For my structural design, I have a few cases that are the longest, but are essentially the same case. Therefore I decided to take one of these cases, along with two unique sections of my building. The longest beam in each is as follows:
Case 1: 37'
Case 2: 32'
Case 3: 19'7"
For beam case one and three, I used a live load of -.05 ksf. Case one will consist of office spaces and dining, so there will be a heavy dead load there as well at -.04 ksf. Case two is the gallery space and so there will be many people walking through that space, and hopefully art to view as well. For this space, I used a live load -.05 ksf as well, but a lighter deal load at -.03 ksf since there won't be as much going on there. As for case two, this will be an outdoor balcony off the second floor, so I used much lighter live and dead loads. I dropped the live load to -.03 ksf and the dead load to -.015 ksf because there is very little this section has to support. Where my design gets tricky, is the main atrium section in which there will be larger dead loads due to the amount of material to support. Similarly, there are openings in the floor that make designing the structural elements far more complex.
For my HVAC system, the first floor is simple. There will be room in between the beams and ceiling to fit various systems in. The second floor will be difficult because much of the main building has the atrium that needs to be open. I may consider utilizing a floor HVAC system for the second floor, or may need to move my HVAC vents aside. By this, I mean that I could hide them in parts where there is ceiling or push them off and angle the openings of the vents inwards. Either way, I'll have to be clever about it.