Notch Design

Compression Edge Notches

For compression edge notches, for sawn lumber (O86 6.5.4.3) and for glulam (7.5.7.4) in the case that the unsupported length of the notch en is greater than the residual depth of the member at the notch, shear resistance is calculated using the formula given in Shear Design but using the net area of the section A_n for A.

For glulam when the unsupported length is less than the residual depth, the gross area A_g is used, and an calculation involving the unsupported length, the depth and the residual depth is included. In Sizer, we report this calculation as the notch factor K_N even though it is unnamed in the O86.

The shear force to be resisted for compression edge notches is the force at distance d from the support.

Tension Edge Notches - Shear Resistance

For tension edge notches, for sawn lumber (O86 6.5.4.3) and for glulam in the case that the notch depth exceeds 0.25 times the member depth d, or the unsupported length exceeds the depth d, shear resistance is calculated using the formula given in Shear Design but using the net area of the section A_n for A.

For glulam where the notch depth is less than 0.25 d and the unsupported length is less than d, the formula using gross area A_g is used.

The shear force to be resisted for compression edge notches is the force at distance d from the support.

Tension Edge Notches - Fracture Shear Resistance

An additional check is required for tension-side notches for both glulam and sawn lumber. A fracture shear resistance is defined as

F_r = f F_f A_g K_N

where

• f = 0.9.
• F_f is the fracture shear strength f_f multiplied by wet service, treatment, system, and load duration factors.
• f_f is the fracture shear strength, defined as 0.5 MPa for sawn lumber and for glulam using a formula based upon lamination width
• A_g is the gross cross sectional area.
• K_N is the a notch factor, a complex formula involving notch length, notch depth, and residual section depth

The shear force to be resisted is the force at the support, not the distance d from the support.

Output

If notch-reduced shear resistance is the critical design ratio for any support on the member, the program shows a line in the Analysis vs. Design table for both shear resistance and fracture shear resistance. The notch factor K_N is shown in the FACTORS table of the Additional data.