WoodWorks Sizer USA – Change History

 

This document provides descriptions of all new features, bug fixes, and other changes made to the USA version of the WoodWorks Sizer program since its inception in 1993. The most recent major version of Sizer is Sizer 2019 , released in December 2019, and significant new features were added with Update 2,  released in June 2021. The latest service update is Update 4 released in November 2021. The latest service update for version 11 is Sizer 11.2, released in December 2019.  

 

This file last updated with changes November 24, 2021.

 

Click on the links below to go to the changes for the corresponding release.

 

      Sizer 2019, Update 4

     Sizer 10.42 – WW 10, SR-4b

      Sizer 2019, Update 3

      Sizer 10.41 - WW 10, SR-4a

     Sizer 2019, Update 2

     Sizer 10.4 – WW10, SR-4

     Sizer 2019, Update 1

     Sizer 10.2 – WW 10, SR-3

     Sizer 2019

     Sizer 10.1 – WW 10, SR-2

     Sizer 11.2 – WW 11.2, SR-1

     Sizer 10.0 – WW 10

     Sizer 11.1 – WW 11, SR-1

      Older versions

     Sizer 11 – WW 11

 


Sizer 2019, Update 4 (Version 12.4) – October 28, 2021

A. Engineering Design

1. LRFD Factors for Bearing Design (Bug 3669)  

For LRFD bearing capacity calculations, the program was not applying the Format Conversion factor KF = 1.67 or the Resistance factor ϕ = 0.9, leading to a capacity 1.5 times less than it should be, or minimum required bearing length 1.5 times greater than it should be.
The Factors table of the Design Check results showed these factors, but they were not being applied to the design. This has been corrected. 

2. Format Conversion Factor for LRFD Rolling Shear Fs (Bug 3670)  

For CLT rolling shear resistance, the program applied a LRFD format conversion factor KF of 2.88 when it should be 2.0 according to NDS Table 10.3.1. This has been corrected.

3. LRFD Time Effect Factor λ for Storage-only Live Loads (Bug 3664)  

For members subjected to live storage loads and no occupancy live loads, the program was applying a time-effect factor λ of 0.8 to the LRFD load combination 2, 1.2D + 1.6L + 0.5(Lr or S), however according to NDS N.3.3, Table N3 a factor of 0.7 should be applied to this combination when L is due to storage.

The incorrect time-effect factor was applied to bending, shear, tension and compression strengths, which were therefore too high by 14% when 2 is the governing load combination. Note that when both live L and storage live loads Ls are present the program correctly applied the 0.8 factor to the D + L + Ls combination and the 0.7 factor to the D + Ls combination. The program now applies 0.7 to D + Ls when there are no live loads, as well. 

4. Creep Factor for Storage Live Loads (Bug 3668)  

Storage live loads Ls are now considered long-term loads when applying the creep factor Kcr from NDS 3.5.2 for total deflection. Previously they were treated as other live loads and the Kcr factor was not applied to these loads.

Storage live loads were introduced for LRFD design in Update 2, but this change also applies to these loads when using ASD.  Application of the creep factor is the only consequence of differentiating Ls loads from L loads when using ASD.

5. Impact Load Duration and Time Effect Factors for Treated Members

The program now applies the NDS provisions limiting the load duration factor CD and the time effect factor  l for members with preservative or fire-retardant treatment. If you have input a factor in Beam or Column View Treatment data group for either Fire-retardant or Incising, then:

a) ASD Design (QA 14)

A load duration factor of 1.6 is applied to ASD load combinations containing impact loads I, rather than the default factor of 2.0 recommended by NDS Table 2.3.2, as per Note 2 under that table. The 1.6 factor is also applied in place of custom load duration factors greater than 1.6.

b) LRFD Design (QA 14a)

The time effect factor l for LRFD load combination 2 with impact loads, i.e., D + 1.6(L + I) + 0.5(Lr or S), is set to 1.0 rather than the 1.25 given in NDS N.3.3, Table N3, as per Note 1 under that table.

Note that for LRFD, impact loads are not included in any other load combination, and it is not possible to enter custom time effect factors.

