissioned by a penitent King Henry II after the murder of the Archbishop of Canterbury and supervised by Peter, a priest and chaplain of St Mary Colegate. The narrow arches served an additional purpose as they acted as a weir reducing the flow of the tide and turning the river above the bridge into more of a lagoon where people could row against the tide; this was much more difficult to do below the bridge.

Puente de Besalú CATALONIA, SPAIN

This is a twelfth-century Romanesque roundarch bridge over the Fluvia river with a gateway at the midpoint. The arches are built on outcrops of natural rock with cutwaters added to break the flow when the river is high.

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BRIDGES S PAN N I N G T HE WO R LD / T he M i ddle A g e s

The famous bridge over the Rhone at Avignon (1187) was built under the inspired vision of a young shepherd, later canonized as St Bénézet for his accomplishment. Medieval bridges were built with chantry chapels, often placed midstream, where travellers could pray for, or give thanks for a safe journey.

Devil’s bridges in Europe, each with its own story, usually have high central arches.

There is also an impressive surviving group of fortified bridges with towers and battlements. Examples are the Monnow Bridge at Monmouth in Wales and Pont Valentré near Cahors in France.

In the late Middle Ages numerous stone arched bridges with remarkable spans were built in mountain valleys where the natural rock formed secure abutments for ambitious arches. Examples are the Pont Grand at Tournon-sur-Rhône over the River Doux with a span of 161 ft (49 m), dating from 1379, and the Pont de Vieille-Brioude over the River Allier with a span of 177 ft (54 m), dating from 1479.

Many medieval bridges have been repaired and remodelled over the centuries and sometimes completely rebuilt after they had collapsed or been swept away. Typical features are cutwaters and refuges above.

Refuges are usually triangular recesses where those on foot could stand as convoys or pack animals passed.

Marco Polo, who is supposed to have visited China in the late thirteenth century, was astounded at the beauty and the number of bridges in China. He wrote of the city of Hangchow: ‘It is commonly said that the number of bridges of all sizes amounts to 1,200. Those that are thrown over the main canals along the principal streets have arches so high, and are built with such skill, that vessels with masts can pass under them. At

BRI DGE S S PANNI NG TH E WORL D / Th e Middle Ages

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Fortified Bridges

Monnow Bridge MONMOUTHSHIRE, WALES

The bridge in Monmouth is the only remaining fortified bridge in Britain with its gateway tower still in place. Entry is now restricted to those on foot. Completed in the late thirteenth century (traditionally 1272), it replaces an earlier wooden structure. Built of red sandstone, it has three arches on hexagonal piers forming pointed cutwaters. In the gatehouse the grooves for the lowering of the portcullis are still visible.

Vieux Pont d’Orthez PYRÉNÉES ATLANTIQUE, FRANCE

In southwest France, the Gave de Pau is crossed by a thirteenth-century bridge with four arches and a tall but narrow gateway tower. Orthez is a pilgrimage town and the bridge an important crossing-point on the route to Santiago de Compostela in Spain.

Originally there were two towers with the central part connected to the riverbanks by wooden platforms. These could be removed, as when Napoleon was being pursued by Wellington’s troops in 1814.

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BRIDGES S PAN N I N G T HE WO R LD / For ti f i ed B r i d g e s

Pont Valentré CAHORS, LOT, FRANCE

This is a six-span fortified bridge across the River Lot to the west of Cahors. Construction began on 17 June 1308. It was completed 70 years later in 1378 with six pointed arches and three towers. It had opened to traffic in 1350 and was originally fortified at both ends, but the western tower has not survived. The bridge was restored in 1867–79 by Paul Gout, who commissioned a carving of the Devil clinging to the tower – a reference to a wager between the original builder and the Devil and the Devil’s attempt to foil the bridge’s completion.

The total length is 453 ft (138 m). A defensive rampart rises from a cutwater to protect the flank of the central tower. The graceful lines of the arches are highlighted by the ‘eyebrows’ over the voussoirs.

Ponte Scaligero VERONA, VENETO, ITALY

The bridge crosses the River Adige. The redbrick upper part is battlemented. It was built in c 1354–56 by Cangrande II della Scala, lord of Verona, as a safe means of escape from the castle. It was totally destroyed by retreating Germans on 24 April 1945 and faithfully reconstructed in 1949–51.

