I'm trying to do some analysis on a Trailer Chassis, which is generally a fairly basic frame made up of lengths of RHS.

My issue is that i'm not sure how i should treat the joins between the tubing etc.  Currently the model is made primarily from weldments, with the addition of some webs and brackets etc.  It's a little complex to run as just Beams, as i don't get proper "nodes" in some areas due to the design.  So i'm running it as all solids.

The thing is, that i've just got bits of tube cut off square butted up to other bits of tube, and normally there would be a nice fillet weld around the whole join.  But simulation doesn't seem to recognise "welds" and hence i've just "bonded" the faces using contact sets.  This seems to work OK, but is this the best option?  It doesn't seem quite equivalent to me, as you get areas where part of the square cut tube would be welded to the radiused corner of the mating tube, but in simulation these faces aren't contacting.  On part of the suspension for the same trailer, there is a section of rectangular tube that joins up with a round tube, which creates a gap that would normally be filled by weld, but there doesn't seem to be a way of "welding" across the gap.  Should i be converting the model into a single solid body and filleting the joins where all the welds would be??

This is kind of a critical project, so no time to go and do a Solidworks Simulation course...