General Mechanical

General Mechanical

Non-zero bending moment on released beam188 elements

    • Catilina
      Subscriber
      Hello all,nI am running a benchmark on beam188 elements to compare with old beam44 elements we usually use in my company. I modeled a simple frame steel structure and released dof's in rotation to model hinges on a beam. All beams are either parallel to XY, XZ or ZY plane and are only subject to gravity load along Z axis. For beam44, it is performed with keyopts and it works well (freed dof gives a 0 value of the internal effort related to). For beam188, releasing e.g. roty dof (using either ENDRELEASE command or doing it manually) should give a zero bending moment MY but it is not the case. There is a non-negligible value (having the same sign as midspan BM) that cannot be ignored, more particularly when the load increases. However, I get the exact maximal bending moment (ql²/ formula for a simply supported beam when I substract the value on the supports to maximal BM on midspan.n Anyone has an idea about why there are still residual efforts when a dof is released in beam188 whereas it works well for beam44 elements ?n
    • peteroznewman
      Subscriber
      Please add some images to show the beams. I don't know what to construct to reproduce your result. Please add some images to show the moment at the end.nPlease File, Archive and make a .wbpz file, then put that in a .zip file and attach that to your reply using the paperclip icon. Say what version of ANSYS you are using.n
    • Catilina
      Subscriber
      Hello,nI am sorry for late reply. Here is attached the db file and its results (with beam188). We use ANSYS APDL V17.1. nHereafter is a picture of the whole structure (with the beam released).nThe second picture shows the BMD with the beam meshed with B44 elements.nThe third one shows the BMD for the same beam meshed with B188 elements.nnnThank you for having answered.nn
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