A box girder or tubular girder (or box beam ) is a girder that forms an enclosed tube with multiple walls, as opposed to an Ɪ- or H-beam . Originally constructed of wrought iron joined by riveting , they are now made of rolled or welded steel, aluminium extrusions or prestressed concrete .
30-569: Alfords Point Bridge is a twin 445-metre-long (1,460 ft) concrete and steel box girder road bridge that carries Alford Point Road as state route A6 across the lower Georges River between Padstow Heights in the City of Canterbury-Bankstown and Alfords Point in the Sutherland Shire in Sydney , New South Wales , Australia. The first bridge opened on 7 September 1973. Although
60-422: A space frame or space structure ( 3D truss ) is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern . Space frames can be used to span large areas with few interior supports. Like the truss, a space frame is strong because of the inherent rigidity of the triangle; flexing loads (bending moments ) are transmitted as tension and compression loads along
90-405: A unibody or monocoque design, the body serves as part of the structure. Tube-frame chassis pre-date space frame chassis and are a development of the earlier ladder chassis . The advantage of using tubes rather than the previous open channel sections is that they resist torsional forces better. Some tube chassis were little more than a ladder chassis made with two large diameter tubes, or even
120-401: A common feature in modern building construction; they are often found in large roof spans in modernist commercial and industrial buildings. Examples of buildings based on space frames include: Large portable stages and lighting gantries are also frequently built from space frames and octet trusses. The CAC CA-6 Wackett and Yeoman YA-1 Cropmaster 250R aircraft were built using roughly
150-500: A racing car space frame was the Cisitalia D46 of 1946. This used two small diameter tubes along each side, but they were spaced apart by vertical smaller tubes, and so were not diagonalised in any plane. A year later, Porsche designed their Type 360 for Cisitalia . As this included diagonal tubes, it can be considered a true space frame and arguable the first mid-rear engined design. The Maserati Tipo 61 of 1959 (Birdcage)
180-662: A rigid space frame. An earlier contender for the first true space frame chassis is the one off Chamberlain 8 race "special" built by brothers Bob and Bill Chamberlain in Melbourne, Australia in 1929. Others attribute vehicles produced in the 1930s by designers such as Buckminster Fuller and William Bushnell Stout (the Dymaxion and the Stout Scarab ) who understood the theory of the true space frame from either architecture or aircraft design. A post WW2 attempt to build
210-561: A single tube as a backbone chassis . Although many tubular chassis developed additional tubes and were even described as "space frames", their design was rarely correctly stressed as a space frame and they behaved mechanically as a tube ladder chassis, with additional brackets to support the attached components, suspension, engine etc. The distinction of the true space frame is that all the forces in each strut are either tensile or compression, never bending. Although these additional tubes did carry some extra load, they were rarely diagonalised into
240-437: A stronger matrix, in part by rotating an alignment of tetrahedral nodes in relation to each other. Space frames are typically designed using a rigidity matrix. The special characteristic of the stiffness matrix in an architectural space frame is the independence of the angular factors. If the joints are sufficiently rigid, the angular deflections can be neglected, simplifying the calculations. The simplest form of space frame
270-469: A true space frame chassis until the Mark VIII , with the influence of other designers, with experience from the aircraft industry. A large number of kit cars use space frame construction, because manufacture in small quantity requires only simple and inexpensive jigs , and it is relatively easy for an amateur designer to achieve good stiffness with a space frame. A drawback of the space frame chassis
300-464: Is a horizontal slab of interlocking square pyramids and tetrahedra built from Aluminium or tubular steel struts. In many ways this looks like the horizontal jib of a tower crane repeated many times to make it wider. A stronger form is composed of interlocking tetrahedra in which all the struts have unit length. More technically this is referred to as an isotropic vector matrix or in a single unit width an octet truss. More complex variations change
330-618: Is often thought of as the first but in 1949 Robert Eberan von Eberhorst designed the Jowett Jupiter exhibited at that year's London Motor Show ; the Jowett went on to take a class win at the 1950 Le Mans 24hr. Later, TVR , the small British car manufacturers developed the concept and produced an alloy-bodied two seater on a multi tubular chassis, which appeared in 1949. Colin Chapman of Lotus introduced his first 'production' car,
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#1732788091829360-410: Is that it encloses much of the working volume of the car and can make access for both the driver and to the engine difficult. The Mercedes-Benz 300 SL “Gullwing” received its iconic upward-opening doors when its tubular space frame made using regular doors impossible. Some space frames have been designed with removable sections, joined by bolted pin joints. Such a structure had already been used around
390-702: The Cleddau Bridge in Wales, West Gate Bridge in Australia and the Koblenz Bridge in Germany. That led to serious concerns over the continued use of box girders and extensive studies of their safety, which involved an early use of computer modelling, and was a spur to the development of finite element analysis in civil engineering . Spaceframe In architecture and structural engineering ,
420-519: The Mark VI , in 1952. This was influenced by the Jaguar C-Type chassis, another with four tubes of two different diameters, separated by narrower tubes. Chapman reduced the main tube diameter for the lighter Lotus, but did not reduce the minor tubes any further, possibly because he considered that this would appear flimsy to buyers. Although widely described as a space frame, Lotus did not build
450-421: The advantage of a box girder is that it better resists torsion . Having multiple vertical webs , it can also carry more load than an Ɪ-beam of equal height (although it will use more material than a taller Ɪ-beam of equivalent capacity). The distinction in naming between a box girder and a tubular girder is imprecise. Generally the term box girder is used, especially if it is rectangular in section. Where
