100 years of steel in architecture
During the 1850s, due to the manufacturing processes being developed in Britain by Sir Henry Bessemer, it became possible - in theory - to produce sufficient steel of adequate quality to make it an economic material to use in building construction. But, despite the early appearance of Bessemer steel, iron - both wrought and cast - dominated the building world until the very late nineteenth century. The first major use of steel dates from the 1880s when it was used for the mightiest engineering enterprises of their age - bridges.
The Brooklyn Bridge in New York was completed in 1883 to the designs of architect and engineer John Augustus Roebling. For 20 years Brooklyn Bridge was - at 486m - the longest suspension bridge in the world and was the first bridge to make extensive use of steel. The Forth Bridge - started in 1882 and completed in 1890 to the designs of Sir Benjamin Baker and Sir John Fowler - is an immense structure which - at a mile and a half in length - was for 30 years the longest bridge in the world. It is formed of huge balanced cantilevers - linked by trussed spans - with large riveted tubes used for the compression members. Tube construction had been used before - notably by Brunel at his bridges at Chepstow and Saltash - but whereas Brunel’s tubes are made of wrought iron, the entire Forth bridge is fabricated of steel.
Early us buildings
During the decades when the Forth Bridge was being constructed, steel was increasingly used to form the structural frames of high-rise commercial buildings in New York and Chicago. Steel gave strength, allowed the creation of flexible open-plan interiors and allowed high-rise steel-framed buildings to be constructed at great speed. As early as 1883 Bessemer steel had been used by architect William LeBron Jenny to form the frame of the Home Insurance Company Building in Chicago.
The dilemma facing architects pioneering the use of steel frames in high- rise buildings was whether to express or to conceal and deny the presence of the structural frame. This was a question given added complexity by the debate over the behaviour of high steel-framed buildings in a fire or other disasters. Most building codes and regulations had evolved to deal with relatively low-rise masonry construction and were gradually revealed to be inadequate or irrelevant when dealing with steel-frame construction. As early as 1889 the pioneering Jenny had decided that the frame should be clearly expressed. In his Second Leiter Building, Chicago (now Sears Roebuck) of 1889-90, the elevations read clearly as a sheath over a steel frame. The artistic potential offered by the plastic and structural qualities of steel was, however, realised more dramatically in France.
Paris and London
In 1905 Georges Chedanne designed an office building for Le Parisien Libere in rue Reamur, Paris, in which the steel frame is expressed with the plastic qualities of rolled steel sections utilised in a striking manner to achieve an organic, Art Nouveau flowing line with a steel frame of minimal section permitting large areas of glazing.
It was not until 1904 that Britain got, arguably, its first fully loadbearing steel-frame structure when architect Mewes and Davis with the Swedish American engineer Sven Bylander constructed the Ritz Hotel in Piccadilly, London. In the us manner the beam-to-stanchion connections are riveted - a practice that involved the installation of small furnaces on site so that hot rivets could be hammered into drilled holes in the frame. The advantage of this system was that the soft rivets fully filled the holes into which they were hammered and pulled the frame together as they cooled and contracted. The riveting of beam to stanchion connections in steel-frame construction was prohibited in the 1894 London Building Act but the fact that the frame of the Ritz Hotel was clad by a loadbearing masonry skin gave the sort of solidity and fire protection demanded by the more cautious building inspectors. The Buildings Acts were more seriously challenged - and in fact consequently amended - by the next of Britain’s steel-framed structures.
Selfridge’s and Kodak
Selfridge’s store in London’s Oxford Street was commissioned in 1908 by a former Chicago store-owner who, initially, employed a Chicago architect - D H Burnham - who had practiced and developed steel-frame construction in the us. Selfridge wanted his store built quickly, with an open interior and extensive external glazing. All this could be best achieved with steel- frame construction if the law would allow. Selfridge eventually triumphed, thanks in large part to the engineer, Sven Bylander (who had worked on the Ritz) who perfected the system for the rapid construction of the frame. Although detailed in the grand classical manner (to the designs of Francis Swales) the stone-clad elevation of Selfridges does to a degree reflect the rhythm of the steel frame behind.
Britain’s first, more explicit, us-style external expression of the steel frame was at the Kodak Building (again for a us client) on Kingsway, London. Started in 1910 to the designs of Sir John Burnet, the elevation of the building is divided vertically by bold pilaster strips which clad and express the steel stanchions while the open areas between the pilasters are generously glazed.
Empire State inspiration
During the late 1920s and 1930s a greater understanding was gained of the structural principles involved. Initially a steel frame was conceived much as a traditional timber box frame, though with far stronger individual elements. But as the structural potential of the malleable nature of steel was better understood, techniques were developed for connecting the steel elements of the frame. Welding (soon followed by bolting) frames together made it possible to conceive the frame as an immensely strong, continuous, structure in which provision for movement could be minimalised and complex expansion joints virtually eliminated. Improved technology and organisation meant that steel frames could also be erected more quickly and efficiently. In 1930 the 50,000 tons of steel forming the structure of the 85 storey, 378m high Empire State Building in New York (designed by Shieve, Lamb and Harmon) were erected in only six months.
