A beam over HSS connection consists of a steel cap plate welded to the top of a HSS column section that supports the bottom flange of a W-shape beam. The cap plate is connected to the bottom flange of the beam via four bolts. The connection is intended to resist combined moments and axial load (in the HSS) without the presence of shear.

Design Considerations

Beam Over HSS connections are checked per the AISC Steel Design Guide 24 and the AISC 360-22 design specification. In VAConnect, the limit states checked for the Beam Over HSS connection are based on those outline in Example 4.1 of Design Guide 24, which according to the design guide examines all of the limit states for this connection type. Note: As with the entire Design Guide 24, the scope is restricted to nonseismic applications.

Force Model

The applied moment (Mu) and axial load (Pu) are resolved into two axial loads (Cu & Tu as determined from statics) that are transferred across the beam flange to cap plate interface. Compression forces (Cu) are assumed to act at the face of the HSS whereas tensile forces (Tu) act at the center of the bolts as shown in the image below. Depending on the magnitude and direction of the applied loads (Mu & Pu), the forces that are transferred across the beam flange to cap plate interface may both be in compression or both be in tension. When both forces are compressive, only one wall of the HSS is considered to resist each of the compressive force.

Column at End of Beam

The capacity of the beam side limit states (Web Local Yield, Web Local Crippling, & Web Compression Buckling) depends on the distance from the concentrated force to the end of the member. In some instances when the concentrated forces on both sides of the column are applicable for the limit state, the Unity Value (i.e. demand to capacity ratio) is checked for both concentrated and the worst case is reported.

Limit States

VAConnect checks the following limit states for Bolted End Plate connections (refer to the program’s detailed reports for specific code references):

• Bolts
  • Tension Rupture w/ Prying (from Beam Flange or Cap Plate)
• Weld
  • Fillet Weld Rupture w/ HSS and Cap Plate Base Metal checks
• Beam
  • Web Local Yield
  • Web Local Crippling
  • Web Compression Buckling
• Column
  • HSS Wall Local Yield
  • HSS Wall Local Crippling

Design Assumptions

VAConnect makes the following design assumptions for Beam Over HSS connections based on AISC Design Guide 24 and AISC Manual provisions:

• The Beam Over HSS connection is based on the AISC Design Guide 24 the scope of which is restricted to nonseismic applications.
• The out-of-plane motion at the top of the HSS must be restrained by adding a stiffener to the web or by another method. See the AISC Manual Part 2 for additional information and details for beams framing continuously over columns.
• Bolts of diameter not greater than 1.5 in. must be used.
• The gauge of the bolts must not exceed the beam's flange width.
• The bolt gage must satisfy the minimum spacing requirements of ACI 360-22 Section J3.4.
• The minimum edge bolt distance for the cap plate and the beam flange must satisfy the ACI 360-22 Table J3.4 requirements.  

Limitations

• Permitted beam and column shapes: W-shapes beams and HSS columns
• Beam is perpendicular to the support column
• Only standard bolt holes are supported
• Only forces in the plane of the connection (axial load and moment) can be checked
• A single beam is framing into the support column
• When an unrecognized beam is imported from VisualAnalysis, the beam’s T dimension is assumed to be the depth minus twice the flange thickness (i.e. the fillets are neglected)
• Only fillet welds are allowed at the HSS to cap plate connection (complete-joint-penetration groove and partial-joint-penetration groove weld are not supported)
• The bolt gauge is not checked against the beam's workable gauge
• Bolt entering and tightening clearances are not checked