Construction Forth Bridge

1 construction

1.1 preparations
1.2 movement of materials
1.3 circular piers

1.3.1 inchgarvie
1.3.2 fife
1.3.3 queensferry


1.4 approach viaducts
1.5 building cantilevers
1.6 opening
1.7 accidents , deaths

construction

the bridge under construction, viewed south queensferry

the bill construction of bridge passed on 19 may 1882 after eight-day enquiry, objections being rival railway companies. on 21 december of year, contract let sir thomas tancred, mr. t. h. falkiner , mr. joseph philips, civil engineers , contractor, , sir william arrol & co.. arrol self-made man, had been apprenticed blacksmith @ age of thirteen before going on have highly successful business. tancred professional engineer had worked arrol before, leave partnership during course of construction. steel produced frederick , william siemens (england) , pierre , emile martin (france). following advances in furnace design siemens brothers , improvements martin brothers, process of manufacture enabled high quality steel produced quickly.

preparations

the bridge under construction

offices , stores erected arrol in connection bouch s bridge taken possession of new works, , expanded considerably on time. accurate survey taken mr. reginald middleton, establish exact position of bridge , allow permanent construction work commence.

the old coastguard station @ fife end had removed make way north-east pier. rocky shore levelled height of 7 feet (2.1 m) above high water make way plant , materials, , huts , other facilities workmen set further inland.

the preparations @ south queensferry of more substantial character, , required steep hillside terraced. wooden huts , shops workmen put up, more substantial brick houses foremen , tenements leading hands , gangers. drill roads , workshops built, drawing loft 200 60 feet (61 18 m) allow full size drawings , templates laid out. cable laid across forth allow telephone communication between centres @ queensferry, inchgarvie, , fife, , girders collapsed tay bridge laid across railway west in order allow access ground there. near shore sawmill , cement store erected, , substantial jetty around 2,100 feet (640 m) long started in 1883, , extended necessary, , sidings built bring railway vehicles among shops, , cranes set allow loading , movement of material delivered rail.

in april 1883, construction of landing stage @ inchgarvie commenced. extant buildings, including fortifications built in 15th century, roofed on increase available space, , rock @ west of island cut down level 7 feet (2.1 m) above high water, , seawall built protect against large waves. in 1884 compulsory purchase order obtained island, found available area enclosed 4 piers of bridge insufficient storage of materials. iron staging reinforced wood in heavily used areas put on island, covering around 10,000 square yards (8,400 m) , using on 1,000 tonnes (980 long tons; 1,100 short tons) of iron.

movement of materials

the bridge uses 55,000 tonnes (54,000 long tons; 61,000 short tons) of steel , 140,000 cubic yards (110,000 m) of masonry. many materials, including granite aberdeen, arbroath rubble, sand, timber, , coke , coal, taken straight centre required. steel delivered train , prepared @ yard @ south queensferry before being painted boiled linseed oil before being taken needed barge. cement used portland cement manufactured on medway. required stored before able used, , 1,200 tonnes (1,200 long tons; 1,300 short tons) of cement kept in barge, formerly called hougomont moored off queensferry.

for time paddle steamer hired movement of workers, after time replaced 1 capable of carrying 450 men, , barges used people carrying. special trains run edinburgh , dunfermline, , steamer ran leith in summer.

circular piers

a completed caisson on inchgarvie granite pier

the 3 towers of cantilever each seated on 4 circular piers. since foundations required constructed @ or below sea level, excavated assistance of caissons , cofferdams. caissons used @ locations either under water, @ low tide, or foundations built on mud , clay. cofferdams used rock nearer surface, , possible work in low tide.

six caissons excavated pneumatic process, french contractor l. coisea. process used positive air pressure inside sealed caisson allow dry working conditions @ depths of 89 feet (27 m).

these caissons constructed , assembled in glasgow arrol brothers, namesakes of unconnected w. arrol, before being dismantled , transported queensferry. caissons built large extent before being floated final resting-places. first caisson, south-west pier @ queensferry launched on 26 may 1884, , last caisson launched on 29 may 1885 south-west pier @ inchgarvie. when caissons had been launched , moored, extended upwards temporary portion in order keep water out , allow granite pier built when in place.

above foundations each of different suit different sites, tapered circular granite pier diameter of 55 feet (17 m) @ bottom , height of 36 feet (11 m).

inchgarvie

the rock on 2 northern piers @ inchgarvie located submerged @ high water, , of other 2 piers, site of eastern 1 half submerged , western 1 three-quarters submerged. meant work had done @ low tide.

