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Castellated beams are electrically welded. So the introduction of the castellated beam was closely connected with the development of electrical welding technology in steel construction, at about the end of the 1920's. The earliest known castellated beams were designed and manufactured in the early 30's by the Skoda factories in Pilsner. These were roof beams with a free span of 12 metres in a factory in Doudlevec (Czech Republic). The first patent application for castellated beams dates from 1937; the British Patent Office granted the - extremely comprehensive and exhaustive - patent in 1939 to the British applicant G.M. Boyd.
A suitable calculation method has proved essential for the broader application of castellated beams. After all, this is not a component that can be dimensioned "intuitively". The initial impetus for the (elastic) calculation method was given in the former Czechoslovakia by František Faltus. In 1942 he published two articles about his calculation method in the professional journal Technický Obzor.
Not until the second half of the 50's was further development undertaken, in both America and Germany. The elastic calculation method was fully perfected during the period 1955-1965.
The plastic calculation method was introduced into steel construction in the early 70's. Applying this to castellated beams demanded quite a lot of further development, since the web openings represent substantial discontinuities in the beam. The theory was underpinned by the necessary experimental research into the failure behaviour and mechanisms of castellated beams. By the mid-70's the calculation method had become more or less crystallized. The Merkblatt of the Beratungsstelle für Stahlverwendung, Düsseldorf, 3rd edition (1976), gives a 53-page richly-illustrated exhaustive overview, including numerous diagrams for determining the choice of section and the geometry of the castellated beam.
Nowadays, of course, castellated beams are calculated by computer. Various software houses have developed sophisticated modules for this purpose and have incorporated these in their steel construction software.
A second important factor in the emergence of the castellated beam is its production technology. Originally the rolled sections were flame-cut using a simple template and a handheld flame cutter. Shortly after the Second World War this became too costly and for that reason automated flame cutters were brought into operation during the 50's. Hubert Litzka developed the first fully automatic production line for castellated beams. This proved to be so successful that for a long time castellated beams were also known as Litzka beams. Alternatively (for standardized light castellated beams) the required rack profile could also be stampcut out of the rolled sections on heavy presses, a method which was mainly applied in America.
In the late 70's mechanically operated fully automatic flame-cutting machines were introduced, which in turn were followed by machines using optical reading heads. The advantage of the latter was that they could work directly from a drawing and so were more flexible. With the introduction of minicomputers, and later PC's, the cutting operation has been further optimized. With computers special patterns can easily be generated if required; for example, those applicable to steeply curved castellated beams.
As castellated beams require a sequence of short welds, the welding is still mostly done by hand. Welding automation has only paid in factories producing vast quantities of standardized (light) castellated beams. A familiar application of such beams is in steel multi-storey car parks (in America).
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