BRI DGE S S PANNI NG TH E WORL D / Fort ified Bridges

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BRIDGES S PAN N I N G T HE WO R LD / Si xteenth a n d S eve n te e n t h C e n t u r i e s

THE SIXTEENTH AND SEVENTEENTH CENTURIES The Renaissance looked back to Ancient Rome as the fountainhead of pure Classical architecture while the surviving marvels of Roman engineering provided inspiration for bridge-builders and for a new generation of masonry bridges built with round and elliptical arches.

Notable among them was the magnificent single arch of the Ponte del Rialto in Venice across the Grand Canal, built of marble in emulation of Ancient Rome. Still more daring were the broad, almost flat, arches of the Ponte Santa Trinita in Florence, designed and built by Bartolomeo Ammanati in 1567–69.

The architect Andrea Palladio, whose I Quattro libri dell’architettura (The Four Books of Architecture) of 1570 served as an authoritative pattern book for more than two centuries, also revived the Roman truss form for both roofs and bridges. This was a rigid self-supporting system of triangles used on Caesar’s Rhine Bridge of 56 BC. Palladio built several timber truss bridges, notably the bridge over the River Brenta in Bassano del Grappa of 1569.

In the rapidly expanding Ottoman empire Mimar Sinan, architect to the Sultan Suleyman the Magnificent, was also a leading bridgebuilder, designing the famous Mostar Bridge and another in Višegrad. In India the Shahi Bridge at Jaunpur, dating from 1564–67, was built with pairs of pavilions, while in Isfahan the Allahverdi Khan and Khaju Bridges were designed as promenades and grandstands as well as shaded river crossings.

In France, Henri IV and his minister, the duc de Sully, were pioneer bridge-builders, ushering in a new era of monumental classical bridgebuilding in Paris. In Britain the construction of Berwick-upon Tweed Bridge in 1610–24 illustrates the ability of engineers to build ambitious bridges over broad, fast-flowing rivers.

LEFT Château de Chenonceau, France

B R ID G E S S PANNI NG TH E WORL D / S ix teen t h a n d S even teen t h Cen t u ries

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Palladian Bridges Palladian bridges, based on a design for a bridge across the Grand Canal in Venice by Andrea Palladio, grace some of the most beautiful vistas in the parks of English country houses. Fine examples were built in the eighteenth century at Wilton House, Stowe and Prior Park. In Russia a bridge based on the English model was built in the landscape park at Tsarskoe Selo.

The beauty of these bridges is that they are transparent – there is a view through the colonnades to the sylvan landscape beyond – and the triple arches below form reflections in the water. All four have colonnades and end pavilions with arches and pediments. As the bridges are roofed, they serve as prospect houses that provide shelter and shade in rain or shine.

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BRIDGES S PAN N I N G T HE WO R LD / Pa lla di a n B r i d g e s

Palladian Bridge, Wilton House WILTSHIRE, ENGLAND

The Palladian bridge across the River Nadder in the grounds of Wilton House was designed by the ninth Earl of Pembroke (the ‘architect earl’), working with the architect Roger Morris.

It dates from 1736–37. This was the first bridge in the Palladian manner to be built in England, the prototype for others.

Palladian Bridge, Stowe BUCKINGHAM, BUCKINGHAMSHIRE, ENGLAND

The bridge in the landscaped park at Stowe was built for Viscount Cobham, perhaps under the direction of the architect James Gibbs. It was designed as part of a carriage drive and the approaches on either side have ramps instead of steps. The bridge was completed by 1742.

Palladian Bridge, Prior Park BATH, SOMERSET, ENGLAND

Prior Park was built for Ralph Allen. The bridge, at the bottom of a steep valley, serves as an eye-catcher for his grand mansion on the hill above. It was to be viewed from the state rooms and the portico. The bridge, dating from 1755, was designed with advice from Lancelot ‘Capability’ Brown and Alexander Pope, the poet.

Palladian Bridge, Tsarskoe Selo ST PETERSBURG, RUSSIA

For the landscape park laid out in the English manner by for Catherine the Great, Vasilii Neelov designed a bridge closely modelled on the bridge at Stowe. With elements built using blue-grey and white marble from the Urals, it is known also as the Siberian Marble Bridge. The base is of granite. The bridge was completed in 1774.

