DR JIM SHIPWAY RETROSPECTIVE

runel had a striking personality, but he was a civil engineer first Band foremost, with a keen inquiring mind, immense energy, and a supreme ability to lead, inspire and persuade others; he was a brilliant innovator who at times it seemed, had an aversion to following any other man’s lead. What was his real contribution to engineering? Several books have been written about , his life and times, and in the scope of a single short article assessing his achievements, it is possible to do justice only to a very few of his works. Since he was best known as a railway engineer and a builder of before he became a designer of ships, two of his later railway bridges have been chosen for comment. Brunel’s chief rival as a railway engineer was (1803–59), also a great engineer and designer of the Conwy and Menai tubular bridges, but his work lacked the flair displayed by Brunel, and he did not have the same genius for calculation.

A note on units: we generally use SI units in Ingenia, but in this historical article we have retained the original Imperial units

In the competition organised by the BBC last year for the title ‘The Greatest Briton’, Churchill led the field of ten entries, and the runner- up was I.K.I.K. BrunelBrunel (1806–59), a brilliant polymath who engineered the and numerous other works, including the design and construction of ships. It was Some thoughts on his astonishing that this man, little- known to the public and from a profession little understood by it, gained second place in a country- engineering wide competition involving such names as Shakespeare, Nelson, and the Princess of Wales. How

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The Great Western Railway Brunel was appointed engineer to the Brunel had a striking personality, a keen GWR in 1833 when he was 27 years old, and it was the first of his railway inquiring mind, immense energy, and a works, extending 118 miles between London and Bristol. It was not supreme ability to lead and inspire others constructed without controversy, since it embodied the startling 7 ft gauge (50% wider than the standard gauge) onwards, but had weakness, in that well (Conwy is still in use today), but and the equally startling two miles long the top flange was vulnerable to the bridges were heavy and , as well as the Maidenhead buckling. Brunel’s skill in design uneconomical in the use of materials, , which had the longest and manifested itself in flanges with curved mainly due to the closed-in plated flattest semi-elliptical arches ever plates and web branches in several webs. Only five such bridges were constructed in brickwork. The fall of forms, stiffening the flange and the built, and none after 1856. this bridge on completion was girder web together. Meanwhile, the open-web or trussed confidently predicted, but it continues girder, with panels, was gaining ground in use to this day. These features of the in America, where timber suitable for Large-span bridge GWR give the flavour of Brunel’s bridge construction was plentiful and development approach to engineering and of his railway construction was booming. achievements in other fields. In the 1840s the plated-web box These girder bridges were used mainly The development of the girder girder made its appearance on a for spans up to 150 ft, and were bridge in railway work took place in the grand scale with the design of the gradually replaced by all-iron bridges of UK mainly between the years 400 ft span Conwy and the same types. The most popular form 1830–1860, and included lattice the Menai tubular bridge with two main was the Pratt, or N-truss, and later the girders, plate girders, tubular girders spans of 460 ft, both by Robert Warren girder. Early Pratt trusses from and hybrids. These years almost Stephenson. These bridges, in which 1845 onwards had iron ties for diagonal exactly paralleled the career of Brunel, the trains run inside the tube, were members and timber verticals forming and it was natural that he was involved Stephenson’s answer to the then the panels, before the advent of iron. in bridge development, making his own seemingly impossible problem of The all-iron Warren girder followed in the unique contribution. The plate girder bridging gaps of that magnitude. His 1850s, with the construction of the bridge flourished from the 1840s solution was innovative and worked Newark Dyke Bridge in England in 1853.

