NDS 4.3 - Adjustment Factors (Sawn Lumber)

4.3.2 - Load duration factor C_D

Refer to NDS 2.3.2 in General Adjustment Factors

4.3.3- Wet Service Factor C_M

The C_M values in NDS Supplement Tables 4A-F are applied based on the moisture conditions specified in Beam View, Column View, and Concept Mode.

4.3.4- Temperature factor C_T

Refer to NDS 2.3.3 in General Adjustment Factors.

4.3.5 - Beam Stability Factor C_L

Refer to NDS 3.3.3 in Bending Members - Flexure.

4.3.6 - Size Factor C_F

4.3.6.1 - The size factors for dimension lumber from the NDS Supplement are implemented in the materials database, and are modifiable by WoodWorks Database Editor.

4.3.6.2 - Size factors for timbers 5" or greater width whose depth is 12" are greater are implemented in Sizer according to the formula in 4.3-1.

4.3.7-Flat Use Factor, C_fu

The flat use factor C_fu is automatically applied to the allowable bending stress for the following cases:

- Beam Mode:

For y-axis design when a standard-size member's cross section is oriented at an oblique angle. The component of the bending stress perpendicular to the wide face is checked against the allowable bending factored with C_fu.

For x-axis design, when a custom-sized member is entered with the width b greater than the depth d.

- Column Mode

When a standard size member is loaded on the d-face.

When a custom-sized member is entered with the width b greater than the depth d and is loaded on the b-face.

4.3.8-Incising Factor, C_i

If you check the Incising check box in beam view, Sizer allows you to enter incising factors, one of which is applied to the F_b, F_t, F_c, and F_v strength properties and the other is applied to the modulus of elascticity E used for deflection stiffness. The default values that appear in these boxes are those listed in table 4.3.8 that apply to incisions up to 0.4" deep, 3/8" long, and 1100 incisions per square foot. Custom factors can be used according to manufacturers specifications.

4.3.9- Repetitive Member Factor -

Sizer applies the 1.15 repetitive member factor if the user has checked the repetitive member checkbox in Beam, Column, or Concept mode.

The NDS permits the application of Cr to the bending design value F_b as long as the following conditions are met:

1. the member is 2 to 4 inches thick
2. there are at least 3 members joined by floor, roof or other load distributing element, ot it is a built-up member with 3 or more plies
3. member spacing does not exceed 24 inches

Sizer does not permit you to specify a repetitive member if any of the above conditions is violated.

4.3.10 - Column Lateral Stability Factor

Refer to NDS 3.7 - Solid Columns.

4.3.11-Buckling Stiffness Factor C_T

This factor is not applied as the program does not handle truss members as given in 4.4.2.

4.3.12-Bearing Area Factor C_b

WoodWorks Sizer automatically applies a bearing area factor calculated as per NDS 3.10.4 to both the supporting member and the main, supported member. Refer to 3.10 - Design for Bearing

4.3.13- Pressure Preservative Treatment

No factor is needed or applied. You must change the Load Duration factor to less than 1.6 for any input load type greater than that if pressure preservative treatment is used.