High forces observed at the edge/corner nodes of portal frame

Creation date: 4/27/2022 6:04 PM Updated: 5/21/2023 3:54 PM

Question:
Why do the results at the edge/corner nodes of the portal frame is very high?
Example:

The shear force, Vxx, at the edge/corner of the portal frame structure is very high under a positive temperature gradient load case. Only a temperature difference of 11 C is applied, but the shear force is up to around 1400 kN, compared to that due to live load HA & HB45, which is only about 190 kN. Shear due to temperature is almost eight times higher than HB45 vehicle.

Answer:

As we know in FEA models results mainly depend upon the nodes. Now in plate elements, as extreme plates, there are no other elements that share the loads that come onto the extreme nodes (in our case per node only 1 element). That is the reason for high results on extreme nodes as compared to the internal nodes which are shared between 4 plate elements.

If you see the extreme plate in detail, forces are high only at the corner line, at the internal line results are approximately equal to the inner element. By default, the program shows only the maximum value of the plate that why it seems like extreme plates are taking very high forces.