Per section 13.4.1, the factored shear resistance, V_r , developed by the web of a flexural member, shall be taken as

V_r = ϕA_v f_s

where

Av

=

= the shear area twh

1. f _s = 0.66f _y when $\frac{h_w}{t_w}\le 440\sqrt{\frac{k_v}{f_y}}$

   where

   kv

   =

   = the shear buckling coefficient defined as: $=4+\frac{5.34}{{(s/h_w)}^2}\text{ if }s/h_w<1$ $=5.34+\frac{4}{{(s/h_w)}^2}\text{ if }s/h_w\ge 1$

2. f_s = f_cri when $440\sqrt{\frac{k_v}{f_y}}<\frac{h_w}{t_w}\le 500\sqrt{\frac{k_v}{f_y}}$

   where

   fcri	=	$=290\frac{\sqrt{f_y{k}_v}}{(h_w/t_w)}$
   kv	=	= is as defined in (a)

3. f_s = f_cri + f_t when $500\sqrt{\frac{k_v}{f_y}}<\frac{h_w}{t_w}\le 620\sqrt{\frac{k_v}{f_y}}$

   where

   ft	=	the tension field post-buckling stress defined as: = ka(0.50fy - 0.866fcri)
   ka	=	the aspect coefficient defined as: $=\frac{1}{\sqrt{1+{(s/h_w)}^2}}$

4. f_s = f_cre + f_t when $620\sqrt{\frac{k_v}{f_y}}<\frac{h_w}{t_w}$

   where

   ft	=	the tension field post-buckling stress defined as: = ka(0.50fy - 0.866fcre)
   fcre	=	$=\frac{180,000k_v}{{(h_w/t_w)}^2}$
   kv	=	as defined in (a)