BRI DGE S S PANNI NG TH E WORL D / Pa l l a dia n Bridges

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BRIDGES S PAN N I N G T HE WO R LD / T he N i netee n t h C e n t u r y

THE NINETEENTH CENTURY The nineteenth century was an age of great engineers, many playing a leading role in bridge-building. In Britain Thomas Telford was followed by a series of great railway engineers: Isambard Kingdom Brunel, Robert Stephenson, with Gustav Eiffel in France and John Augustus Roebling in America. This was a century of new materials and structural techniques – notably iron and steel – but also stone and brick on a grander scale that ever before. Telford pioneered the large suspension bridge over the Menai Straits, Stephenson the wrought-iron tube for trains on Britannia Bridge nearby.

Engineers improved the technology for sinking foundations to bedrock.

Previously the length of available wooden piles and soils which were too soft or too hard for pile-driving had been major constraints.

Pneumatic caissons changed this and in 1859 the central pier of the Royal Albert Bridge over the Tamar at Saltash was built on a wroughtiron caisson sunk to bedrock in 70 ft (21 m) of water and 16 ft (5 m) of mud.

The discovery of hydraulic cement in 1796 on the Isle of Sheppey in England also helped to open a new era. It had the ability to set under water and was used for aqueducts, piers and abutments.

The Goltzsch Viaduct in Germany is the largest brick bridge in the world built in 1846–51 linking Saxony and Bavaria. Germany’s growing steel industry fuelled the construction of advanced steel bridged with wide-arched steel spans in the 1870s over the Rhine at Koblenz and Duisburg. The Romantic movement equally prompted numerous bridge with historicising

elements such as towers, turrets and battlements. German precision engineering endowed the county with many ingenious examples of moving bridges – swing bridges, lift bridges and transporter bridges.

For railway building extensive use was made of trestles viaducts, first timber then steel.

The most notable of the early trestles was the Portage Viaduct in the USA (1852), a remarkable timber structure designed by Silas Seymour, carrying the Erie Railroad over the Genessee river, 234 ft (71 m) above the water. It was 876 ft (276 m) long. It was destroyed by fire in 1875, to be replaced in iron, and later in steel.

The first true steel bridge was the Eads Bridge (1874) over the Mississippi built by the Keystone Bridge Company with tubular arch steel spans of over 500 ft (91 m).

LEFT Menai Straits Bridge, Anglesey and Gwynedd, Wales

BRI DGE S S PANNI NG TH E WORL D / Th e Nin eteen t h Cen t u ry

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BRIDGES S PAN N I N G T HE WO R LD / Aqueduc ts L i ve A g ai n

Aqueducts Live Again The nineteenth century saw ambitious aqueducts being built to carry canals across valleys, aqueducts broad enough for canal and river barges and tow paths. There was a revival in building aqueducts to bring plentiful clean water to cities and also to factories where steam machinery required huge quantities of water.

Aqueduc de Roquefavour, Ventabren BOUCHES-DU-RHÔNE, FRANCE

Claimed as the largest stone aqueduct in the world, this was built in 1841–47 to bring water along the 50 miles (80 km) of the Canal de Marseille to the French port on the Mediterranean. In the 1830s rapid population growth followed by cholera epidemics prompted the city’s mayor to bring in water

from the nearest large river, the Durance.

The plan was to harness the water at a height sufficient for it to flow by gravity to the highest point in the city. This was mountainous terrain and the biggest challenge was crossing the valley of the Arc near Aix-en-Provence.

The project’s chief engineer, Franz Mayor de Montricher, proposed a 1,312-ft (400-m) aqueduct at Ventabren, emulating the Roman Pont du Gard. Montrichet had been trained at the École des Ponts et Chausées.

Construction took six years, from 1841 to 1847, and involved 5,000 labourers and 300 masons. The majestic construction combines monumentality with lightness. The openings of the arches are markedly bigger than the piers, which are narrower than those of railway or canal viaducts as the aqueduct carries only a narrow water channel. Monumentality comes from the rugged stonework of the piers, with smoother stone confined to the upper levels. Like the Pont du Gard, Roquefavour has a smaller arcade along the top with three arches to each large arch below. The outline of every arch is emphasized by voussoirs and a bracketed cornice crowns the top. Where the piers are tallest they are given support by lower arches.

