General Mechanical

General Mechanical

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Composite beam: Stiffness behaviour

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    • Noah Böhm
      Subscriber

      Hello together,

      I modelled a composite beam consiting of a steel girder and a cross laminated timber (CLT) slab in mechanical. The beam is a single span system with a line load.

      Every layer of the CLT is modelled individually. The material modell of the timber is defined as an orthotropic elasticity with three different modulus of elasticity for each direction.

      For a load in the linear elastic range, i evaluate the deflection at midspan and use this to determine the elastic bending stiffness. 

      I compared the results to an analytical caluclation approach, a simplified truss modell with 2d elements for the timber and another numerical modell with 3d elements for the timber. All these calculations lead to significantly lower deformations (10 to 25 %) although all parameters were inserted the same. 

      If I calculate the CLT plate or the steel beam alone, the result is the same in all programmes as in ansys. if I set the modulus of elasticity at right angles to the plate plane very high in ansys, the result is also the same. 

      The composite bending stiffness is therefore determined much lower with ansys because the modulus of elasticity at right angles to the plane of the panel has a much greater effect than with the other programmes.
      why is this the case? have i chosen a wrong setting in ansys?

      Thank you for your help!

       

       

    • Ashish Khemka
      Forum Moderator

      Hi,

      Please see if the following forum thread is of use to you: CLT modelling (ansys.com)

      Thanks,

      Ashish Khemka

    • Thomas Hirche
      Ansys Employee

      Hi Noah,

      I think there was some confusion with the shortcut CLT. In your case it describes the plywood laminate pattern. The link you've been provided with talks about Classical Laminate Theary (CLT). Apologies for that. However, it is difficult to spot the issues just from your description. A first guess is that it is rather a problem of the contact settings between crosswood structure and steel profile. We could help you in detail, but you would need to create a service request within Ansys Support. Then we also can review your models guiding you through the correct settings.

      Kind regards

      Thomas 

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