Khaja,
there is a page full of posts from more than four years listed when using the 'Search' tab for "ductile iron" in the CAESARII forum . others have learned to analyze ductile iron. you can learn too. first go through the design differences of dimensions for ductile iron pipe, fittings, and the flanged connections that result in much more weight. that will help you in starting the model.
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R Yee