Chepstow Bridge, 1852 In 1852 Brunel was engineer to the , and had to bridge the at . The Wye had a tidal range of 40 ft, the second highest in the world, and was swift- flowing. The Admiralty insisted on a 300 ft clear width for shipping and 50 ft headroom at high tide. They further

The 400 ft spanning Conwy tubular bridge by Robert Stephenson (left) which is still in use today. Bridges such as ingenia Conwy and Menai were excellent engineering achievements but were often uneconomical with materials (Photo: Philip Hawkin) 58 RETROSPECTIVE

insisted that the navigation channel be requiring caisson construction for the closed only for the duration of one tide, river piers. This resulted in an Bridge on the River Wye i.e. for 12 hours only. Stephenson had asymmetrical bridge of which one half Brunel’s Chepstow Bridge (above), no such problem at Conwy or Menai. was three 100 ft plate girder spans, and which was built to specific Brunel had a strong artistic streak, the other half was a 300 ft span of quite requirements by the Admiralty, was and most of his work, though functional, different design. The twin tracks were of remarkable for many reasons. It was had much of elegance: for example the the 7 ft gauge, which imposed loading one of the first open-web girder roofs at Paddington Station; Clifton 50% greater than the standard gauge. bridges in Europe, incorporating ; tunnel portals at The greatest obstacle was the 100 ft by 50 ft open panels crossed Box and elsewhere; and his elliptical maximum of 12 hours allowed for the with chain diagonals as shown in the arch work at Maidenhead, Hanwell possession of the river channel. Brunel photo above. (Photo: ) and other masonry bridges. The decided on a separate bridge for each Chepstow Bridge, however, was a plain track, making for smaller pieces to be answer to an engineering problem, and lifted into place. Each bridge was to was ungainly and lacking in charm and be of three panels, each of elegance. Nevertheless it embodied approximately 100 ft, making a engineering of the highest order. gigantic N-truss. The top chord of the The diagram below shows how, with The site is remarkable for the truss was a 9 ft diameter tube built up just 12 hours allowed for occupation contrast between the two sides of the from wrought-iron plating, and the web of the river channel, the main river. On the east side there is a members were chain links chosen for Chepstow Bridge member was erected limestone cliff 120 ft high, and on the lightness and easy handling. The west there is low-lying alluvial material vertical members of the truss were

Final

300 ft 3rd Final position 9 ft

3rd position

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The construction of The at (left). The two main spans, each of 455 ft, were lifted into place one at a time; both met at the centre pier which was founded on rock 16 ft below the bed of the 70 ft deep river. The parabolic tubular arch is matched exactly by the sag of the chains, the two being vertically braced apart and strengthened with cross-bracing

A–frames, and joined the tube to the designed, would be an improvement. The 300 ft spans at Chepstow lasted plate girders supporting the deck. The Thus the Warren girder with its 110 years until 1962, when they were heaviest part of each bridge was triangular open web arrived at Newark replaced owing to the increase in therefore the 300 ft long tube, which Dyke in 1853 and slightly later at loading from heavier traffic. Thus weighed 161 tons and spanned the Crumlin. In the USA, advances in passed into history these remarkable entire navigation channel. Brunel’s plan design, mainly in timber, had been iron spans, the first in Europe to have was to launch the tube on barges made in the 1840s and later by Pratt, open-web N-truss panels. There were across the channel, then lift it in stages Howe, Whipple and others who no others in iron outside America until by jacks to the required clearance in developed the concept of panels in J.H. Latham’s railway bridge at the course of a single day. The framed structures for modest spans. Allahabad, India, in 1859–65, which scheme worked brilliantly, and the first But Brunel led the field in Europe. had spans of 210 ft, a long way short of the two bridges was completed in At Chepstow his gigantic, open, 100 ft of Chepstow. three months between April and July panels, 50 ft high, crossed by chain 1852. The second bridge was diagonals, were an impressive completed the following year. advance, and the N-truss became The Royal Albert Bridge, But the real genius of the design lay established as a cheap and easily Saltash, 1859 in its structural form, in the fact that it constructed structural form. Nor was Saltash Bridge is frequently described as was virtually the first open-web girder the economy of the bridge the last and greatest of Brunel’s railway in Europe. Until that time all major iron compromised by high stresses. An works, since its completion in 1859 railway bridges in Britain had closed, analysis of the forces by the author in coincided with the year of his death. If plated web members joining the the members under the heavy 7 ft Chepstow Bridge lacked charm, the flanges, as seen in the Conwy and gauge loading showed stresses easily same cannot be said of Saltash, Menai bridges, and Fairbairn’s patent compatible with those accepted for although its two main spans form what

