Hi,
Please could one of the support explain why the simple 2D portal frames I have developed show strange deflection patterns.
I have developed a 2D test model to justify the general behavior of a larger 3d model by doing the following:
I developed 3 identical portal frame models (as separate structures in one rtf file) and applied an identical nodal load to each at the same node. All 3 models have fixed supports.
I then kept all the member joints fixed in the first model. The second model I applied moment releases "fixed-pinned" to both vertical columns to release moment between the beam and column. The third model I applied "pinned-pinned" moment release to the beam.
Model 2 and 3 should have identical behavior in both load distribution and deflection. However, this is not the case. The bending moments, shear forces and axial forces are identical in both but the displacement plots are both incorrect.
In model 2 it displays the displacement of the columns as being in double curvature which cant be as there is no reversal of bending moment in the column. It displays the deflection of the beam correctly as 0 (only axial force in the beam).
In model 3 it displays the displacement of the columns correctly but displays the beam as having single curvature which cant be the case as there in no bending moment in beam due to the releases.
The correct answer would be a combination of model 2's beam and model 3's columns.
Please confirm the issue is? I have attached the test model.
Regards
Dane