BRI DGE S S PANNI NG TH E WORL D / Aqu edu c t s L ive Aga in

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Acueducto del Águila, Nerja ANDALUCIA, SPAIN

Like many great aqueducts, both Roman and much more recent, the Eagle Aqueduct is major landmark. It is on the Barranco de la Coladilla de Cazadores. It was constructed between 1879 and 1880 to bring water from the town of Nerja to a sugar refinery in Maro, Las Mercedes, also known as the Fábrica San Joaquin de Maro, built in 1884.

It was commissioned by the factory’s owner, Francisco Cantarero Senio, whose name is inscribed on the structure. It is now used for irrigation.

The aqueduct is quite close to the coast and during the Spanish Civil War was damaged by naval bombardment. It was extensively restored in 2011 and now glows in a bright livery of yellow and terracotta red. The red emphasizes the constructional elements of piers and arches – the yellow is used for the spandrels above the arches. These colours echo those of Moorish buildings which survive in Andalucia. It consists of four tiers of arches, increasing in number as the ravine widens towards the top. The pavilion in the centre has a spire topped by a weather vane in the form of a double-headed eagle. On one side of the pavilion a worn plaque proclaims Pura Y Limpia Concepción – Pure and Clean Conception.

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BRIDGES S PAN N I N G T HE WO R LD / Aqueduc ts L i ve A g ai n

BRI DGE S S PANNI NG TH E WORL D / Aqu edu c t s L ive Aga in

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Double-Decker Bridges

Oberbaumbrücke, Berlin

One of the earliest double-decker (or double-decked) bridges is Robert Stephenson’s High Level Bridge across the River Tyne in Newcastle, completed in 1849, with railway lines on the upper level and road vehicles below. Tower Bridge in London has a footbridge at the upper level which can be used when the bridge decks are raised to allow ships to pass.

The Oberbaum Bridge over the River Spree in Berlin is an enchanting, almost fairy-tale example of a bridge in historicist style. The architect Otto Stahn designed it in the north German brick gothic style of the late Middle Ages with tower and battlements as well as clocks which look like altar ornaments. The name baum (tree) comes from the wooden booms covered in metal spikes on an earlier bridge that were used to deter smuggling – one upstream, the other downstream.

The world’s busiest bridge, the George Washington Bridge, connecting New York City with New Jersey, has two levels to carry the intense traffic, as do numerous river and estuary bridges in the USA. Also comparable are the Tsing Ma and Kap Shui Mun Bridges in Hong Kong, where metro trains run below six traffic lanes.

GERMANY

The present bridge opened in 1896 to coincide with the Berlin Trades Exhibition.

The twin towers were inspired by the Middle Gate Tower in the city of Prenzlau in the Prussian state of Brandenburg. The bridge lay on the planned route of the Berlin U-Bahn and the first section opened in 1902. In April 1945 the German army blew up the central section of the bridge to halt the advancing Red Army. After the war, when Berlin was divided into four sectors by the victorious Allies, the Oberbaum Bridge served as a crossing between the American and Soviet sectors. When the Berlin Wall was built in 1961 the West Berlin U-Bahn had to terminate at the bridge.

The Wall came down in 1989 and the bridge was restored by Santiago Calatrava with a discreet but distinctively modern steel central section accommodating the railway. This opened in 1994. Viewed across the water, the bridge presents an animated appearance with the yellow trains of the U-Bahn visible at the upper level, above the battlements, and the road traffic concealed within elegant open gothic arcades carried on shallow brick arches.

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BRIDGES S PAN N I N G T HE WO R LD / D ouble D ec ke r B r i d g e s

BRI DGE S S PANNI NG TH E WORL D / Dou ble Dec ker Bridges

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Pont de Bir-Hakeim PARIS, FRANCE

This elevated double-decker bridge has long delighted Paris’s Metro passengers with its grandstand view of the River Seine as they cross from the Left Bank to the elegant 16th arrondissement. Constructed in 1903–5, it is a steel arch bridge with two arms meeting on the narrow Île aux Cygnes in the middle of the river. The lower level is for motor vehicles and pedestrians. The upper level for the Metro is supported by tapering steel columns with a distinctive Art Nouveau flourish. A central stone arch supports the Metro as it crosses the island.

