Reinf. Conc. Beam on Wall Model

[runcc]

I'm trying to design a single story cast-in-place reinforced concrete room comprised of concrete walls and a concrete roof. My initial thought is to have beams spanning across the room every 10-12 feet on center. The beams will span approximately 50 feet. The walls will be 8" thick and about 19' tall and my initial calcs indicate that the beams should be around 18" wide and 36"-40" deep. When modeling a frame comprised of a beam and the portion of wall that is sits on, is there a rule of thumb for how wide a section of wall to use? It seems like I should use a section of wall that is 2 or 3 times wider than the beam in order to provide a more realistic stiffness for the frame calculations, but then transferring the moment from the beam to the wall seems like an issue if the beam is only 18" wide, but I have assumed a 54" width of wall.

Would it make more sense to add a pilaster at each beam and then just model the beam and pilasters as a frame?

 

[Teguci]

ACI 318 places a limit on the wall width to be considered for a point load - beam width + 4 x wall thickness up to center to center distance between loads.

I like pilasters. Especially for connecting large beams.

Wall and beam must be connected - do a quick sketch for developing the connection across the interface.
What is the lateral system for the wall?
Consider some eccentricity on the top of wall due to volume change.
Check slender wall buckling.
How will you handle local fixity - top of wall will lean in and wall at the base of the beam will be locally pushed out.
Consider constructability and phasing.

8" load bearing wall for 19' ht seems very aggressive.