I’m creating a dog run with wood and am trying to analyze the weight of the combined pieces. I want to do this because I want to know where the pieces need the most support? Example; If I combine several beams together to make a frame, what happens to the weight distribution if the beams become longer or shorter?
If you live where there are code requirements you may need PE.
If there are codes talking to your locale permitting folks will give idea what you will have to deliver to them.
Why do you limit question to Su only. I was able to find spread sheets in the past for my use that are free. You may want to search the net also.?
You more than likely need to do a static analysis only so there should be many free programs. Dynamic is a different story.