2 KudoZ points awarded for this answer. Comment: "This is the right answer for the term I stated, but in the end I went with "forces affecting the door", as the text is essentially kept very general (non-technical) and the "Türkräfte", which is the original term used, is not specific, either. Upon reading the text several more times, I concluded that it was intentionally non-specific and translated it in that vein."