How innovative to be considering steel castings in your platform design. I hope I can help. As you know, the characteristics of today's steel castings have nothing to do with its earlier cousin: cast iron. Steel castings are higher strength, weldable and more ductile. You generally see castings in conjunction with cable and glass structures, or in complex tubular joints for buildings or bridges. While common in Europe, there is a definite trend emerging in North America. At the CDP building in Montreal for example, steel castings were used for the first time on complex steel tube joints for an 8-storey high glass facade. The foundry was Castech.
I wrote a short article (how's your French?), with photos, of a talk that was presented at a North American Steel Construction Conference. www.quebec.cisc-icca.ca/content/messageboard/archives/000052.asp
The talk is part of the proceedings that I received on a CD, but I have permission from the author and AISC to make it available. www.quebec.cisc-icca.ca/Library/pdf/castings_schober.pdf
The author, Hans Schober, is a partner at the renown German firm in Stuttgart: Schlaich, Bergermann and Partner (www.sbp.de). Hans Schober showed several impressive examples of steel castings in cable net walls and tubular bridge structures. Although most of the examples were "high-profile" projects, suggesting that perhaps steel castings are not cheap, there were always valid reasons that justified their use.
Hence, for castings to work, you need a reason! Do you have repetition (so the cost of making the mould is partly amortized)? (A must) Are there many elements coming to one point? Do you want to use castings in a high-stress zone? Do you have a foundry in your area that has the expertise? Would castings provide aesthetic advantages? If you answer yes to at least 3 of these questions, then maybe it deserves further investigation.
I heard of a rough `rule of thumb' that if the connection started to cost four times as much as the material it is made of, then steel castings start to be interesting. You should note that the surface of the castings is not the same as the surface of a rolled steel shape or plate. Also, there are limits in thickness (6 mm is suggested), and it is not possible to apply mechanical energy to modify or increase the properties of the moulded material. The material standards for castings are not the same as the standards used for rolled steel shapes and plates.
Since I answered this question, I met one of the engineers of the design team who said the project had gone through. Congratulations! However, he admitted it was not obvious in the beginning how to get involved, as this was the first time he had dealt with steel castings. As architects express steel more and more, I am confident that their use will increase, and innovations will continue.
This question appeared in the "Ask Dr. Sylvie" column of Advantage Steel no. 22, Spring 2005.