Why are my beams floating away when i try to do an analysis. Some stay, some float away and are ignored for the use of the analysis. I never checked a box that said "please make my life a living hell and do everything that could be of no use to me" I also never checked a box that said "please make all my beams float away into space, i put them there just for the fun of it, not to be analyzed..."
GRRRRR
Someone help
My guess is you have a funadamental problem with your boundary conditions. While SW Simulation can give you results, it only knows what you tell it. You must define proper boundary conditions with each and every part. As Derek mentioned, part of this includes contacts. SW SImulation doesn't "understand" two objects colliding with one another unless you tell it to look for this by defining contact sufaces.
Without a screenshot or description of what you're modeling, it's really hard to hazard a guess at anything specific.
If you have an assembly with multiple parts and do not define how they interact (with contacts for example), SW Simulation will apply loads and unless you have a contact or BC to stop a part, it will "fly off".
Please note: MATES ARE NOT CONTACTS! Because you define two parts of an assembly as coincident when you built it HAS NOTHING to do with how they behave in Simulation. The default contact is bonded which means and touching pieces will have their nodes glued together. If you have a TINY gap between them and don't define a no-penetration contact, one part can and will "fly away".
What you should consider doing is drawing a free body diagram of the item you're simulating. Take each part with applied loads and determine what forces will counter those loads. Those counter forces must be boundary conditions or contacts.
Since you're getting parts that are flying off, you're missing an opposing force to keep it in place. This may be friction, a no-penetration contact gap, or a non defined fixture.