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Can I model castellated/ cellular beams in Diamonds?

For the global analysis (determing M,N,V in a construction) I-shaped cross sections with reduced properties (calculated near the openings) can be used:

  • Find the parent section in the Diamonds section library and adjust its height H.
  • Adjust the properties Iy, Wy (elastic and plastic), IT and AVz (substract opening from the properties of the gross section)
  • Adjust the imperfection factor for lateral torsional buckling to
    • curve c (=0,49) for double symmetric castellated beams (circular or hexagonal openings) made from hot rolled parent sections
    • curve d (=0,76) for all others
  • Check that the cross section of the tee section (part of the web above and below the opening) is less conservative than the cross section of the entire beam. If not, also adjust the cross section classification.


Next to the usual checks from EN1993-1-1 (implemented in Diamonds), the additional checks mentioned below also apply (not implemented in Diamonds). These additional checks are mainly local and relate to the tee section (part of the web above and below the opening) and the web post (part of the web between two openings).

  • Buckling of compressed tee due to global bending
  • Resistance of tees in Vierendeel bending
  • Web post shear, bending and buckling

Also note that the deformation will be larger than calculated with Diamonds because of the effects for Vierendeel shear deformation along the openings. This can be calculated with a Vierendeel (framework) analogy.


A new Eurocode part is in the making about these beams (EN1993-1-13: Steel beams with large web opening). Current design rules can be found in:

  • Lawson, R. M., & Hicks, S. J. (2011). Design of composite beams with large web openings (SCI P355). SCI (Steel Construction Institute).
  • CTICM. Arcelor Cellular Beams: Detailed Technical Description.


More extensive calculations are possible with:


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