BUILDING BRIDGES BASICS by Prof/Dr ROLAND PAXTON MBE FICE FRSE School of the Built Environment Heriot-Watt University A presentation at Burntisland Primary School 16 Jan 2014 Context: Industrial Revolution Transport Infrastructure in 1750-1890 + a peep at the present day! [c.1800 a horse pulled about 1t on a road 10t on a railway and up to 100t on a canal]

Roads - poor state, improved by Telford & McAdam - neglected as railways developed from 1830 – improved in motor age from 1900

Canals – Forth & Clyde (ship) 1790, Crinan (ship) 1809, Caledonian (ship) 1822, Edinr & Glas Union 1822 – superseded by railways

Railways – Kilmarnock & Troon 1811 (locomotive 1816) - 1831 Edinr & Dalkeith, Glasgow & Garnkirk – nationwide by1890

Harbours - improvements at Glasgow, Dundee, Aberdeen, Leith and many smaller ports – steam navigation developed from 1820

Bridges were an essential component of infrastructure

Bridges usually made of: WOOD STONE [& cement concrete] IRON [& steel] Steel-reinforced CONCRETE

The internal forces to which these materials are subjected under load to achieve a desired span are [as demonstrated by ruler] either:

TENSILE (pulling apart) COMPRESSIVE (pushing together) or a combination of both

Harnessing these forces satisfactorily depends on the properties of the materials and how they are deployed in the structure. There are 3 main bridge types: MAIN BRIDGE TYPES BEAM, ARCH, & SUSPENSION [and combinations]

Arrows show the directions of the forces on ground which must be firm enough to resist them. Examples of these types are: Edinr & Dalkeith Railway Braid Burn c.i. beam bridge 1831 being raised in 2001 TERMS

Pons Fabricus in Rome – more than 2000 years old. Arch bridges were and, probably still are, the most common type of permanent bridge, but from c.1890 the availability of steel and concrete resulted in many beam bridges being erected

Voussoir joints radiate from mid-span at about water level Carr Bridge 1717 in August 2012 Traditional arch construction of the kind used for the rest of the century in the Highlands Arch bridge model assembled in a few minutes – try making one!

Arch joints radiate to a point here ̥

SUSPENSION BRIDGE CHAIN DEMONSTRATION

IMAGINE THE CHAIN BETWEEN ITS SUPPORTS REPRESENTS THE WEIGHT OF BRIDGE

WHEN THE CHAIN DIP IS SAY 1/3 SPAN THE TOTAL LOAD IS EASILY SUPPORTED BUT REQUIRES TALL TOWERS

WITH 1/20th SPAN DIP A LARGE CHAIN FORCE IS NEEDED IN SOME EARLY DESIGNS MOST OF WHAT WOULD NOW BE REGARDED AS AN ACCEPTABLE DESIGN STRESS IN THE CHAIN WAS USED JUST TO SUPPORT ITS OWN WEIGHT!

2000 ft span -1/20 dip Stirling Bridges 1214, 1832, 1880-1900 – note bridge types Leaderfoot Viaduct 1865 125ft high Drygrange Br 1780, 105ft span – largest Scottish arch then

Bypassed 1973 by steel box beam bridge 186ft span State in 1995

Restoration nearly completed in 1996 Restored 1996 Kilmarnock & Troon Railway – opened 1811 - Laigh Milton Viaduct – the world’s earliest surviving viaduct on a public railway – collapse begun but conserved 1995-96 for £1.1m Laigh Milton Viaduct on Kilmarnock & Troon Railway in 1811

3ft long iron plate rail of Jessop ˄ ‘Killingworth’ type of type fixed to 15inx15inx10in locomotive called ‘The Duke’ stones at each end to form the was used in 1816 to haul coal railway. Rails broke under the engine’s weight and vertical piston action and horse traction was resumed resumed Laigh Milton Viaduct under conservation in 1995 Ballochmyle Viaduct 1850 – 181ft (55m) span 176ft (53.5m) wide - largest masonry railway arch in UK - Engineer John Miller © RCAHMS

˂˂˂˂˂Royal Border Viaduct 2152ft long - directly connected London and Edinburgh by railway in 1850

Royal Tweed, max span 361ft reinforced concrete – longest of type in UK in 1928

Berwick Old 1610-34, 1164ft long, 17ft wide, max span 74ft

Bridges at Berwick-upon-Tweed Note developments in type over three centuries and arch spans becoming five times longer ˂ Paxton House

