I have had a few projects experience on this subject, I recommend you to copy the slant beam in the ide with the copy option after entering it correctly for 1 time. otherwise, the beam is modeled as rotating around itself, which is very difficult to solve. On the other hand, I would not recommend modeling the tribunes as beams as it will throw unnecessary reinforcement in time and on-site applications, I think the tribunes should be modeled as inclined slabs, and if necessary, additional reinforcement should be added to the appropriate places. Although I tried to solve the tribune in other programs, no program offers a complete model option in this regard. Options such as stairs should be considered. good work.