A Welded Flange Plate connection consists of two steel plates that are welded to both the support and the flanges of the beam to resist moment. VAConnect assumes that the Welded Flange Plate connections possess sufficient rigidity to maintain the angles between the connected members and behave as fully restrained moment connections as discussed in the AISC Steel Construction Manual Part 12. While various simple shear connections can be used in conjunction with welded flange plates, VAConnect uses a shear tab to resist the applied shear loads.

Design Considerations

Welded Flange Plate connections are checked per the AISC 360-22 design specification. VAConnect allows the flange plates to be connected to the support with either a double sided fillet weld or a complete-joint-penetration groove weld. The capacity of the complete-joint-penetration groove welds are not checked since the strength of the joint is controlled by the base metal according to AISC 360-22 Table J2.5. The length of the weld at the support can be manually set to a value less than the width of the flange plate, which is needed for cases when the flange plate is wider than the support. Fillet weld are used to connect the flange plates to the flanges of the beam. The end weld (i.e. the weld along the back edge of the flange plate perpendicular to the beam's span) can be enabled or disabled. When the end weld is disabled, the weld group is two parallel lines and when enabled the weld group is a U-shape. To avoid overhead welding in the field, the top flange plate is typically narrower than the beam's top flange (with an end weld) while the bottom flange plate is typically wider than the beam's bottom flange without an end weld. To allow enough room for placement of the fillet welds, VAConnect requires the difference between the width of the flange plate and the width of the beam's flange to be greater than or equal to two times the size of the weld.

Load Distribution - Moment, Axial, & Shear

Shear is transferred from the web of the beam to the support through the shear tab connection. Since the angle between the beam and the support in a fully restrained moment connection remains unchanged under loading, eccentricity is neglected when checking limit states pertaining to the shear tab.³ To satisfy equilibrium, the moment from the eccentric shear force (eccentricity · F_v) is added to the moment applied to the connection (M_z). The axial force is assumed to be distributed uniformly to the flanges of the beams (the shear tab connection is therefore assumed to have negligible axial stiffness compared to the flange plate connections). The moment at the connection is resolved into an effective tension-compression couple acting as axial forces at the beam flanges. Finally, the forces in the flanges plates can be calculated as R = (M_z + eccentricity · F_v) / d ± F_a/2.

Limit States

VAConnect checks the following limit states for Welded Flange Plates (refer to the program’s detailed reports for specific code references):

• Shear Tab
  • Bolt Group Capacity (Shear, Bearing, & Tearout)
  • Bolt Group Capacity (Shear, Bearing, & Tearout) - Beam Web
  • Fillet Weld
  • Base Metal
  • Base Metal - Support
  • Block Shear
  • Shear Yield
  • Shear Rupture
• Top & Bottom Flange Plate
  • Tension Yield
  • Tension Rupture
  • Compression Buckling
  • Block Shear
  • Fillet Weld - Plate to Flange
  • Base Metal
  • Base Metal - Flange
  • Weld - Plate to Support
  • Base Metal
• Connection Detailing
  • Shear tab maximum plate height
  • Shear tab maximum plate thickness
  • Shear tab fillet weld maximum and minimum size
  • Shear tab number of fillet weld lines
  • Welds are adequate to developed shear tab strength
  • Maximum and minimum bolt spacing
  • Maximum and minimum bolt edge distances
  • Flange plate fillet weld maximum and minimum size
  • Flange plate's width-to-thickness ratio is nonslender

Limitations

• Permitted beam shapes: I-Beams
• Permitted supporting member shapes: I-Beams, Channels, HSS, Pipe, or Rectangle. The support member is only limited when importing from VisualAnalysis.
• The support element is only considered as far as it affects the weld design (e.g. base metal check, minimum and maximum fillet weld sizes)
• Weld base metal checks assume that there is not a connection on the opposite side of the support
• Beam is nearly perpendicular to the support
• A single member framing into a support
• Only a single vertical row of bolts is allowed for the shear tab
• Web and flange yield and rupture are not supported
• Only standard bolt holes are supported
• Only forces in the plane of the connection (shear, axial, and moment) can be checked
• 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 and complete-joint-penetration groove weld are allowed at the support (partial-joint-penetration groove weld are not supported)
• The flange plates are assumed to resist the moment and axial load and no shear

Block Shear

The block shear failure method at the plate-to-flange connection depends on the both the end weld condition and the relative width of the plate to the flange. VAConnect automatically checks the all of the applicable block shear cases as outlined in the figures below.