For my building, I decided to use concrete elements on the first floor and wood elements for the two upper floors. While I want the central, open atrium to be the main feature and for the structural system to be mostly hidden for the bottom floor, I want the structural system to be more visible in the top floors since wood can be more aesthetically and bring a more natural element to the space. I did not want to use any steel structural framing because steel has significant environmental impacts, while concrete has the potential to be sustainable through the use of alternative cements, and wood is a renewable resource. With this in mind, these are the elements I have chosen for my structural system:
- 3” lightweight concrete on 2” metal deck for the floors
- 72” x 48” x 18” rectangular concrete footings
For the first floor:
- 18” x 24” rectangular concrete columns
- 12” x 24” rectangular concrete beams
For the other floors:
- 14” x 22” timber columns
- 8.5” x 17.875” Southern Pine Glulam Beams
Here is a screenshot of my structural framing system:
Since my building is very rectangular, I placed my columns at grid intersections. I was able to keep the columns at the edges of my building, so there are none in the middle of any rooms. I had to work my beam systems around the two sets of stairs and elevators in my building as well as the skylights in my roof. I also extended some beams to accommodate the terrace on the east side of the building.
One thing I am still considering is using trusses instead of beams in some areas of the first floor (such as around the lobby) in order to have longer spans, fewer columns, and more open space. I would also be interested in using CLT for some of the floors.
Looking at the model coordination, it is clear that some issues still need to be resolved, such as columns interrupting windows.