Staad Pro - Warning Out of Plane Loads Applied in PLANE Structure

Hi - I two warnings in my analysis output file. I do not have any loads applied other than X and Y direction as far as I can tell (attached load excerpt). Is there some obvious reason I am missing for this warning?

  • In load cases 4 and 5, you have applied a distributed load on some members along their local Y axis.

    124 TO 126 UNI Y 32

    If the local Y is at an inclination to the global XY plane, these loads are acting at an inclination to the plane.

    Other reasons :

    If you have unsymmetric sections like Z shapes or single angles, even if they are in the XY plane, they can deform out-of-plane.

    If the model has solid elements, Poisson's effect will produce out-of-plane effects for inplane loads.

    Change the structure type to SPACE, and, check whether there are deformations or reactions along global Z. Then, try to find the cause.

     



  • Kris - I changed to space eval and yes...I had some global z reactions from the local Y member loads. I'm not sure why as it seems I am applying the load only in the X-Y plane.  

    More info on the model...

    This is an arched frame roof with with straight side walls.

    The structure has a dual pipe inner and outer chord members (I input combined shape prismatic member properties).

    The arch portion is modeled with curved members.

    Curved members have the local Y member load since that seems to be the only way to apply them (wind pressure).  This is causing the out of plane loading.  

    I did not beta any members, so as far as I can tell the local Y axis of each curved member IS in the x-y plane.  With loads in model view this appears to be true.

    Any other thoughts?

  • The use of curved members is the most likely reason. The local Y for these members would be normal to the plane of curvature and so loads in local Y would be out of plane loads. We do not recommend using curved beams anyway, in spite of the fact that it has a superior stiffness matrix, due to several limitations that exists in the current implementation. For details of these limitations, you may refer to the following forum post

    communities.bentley.com/.../8353.aspx

    So try replacing these curved members by a series of straight segments and it would most likely take care of the warnings. If not, you may upload the file and we can take a look.