A beam-end notch will be necessary when connecting a beam directly to the web of the supporting beam – the connection itself may be any of the bolted connections including: an end-plate, fin-plate or a bolted cleat.
Welded beam-to-beam connections will also need to be notched, but the method will be different from that of a bolted connection and will be discussed separately under Welded Connections.
If the incoming beam is smaller than the supporting beam then only the top flange will need to be notched, if the beam is equal to, or larger, then the top and bottom flanges will need to be notched
Notches may be applied to Beam-to-Beam and Beam-to-Column Web connections
Beam to Beam Connections
Calculating the Notch Depth
The notch depth must be greater than (hw1) which is the sum of the supporting beam flange thickness and the root radius (tf + r1). As this value will differ widely, often by less than a millimetre, it makes sense to standardize the depth.
Standardizing the depth carries many advantages, it enables the Standardizing of the connection as a whole, in doing so, simplifying the detailing, fabrication and erection of the beam. The BCSA and SCI in compliance with Eurocode 3, recommend the notch depth be standardized at 50 mm – but this will only work for beams greater than approximately 250 mm - and less than approximately 900 mm in depth. See Table 1 – Notch Depth (n2)
Calculating the Notch Length
The Notch length (n1) is calculated from the following:
0.5 x the beam flange width – (0.5 x the beam web thickness + the Nominal Clearance + c1). (c1) is the clearance between the toe of the beam flange and the inside face of the notch.
Some suggest (c1) should be standardized at 10 mm, which is fine for most medium size beams, but with larger beams and those with a wide flange this may present some erection difficulties. Another method to calculate the value for (c1) is slightly more complicated, but will work for all beams however large or small.
c1 = (0.4 x b) + 7 – where b = the supporting beam flange width.
Applying this method will see the value for (c1) increase as the supporting beam becomes larger – this will be found to accord with suggested notch lengths given in the steel tables.
A final note on the notch length:
The calculation method above will determine the notch length measured from the end of the end-plate or cleat. Most fabricators will prefer the notch length be detailed from the end of the beam web – in which case, the thickness of the end-plate or Cleat Protrusion should be taken into account and deducted.
Stiffening a Notch
Generally, a notch length should not exceed 200 mm without being checked by the responsible engineer – in such cases it may be necessary to stiffen the notch. Below are 3 options:
- Weld a doubler-plate to the web of the incoming beam either on one or both sides. The thickness of the plate should not be less than the web thickness of the beam
- Weld a longitudinal stiffener to the web of the incoming beam – it should extend approximately 2 x the notch depth beyond the back face of the notch. Again, the thickness of the stiffener should not be less than the web thickness of the beam.
- For particularly deep beams, weld an additional transverse stiffener to the beam web.
Note that notch stiffening should be approved by the responsible engineer.
Beam to Column Web Connections
When connecting a beam to the web of a column, the width of the notched section is determined by the straight section of the web between the flange root (hw). From there, it’s a matter of establishing the incoming beam flange width.
The gauge should be one of the recommended options, enabling the use of a Standard End Plate.
The length of the notch (n1) is calculated in the same way as for a beam-to-beam connection.