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3D Meshing – Concrete-Rebar Contact Meshing

    • andrefpitt
      Subscriber

      Hello everyone.

      I'm trying to extract the correct values of stresses acting on the concrete slab caused by the reinforcement anchorage pull-out (see figure below). The main objective is to map and extract (if possible) the cone stress in the concrete around the reinforcement area due to the tension/pull-out forces. To achieve I tried 2 different models.
       
                
      1) In the first one, the reinforcement has been modelled as volumes embedded
      into the slab, however, the element number limitations didn't allow me to compute the results. I have been trying to add inflation and reduce element sizes, but getting the numbers down to the allowable has been difficult. And I'm not confident that this way would show the cone effect in the slab.

             

      2) In this second model, the reinforcement has been modelled as line beam (type reinforcement) and the mesh did work well limiting the size of the elements in the reinforcement. Despite being able to mesh and get the stresses in the rebars, the mesh has been done poorly, without a proper mesh connecting the reinforcement to the slab, in that way, I haven't been able to get the stresses in the slab nor a glance to the cone stress effect in the slab. 

       
           

      My question is, is there a way to either go around the elements limitation in case 1 or a way to add a contact mesh in case 2 to extract the results?

       

      Thank you so much for your time and assistance,

    • Bill Bulat
      Ansys Employee

      Perhaps your student version imposes a limit on the number of nodes and/or elements you may have in any given model?

      It seems to me that, at least for the purpose of demonstrating that this conical stress distribution can be obtained, you need not model the entire slab or all of the rebar. Perhaps you could model a relatively thin slice (narrow in the y direction) that includes only 2 or 4 rebar. Personally, I would strive for a conformal mesh between the individual rebars and the slab into which they extend so that no contact elements are created on the rebar/slab interfaces. You could also limit the extent of the geometry in the x direction, since stresses will likely be localized to the rebar/slab interfaces.

      I don't know what kind of contact got created in your model in which the rebar was modeled with beam elements. I suspect there may be no connection between the beam elements and the slab under the surface of the slab, in which case the model would not adequately represent the physical connection. So, without employing other "tricks" that may require the use of APDL command objects to access MAPDL solver features that are not natively exposed in Mechanical, I would for now recommend sticking to modeling the rebar as solid cylindrical bodies.

      Kind regards,

      Bill

       

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