It sounds like changing your boundary restraints in this case might not have a big effect on your results. Are you looking for stresses in those bottom beams? If the load is purely vertical I would expect it to mostly travel directly down the columns and into the floor. Creating a virtual wall and setting up a no pen contact between the bottom beams would be another option but your solution would take much longer. This looks like a good example for using symmetry planes to cut down on simulation time.
Thanks for the reply.
Well just the stress all round really, but am i correct in saying that with the bottom rails being fixed, it wont show the streses in those members?
I'm still quite new to the simulation side of things, when applying a symmetry, do i need to cut the model in half then apply the symmetry to those cut faces? or is there a way to do it using planes?
I'll go run it again and i'll put it up for anyone to have alook.
Hey Robert - Since those beams are not truly fixed to the floor you will just not see the correct stress. From a simulation perspective, using a fixed face cuts down on simulation time and gives you a good initial result of where your stress hot spots might be. If those beams weren't fixed in place and no friction was applied to the contact between the beam and the floor, the smallest lateral load could result in the entire structure flying off into space (you would see a large displacement warning in the middle of the analysis). In reality it is the friction force which would resist any potential lateral loads. You could set a coefficient of friction in the no penetration contact but I don't think you need to. Those bottom beams really aren't doing much in your loading case.
As for symmetry, it looks like you could cut the model into a 1/4 and apply symmetry to each cut face. I would suggest making a new config and applying the cut at the assembly level. Let me know how it goes.
The symmetry suggestion is a great one.
Fixed is a good first approximation.
From there I'd go with 1 fixed and the rest Fixed in the normal. This allows the rest to move in the plane. With symmetry, you can just use normal because the sym bc will keep things in place.
After that you are taking about contact. I don't think you need that level.