6. Calculation of Emin for SCL Members (Bug 3682)  

When calculating Emin for SCL products using NDS Equation D-4, the program now uses True E rather than Apparent E, and does not include the 1.03 factor that is intended to convert Apparent E to True E.

This change was made because the value 1.03 is appropriate only for sawn lumber and varies for different SCL products; it is 1.05 for the recently added Versa Lam product.

Aside from Versa Lam, this affects only custom database files you create with Database Editor.

a) When Using Apparent E

Some manufacturers publish a note in their product literature giving the factor to be used in place of 1.03 in NDS D-4, on the assumption Apparent E is being used for design. Our method is equivalent to applying those notes when you select Apparent E in the design settings.  

b) When Using True E

When True E is selected in the Design Settings, Apparent E no longer has any function in the program, so it is now possible to create a database with meaningful values only for True E. Some manufacturers only publish True E. 

c) Old Database Files

For custom database files from previous versions that only have one E value, we assume it is E Apparent and the program continues to use the old method of calculating Emin via D-4 with the 1.03 factor.

It is possible to update these files using the current Database Editor to add True E values.

B. Loads Analysis

1. Companion Live Load Factor for LRFD Load Combinations (Bug 3676)     

The program now implements ASCE 7 2.3.1, Exception 1 where the load factor for the live load L in LRFD load combinations 3 and 4 is permitted to be reduced from 1.0 to 0.5 for those occupancies where the minimum uniform live load, Lo, in Table 4.3-1 is less than 100 psf (with the exceptions of garages or public assembly occupancy).

a) Load Combinations Affected

The combinations generated by Sizer that this affects are 

1.2D + 1.6 Lr + L

1.2D + 1.6 S + L

1.2D + 1.0W + 0.5 Lr + L

1.2D + 1.0W + 0.5 S + L

1.2D + 1.0W + L

b) User Interface

A check box has been added to the Load types and combinations data group of the Load Input view, to allow you to direct the program to use 0.5 L in place of L in the above combinations if the member meets the ASCE 7 criteria. 

This option is unchecked by default, but you can check it and save it as a default for new files along with the other Load View options.

c) Applied Limit

On the assumption that the user-input loads correspond to the minimum required for the occupancy, the program does not allow the use of the 0.5 factor when the uniform live load on the member is greater than 100 psf. This is determined from the sum of the magnitudes of full area live and storage live loads. For joists, line loads converted to area loads with the tributary width are also included, and the lower magnitude of the two ends of a full trapezoidal load is considered a uniform load for this purpose.

This limitation has been added to avoid non-conservative designs for those users who are unaware of this option. Note that it does not consider point loads, partial loads, trapezoidal area loads, the higher portion of trapezoidal line loads, etc., so that your judgement in setting the option in Load View is still required.

2. Deflection Combinations when LRFD Selected (QA 8)  

For deflection calculations when LRFD is selected as the design procedure, the program sometimes calculated deflections using LRFD load combinations intended for strength design, instead of the ASD combinations that should be used for deflection for both design methodologies.

This occurred when there were more LRFD combinations than ASD combinations; the additional LRFD combinations would be evaluated for deflection. Additional LRFD combinations are created if there are any Snow, Roof Live, or Storage Live loads on the member.

This only had an effect when deflections from one of the extra LRFD load combinations governed over all of those calculated using the ASD combinations, so it was a conservative error, which has been corrected. 

3. Storage Live Load Type for Concentrated Live Load (QA 6)  

You can now choose between Live and Live storage loads when creating a concentrated live load. This allows you to design for the weight of heavy stored items such as books, safes, etc. positioned anywhere in a room.

When Live storage is selected:

-       the time-effect factor for the LRFD load combinations with principal live load is 0.7 rather than 0.8

-       live loads are considered as long-term loads to which the creep factor Kcr from NDS 3.5.2 is applied for total deflection.  

4. Time-effect Factor for Concentrated Load (QA 12)  

For LRFD load combinations 2 and 3 where L is a concentrated load, a time effect factor λ of 1.0 was applied instead of the 0.8 required by NDS Table N3. This affects the following combinations

1.2D + 1.6 L

1.2D + 1.6 L+ S

1.2D + 1.6 L+ Lr

1.2D + 1.6 Lr + L

1.2D + 1.6 S + L

Due to Change QA 6, above, the time effect factor is now also applied to those combinations where L is replaced by Ls or L + Ls. For those combinations containing 1.6 Ls with no L, 0.7 is used as the time effect factor. 

