Steel Buildings in Europe

Part 11: Moment Connections 11 - 12 3 BEST PRACTICE GUIDELINES FOR MOMENT CONNECTIONS Any moment-resisting connection will involve additional expense compared to simple (shear only) details. Connections should be detailed to carry the applied forces and moments in the most economical way. This may involve providing larger member sizes, or changing the geometry of the connection, to reduce the fabrication effort involved in fitting stiffeners. The following Sections offer guidance on appropriate detailing. 3.1 Eaves haunch The ‘haunch’ in a portal frame is usually taken to mean an additional triangular cutting that is welded below the rafter beam at the connection to the column. The length of the cutting will generally be around 10% of the span, or up to 15% of the span in the most efficient elastic designs. The haunch is generally cut from the same section as the rafter, or a deeper and heavier section. Pairs of haunch cuttings are fabricated from one length of member, as shown in Figure 3.1. If the haunch is cut from the rafter section, the maximum depth of the haunched section is therefore just less than twice the depth of the rafter section. Deeper haunches require larger sections, or fabrication from plate. Figure 3.1 Fabrication of haunch cuttings 3.2 End plate End plates are generally fabricated from S275 or S235 steel. For class 8.8 bolts and S275 steel, the end plate thickness should be approximately equal to the bolt diameter. Common thicknesses are: 20 mm thick when using M20 class 8.8 bolts 25 mm thick when using M24 class 8.8 bolts The end plate should be wider than the rafter section, to allow a weld all around the flanges. The end plate should extend above and below the haunched section, to allow for the fillet welds. In the compression zone, the end plate should extend below the fillet weld for a distance at least equal to the thickness of the plate, as shown in Figure 3.2, to maximise the stiff bearing length when verifying the column in compression.