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Beam bridge: bridge deck in bending deck could be solid beam eg concrete, or box section steel or concrete box section, or truss Simple beam bridge: stone slabs on stone supports Dorset

Engineering Structures 101

Bridges

Compiled by Professor Martin Fahey School of Civil and Resource Engineering The University of Western Australia

Pons Augustus, Rimini, Italy, AD 14 Typical

Roman circular arch bridge

Arch Bridges:

Types of Arches

Pont Neuf (“New Bridge”), Paris, 1578 / 1604 Circular Arch Bridge.

Pont d’Avignon, France, River Rhone, 1188 Frére Benoît (St Bénézet), leader of “Brothers of the Bridge” [revival of the Roman Guild of Bridge Builders Fratres Pontifices (Ponti-fices = bridge-builders) or Frères Pontifes] Destroyed deliberately by one of the Avignon Popes for

defence reasons Arches made up of three arcs of a circle

Ponte Vecchio (“Old Bridge”), Florence, 1345 Taddeo Gaddi

Only bridge over the River Arno not destroyed by retreating German Army in WW2 A segmental arch bridge (arches are segments of

circles)

Pont de la Concorde, Paris, built by Perronet, 1791 Segmental arches (rubble from La Bastille used to construct the piers)

Construction of Pont de la Concorde, Paris

Common Bridge Types Note that in all cases, the main elements can be solid

or trusses.

Beam bridge:

bridge deck in bending deck could be solid beam (eg concrete), or box section (steel or concrete box section), or truss

Simple beam bridge: stone slabs on stone supports (Dorset, England)

Britannia Bridge, Menai Straits, Wales, 1850

First railway bridge designed as deep box girder (two side-by-side rectangular tubes each containing a single rail line) The designer (Robert Stephenson) included towers for adding suspension chains if necessary Main spans 460 t wrought iron, total span 461 m consisting of two continuous wrought

iron tubes side-by-side Destroyed by fire in 1970 by two boys!

14th Street Bridge over the Potomac River Continuous riveted steel girders Note the absence of

internal hinges, and the roller supports at the piers

Continuous steel plate girder bridge This 3-span bridge has a composite section consisting of the steel

girder and the concrete roadway on top (Near Lausanne, Switzerland)

Continuous steel box girder bridge over the Rhine, Bonn, Germany, 1967 Note varying

depth of the box sections

Steel box girder bridge in Koblenz, Germany, collapsed during construction due to buckling Similar collapses occurred at Millford Haven, Wales, 1970 (4 deaths), and the Westgate Freeway Bridge,

Melbourne, 1970 (35 deaths), both designed by Freeman Fox

Concrete box section beam bridges: one

of the Florida Keys bridges, USA (above), and the Linn Cove Viaduct, North Carolina, USA (right)

(The Windan Bridge over the Swan River

on the Graham Farmer Freeway is a concrete box section bridge, but constructed by incremental launching)

Mt Henry Bridge Widening

Simply-supported box-section prestressed concrete bridge, BART system, San Francisco

One way of strengthening a simple beam is

to use a truss

Railway engineers in the US adopted wooden truss methods for bridge construction for the development of the railway system in the US Pictures show some of the (many) types of trusses that were developed

Fink “through truss” 1868, Ohio, US Compression columns are

hollow wrought iron tubes

Bollman Truss Bridge, Laurel, Maryland, USA The existing bridge was built in 1869 along the B&O Main Line , and moved to the current location in 1888

Crumlin Viaduct, Ebbw Vale, Wales Designed by Brunel(1806-59), this early railway viaduct is interesting in that it is constructed entirely from pin-connected iron members Deck support is by Warren truss elements, simply supported

Lift bridge, Sacramento River Delta A Warren truss with verticals is used throughout

Lift span is simply supported The double spans on each side are determinate due to

internal pins (Near Rio Vista, California)

Simply-supported steel truss railway bridge, UK

Steel Pratt truss spanning between columns

Merchant Exchange Building

The outside trusses of this building consist of X-braced 50-

ft square panels The clear span between supporting

columns is 100 ft, and the end of the building (foreground) has a 50-ft overhang (Chicago, Illinois)

Trusses are common elements

in many types of buildings

Circular Arch Bridge: Pons Fabricus (Ponte Fabrico), Rome, Tiber Built in 62 B.C by L.Fabricius Oldest surviving bridge in Rome Still used by pedestrians Note the hole through the centre - relieved water pressure in flood

conditions

Earliest existing cast iron bridge: Ironbridge, River Severn, England,

built by Abraham Darby, 1779.

Ironbridge, River Severn, England, built by Abraham Darby, 1779

Members in compression; connections using dowels etc.

