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How to compute geometric stiffness for volumes [ Reply ]
By: Balmes on 2017-05-30 12:12
[forum:866]

Question : I would like to account for stiffening effects due to pretension in computing modes of a volume structure.

Answer : stiffnening effects are due to the existence of geometrically non-linear effects. You must thus

  • Perform a static computation to your loads (calling fe_simul static for example) and store the response in the stack as
    mdl=stack_set(mdl,'curve','StaticState',def).
  • Assemble matrices that account for prestiffening effects (note the MatDes=5 and not 1). Typically a call of the form 
    [SE,Case]=fe_case(mdl,'assemble -matdes 2 5 -SE NoT')
  • Compute modes 
    def=fe_eig({SE.K,Case.T},eigopt)