Home Forums NextFEM Designer support forum WoodCheck deflection limit state

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    Hello, I was verifying some roof beams with wood check and the index for the deflection limite state was very high (not verified). Upon checking deformation, the calculated final deflection looks like an order of magnitude higher than it should be. I took the instantaneous values from nextfem designer output tables and multiplied every single one by 1+kdef for permanent and the combination with psi0 and psi2 as written in the manual for the variables, but I don’t get the same value. In this case it is dy=0.0210949578 m from woodcheck log file and 0.00318431 m from hand calculation.
    Besides this, it is not that clear to me how the software chooses the main variable load and where to specify the type of variable load for the appropriate choice of psi0 and psi2 values, especially if there is more than one in the same model applied to different structural elements, for instance Cat. A for the floors and Cat. H for roof maintenance. Maybe I am missing out some input data I should specify.
    I made a simplified model to test out just the single beam for deflection, I attach it here. Thank you in advance.

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    NextFEM Admin

    the principal variable loading case is assumed automatically as the case with the highest combination multiplier amongst all the variable cases. In you model, it is Q-CatH. This is always conservative, as the greatest factor in combination leads to the higher factor for deflection calculation as per NTC2018 C4.4.7.

    With kdef=0.8 (SCL=2) you may have (values in m):
    Secondary-variable Neve: (psi0 + psi2 * kdef) * f = 0.0004886155
    Permanent G1-PP: (1 + kdef) * f = 0.00010358946
    Permanent G2-Cop: (1 + kdef) * f = 0.0017873568
    Principal-variable Q-CatH: (1 + psi2 * kdef) * f = 0.00053534396
    Secondary-variable Vento_press: (psi0 + psi2 * kdef) * f = 0.000373014

    for a final sum of 0.00328791972.
    It seems the model you sent behaves differently – we’re investigating the issue, please keep your program up to date – if this is the case, we’ll release a patch asap.


    Ok thank you, so hand calculation was right. Thank you also for explaining the choice of the combination multipliers for variable loads.
    Yes the program is updated, so I’ll wait for you to release a patch.


    One more question. You used for Q-Cat.H psi2=0.3 which is not the psi2 for Cat. H, it is 0. Where is this value taken from?

    NextFEM Admin

    psi values can be specified from the Load combination generation mask (Assign / Generate combinations).

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