+xFor simple structures like frameworks, and easy laminates, you could easily calculate rough but quite accurate numbers, if you got some education in mechanics. Unfortunately this is nothing you can learn within an hour internetting. This usually takes at least 3 semesters at the university. Especially if you really want to be shure you are doing it right.
You could make smaller models and get results for a full scale model by experiment. But neither length not thickness are acting linear when it comes to bending, so again you need the mechanical understanding to get anything helpfull out of experiments.
Thank you for your explanations!