Buildwise Bridge, River Severn, Thomas Telford (1796): cast-iron

bridge half the weight of the Ironbridge

Craigellachie Bridge over the River Spey An historic bridge, being the first such wrought iron truss arch bridge to be built by Telford in 1815

St Louis Rail Bridge, St Louis USA, Mississippi River James Eades, 1874 First true steel bridge Three spans, each 152 m Foundations were a major technical challenge (see next

slide)

Caisson used to construct piers of

St Louis Bridge Deepest point had 23 m water depth and 30 m below riverbed (50 m, or 5 atmospheres, of water pressure)

Men worked in pressurised chamber at pressures up to 240 kPa (2.4 atmospheres) Because

of this, there were 91 cases of the bends, 2 crippled for life, 13 deaths Would have been much worse except they realised slow decompression and short shifts were necessary

20 m

40 m

Gateway Arch, St Louis,

USA

This free-standing arch is 630

ft high and the world's tallest

Built of triangular section of double-walled stainless steel, the space between the skins being filled with concrete after each section was placed

Shape is almost perfect

“inverted catenary”

Base of the Gateway Arch The size of cross-section of the arch rib can be seen by comparison with the figures on the ground The section of the arch

at the base is an equilateral triangle with 90 ft sides The arch is taken 45

ft into bedrock (St Louis, Missouri)

Construction of the Gateway Arch (St Louis, Missouri) Arch is not

stable on its own until complete.

Interior of Carmel Mission Built in 1793 it

is an interesting design in that the walls curve inward towards the top, and the roof consists of a series of inverted catenary arches built of native sandstone quarried from the nearby Santa Lucia Mountains

(Carmel, California)

Garabit Viaduct, River Truyère, St Flour, France (Viaduc du Garabit)

Built by Gustav Eiffel, 1884 Last (and best) of his many wrought iron bridges Two-hinged arch design became standard for many to follow Note shape of the arch

Garabit Viaduct, River Truyère, St Flour, France (Viaduc du Garabit).

Built by Gustav Eiffel, 1884 Last (and best) of his many wrought iron bridges Two-hinged arch design became standard for many to follow This photograph taken September 2002.

Garabit Viaduct, Gustav Eiffel, 1884 The hinge at one end of the

arch.

Garabit Viaduct, Gustav Eiffel, 1884

The bridge has been repainted recently to a colour that matches the original colour selected by Eiffel.

(photograph taken 2002)

stability) and are narrow, but deep, at the top

Garabit Viaduct, Gustav Eiffel, 1884

Construction of the Garabit Viaduct Hinged arch segments were tied back to the towers using cables until they joined together Compare with Sydney Harbour Bridge

construction (see later)

Pia Maria Bridge, Porto, Portugal

Gustav Eiffel

Eiffel Tower, Champs du Mars, Paris 1889 Grew from Eiffel’s bridge-building expertise Was world’s tallest structure for 40 years 300 m tower built of puddled iron The

“arch” shape at the bottom is purely decorative.

Graceful ironwork arches in the Musée d’Orsey, Paris, which is now the most beautiful museum in Paris (more manageable in short visit than the Louvre), having being converted

from a disused railway station

Different types of arch bridge configurations.

Pont Alexandre III, Paris, 1896 / 1898 (Widely regarded as the most beautiful of all of the bridges of Paris This photograph pre-dates the painting of the bridge for the 1989 bi-centenary of the French Revolution - much gold leaf added

then)

Steel arch of Pont Alexandre is a 107 m span ellipse with a rise/span ratio

of 1/17 Note the central hinge

Pont Alexandre III Detail of bridge structure Note the the casting over the gap in the parapet and deck expansion joint at the top of the slide, and the gilt ornamentation covering the support pin at the end

of the arch rib

Without appropriate deck discontinuities, the bridge would not behave as a simple 3-hinged structure.

Pont Alexandre III Detail of bridge structure Note the gilt ornamentation covering the support pin at the centre of the arch.

Pont Alexandre III Re-gilding carried out for the bi-centenary of the French Revolution (1788 – 1988) Dome in the background is Les

Invalides, the site of the tomb of Napoleon I

Sydney Harbour Bridge, completed 1932

Almost longest arch bridge in the world (Longest is Bayonne Bridge, New York, completed

a few months earlier, which is 1.5 m longer) Two-hinge arch The span between abutments

is 503 m to allow unobstructed passage for ships in Sydney Harbour It contains 50,300 tons

of steel (37,000 in the arch) It is the widest (49 m) bridge in the world

Sydney Harbour Bridge, completed 1932

Sydney Harbour Bridge, completed 1932

Stages of construction of the Sydney Harbour Bridge

Plougastel Bridge, River Elorn (Brest), France, 1929 Built by great French engineer

Eugène Freyssinet, pioneer of reinforced concrete construction

For construction of the arches of the Plougastel Bridge, Freyssinet built a single timber form, mounted on floating concrete caissons, which was floated into position, and the

caissons sunk onto the bottom

Plougastel Bridge: Picture shows one arch completed, and the timber form in place for

construction of the second arch

Salginatobel (Salgina Gorge) Bridge (1930) in the Davos Alps, Switzerland This 3-hinged concrete arch bridge designed by Robert Maillart has a span of 90 meters and a rise of 13 meters The arch rib increases in depth from the supports to the quarter-span points where it becomes integral with the deck, and tapers to the mid-span hinge This bridge was designated as an International Historic Civil

Engineering Landmark in 1991.

