Maintaining the geometric requirements ensures the plate will be the critical element of the connection. The connection will possess sufficient rotation capacity to accommodate the simple beam end rotation as required by Section B3.6a of the AISC Specification. Bolt bearing will occur before bolt shear and plate yielding will occur before weld rupture; thereby, a ductile limit-state will control the strength of the connection.

No, through-plates are not required for all single-plate connections to HSS columns. The AISC Steel Construction Manual, Part 10, Design Considerations for Simple Shear Connections to HSS Columns Section provides recommendations. The Through-Plate Connections Section states:

“Through-plate connections should be used when the HSS wall is classified as a slender element (b/t > 1.40(E/Fy)^0.5 or 33.7 for Fy = 50 ksi for rectangular HSS; D/t > 0.11E/Fy or 63.8 for Fy = 50 ksi for round HSS) or does not satisfy the punching shear limit state. A single-plate connection is more economical and should be used if the HSS is neither slender nor inadequate for the punching shear rupture limit state.”

Single-Plate Connections to HSS Section states:

“As long as the HSS wall is not classified as a slender element in accordance with AISC Specification Table B4.1a, the local distortion caused by the single-plate connection will be insignificant in reducing the column strength of the HSS (Sherman, 1996). Therefore, single-plate connections may be used with rectangular HSS when b/t ≤ 1.40(E/Fy)^0.5 or 33.7 for Fy = 50 ksi. Single-plate connections may also be used with round HSS as long as they are nonslender under axial load (D/t ≤ 0.11E/Fy or 63.8 for Fy = 50 ksi).

Yielding (plastification) of the HSS face has not been a governing limit state in physical
tests. Punching shear (shear rupture), however, should be checked as follows:

where

F_u = specified minimum tensile strength of the HSS member, ksi
R_r = required shear strength, kips
e = eccentricity, taken as the distance from the HSS wall to the center of gravity of the
bolt group, in.
l_p = length of the single-plate shear connection, in.
t_des = design wall thickness of HSS member, in.
Φ = 0.75
Ω = 2.00”