RCDC Beam design - effective depth Calculation

Bentley Team,

How is the effective depth for beam being calculated for a beam with two or more numbers of layers in RCDC software?

Please provide the basis and validation for the same.

I could find some formula related to effective depth in FAQ in the link below, but that is not giving correct value for the design I have.


  • Hello,

    In RCDC the effective depth of a beam is calculated in the fllowing manner.
    If D is the total depth and d is the effective depth, then
    d = D - Clear Cover - 16mm -12.5mm
    d= D- Clear Cover -28.5mm

    Here, clear cover thickness includes stirrup dia. For effective depth calculation it is assummed that 2 layers of reinforcement is present and effective depth is calculated from the top most fibre to the mid depth of spacer bar. Though it is conservative in some cases, but we are in safer side. Considering this fact, a value of 16mm is considered as the bar dia of bottom most layer reinforcement. Then 25mm spacer bar is considered for which we take half the depth in claculation as 25/2=12.5mm.

    After getting the d value it is again rounded down to nearest 5mm interval, which in turn make the aforementioned 28.5mm value, 30mm.

    Can you please check and let me know if this matches with your calculation?

    Thanks & Regards,

    Abhisek Mandal

    Global Technical Support

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