The AISC specification for ASD specifies the following allowable shear stresses F v , ksi ( ksi X 6.894 = MPa)

allowable-stress-design-for-shear-in-buildings

When the shear in the web exceeds F v , stiffeners are required.

Within the boundaries of a rigid connection of two or more members with webs lying in a common plane, shear stresses in the webs generally are high. The commentary on the AISC specification for buildings states that such webs should be reinforced when the calculated shear stresses,

Civil Engineering and building

such as those along plane AA in Fig. exceed F v , that is, when SF is larger than d c t w F v , where d c is the depth and t w is the web thickness of the member resisting S F. The shear may be calculated from

S F = M 1 / 0.95d 1 + M 2 / 0.95d 2 – V s

where V s = shear on the section

M 1 = M 1L + M 1G

M 1L = moment due to the gravity load on the leeward side of the connection

M 1G = moment due to the lateral load on the leeward side of the connection

M 2 = M 2L – M 2G

M 2L = moment due to the lateral load on the windward side of the connection

M 2G = moment due to the gravity load on the windward side of the connection