From 1820-26 the world’s longest span bridge for carriage traffic - now the longest serving in this capacity at 193 years Union Bridge R. Tweed near Paxton in 2013. Span 437ft; dip 26ft Engineers: Capt S. Brown John Rennie UNION BRIDGE 1820 Note state of bridge on 5 October 2013 and one of four replacement hangers and caps to ˂ ˂ low chain pairs near mid-span

Forth Bridge under balanced cantilever construction in 1888 ˂ties - in tension ˂tubes – in compression

suspended span

weight weight

Human cantilever (anthropomorphic) Forth Bridge model - tubes in compression , top members in tension

Forth Bridge

Joining steelwork by means of hydraulic riveting near cantilever top in 1888 caisson used to found piers The 2-mile long Tay Bridge opened 1878, then the world’s longest railway bridge. Engineer:T. Bouch 85 spans (67-164ft) &13 taller navigation spans up to 245ft

West ˃˃˃˃˃˃˃ Tay Bridge overturned in Force 10 gale 28/12/1879 Pier bases bolted through only 2 courses of masonry Tay Bridge girder on its side with carriage on sand bank after disaster – January 1880 Tay Bridge as rebuilt by 1887 My first ICE/ASCE IHCEL plaquing 12 Septr 1987 1987 Coalbrookdale Bridge 1781 – span 100ft 6in, 6in greater than central arch of Blackfriars Bridge (London 1769). Made practicable by improved iron making. The world’s first significant iron bridge - semi-circular arch elevation Linlathen East bridge c.1804 Scotland’s oldest iron Bridge?

Linlathen Iron Bridge c.1804 being tested at 5kNm² loading 1812 – 150ft span – Telford/Hazledine – First of new type of iron arch achieving spans greater than could then be managed in stone. Followed by Craigellachie Bridge in 1814 Craigellachie Bridge 1814 of 150 ft span in August 2012 Glenfinnan Viaduct - 21 mass concrete arches of 50ft 15m span

ICE/PHEW centenary Jacobite ‘Special’ in 1997 Loch-nan-Uamh Viaduct c1899 - mass concrete Horse & cart remains found by a radar scanning project in 2001

Rhibuie Road 1819 about 2km from Cluanie Inn. One of more than 1000 Highland bridges erected under Telford’s direction Skye Bridge 1995 - prestressed concrete crossing c.500m gap and Kyleakin Lighthouse 1857 Glencoe Road Improvement c.1932. Reinforced concrete beam bridge now replaced

Dunkeld Bridge 1808 over River Tay Telford’s largest Highland bridge 7 arches – largest 90ft span – hollow spandrel construction – parapet on arc of great radius Dunkeld Bridge 1808 (Telford) – interior Hollow to reduce the weight on foundations and facilitate inspection Central Scotland Canals 1768-2013 Engineers:Smeaton, Watt, Mackell, Rennie, Baird, Telford In 1858 Campsie Branch of Edinburgh & Glasgow Railway routed through arch. Photo: c.1890.

Forth & Clyde Canal:

Luggie Aqueduct - Scotland’s first Erected 1772-74 Forth & Clyde Canal ‘Swift ‘ boat c.1830

˂ E&G Union Canal level FALKIRK WHEEL˃I F & C profile Grangemouth end

F & C Top of typical opening bridge – masted ships Accommodated – Smeaton drawing c1770 Forth & Clyde Canal ˂˂ Glasgow

Union Canal Edinr˃˃ Millennium Canal Forth & Clyde and Union Canal Regeneration 11-lock [110 ft] connection 1822 Falkirk Wheel 2002 Falkirk Wheel

Two 35m long rotating arms. c.1800t loads with up to 4 boats - essentially balanced but driven by small motors to overcome friction and wind. Water loss minimal We’ve come a long way in Scotland from pre-1800 stone arches of up to 105ft [32m] span to steel masterpieces i.e. 1871 – Tay 245ft [75m] 2 miles long 1890 - The Forth Bridge main spans 1710ft [521m] 1964 - Forth Road Bridge main span 3300 ft [1005m] [2016] Third Forth Crossing 2 main spans 650m [2130ft]

Note the slenderness of both bridges