the southern piers on inchgarvie sited on solid rock slope of around 1 in 5, rock prepared concrete , sandbags make landing-spot caissons. excavation carried out drilling , blasting, no blasting done within 1.5 ft (0.46 m) of caissons, , remaining rock quarried within 6 in (150 mm).

fife

once positions of piers had been established, first task @ fife level site of northernmost piers, bedrock of whinstone rising level of 10 20 feet (3.0 6.1 m) above high water, height of 7 feet (2.1 m) above high water. south piers @ fife sited on rock sloping sea, , site prepared diamond drilling holes explosive charges , blasting rock.

queensferry

the tilted caisson



the mode of sinking queensferry caissons

the 4 queensferry caissons sunk pneumatic method, , identical in design except differences in height. t shaped jetty built @ site of queensferry piers, allow 1 caisson attached each corner, , when launched caissons attached jetty , permitted rise , fall tide. excavation beneath caissons carried out @ high tide when caisson supported buoyancy, , when tide fell air pressure reduced in order allow caisson sink down, , digging begin anew.

the north-west caisson towed place in december 1884, exceptionally low tide on new year s day 1885 caused caisson sink mud of river bed , adopt slight tilt. when tide rose, flooded on lower edge, filling caisson water, , when tide fell water did not drain caisson, top-heaviness caused tilt further. plates bolted on divers raise edge of caisson above water level, , caisson reinforced wooden struts water pumped out, pumping took place , water pressure tore hole between 25 , 30 feet (7.6 , 9.1 m) long. decided construct barrel of large timbers inside caisson reinforce it, , ten months before caisson pumped out , dug free. caisson refloated on 19 october 1885, , moved position , sunk suitable modifications.

approach viaducts

the approach viaducts north , south had carried @ 130 feet 6 inches (39.78 m) above level of high water, , decided build them @ lower level , raise them in tandem construction of masonry piers. 2 viaducts have fifteen spans between them, each 1 168 feet (51 m) long , weighing on 200 tonnes (200 long tons; 220 short tons). 2 spans attached make continuous girder, expansion joint between each pair of spans. due slope of hill under viaducts, girders assembled @ different heights, , joined when had reached same level. lifting done using large hydraulic rams, , took place in increments of around 3 feet 6 inches (1.07 m) every 4 days.

building cantilevers

the tubular members constructed in no. 2 workshop further hill @ queensferry. bend plates required shape, first heated in gas furnace, , pressed correct curve. curved plates assembled on mandrel, , holes drilled rivets, before marked individually , moved correct location added structure. lattice members , other parts assembled @ south queensferry, using cranes , highly efficient hydraulic rivetters.

opening

the bridge completed in december 1889, , load testing of completed bridge carried out on 21 january 1890. 2 trains, each consisting of 3 heavy locomotives , 50 wagons loaded coal, totalling 1,880 tons in weight, driven south queensferry middle of north cantilever, stopping measure deflection of bridge. represented more twice design load of bridge: deflection under load expected. few days there had been violent storm, producing highest wind pressure recorded date @ inchgarvie, , deflection of cantilevers had been less 25 mm (1 in). first complete crossing took place on 24 february, when train consisting of 2 carriages carrying chairmen of various railway companies involved made several crossings. bridge opened on 4 march 1890 prince of wales, later king edward vii, drove home last rivet, gold plated , suitably inscribed. key official opening made edinburgh silversmith john finlayson bain, commemorated in plaque on bridge. when opened had longest single cantilever bridge span in world, until 1919 when quebec bridge in canada completed. continues world s second-longest single cantilever span, span of 1,709 feet (521 m).

to make fullest use of bridge, several new railway connections built, bringing main line routes bridge. construction of of these lines completed on 2 june 1890, delaying implementation of full express train service on bridge until date. then, there considerable congestion @ edinburgh waverley station remarshalling of portions of new, more intensive train service.

accidents , deaths

at peak, approximately 4,600 workers employed in bridge s construction. wilhelm westhofen recorded in 1890 57 lives lost. in 2005 forth bridge memorial committee set erect monument lost, , team of local historians set out name died. of 2009, 73 deaths have been connected construction of bridge , immediate aftermath. thought figure of 57 deaths excluded died working on approaches bridge, parts completed subcontractor, died after sick , accident club stopped. of 73 recorded deaths, 38 result of falling, 9 of being crushed, 9 drowned, 8 struck falling object, 3 died in fire in bothy, 1 of caisson disease, , cause of 5 deaths unknown.

the sick , accident club founded in summer of 1883, , membership compulsory contractors employees. provide medical treatment men , families, , pay them if unable work. club paid funerals within limits, , provide grants widows of men killed or wives of permanently disabled. 8 men saved drowning rowing boats positioned in river under working areas.