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3.6.3 Strength in Compression
The net cross sectional area multiplied by the factored allowable compressive stress fc is compared to the factored axial load.
For columns and wall studs, the net area is just the gross area, b x d. For CLT wall panels, the cross-sectional area of the layers in the longitudinal direction is multiplied by the one-foot design width.
3.7.1-Column Stability Factor, CP
For sawn lumber, glulam, and SCL, the column stability factor is calculated as per 3.7.1. For CLT, the alternative formulation from 15.
3.7.1.2 Effective column length, le
The Lateral Support Spacing and End Conditions for (Ke)(l) fields of the Column mode permit you to specify both the effective length factor, Ke, and the column length between points of lateral support. The input field Lb corresponds to the laterally unsupported length in the plane of the depth of the column while Ld corresponds to the length in the plane of the width of the column. Either can correspond to l1/d1 or l2/d2 from NDS 3F; the notation has no effect on design results.
The end-fixity conditions that Sizer allows are pinned or fixed for the bottom, and pinned or free for the top of the member. You cannot have a pinned-free condition.
Sizer shows the pinned top with a roller at the top, which is exactly the same as the second case in Appendix G, except is showing that the pinned end is free to move axially while it is restrained from moving horizontally. This way, there are no axial forces developed due to the shortening or lengthening of the member.
Note that as the free end-condition allows the top to move laterally, additional bending moments will develop due to eccentric axial loads. This is called a drift effect and Sizer does not include the drift effects in the analysis of the member.
The effective column length, le, is equal to the full height of the column while in Concept mode.
3.7.1.3 Slenderness Ratio for CP
For solid columns, Sizer uses the larger of the slenderness rations Ke lb / b or Ke Ld /d when calculating the column stability factor.
3.7.1.4 Slenderness Ratio Limit
Sizer limits the slenderness le/d to 50 for all loading conditions, except for load combinations including construction loads, for which the limit is 75.
For CLT, the slenderness ratio is calculated as per NDS Appendix H., which says r √12 can be substituted for the depth d, where r is the radius of gyration. CLT Handbook 8, 4.1.4.1 - Slenderness Ratio gives the calculation for this slenderness ratio.
Note that this slenderness ratio is used only to determine whether the panel is under the limit of 50 in NDS 3.7.1.4, it is not used in the calculations for the column or beam stability factors.
C3.7.1 Alternative Formula for CLT
For CLT wall panels, the alternative formulation Eqn. C3.7.1-1 from NDS Commentary C3.7.1, is used instead of Equation 3.7-1. This formulation is also in CLT Handbook 8, 4.1.4.1 and is described there.