ingenia designs. But there were the wrought iron construction of the is generally avoided in architecture; an stirrings that the heaviness of these time, and Brunel test-loaded a span to unresolved duality. This occurs when bridges was uneconomic, and that a 65% above the designed loading with two bridge spans, or building features, framed structure, if it could be satisfactory results. are identical and side by side. The eye

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455 ft

56 ft 3 in

100 ft

Brunel’s Saltash Bridge carried the Railway across the . The diagram above shows tends to move restlessly between them, In 1859 the only railway bridge of the erection of one of the two generating a sense of unease. Whereas similar span in Britain was Robert main spans, put into place on 16 if a bridge has, say, three spans with the Stephenson’s Menai Bridge, which had February 1859. The foundation centre one slightly larger, the eye tends two spans of 460 ft. Each span carried construction alone had taken three to rest on the centre, and is at peace. a single track, and weighed in the years. Saltash carried the Cornwall region of 1587 tons. The solid, plated, The open web design meant that the weight of the bridge was about Railway’s single line across the River web sides accounted for about 40% of a third less than for solid plated Tamar in 17 approach spans and two this weight. web constructions such as Robert main spans of 455 ft each, resting on a It is unlikely that Brunel was Stephenson’s Menai Bridge single river pier and on each bank. This tempted to emulate this design, and arrangement was dictated by ground instead he created a unique bowstring conditions and the depth of water in the truss in which a tubular arch acts in Tamar. The foundation construction took conjunction with chain ties to form a three years and the pier was founded remarkably rigid braced structure. The on rock 16 ft below the bed of the river, rise of the arched tube is a shallow which is 70 ft deep. The Admiralty parabola matched exactly by the sag demanded a clear width of 400 ft and of the chains, the two being braced The completed Saltash Bridge (below) headroom of 100 ft above high water. apart by vertical members with light ingenia

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cross-bracing between them. The Ullapool, in Wester Ross, and it has Yet, apart from the minor bridge at bridge deck is suspended equally from rigid tie members in place of chains. Auchindrean, the form of the Saltash the tube and the chains. The weight of The elegance of the original design spans has never been repeated, (the this arrangement (designed to carry the of the Saltash spans arises from the Pauli truss is a different form), and it heavier 7 ft gauge loading) was shallow parabolic curves and the remains a remarkable solution to a approximately 1069 tons, or 67% of absence of fuss in the details of the particular problem. Why is this? the weight of the same Menai span. bracing. Since they were built, however, Structurally the bridge was a The chain ties could equally well have the applied loading has increased and significant advance on the Menai been rigid tension members, and led to additions to the bracing both Bridge, but in comparison the indeed the use of chains led to laterally and in the elevations; this has construction of the Saltash structure intricacies in construction, which must detracted somewhat from the original was complex and demanding. The have been a mixed blessing. The only graceful appearance. The lightness of arched tube was elliptical in cross- other bridge of the Saltash type known the trusses, incidentally, was not section and parabolic in elevation, and to the author is a 102 ft span minor attained at the expense of high stresses had to be built up laboriously from road bridge at Auchindrean, near or inadequacy in the strength. An wrought iron plates. The chains had to analysis by the author of the stress in be manufactured and each link tested the major components of the structure individually. The details of the The 102 ft span road bridge at (the tube and chains) shows values attachment of the verticals to the tube Auchindrean near Ullapool (below) easily compatible with the and chains involved extremely careful uses rigid tie members instead of chains to emulate Brunel’s recommended stresses of the day for workmanship for lack of fit to be matching parabola design for the wrought iron, both in compression and avoided. The temporary works, i.e. Royal Albert Bridge at Saltash under tension. This remarkable bridge scaffolding and centring for the arch is still in use today, more than 140 and chains, were also complicated, years after its completion. and had to be substantial. The ingenia

