So four pieces of aluminum tube will be welded together to make a frame. Are the welds both on the inside corner and the outside and highlighted in yellow below?
Where are the screws placed? I assume the rubber strips are laid on top of the tube frame, then screws go vertically through the rubber and into the top face of the aluminum tube, but they don’t reach the bottom face of the tube, is that right? Is it just 2 screws, one at each end of the rubber strip?
The elements on the tube are not good quality. They have a very high aspect ratio.
You will get better quality elements if you have a tube created by a sheet body with just four faces.
Here is what the geometry looks like without solid tubes for just these top two tubes.
Now the tube is meshed with shell elements and has an assigned thickness. This will use far fewer nodes and elements.
I will address the question of the soil in the next reply sometime later.