Concrete Shear Capacity

Beam shear or one-way shear capacity is taken at a distance of d from the support face of the beam. The value d per ACI 11.1.3.1 is taken as the reinforcement depth for the bottom flexure bars using the user defined cover to center of bars based on the number of bar layers at a given location.

The shear capacity of the concrete in the beam is calculated using one of the following two equations depending on the presence of axial compression load in the beam:

V_{c} = 2 \sqrt{{f^{'}}_{c}} b_{w} d

Equation ACI 11-3

V_{c} = 2 (1 + \frac{N_{u}}{2, 000 A_{g}}) \sqrt{{f^{'}}_{c}} b_{w} d

Equation ACI 11-4

where

N_u	=	the maximum factored axial compressive load in pounds at the location of Vu (not accounting for effects due to creep and shrinkage)
d	=	the reinforcement depth for the bottom flexural bars using the user defined cover to center of bars based on the number of bar layers at a given location
V_c	=	0 if axial tension exists in the member

Note: None of the other checks for ACI 8.11 are considered. It is the engineer's responsibility to make sure that a gravity beam that has been assigned as a joist satisfies all applicable sections of ACI 8.11.

If lightweight concrete is specified and f_ct is defined, thenf_ct/6.7 will be used instead of $\sqrt{{f^{'}}_{c}}$ as long as $f_{c t} / 6.7 \leq \sqrt{{f^{'}}_{c}}$ , per ACI 11.2.1.1. When f_ct is not specified then $0.75 \sqrt{{f^{'}}_{c}}$ is used instead of $\sqrt{{f^{'}}_{c}}$ , per ACI 11.2.1.2.