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connection at the ends of both tube the properties of materials then Brunel lifted a corner of the veil over his and chains by massive pins demanded available, and by the limitations of soul, and wrote: more than ordinary skills in construction, but he did not allow ‘Finally, let me impress upon you the construction. Curved work is always these constraints to limit his ideas. It advantage of prayer…of this I can more expensive than straight-line sometimes seemed he cared little for assure you, that I have ever, in my fabrication, and the Saltash trusses the expense incurred or the concern of difficulties, prayed fervently, and that had more than their share. Finally, the the shareholders and directors, but he – in the end – my prayers have truss form did not lend itself to easy was a man who got things done, been, or have appeared to me, to be erection methods such as rolling-out superbly. granted, and I have received great or cantilevering. All these factors Next to his originality of thought was comfort.’ added to the time and cost of his remarkable insight into the behaviour Perhaps this was a clue to Brunel’s inner construction. The panel truss girder of structures. This may have been life, about which he never spoke: he had already appeared over the horizon strongly intuitive, but it was a perception believed in God and trusted in Him. and offered greater simplicity and which was backed by wide experience Isambard Kingdom Brunel may have economy in building. and observation, and by calculation. In been a runner-up in the BBC The Saltash design was unique and reading of the construction of Conwy competition, but he has surely emerged a masterpiece, but it was a blind alley and Menai bridges, it often seems that as the greatest of the world’s and did not advance the development the calculations came after construction, engineers. ■ of the . It remains a which was at best an informed guess. unique tribute to Brunel’s outstanding But it was not so with Brunel. Whether References genius. he was designing the complex structure Brunel, I.: Life of Isambard Kingdom of the Saltash Bridge, or the hull of the Brunel, civil engineer. Published Great Britain, or the elegant arches of originally 1870, Longman Green & Brunel’s contribution to the roofs at Paddington, or the timber Company, London. engineering of the , his Shipway, J.S.: Some aspects of the It would take several articles of this analyses of the forces and stresses development of the girder bridge, length to cover adequately Brunel’s were based on a deep understanding of 1820–1890. Ph.D. thesis, Heriot Watt achievements and his contribution to structural behaviour. Always, his designs University, Edinburgh, 2002 engineering, but some conclusions were bold and imaginative, often daring. (unpublished). can be drawn from the limited He had a remarkable confidence that examples given above. his structures would behave as he At the time of his death he was a predicted, shown, for example, in his Dr Jim Shipway is a Fellow of the vice-president of the Institution of Civil design for the Maidenhead Bridge. Institution of Civil Engineers and is a Engineers, and he attended its Yet Brunel left nothing to chance. In a member of its Panel for Historical meetings throughout his professional letter on design to one of his assistants Engineering Works. He retired in 1998 life whenever he was in London and it in 1854 he wrote, memorably, ‘always and recently was possible for him to do so. He put rather an excess of material in completed a PhD believed in sharing his knowledge and quantity’. His works were built to last, at Herriot-Watt experience, and he was against the and there was no short-cutting or University on patent laws, which he felt restricted the skimping, or lack of care in the detailing. some aspects of spread of knowledge and invention. The sequence of erection procedures the development Brunel’s greatest gift was originality was planned in meticulous detail, with of the girder of thought, seen for example in the careful forethought for every eventuality. bridge. Much of adoption of the 7 ft gauge, and the His remarkable insight resulted in few his career was brilliant solutions to the separate mistakes. His immense energy allowed spent in civil engineering consultancy, problems of bridging at Chepstow and him continuous travelling for long including some years with Ove Arup Saltash, as well as in other fields such periods, in which he was able to & Partners where he led the Glasgow as ship design and the development of supervise distant site works and so office and later was with the firm in the screw propeller. This originality was maintain the highest standards of Nigeria. He has had three technical always fully directed to improving construction. papers published by the ICE, mainly solutions to the problems in hand. He Finally, in a private letter to his eldest engineering history and is the was constrained by circumstance, and son in 1858, the year before his death, recipient of two awards. ingenia