480-480: The cells don't share loads from the entire girder, but merely act to stiffen one plate in isolation. Design of such complex integrated structures requires mathematical modelling techniques in advance of Fairbairn's day. Fairbairn's theoretical girder appeared at just the right time for the increasing demand for long railway bridges. Robert Stephenson engaged both him and Hodgkinson as consultants to assist with his Britannia and Conwy bridges, both of which contained
510-427: The cellular construction of the bottom flange was adopted, not because of the nature of the forces it had to withstand, but because of their magnitude and the consequent "practical difficulties which would have been encountered, had it been attempted to achieve the requisite sectional area in a solid mass") In some ways this isn't a "cellular girder" as such (compared to a spaceframe or geodesic construction ) as
540-414: The deck was built wide enough to accommodate three lanes of traffic, it carried one lane of traffic in each direction. In 1980 the lane arrangements on the bridge were changed to provide a third lane, and a tidal-flow traffic management system was introduced, with two lanes northbound in the morning and two lanes southbound in the evenings. When the first bridge was built, a second set of piles and abutments
570-546: The girder carries its "content" inside the "box", such as the Britannia Bridge , it is termed a tubular girder. Tubular girder is also used if the girder is round or oval in cross-section, such as the Royal Albert Bridge . Where a large box girder contains more than two walls, i.e. with multiple boxes, it is referred to as a cellular girder. The theoretical basis of the box girder was largely
600-406: The individual columns. Buckminster Fuller patented the octet truss ( U.S. patent 2,986,241 ) in 1961 while focusing on architectural structures. Gilman's Tetrahedral Truss of 1980 was developed by John J. Gilman ; a material scientist known for his work on the molecular matrices of crystalline solids. Gilman was an admirer of Buckminster Fuller's architectural trusses, and developed
630-497: The length of each strut. Chief applications include buildings and vehicles. Alexander Graham Bell from 1898 to 1908 developed space frames based on tetrahedral geometry. Bell's interest was primarily in using them to make rigid frames for nautical and aeronautical engineering, with the tetrahedral truss being one of his inventions. Max Mengeringhausen developed the space grid system called MERO (acronym of ME ngeringhausen RO hrbauweise ) in 1943 in Germany, thus initiating
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#1732788091829660-463: The lengths of the struts to curve the overall structure or may incorporate other geometrical shapes. Within the meaning of space frame, we can find three systems clearly different between them: Curvature classification Classification by the arrangement of its elements Other examples classifiable as space frames are these: Chief space frame applications include: Buildings Vehicles : Architectural design elements Space frames are
690-588: The railway track within a large tubular girder. Shortly afterwards Brunel also chose to use a pair of small diameter round girders as part of a larger truss at Chepstow . However, although many of the longest-span railway bridges in use in the 1860s used tubular or box girders Benjamin Baker in his Long-Span Railway Bridges was already dismissing the 'box girder with web plates' as 'the most unfavourable type for long-span railway bridges which it will be necessary for us to investigate'. The Coronado Bay Bridge has
720-509: The same welded steel tube fuselage frame. Many early “whirlybird”-style exposed-boom helicopters had tubular space frame booms, such as the Bell 47 series. Space frames are sometimes used in the chassis designs of automobiles and motorcycles . In both a space frame and a tube-frame chassis, the suspension, engine, and body panels are attached to a skeletal frame of tubes, and the body panels have little or no structural function. By contrast, in
750-548: The tallest box girder. Box girder bridges of shallow rectangular cross-section and aerofoil characteristics became extensively used in road bridges from the 1960s onwards, such as the Severn Bridge , being much lighter than the deeper truss -type girder construction used on previous bridges such as the Golden Gate Bridge . In the early 1970s, a number of box girder bridges collapsed during construction:
780-529: The use of space trusses in architecture. The commonly used method, still in use has individual tubular members connected at node joints (ball shaped) and variations such as the space deck system, octet truss system and cubic system. Stéphane de Chateau in France invented the Tridirectional SDC system (1957), Unibat system (1959), Pyramitec (1960). A method of tree supports was developed to replace
810-461: The work of the engineer Sir William Fairbairn , with the aid of the mathematician Eaton Hodgkinson , around 1830. They sought to design for the most efficient beam possible in the new material of riveted wrought iron plates. Most girders are statically loaded such that one web is in compression, the other in tension. Fairbairn's original cranes used a cellular construction for the compression face for their jib, so as to resist buckling. This jib
840-687: Was built a few metres downstream, allowing for future duplication. The second bridge was opened for southbound traffic on 22 August 2008, leaving the first bridge for northbound use only. There are two other road crossings over Georges River downstream of the Alfords Point Bridge: the Captain Cook Bridge , which opened in 1965 and connects Sans Souci to Taren Point ; and the Tom Uglys Bridge , which opened in 1929 and connects Blakehurst to Sylvania . The bridge
870-567: Was built as the last link in the Hornsby-Heathcote county road (although a number of route realignments followed), and serves a metropolitan function. Construction of the bridge allowed the decommissioning (in 1976) of Lugarno ferry, which had operated since 1843 on Surveyor-General Thomas Mitchell's line of the Illawarra Road. The ferry had operated between Lugarno and Illawong . Box girder Compared to an Ɪ-beam ,
900-588: Was curved, tapered and formed of riveted wrought iron plates. Three cells were formed inside the concave (lower) face of this girder, again of riveted plates. Where a tubular girder is used as a bridge span (i.e. loaded in the centre rather than at one end, like a crane) the compressive force is in the top web of the girder and so the cells are placed at the top. Dynamic forces (moving loads, wind) may also require both faces to be cellular. (The preserved Britannia Bridge section shows that both top and bottom flanges were of cellular construction, but (according to Fairbairn)
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