Shear Design

Using O86 6.5.4 for sawn lumber, 7.5.7.3(b) for glulam, and 15.3.3.4 for SCL SIzer determines shear resistance with equations of the form

V_r = 2/3 f F_v AK_zvK_N

• f = 0.9.
• F_v is the specified shear strength f_v multiplied by wet service, treatment, system, and load duration factors.
• A is the cross-sectional area. Under different circumstances, gross cross sectional area and net area after notch removal are used.Refer to Notch Design for more details.
• K_zv is a size factor defined differently for each material.
• K_N is the a notch factor, defined differently for glulam and sawn lumber. CLT and SCL members are not notched. Refer to Notch Design for more details.

For glulam design, this formula applies to columns and optionally to beams less than 2 cubic meters in volume. For beams greater than 2 cubic meters, a formula from 7.5.7.3(a) based on gross loading must be used, and it can be used for smaller beams. Refer to Glulam Shear Design for more details.

For both sawn lumber and glulam with notches, an additional fracture shear check is required. Refer to Notch Design for more details.

A different procedure from 8.4.4 is used for CLT, refer to CLT Shear Resistance. O86 15.3.2.4 is used for I-Joists, for which V_r comes directly from the database for each section.

As per 6.5.4.2.1 for sawn lumber and similar clauses for glulam, SCL, and CLT, Sizer compares the factored shear resistance moment resistance V_r to the applied shear force V at a distance d from the inner edge of the support, which is equivalent to ignoring the effects of loads between that point and the support.

Sizer also identifies the unusual situation where the shear force is at its maximum interior to the span. It issues a screen warning and a note in the Shear Analysis diagram for this circumstances, and designs for the interior shear.

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