5. Pattern Load Combinations for Storage-only Live Loads (QA 11)

Pattern load combinations were not being created for Storage Live loads Ls unless a Live load L was also present. The program now creates pattern combinations with only Ls in the pattern if there are no live loads L on the member.

6. Storage Live Loads in Fire Load Combinations (Bug 3666)  

When the LRFD design procedure is selected, the program was not including storage live loads Ls in the load combinations for fire design, so that live storage loads were not included in fire analysis, and if only live storage loads were applied, no fire design would be done.

Live storage loads are now included in fire load combinations, and fire design is independent of the design procedure selected, as it should be.

7. Self-weight Contribution to Counteracting Dead Loads (Change 113)

For load combinations for dead loads counteracting wind and seismic loads, e.g, 0.6D + 0.6W, the dead load due to self-weight of the member was being factored by 1.0 rather than 0.6. This has been corrected.

C. Materials and Database 

1. Boise Versa-Lam Materials (Change 193)

Database files for made for Boise Versa-Lam beams, columns, built-up beams and columns, wall studs, and built-up joists have been added to the program. Design values for these materials are from the ICC ESR-1040 and APA PR-L266 Evaluation Reports and from the Versa Lam LVL Specifier Guide.

The database has been organized into two “species” corresponding to Southern pine (density = 41.5 lb/cu.ft.) and Douglas fir (37 lb.cu. ft) with the grades marked “SP” in one and those marked “DF” in the other.  

Notes in the Evaluation Reports and Specifier Guide that say to use 1.05 in NDS Equation D-4 for Emin  have been implemented by using True E rather than Apparent E and removing the 1.03 factor from the equation. See bug 3682 Calculation of Emin for SCL Members for more details.

Design notes have been added that for Versa-Lam designs that refer to the Evaluation Reports, Specifier Guide, to side load connection design, and design assumptions regarding service conditions, treatment and notches. 

The description of the Versa-Lam materials has been abbreviated from what would appear by echoing the inputs to avoid redundancy, and appear as, e.g.

Versa-Lam® LVL Built-Up, 1.8E 2650 DF..

Versa-Lam® LVL, 1.8E 2650 DF..

2. Glulam and LVL Sill Plates (190a)

The sample LVL material that comes with the program installation, and the Glulam Balanced and Glulam Unbalanced materials  have been added to the choices for sill plates acting as supporting members. The weak axis fcpy property is used as the compressive strength perpendicular to the grain, on the assumption that the members are laid on the flat.

3. Glulam Joist Materials (190b)

For the Glulam Balanced and Glulam Unbalanced joist materials, the thicknesses more than 3.5” (4” nominal) have been disabled by default, as such sizes are not practical for use as joists. The Glulam Uniform joist material has been removed, as this material is ordinarily used for columns. 

D. Input and Program Operation

1. Load View Tab Order (Change 181a)

The order in which the program sets the input focus on the inputs in Load view when using the Tab key was inconvenient for many users as it started with the Magnitude fields and proceeded through to the Location fields, then back to the Name field at the start of the form, then to Add, then to the Type and Distribution inputs, then to Modify, Delete, etc.

It is believed that this order had been inadvertently set while testing the program.

The tab order has been reset to run through the inputs in roughly the order they appear in the form:

Name -> Type -> Distribution -> Magnitude (2) -> Location (2) -> Pattern Load -> Add -> Modify -> Delete -> Delete All –> Repeating Point Load -> Save as Default Loads -> Apply Auto Eccentricity -> Load list -> All the options and settings in the order that they appear

Also, the program now changes the focus to the Name input upon on certain operations, such as adding, modifying, or deleting loads. Previously it was going to the Magnitude field after these events.  

2. IBC Load Combination for Wet Service Conditions (Change 159)

The checkbox for in Load Input view allowing you to apply IBC Table 1604.3, Note d was disabled when you had wet service conditions selected, so that you were not able to apply the 1.0 load factor to dead load deflections allowed by this note for wet service conditions. This has been corrected, and the setting is enabled for wet service conditions, and when checked, the 1.0 factor is applied.