The steel arches across the river have open spandrels and, in the spirit of an engineering conjuring trick, the arches do not rest directly on the cutwaters in the river but are supported on small but stout pins, emphasizing the manner in which the weight of steel can be safely transferred across a narrow point thanks to the laws of compression. The spandrels carry four vigorous sculptural groups: two portraying Science and Labour are by JulesFélix Coutan and those of Electricity and Commerce by Jean-Antoine Injalbert.

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BRIDGES S PAN N I N G T HE WO R LD / D ouble D ec ke r B r i d g e s

BRI DGE S S PANNI NG TH E WORL D / Dou ble Dec ker Bridges

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Trestle Bridges Trestle bridges, whether built of timber or steel, were – and are – among the most awe-inspiring railway bridges ever built. They are at their most sensational when they cross steep-sided ravines, sometimes on a dramatic curve. Their appeal lies in their apparent gravity-defying daring, built with tall slender supports often tapering towards the top. They were used where timber was plentiful and other materials such as stone and concrete could only be brought in when the railway was operational.

Kinzua Viaduct, Kinzua Bridge State Park PENNSYLVANIA, USA

Before its dramatic collapse in 2003 this was the centrepiece of a state park in Pennsylvania.

It was rated as the fourth-tallest railway bridge in the USA and listed on the National Register of Historic Places. Restoration had begun in 2002, but in 2003 a tornado struck the bridge, prompting a large section to collapse.

Corrosion of the anchor bolts pinning the bridge to its

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foundations contributed to the failure. The bridge– originally built in 1882 by the New York & Erie Railroad to serve lumber mills in the northwest of the state – was called the Eighth Wonder of the World. In 1900 it was dismantled and rebuilt using steel so that it could carry heavier trains. It was 301ft (92m) tall and just over 2ft (625m) long.

BRIDGES S PAN N I N G T HE WO R LD / Trestle B r i d g e s

BRI DGE S S PANNI NG TH E WORL D / Trest le Bridges

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BRIDGES S PAN N I N G T HE WO R LD / Trestle B r i d g e s

Viaducto La Polvorilla, San Antonio de los Cobres SALTA, ARGENTINA

The viaduct carries the world’s fifth-highest railway line across the Andes. The railway, started in 1921, links northern Argentina with Chile. It has 29 bridges, 21 tunnels, 13 viaducts, 2 spirals and 2 zigzags, climbing in a steady but never steep grade. The engineer for the line was the American Richard Maury. Maury, who took Argentine nationality, had first worked on the Pennsylvania Tunnel from New York City to New Jersey and arrived in 1906 to work for the national railway company of Argentina.

He became an expert in mapping routes for mountain railways. The train is known as the Tren a las Nubes (Train to the Clouds). It now takes tourists from Salta on a 15-hour excursion to the viaduct.

The viaduct stands 13,850ft (4,220m) above sea level. Built on a curve, and 735ft (224m) long and 230ft (70m) high, the viaduct was finished in 1932, but the complete railway was not inaugurated until 1948.

BRI DGE S S PANNI NG TH E WORL D / Trest le Bridges

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CONTEMPORARY BRIDGES In the 1990s the approach of a new century opened up an era of collaboration between engineers and architects in producing adventurous and graceful bridge designs. The trend was set by Santiago Calatrava, Spanish by birth, who trained as both engineer and architect and also works as a sculptor.

He pioneered a new vocabulary of expressive shapes, transforming many of his bridges into works of art. He brought a new three- dimensional form to bridge design and arch trusses surged sideways as well as upwards. He also introduced a bold asymmetry into some of his designs, notably the harp-like Puente del Alamillo in Seville which was completed in 1992.

This was a cable-stayed bridge and over the last 20 years cable-stayed bridges have replaced suspension bridges as the favoured technology for major crossings. As cablestayed spans were shorter, and their relative cheapness a principal attraction, this did not augur well. The involvement of architects changed this and cable-stayed bridges of dazzling beauty are now being built. Most acclaimed of all is the Viaduc de Millau designed by the architect Norman Foster working with the engineer Michel Virlogeux.

