Effective Width of Compression Area

The effective width of compression area for an interior beam is calculated as follows:

b_{e f f} = {[(\frac{ϕ}{16}) (\frac{f_{y}}{460}) (\frac{300}{s}) (\frac{40}{f_{c u}})]}^{0.3333} \times 1, 000 + 2.5 g

where

ϕ	=	transverse reinforcement diameter (program assumes 16 mm),
f_y	=	reinforcement strength (program assumes 460 N/mm²),
s	=	bar spacing (program assumes 300 mm),
f_cu	=	concrete strength for the in situ concrete (as specified by the user, generally 30 N/mm²),
g	=	gap, not to exceed 100 mm

b_eff is limited by distance to adjacent beams, slab edges or openings and by span/4, if appropriate. For edge beams the contribution of the edge to b_eff is the lesser of the slab edge distance and six stud diameters. If Hollowcore slab is being used and it is parallel to the beam on one side, the contribution of that side to b_eff is equal to six times the stud diameter.