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NDS 5.3
The following factors apply to glulam design, and are shown in the Modification Factors table in the Additional Data of the Design Check Summary.
5.3.2 Load duration factor CD
Refer to NDS 2.3.2 in General Adjustment Factors
5.3.3 Wet Service Factor CM
The CM values in NDS Supplement Tables 5A-D are applied based on the moisture conditions specified in Beam View, Column View, and Concept Mode.
5.3.4 Temperature factor Ct
Refer to NDS 2.3.3 in General Adjustment Factors.
5.3.5 Beam Stability Factor CL
Refer to NDS 3.3.3 in Bending Members - Flexure. For oblique beams, CL is calculated for each direction using the corresponding FbE, Fb, E'. Refer to NDS Appendix D and Supplement Table 5- Glulam E'min for more information specific to glulam lateral stability.
The lesser of Cv and CL is applied for bending moment design as per 5.3.6. When both are less than one, both are shown in the Modification Factors table, and a note appears below the table saying that only the lesser is used.
5.3.6 Volume Factor, Cv
The volume factor Cv is applied according to NDS 5.3-1, including the determination of the distance L between the points of zero moment.
The member width b used in this equation is the width of the widest lamination in the layup, as entered in the Glulam section of the Beam input view. A check box allows you to use the member width as the value b despite having a narrower lamination width, which could result in a smaller volume factor Cv. This would ordinarily be done for glulam members constructed from remanufactured lumber, which require that the member width be used.
The lesser of Cv and CL is applied for bending moment design as per 5.3.6. When both are less than one, both are shown in the Modification Factors table, and a note appears below the table saying that only the lesser is used.
5.3.7 Flat Use Factor, Cfu
The flat use factor Cfu is calculated according to the values in NDS Supplement Tables 5A-D. Flat use is determined by orientation with respect to the laminations rather than a determination of the relative sizes of b and d. It automatically applied to the allowable bending stress for the following cases:
- Beam Mode: a member's cross section is oriented at an oblique angle. The component of the bending stress perpendicularly to the wide face of the laminations is checked against the allowable bending factored with Cfu.
- Column Mode: a member's cross section is oriented so that the wide face of laminations is loaded.
5.3.8 Curvature Factor
This factor does not apply to members considered by Sizer.
5.3.9 Stress Interaction Factor Cl
Despite allowing tapered notches on the top of the member, Sizer does not apply the stress interaction factor to the bending strength Fbx. Sizer limits tapered notches to 1/3 span length from member ends, as per 5.4.5.2, which is a zone in which the bending stress tends to zero. It is the responsibility of the designer to check whether the stress interaction factor results in critical bending design within the zone of 1/3 the member length from the member end.
5.3.10 Shear Reduction Factor Cvr
Sizer identifies when the member has been notched or when there have been impact loads applied for a particular load combination and applies the 0.72 to the Fvx and Fvy values factor for these situations. The factor is presented in the Modification Factors table in the Additional Data of the Design Check Summary under a column Cn*Cvr, in combination with the notching factor from NDS 3.4.3.2.
5.3.11 Column Lateral Stability Factor
Refer to NDS 3.7 - Solid Columns.
5.3.12 Bearing Area Factor Cb
WoodWorks SIZER automatically applies a bearing area factor calculated as per NDS 3.10.4 for both the supporting member and the main, supported member.. Refer to 3.10 - Design for Bearing
5.3.13 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 if pressure preservative treatment is used.
Notes to Tables 5A - 5D
The following factors apply to special cases listed in the notes to Tables 5A-5D, and when applied by Sizer appear in the Notes column of the Modification Factors table in the Additional Data of the Design Check Summary.
Non-edge bonded laminations ( 5A Note 5; 5A Exp. Note 3; 5B note 2; 5C Note 2, 5D Note 2 )
This factor applies to the transverse shear value Fvy only. It is applied if in the Beam input, the maximum lamination width entered is less than the member width, and the check box Non edge bonded laminations is checked. If so, a factor of .5 applies to the Fvy value if there are 5, 7, or 9 laminations, and .4 otherwise
Wane ( 5A Note 6, 5A Exp. Note 4 )
A small number of Southern Pine combinations can be composed of lumber with wane, or edges of lamination pieces that are not completely squared. If the lay-up actually does contain wane, then the Fvx is factored by.67 if the wane is on both sides and .83 if it is on one side. A dropdown box in Beam input view becomes active if you select a material that can have wane, and allows you to select None, One side, or Both sides.
Fbx for Deep Axial Members ( 5B Note 4, 5D Note 3 )
For glulam members stressed primarily axially, and greater than 15” deep without special tension laminations, the Fbx value is multiplied by 0.88. On the advice of AITC, the glulam authority at the time, we assume that all axial materials do not have special tension laminations.
Ex for 28F and 30F > 15 laminations ( 5A Note 9, 5A Exp. Note 7 )
Sizer has not implemented this note, as it refers to a limited range of sections in rarely available combinations, for which the Ex value is 2.0 million psi rather than 2.1 million psi. You can design for such members by using database editor to copy the glulam database, and adding 28F and 30F materials with E = 2.0 million and the appropriate range of depths.