63 ■ ■ Labour’s longest ever serving MP, Labour’s the House of from Benn retired Tony Ideally placed to speak on the pivotal enhancing national capabilities excellence and inspiring recognising the next generation leading debate. and to highlight the dynamism and in engineering. excitement of a career strategic With this in mind, the refreshed priorities focus on the importance of engineering and technology to wealth and the quality of life: creation we can all be helped to understand the we can all be helped and the of the decisions nature real that may flow long-term consequences them.’ from as one of Benn is widely regarded Tony living parliamentarians. greatest Britain’s With that began when a political career the House in 1950, and a he entered National Executive member of Labour’s Benn was a Cabinet for 35 years, Tony Minister in the Wilson and Callaghan Governments 1964–79, and from 1971–2. Chairman of the Labour Party, Commons in May 2001, ‘to devote politics’. time to more has on society, that engineering effect RAF pilot, a BBC Benn was an Tony in politics prior to his career Producer and Postmaster General early in his Minister in As a Cabinet political career. the Wilson and Callaghan governments Minister of Technology, included his roles of State for both Industry and Secretary of the Council of Energy and President Energy ministers. European ● ● ● Refreshing The Academy’s visual identity The Academy’s Refreshing is another major and exciting focus of the development that will help increase recognition and public profile Academy’s organisation. Its as a progressive and implementation are revision is taking place and the project currently due for completion by midyear. The fundamental purpose of The ‘It is no exaggeration to say that, ‘It is no exaggeration ‘It is also true that with the resources of the the area Going on to address to be made ‘If the right decisions are needed is clarification ‘What is really humble beginnings. To build on these humble beginnings. To Council successes, The Academy’s the decided to refresh recently strategic objectives. The organisation’s aim – in this the 21st anniversary year its Royal of The Academy receiving the focus Charter – has been to ensure clearly on the impact The remains to have rather than Academy desires simply the activities it undertakes. the engineering Academy is to promote of the country and technological welfare Tony Benn urges engineers Benn urges Tony political to be more Industrial Revolution and now the age Industrial Revolution Space travel, the of Atomic energy, Internet.Computer and the at its disposal, the with the tools now itself by human race could obliterate of nuclear, the indiscriminate use chemical and biological weapons, or on the even by neglecting the effect of pollution. environment now available we could almost certainly eliminate many – if not most – of disease, problems: greatest mankind’s ignorance and poverty.’ public engagement in science and technology issues, the message was clear. by the governmentsthere of the world public needs to be a far greater understanding both of the dangers and open to us the opportunities which are right us to take the – which require political and moral decisions. of the choices we have to make so that priorities

he Rt. Hon. Tony Benn P.C. he Rt. Hon. Tony spoke to an enthralled audience on Engineering and Society at

In the subsequent years, The Royal Urging engineers to take a more ‘The advance of civilization is

strategic Refreshing The Academy’s

T In June 1976, 126 leading British engineers met at Buckingham Palace for the inaugural meeting of the by Fellowship of Engineering. Chaired was the creation Prince Philip, the result national academy of of Britain’s engineering, consisting of engineers all disciplines who wished to from the contribution and further recognise to society. of their profession Academy of Engineering, as it became from deal in 1992, has achieved a great active role in political decision-making, in active role used a the former industry secretary timeline of civilisation development to of illustrate the fundamental role Speaking history. engineers throughout to a packed hall, he said, state of technology by the recorded Stone the periods from used at different Age to the the Iron Age, through The Royal Academy of Engineering’s Reception on 15 Annual New Year January 2004.

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