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Sizer performs rudimentary design for SCL materials such as LVL and PSL according to NDS Chapter 8.
Modification Factors
The program does not allow for wet service factor CM (8.3.3) or preservative treatment (8.3.10). It does include the load duration factor CD(8.3.2), temperature factor Ct(8.3.4), beam stability factor CL (8.3.5), a repetitive member factor Cr of 1.04 (7.3.6), volume factor CV (8.3.6), column stability factor CP (8.3.8), bearing area factor CB (8.3.9), and fire retardant treatment factor .
The modification factors to be considered in beam and column modes for SCL design are:
Load Duration Factor CD (NDS 8.3.2)
The load duration factors for each load type as given in NDS 2.3.2 apply to SCL as they do to all materials.
Service Condition Factors CM (NDS 8.3.3 and 8.1.4)
The Service Conditions input field is disabled when SCL is chosen. CM will be taken as unity. The text output report will show a “-“ for the CM factor for all design criteria.
Temperature Factor Ct (NDS 8.3.4)
The temperature factors for each criterion as given in Section 2.3.3 apply to SCL as they do to all materials.
Beam stability factor CL (NDS 8.3.5)
For SCL, the CL factor is determined by NDS 3.3.3, as for all materials, and applies to bending moment calculations only.
According to 8.3.6, if Cv is less than 1.0, then the CL factor is not to be applied simultaneously with CV, and the lesser of these factors apply. If it is greater than 1.0, they both apply.
The CoVE is set to 0.10 in the model database The input fields for lateral supports are enabled for SCL.
Volume factor Cv (NDS 8.3.6)
The volume factor CV for each section is entered in Database Editor when you make your custom SCL material database.
The volume factor Cv applies to strength in bending and column tension strength . It is determined by the manufacturer for each if its products as follows:
Volume factor, SCL shallow members
Cv = (12/d)1/m1 , d <= 12”,
Volume factor, SCL deep members
Cv = (12/d)1/m2, d > 12”,
Maximum volume factor - SCL
Cv <= CVmax
where,
d = the actual depth of the member in inches
m1 = a proprietary volume factor parameter ranging from 0 and 30
m2 = a proprietary volume factor parameter ranging from 0 and 30 .
CVmax = a proprietary maximum allowable CV .
According to 8.3.6, if Cv is less than 1.0, then the CL factor is not to be applied simultaneously with CL, and the lesser of these factors apply. If it is greater than 1.0, they both apply.
Note that from these equations, in the usual case that m > 1, Cv = 1.0 for 12” sections, it is greater than 1.0 for sections less than 12”, and is less than 1.0 for sections greater than 12” deep.
In the Evaluation Reports , the values of m1 and m2 vary widely between 7 and 12.5, and often depend on the grade or a range of section depths. In general, CVmax is implemented as a depth below which CV is constant, which we will call dmin, which is variously 1.5”, 1.75”, 2.5”, and 3.5”.
The program allows the user to update the size factor for bending in Database Editor. The default values of this factor for model databases currently supplied with Design Office is m1 = m2 = 7.35 for LVL and m1 = m2 = 9 for PSL.
Repetitive member factor Cr (NDS 8.3.7)
The system factor Cr for SCL used in a load sharing system is 1.04. This factor applies only to strength in bending .
Column Stability Factor CP (NDS 8.3.9 and 3.7.1)
For all materials, unbraced columns in compression are subject to a factor CP, as given in Equation 3.7-1 of the NDS.
This factor is calculated and applied to SCL columns as to all other materials. The c factor of 9 in Equation 3.7-1 is set to 0.9 for SCL, as it is for glulam.
Bearing Area Factor, Cb (NDS 3.10.4, 8.3.1)
A strength increase factor Cb is applicable to all materials for interior supports with bearing lengths less than 6” . This factor is listed in Table 8.3.1.
This factor is implemented for SCL as for all materials.
Notches (NDS 8.4.1.1)
Notches are now allowed for SCL, with the following restrictions, with dn and Ln being the depth and length of the notch. These are the same rules as for glulam, with the omission of the 3” absolute limit on tension-edge notches for glulam ).
1. On member ends only ( i.e. end of entire beam, not end of span). No interior notches.
2. On the tension side, over a support only (not over cantilevered end).
3. On the tension side, dn <= .1d.
4. On the compression side, dn <= .4d.
5. On the compression side, Ln <= Ls / 3.
6. On the tension side, Ln = Lb.
The notch-related controls in the Beam View are enabled for SCL.
The notch reduction factor is calculated as described in NDS 3.4.3.2 and applied to SCL.
Fire retardant treatment factor Cfrt (NDS 2.3.4, ASD SCL Guideline 5.4)
NDS 2.3.4 refers only to lumber and glulam when saying that the adjustment factors for fire retardant must come from the fire retardant service providers; however the ASD SCL Guideline 5.4 allows for this some SCL manufacturers provide data on this so this factor is included for SCL products.
Design
SCL materials are designed for shear, bending, deflection, axial, combined axial and bending and bearing according to the provisions of NDS Chapter 8.
Biaxial beam bending and column combined bending and axial loads
NDS 3.91 – Bending and tension (column design)
The equations for combined axial loads and column tension apply to SCL as for all other materials. The implementation of these for anisotropic materials such as SCL and glulam is implemented in Sizer, as described in NDS 3.9.
NDS 3.3.3.10 and 3.9.2
Equation 3.9-3 applies to all bending members, including SCL, whether or not axial loads are present, by virtue of 3.3.10. The implementation of this equation for anisotropic materials such as SCL and glulam is described in NDS 3.9. .
NDS 3.9.3
This is a case of eccentric compressive loading for columns, containing more complicated versions of the equations in 3.9.2, using the same terms. The implementation of this for SCL and glulam columns is as described in NDS 3.9.
The program makes sure that the SCL volume factor Cv is excluded from the definition of Fb* in 3.9.1.
Equation 3.9-2 deals properly with the case the width is greater that the depth, as this case affects the biaxial bending only for