In Britain and Ireland the architectural practice Wilkinson Eyre is producing a stunning series of designs, superbly tailored to their landscaped surroundings. Like the Viaduc de Millau their bridges touch the ground lightly. Wilkinson Eyre also designed the most acclaimed of recent lift bridges, the moving eye footbridge across the Tyne between Newcastle and Gateshead. At night a new fascination is added by a constantly changing play of coloured light. This new night life of bridges is an enlivening element in a city, seen at its most

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glorious in the firework displays on Sydney Harbour Bridge ushering in the New Year.

At a simple but practical level bridge-building plays a key role in providing lifelines for remote and struggling communities. Here the world’s leader is Toni Ruttimann, who has built more than 600 suspension and hump bridges in South America and Southeast Asia, across mountain ravines and river deltas, none costing more than $500.

Bridges have also been revived as an element in landscape gardening, most notably by Charles Jencks in the grounds of his home, Portrack House, in Scotland. Another inventive and delightful conceit is the Murinsel, or Shell Bridge, in Graz, forming an island in the middle of a fast-flowing river. A new generation of moving bridges, all innovative in technique and design, are further testimony that the twenty-first century is set to be a new, great age of bridge-building.

R I G H T Murinsel, or Shell Bridge, Graz, Austria

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Longest Suspension Bridges

The world’s longest suspension bridges are measured by the length of the deck suspended between the two towers. The Golden Gate Bridge in the USA with a 4,200-ft (1,280-m) span held the record in 1937. It was overtaken by the VerrazanoNarrows Bridge, also in the USA, with a 4,260-ft (1,298-m) span, in 1964, and this by the Humber Bridge in England, with a 4,626-ft (1,410-m) span, in 1981. The AkashiKaikyō Bridge in Japan, with a central span of 6,532 ft (1,991 m), became the record holder in 1998.

Engineers – and politicians – continue to plan still longer suspension bridges which may or may not prove practical to build and finance.

One of the most ambitious is the proposal for a suspension bridge across the Straits of Messina, linking the toe of Italy in Calabria to Sicily. This requires a 10,827-ft (3,300-m) span to cross a deep channel and was cancelled in 2006 amidst controversy over the cost.

Preliminary work began again in 2009 but four years later the project was again cancelled.

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Another major project, for a bridge with a 9,800-ft (3,000-m) span across the Sunda Strait linking Java to Sumatra has been approved by the Indonesian Government. The project which originated in 1960 was halted in November 2014.

A B OV E Golden Gate Bridge, San Francisco, California, USA R I G H T Akashi-Kaikyö Bridge, Honshu and Awaji, Japan

BRIDGES S PAN N I N G T HE WO R LD / Long est Sus p e n si o n B r i d g e s

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Akashi-Kaikyõ Bridge, HONSHU AND AWAJI, JAPAN

The centre span of 6,532 ft (3,911 m) makes the Akashi-Kaikyõ Bridge, also known as thePearl Bridge, the longest suspension bridge in the world. While it was still under construction the Kõbe earthquake on 17 January 1995 moved the two towers apart so that 3 ft (1 m) had been added to the length of the main span from the original design. The six-lane road bridge across the Akashi Strait, with three spans in all, connects Kōbe on the main island of Honshu and Iwaya on Awayi Island. The bridge took almost 12 years to build and was opened for traffic in 1998.

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BRIDGES S PAN N I N G T HE WO R LD / Long est Sus p e n si o n B r i d g e s

Xihoumen Bridge, Zhoushan ZHEJIANG, CHINA

The world’s second-longest suspension span is the Xihoumen Bridge of 5,413 ft (1,650 m), built in the Zhousthan Archipelago, the largest offshore island group in China. The bridge opened in December 2007 after suffering slight damage from a shipping collision the month before.

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BRIDGES S PAN N I N G T HE WO R LD / Long est Sus p e n si o n B r i d g e s

Great Belt Bridge GREAT BELT STRAIT, DENMARK

The world’s third-longest suspension bridge is in Denmark. Part of the Great Belt Fixed Link, joining the islands of Zealand and Funen, the East Bridge section is a road bridge linking Zealand and the island of Sprogø in the middle of the strait. It is built of concrete and steel and has a central span of 5,328 ft (1,624 m). It opened in 1998.

