Axial Compression

Using O86 6.5.6.2 for sawn lumber, 7.5.8.5 for glulam, 8.4.7.2 for CLT, and 15.3.3.5.2 for SCL, SIzer determines resistance to axial compression loads in columns, wall studs, and wall panels with an equation of the form

P_r = f F_c AK_CK_Zc

• f = 0.8
• F_c is the specified strength f_c multiplied by wet service, treatment, system, and load duration factors.
• A is cross sectional area of the member
• K_zc is a size factor defined differently for each material.
• K_C is the slenderness factor calculated with 6.5.2.2 for sawn lumber and identical clauses for glulam and SCL which takes into account the distance between lateral supports on each column face and column end fixity conditions. It is a measure of the propensity of the column to buckle.

The slenderness factor and size factor are evaluated for buckling in each orthogonal direction and the worst case of the resulting resistance P_r is compared to the axial force on the member for each load combination.

The program shows both b- and d- direction resistance and factors in the Design Check results.

Refer to Axial Design for CLT Wall Panels for more a more detailed explanation of CLT compression design.

Built-up Columns

Sizer implements O86 6.5.5.4 for built-up beam compressive design. An input allows you to specify whether the member is nailed, bolted, connected by split rings, or "not adequately connected". A factor corresponding to each method is applied to the compressive strength in the direction of buckling along the member depth. This direction is also evaluated with the K_zc calculations based on single-ply with, with no factor applied. If it is not adequately connected, only the single ply calculation is done. The factors are also evaluated in the direction along the member width b, and the worst of the 3 cases is used for design.