Difficulties in Fe-modelling of an I-beam Subjected to Torsion, Shear and Bending (Civil Project)

In this thesis six different models of IPE240 have been created in order to study their behavior under shear, bending and torsion. These models simulate IPE240 but differ in the boundary conditions, in the loading and the length of the beam and in some connections which connect certain elements.

In this study the modeling and simulation of the steel member is executed in ABAQUS Finite Element Analysis software with the creation of input files. When developing a model for the finite element analysis a typical analysis process is followed. All the parameters that are required to perform the analysis are defined initially to geometry which is half the beam due to symmetry, and the material properties of each model are defined too.

Then a mesh is generated for each model, the loads of each model are applied which are expressed as initial displacement. Subsequently, the boundary conditions for each model are defined and finally the model is submitted to the solver when the kind of analysis has 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 model are studied. In these contour plots, a large concentration of stresses and problems which arise in each one of the models are notified. As it has been observed in all models, the beam yields at the flanges of the mid-span and collapses at the mid-span. Therefore, the failure at the mid-span is more critical than the failure at the support. Moreover, the beams are weak in bending due to the fact that they twist 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 occurred at 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 hand calculations 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, while comparing the load-displacement curves of the two different plastic behaviors, it is observed that the model with an elastic-plastic with a yielding plateau slope behavior has smaller maximum load resistance 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 the models and a way of solving them is suggested.
Source: KTH
Author: Alexandrou, Miriam

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