Difficulties in FE-modelling of an I-beam subjected to torsion, shear and bending.

University essay from KTH/Byggvetenskap


In this thesis six different models of IPE240 have been created in order to study their behavior undershear, bending and torsion. These models simulate IPE240 but differ in the boundary conditions, inthe loading and the length of the beam and in some connections which connect certain elements. Inthis study the modeling and simulation of the steel member is executed in ABAQUS Finite ElementAnalysis software with the creation of input files. When developing a model for the finite elementanalysis a typical analysis process is followed. All the parameters that are required to perform theanalysis are defined initially to geometry which is half the beam due to symmetry, and the materialproperties of each model are defined too. Then a mesh is generated for each model, the loads of eachmodel are applied which are expressed as initial displacement. Subsequently, the boundary conditionsfor each model are defined and finally the model is submitted to the solver when the kind of analysishas been defined. Namely, the analysis which is performed in this thesis is static stress analysis.When the ABAQUS has run the models, the contour plots for the von Mises stresses for each modelare studied. In these contour plots, a large concentration of stresses and problems which arise in eachone of the models are notified. As it has been observed in all models, the beam yields at the flangesof the mid-span and collapses at the mid-span. Therefore, the failure at the mid-span is more criticalthan the failure at the support. Moreover, the beams are weak in bending due to the fact that theytwist almost 60-90 degrees under a large initial displacement at the control node. Additionally, much localized failure and buckling occurred at the mid-span, and local concentrated stresses also occurredat the bottom flange at the support due to the boundary conditions details.Thereafter, a verification of the results of the ABAQUS through the simple analytical handcalculations is performed. It is concluded that the error appearing in most selected points is small.However, in some points in the web of the mid-span the error is greater. Additionally, whilecomparing the load-displacement curves of the two different plastic behaviors, it is observed that themodel with an elastic-plastic with a yielding plateau slope behavior has smaller maximum loadresistance than the model with a true stress-strain curve with strain hardening behavior.Finally, some errors and warning messages have occurred during the creation of the input files of themodels and a way of solving them is suggested.

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