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Santiago Calatrava The grand romantic among contemporary bridge designers appropriately bears the names of two Spanish medieval orders of chivalry. He is unusual too in having qualified as both architect and engineer, making his bridges the product of a single mind.His numerous bridges have strongly expressive shapes making use of supple, muscular curves. They come in many different forms: suspension and cable-stayed bridges, bowstring truss bridges and moving bridges. Most have an all-white livery emphasizing their clean lines, but recently bold colour has been used too.

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Puente de la Mujer BUENOS AIRES, ARGENTINA

The Woman’s Bridge is a swing bridge 558 ft (170 m) long serving Dock 3 of the Puerto Madero development on the bank of the Rio de la Plata. Construction of the port had begun in 1887 by a local businessman, Eduardo Madero. It slowly decayed after a new city port was completed in 1926 until, in 1989, a development corporation was established to regenerate the area. Nearby warehouses have been transformed into smart apartments and are linked by the new bridge to an area of thrusting high-rise development.

BRIDGES S PAN N I N G T HE WO R LD / Sa nti a g o Ca l at rava

Calatrava designed the bridge with a single needle-like mast, which rotates with the 336 ft (102.5 m) central section of the bridge, allowing vessels to pass in less than two minutes. The steel needle has a concrete core. Inclined at a 39â ° angle, it anchors the suspension cables carrying the deck.

The bridge was manufactured by the Urssa factory in the city of Vitoria in the Basque region of Spain. The bridge was begun in 1998 and inaugurated on 20 December 2001.

Chords Bridge JERUSALEM, ISRAEL

Chords Bridge, Jerusalem, Israel Also known as the Bridge of Strings, thanks to its resemblance to a harp, this is a light-railway bridge at the western entrance to the city.

The single, angled pylon and multiple cable stays develop the form of Calatrava’s giant Puente del Alamillo in Seville, Spain. While the Seville bridge is straight, the Jerusalem bridge is built on a scimitar-like curve so that the cables form constantly changing patterns from different viewpoints. The mast, 387 ft (118 m) high, supporting 66 steel cables, was the tallest structure in Jerusalem at the time of its completion in 2008. The bridge is extensively clad in Jerusalem stone.

The Chords Bridge has been likened to a desert tent while the strings, according to Calatrava, symbolize the harp of King David, founder of the city. Calatrava says he was invited by the city’s mayor, Ehud Ollmert, to design the ‘most beautiful contemporary bridge’, but the strikingly futurist design of the bridge has excited controversy from those who feel it is out of its element and the site too cramped. The slenderness of the pylon is in striking contrast to the muscularity of earlier Calatrava bridges, creating a tensile grace that is a triumph of the minimalist, light-touch approach. A pedestrian bridge with glass floor and balustrade runs along the inner side of the bridge connecting with the central bus station.

Begun in 2005, the bridge was inaugurated on 25 June 2008 and the new light railway, the Red Line, came into operation on 19 August 2011. The final cost was around $70m.

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Chords Bridge JERUSALEM, ISRAEL

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BRIDGES S PAN N I N G T HE WO R LD / Sa nti a g o Cal at rava

Peace Bridge ALBERTA, CANADA

This elegant sleeve design, very different from earlier Calatrava bridges, arose from strict requirements that it should be built without piers in the water, minimizing the ecological footprint, and that the height should be kept low on account of a heliport nearby. The City of Calgary commissioned the bridge to serve an increasing number of people commuting to work on foot and by bicycle, many using the Bow River pathway and crossing the river from the Sunnyside community to downtown. It is used by an estimated 6,000 people daily.

Good lighting and visibility was crucial to safety in the evening. It is a helical steel structure, tubular in form, with glass panels providing light and visibility. The central bicycle lanes are flanked by walkways providing panoramic views over the river. The internal width is 20 ft (6.3 m) and the length of the span over the river 413 ft (126 m). The tubular structure was manufactured in Spain and shipped to Calgary. Assembly of the bridge pieces began in the autumn of 2010 and the structure put in place over the river in November 2011. It opened on 24 March 2012. While most of Calatrava’s bridges are white, this catches the eye with its bold lattice pattern, the red echoing the colour of the Canadian and Calvary flags.