De La Warr Pavilion
Welded joints enabled designers to abandon bulky riveted or bolted joints and to create an integrated structure that would be light, minimal and elegant. Perhaps the best and earliest expression of this is the De La Warr Pavilion at Bexhill, in Britain, designed in 1935 by Mendelsohn and Chermayeff with engineers Helsby, Hamann and Samuely. The welded structural steel frame is externally light and graceful with slender steel columns being stiffened by the use of reinforced-concrete floors. Indeed one of the secrets of this building’s success is the integration of steel and reinforced concrete to maximise the potential offered by both.
Peter and Alison Smithson’s Smithdon School at Hunstanton, Norfolk, built between 1950 and 54, is an outstanding example of immediate post war steel construction in England - a period when steel was rationed. However, the architects - inspired by the us work of Mies van der Rohe - decided on a steel-frame structure in which the beams and stanchions were exposed both internally and externally. Indeed the expressed structure was to be the building’s only ornament. The framework was fabricated from 230mm rolled steel I-section beams and stanchions welded on-site into H-frames and then welded into position. Smaller section steels were welded onto, and set at right angles to, the main stanchions. These ‘facing frames’, as they were called, were to act as lateral bracing. This frame design, and the welded joints, were intended to display the ‘plastic theory’ of structural steelwork and to reduce the need for expansion joints - there are only two in the building’s 88m length. Unfortunately the frame did move and the windows - set directly between beams and stanchions and not within sub-frames - started to fall out or shatter. Notwithstanding this practical problem, the building still looks superb, and its pioneering - if flawed - role in the development of structural steelwork in Britain is now recognised by its Grade I listing.
As the Hunstanton school was under construction, Britain acquired - if only for a short time - one of its most characterful and intriguing steel structures. The Skylon - which hovered magically over London’s South Bank forming the ‘vertical feature’ of the 1951 Festival of Britain complex - was designed by Jacko Moya of Powell and Moya with the veteran structural engineer Felix Samuely. The main structure - a cigar-shape tube - was made of latticed steel work clad with aluminium, and stood 76.2m high. This massive tube appeared to defy gravity by being suspended by discreet wire cables which were, in their turn, supported by three welded steel pylons. These pylons had cables from their tops which reached down to the ground as ties and extended up, as guys, to fixings midway along the length of the tube. To provide adequate stiffness and to limit deflection, the wire cables were pre-tensioned.
The Centre Pompidou in Paris was completed to the designs of Richard Rogers and Renzo Piano in 1977. It was to be a great arts centre offering inspiration and education to all with its cultural excitement and openness expressed physically by means of a fully glazed exterior and an uncluttered wide-span interior capable of responding easily to changes of function and use. The building’s structure and services were to be honestly expressed and, like its flexibly planned interior, capable of change as circumstances demanded. The building is a massive steel frame with the interior spanned by huge trusses supported on columns placed outside the lightweight and generally glazed walls of the building. The frame is in constant movement with floor trusses drooping as much as 7cm at their centre points, so the junction between columns and trusses had to be not only immensely strong but also flexible. The architects and their structural engineers came up with the building’s famed ‘gerberettes’ - cantilevered bracket projections or rocker arms which, with the help of prestressed vertical stays, give the columns some tensile strength and additional compressive strength. These gerberettes are made of cast steel which, malleable and of great strength, is an ideal material for bearing structures. Despite various ad-hoc additions and alterations over the years, the Centre Pompidou remains a monument to the beauty and potential of steel construction.
Broadgate phase 11
Architect som supervised the last series of buildings of the Broadgate development in the late 1980s with one in particular, termed phase 11, being an intriguing example of expressed steel construction. The problem was to span a 70-80m area of tracks with a 12-storey building with no columns coming down between the tracks. The solution was to construct four massive parabola-shaped arches from which the floors of the building are either hung or off which they rise. Each arch is constructed of two steel sections linked by trellis work while the feet of each arch are linked at the base by a continuous tension member or tie beam. The floors of the building above the arches are supported by compression-loaded columns, in turn supported by the arches. The lower floors are suspended from the arches so that the floor columns at lower level are, in fact, tension- loaded. The cross-section of the columns remains the same throughout the building, which is possible because the floor plates of the columns brace the structure to prevent buckling. Additional bracing is visible externally in the form of diagonal compression struts linking the external steel frame (exposed and set forward to comply with fire codes) with the wall ofthe building.
The station, completed in 1994 to the designs of architect Nicholas Grimshaw and Partners with engineer yrm/Anthony Hunt Associates, reveals how the technology of steel construction has transformed the idea of the mighty station shed - a building type which was first given form in the 1850s through the pioneering application of structural ironwork combined with glass.
The essential structural component at Waterloo is a three-hinged trussed arch fabricated of tubular steel components which are triangular in section, except for the larger elements which are curved. Because the long platform tapers and curves dramatically, each arch is asymmetrical, being formed by two trusses, one long and one short. Consequently, the middle hinge of each arch - that set between the two trusses - does not fall along the structure’s central axis.
The roof surface is set over the structure and is formed by corrugated stainless steel panels between the trusses with a band of overlapping glass panels above.
The building’s dramatically sinuous form, as it curves and tapers away from the main concourse, means that many of its components are individual and virtually hand-crafted. This gives the whole structure a curiously traditional character - like some Gothic construction - and makes it far more than a mere piece of high-tech industrialised building.
For the past 100 years steel has given tangible form to the spacial fantasies of innovative architects and made it possible to meet the commercial requirements of demanding clients. Steel has proved itself the structural material of the century.