Wood bearing and notches

A reaction bearing on a sawn lumber or glulam member, perpendicular, parallel or at an angle to the grain, and a member end notched at its support, to NDS 2024 3.4.3, 3.10, 4.4.3 and 5.4 with ASCE 7-22 combinations, in ASD or LRFD.

Inputs of the bearing check #

• Member: sawn lumber (species, grade, size, or Fv, Fc⊥ and Fc entered) or glulam (Table 5A stress class, b, d).
• Bearing: the reaction per load type, the direction (perpendicular to grain for a beam on a support, parallel to grain for end-grain bearing, or at an angle θ), the bearing length lb and width (0 = the member width), whether the bearing is at the member end (Cb = 1.0 within 3 in of the end, NDS 3.10.4), the deformation limit (0.02 in with 0.73 Fc⊥, NDS 4.2.6) and, for end-grain bearing, whether a metal bearing plate is provided.
• Notch: none, on the tension face (bottom) or on the compression face (top) at the support, the depth remaining dn and, for a compression-face notch, the distance e the notch extends past the inner edge of the support.

Checks performed #

The shear at the support is taken as the reaction. Glulam notches take Cvr = 0.72 on Fvx (5.3.10, 5.4.5.4).

Drawings #

The drawing sheet (Drawing sheet / DXF buttons, and the report appendix) shows the member end in elevation with the bearing length, the notch as entered (dn, e), the reaction by type at the angle to grain used by the check, and the bearing area bw x lb on the member (on the end grain for bearing parallel to grain). The support is drawn as a block the bearing length long: its material, size and fastening are not part of the calculation, nor is the bearing's distance from the end when it is not at the end.

Limitations #

• Checked against the NDS 2024 text (steps cite section and page): 3.4.3.1 (Eqs. 3.4-3 and 3.4-5), 3.10.1 to 3.10.4 (Eqs. 3.10-1, 3.10-2), 4.2.6 (Eq. 4.2-1, 0.73 Fc⊥), 4.4.3.1, 5.3.10, 5.4.5. Corrected: a compression-face end notch in sawn lumber is limited to d/4 like a tension-face notch (NDS 2024 and 2018 4.4.3.1; the module had allowed 0.4 d, the glulam limit); the glulam notch provisions are 5.4.5 in NDS 2024 (5.4.4 was cited) and the 3 dn length limit of a glulam compression-face notch is now checked; Fc⊥ takes no λ in LRFD (Table 4.3.1).
• A taper cut at the end is treated by NDS 2024 3.4.3.1(c) and (e) like an end notch: on the tension face as a tension-face notch, on the compression face with dn measured at the inner edge of the support (enter it as a compression-face notch). Notches away from the supports (3.4.3.1(f), 4.4.3.2) and SCL members (8.4.1) are not covered. A compression-face notch must also stay out of the middle third of the span (advisory).
• The reference values (Supplement Tables 4A, 4B, 4D, 5A) stay marked [verify]: the NDS 2024 Supplement is not on disk (research/DOCUMENTS_NEEDED.md).

Verification examples #

Published values of AWC Structural Wood Design Examples 2015/2018 Example E1.3 (as tabulated in the free Tekla Tedds verification example), Breyer Ex. 6-18 / 6-19 and Aghayere & Vigil Ex. 5.9 (as tabulated in the free calcs.com validation pages), and hand calculations in closed form (backend/tests/test_verify_wood_bearing.py); the hand cases are a 4x10 DF-L No. 2 with D 1500 + L 2500 lb on 3 in of bearing. No free published notch example was found.