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Alain Spielmann Alain Spielmann is a French architect who over a long career has added a new dimension to bridge design. He believes a bridge is more than a link between two points and should celebrate the crossing itself – for example the fine elevated view of a river from many bridges. His bridges often incorporate viewpoints where people can pause or even come to sit and enjoy the bridge and the scenery.

Pont des Eyzies-de-Tayac-Sireuil DORDOGNE, FRANCE

This undulating footbridge was added by Alain Spielmann to an existing stone bridge. It is constructed with a timber deck 7½ ft (2.3 m) wide slightly below the roadway, giving the main bridge a dramatically waving silhouette on one side. Work was completed in 1999.

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BRIDGES S PAN N I N G T HE WO R LD / Contemporar y B r i d g e s

Viaduc de la Grande Ravine TROIS BASSINS, RÉUNION

The challenge on this French island in the Indian Ocean was to design an elegant bridge that would cause the least disturbance to the astonishing scenery of a deep, thickly wooded ravine which drops 532 ft (162 m) to a narrow valley floor.

The bridge is part of a new 30-mile (50km) highway, the Route des Tamarins, which crosses numerous ravines and required three tunnels and four major bridges of which this is the longest. The design adopted is a 940-ft (286.5m) box girder supported by two slender struts at a shallow 20⁰ angle, anchored into concrete abutments. To construct the main span without using wind-prone towers, the French bridge construction company Freyssinet designed a cable-stayed system to support two half decks as they were launched out from either side of the ravine. The bridge was completed in 2009.

Pont de Saint-Pritz, Laval MAYENNE, FRANCE

This muscular steel bridge of 1990–97 illustrates Alain Spielmann’s belief that bridges should offer a chance to enjoy the beauty of the surrounding scenery and the new views opened up from the bridge itself. He has taken the idea of the small refuges on medieval bridges – which allowed those on foot to pause with their goods while horses or carts passed by – and introduced pairs of generously sized semi-circular belvederes or balconies on both sides of the piers supporting the main span. The three spans of 144 ft (44 m), 236 ft (72 m) and 144 ft (44 m) create a bridge of 525 ft (160 m) in length. The belvederes are a continuation of elements from earlier bridges by Spielmann at Guétin, Dole and Blois.

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Wilkinson Eyre

Gateshead Millennium Bridge

As a boat-builder takes pride in ‘throwing’ a beautiful curve so Wilkinson Eyre have proved masters of elegant, often attenuated line. The Gatwick airport air bridge rises in the gentlest of arcs while the Gateshead Millennium, or Blinking Eye, Bridge has the lines of a human eyelid. They have moved from the traditional half circle and ellipse to serpentine curves, first concave then convex

There is no more thrilling sight in an English city than the river bridges in Newcastleupon-Tyne at dawn or dusk. The latest is an adventurous moving bridge linking Gateshead with Newcastle-upon-Tyne which opens and closes like a human eyelid. It takes just four minutes for the Blinking Eye Bridge to open and four to close again (with a short stop in between), gliding through the air in impressive and almost eerie silence.

TYNE AND WEAR, ENGLAND

The bridge, which opened in 2001, has twin decks: one for pedestrians and the other for cyclists. The cycle deck is formed of an open aluminium grille which allows rain to run through and creates an intriguing halo when it is silhouetted against the sky as the bridge opens. ‘Every element is functional but designed to contribute aesthetically,’ says Martin Knight, the project architect.

The two decks are separated by what the architects call a stainless-steel ‘hedge’ with inbuilt seating on the pedestrian side. This acts as a windbreak, reducing the speed of the wind and preventing buffeting. It neatly contains the lighting, making the whole bridge glow at night.

The soaring main arch is illuminated from the ends by iridian light-fittings evolved for rock concerts. These provide constantly changing colour which can be orchestrated into complex patterns by a computer.

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BRIDGES S PAN N I N G T HE WO R LD / W i lki ns on E yre

BRI DGE S S PANNI NG TH E WORL D / Wil kin s on E yre

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