Schwandbach Bridge, 1933, Switzerland Concrete arch bridge designed by Robert Maillart Note the

sloping walls supporting the deck off the arch

Two slender fixed arch concrete highway bridges, crossing the Moesa Torrent, on the San Bernardino Pass road, Switzerland Designed by Professor Christian Menn, they are fine examples of modern concrete bridge design Arch span: 112 meters, column spacing on both approaches: 17 meters Scale

of the structure can be seen from the figure, bottom left.

Bixby Creek Bridge, Carmel, California, 1932 This fixed reinforced concrete arch

bridge spans 218 m across a deep river valley

Fursteuland Bridge, River Sitter, Switzerland A fixed reinforced concrete arch bridge,

crossing the valley in a single 135 m span

Gladesville Bridge, Sydney, Australia, 1964 Concrete arch bridge

Krk Bridge, Croatia (1964) World’s longest span concrete arch bridge (390 m)

Wenner Bridge, Austria Timber arch bridge

Menai Straits Bridge Linking Wales and Isle of Anglesea Designed by Telford and completed in 1826 First major suspension bridge Span of 176 m was unheard of for any bridge and the chains were made of a new material: wrought iron links, all individually tested Span and 33 m headroom were required for shipping Following this

example, many chain bridges were built

Menai Straits Bridge, 1826

Menai Straits Bridge

Linking Wales and Isle of Anglesea This bridge, designed by Telford and completed in 1826 could be described as the first major suspension bridge The span

of 176 m was unheard of for any bridge and the chains were made of a new material:

wrought iron links, all individually tested Span and

33 m headroom were required for shipping

Following this example, many chain bridges were built

Clifton Bridge, River Avon near Bristol, England Designed by I.K Brunel in 1830, but not completed until 1864, five years after his death Main span 214 m; road 73 m above the river Telford advised Brunel against this design on account of its windy location, and the wind problems he (Telford) had with the Menai Straits Bridge

The chain (really 3 chains each side) used for the Clifton Bridge came from an earlier bridge

Brunel had designed, the Hungerford Bridge in London (1845)

Clifton Bridge, River Avon near Bristol, England Designed by I.K Brunel in 1830, but not completed until

1864, five years after his death Main span

214 m; road 73 m above the river Telford advised Brunel against this design on account

of its windy location, and the wind problems

he (Telford) had with the Menai Straits Bridge

Hammersmith Suspension Bridge, 1887, London, England Main span of 122 m

Double chains used in the Hammersmith Suspension Bridge, 1887, London, England

Brooklyn Bridge over the East River, New York 487 m span Designed by John Roebling, completed by his son (Washington Roebling) in 1883: First bridge to use steel wire suspension cables Much of the difficulty of construction was associated with the caissons

required to form the tower foundations

Brooklyn Bridge, New York

George Washington Bridge, New York 1931 Span (1067 m) was 518 m longer than

the record at the time

George Washington Bridge, New York 1931 Towers originally meant to be clad, but people

grew to like the look of the lattice structure, and so it was left as is

George Washington Bridge, 1067 m span

Golden Gate Bridge, 1937 Main span of 1280 m was the longest single span at that time and for 29 years afterwards Principal designer Joseph Strauss had previously collaborated

with Ammann on the George Washington Bridge in New York City

Towers are 305 m high, the tallest of

their time

Golden Gate Bridge, 1937 View from the top of one of the towers, showing the main cables and suspender cables Section of the cable, showing it to be made up of a bundle

of small cables

Golden Gate Bridge, 1937 Cable “saddle” on top of one of the towers

Forth Road Bridge, over Firth of Forth, Scotland Opened on September

4,1964.

Following sequence of slides illustrates some stages of construction

The wires are 5 mm diameter with an ultimate strength of 1500 MPa Each ‘strand’ contains 314 wires

, and there are 37 stands in each cable: 11,618 wires and 600 mm diameter

Forth Road Bridge View from the top of the south main tower The so-called 'cable-spinning' operation, originally devised by Roebling, consists of unreeling a continuous length of wire back and forth across the bridge until a 'strand' is built up The wire is looped round the wheel of the traveling sheave (shown)

which is connected to an endless hauling rope

Forth Road Bridge Looking up the cable to the south tower saddle Note the bundles or 'strands' of wires that will form the finished cable The individual wires are colour-coded

to assist in the spinning operation

Forth Road Bridge

Cable saddle at the top of the side tower

Note the size of the saddle which has to take the resultant vertical component of cable tension due to the angle change in the cable at this location