3. LRFD in Building Codes Box (Change 182)

The Building Codes informational dialog box that is invoked from the Welcome box now mentions that either LRFD or ASD design can be used, and that load combinations for deflection are always ASD. It previously said all load combinations were ASD.

LRFD design was introduced in version 2019, Update 2.

4. Temperature Input Editability (Change 145)

The Temperature drop list in Beam Input view has been changed such that you can only select from the three temperature range options. Previously it was possible to type a value in, which would have no effect. 

5. Notes in Design and Default Settings

The following corrections were made to the informational notes that appear at the bottom of the Design and Default Settings input forms.

a) Asterisked Items in Design Settings (Change 186)

A note in the Design Settings said that all items marked with an asterisk are saved to the project file; however only two items had an asterisk even though all but three are saved to the project file. The note has been changed to say that all items except those with an asterisk are saved to the project file.

Asterisks have been removed from the Ignore cantilever deflections… and Unsupported length Lu… settings, which are saved, and added to the Report interior and cantilever deflections separately, Report dead load deflection, and Fire resistance rating settings, which are not saved.       

b) References to Beam and Column Mode Inputs (Change 188)

In notes in both the Design and Default Settings about items from Beam or Column input mode that are also saved as settings, the references to these items are now capitalized, e.g. Temperature instead of temperature and Span Type instead of span type.

The reference to Column mode input was also removed from the Default settings as the items referred to are only in Beam mode.

E. Text Output

1. Design Notes and Warnings

The following problems with Design Notes and warning messages that appear in the output reports have been corrected

a) Warning Message for Deep Custom Lumber Sections (Bug 3615)

For dimension lumber sections that are deeper than the deepest in the beam or column database file, a warning message appeared in the Design Check output that is intended for members that are too thick for the lumber grade properties from NDS Table 4A/B, even though the sections are less than 4” thick and should not show the message.

b) Fire Rating Design Note in Concept Mode (Bug 3586)    

A design note saying "Joists, wall studs, and multi-ply members are not rated for fire endurance" appeared in the Concept Mode Design Summary, even when fire design was not performed for any member. This note has been removed as it was intended for a structure-wide fire design setting, but fire design is now activated on a group-by-group basis. The reference to multi-ply members was also obsolete, as it was based on the IBC empirical procedure that has been removed from the program.

c) Reversed Nail Spacings in SDPWS 3.1.1.1 Design Note (Change 189)

The design note that appears when the option for repetitive member factors for wall studs from SDPWS 3.1.1.1 is selected in Column Input view had the nail spacings 6” and 12” reversed in the following: “Wall must be covered with blocked and fastened with a minimum of 8d nails spaced at most at 12” at the edge and 6” interior”.  It now says 6” at the edge and 12” interior.

2. Factors Table of Design Check

In the Factors table of the Additional Data section of the Design Check report, the following problems were corrected. Note that the correct values were used for design; these were just display issues.

a) LRFD Factors for Tension Design (QA 9)  

The LRFD resistance factor f and format conversion factor KF for tension strength Ft. were showing the values for compression strength, that is, ϕ was shown as 0.9 instead of 0.8, and KF 2.4 instead of 2.7.    

b) Temperature Factor for CLT Wall Stiffness (QA 13)  

For CLT wall panels, in the Factors table of the Design Check output, a dash was shown instead of the temperature factor Ct for the EIapp design criterion.

3. Units Shown in Design Strength Output

The following problems with the units shown In the Analysis vs. Allowable Stress table of the Design Check output were corrected.

a) Unit for Tensile Axial Stress (Change 114)

The unit for the tensile stress due to uplift loading for columns and walls was shown as a force value, lbs or kN. It is now shown as a stress; i.e. psi or N/mm2  

b) Weak Axis Bending Moment Unit (Change 156)

The unit for bending stress in the y-axis direction for rotated beams was shown as a moment value, lb-ft or kN-m. It is now shown as a stress; i.e. psi or N/mm2 

4. Unit Conversion in Output of I-joist Shear Constant K (Bug 3582)    

When metric units were in use, the value of the I-joist shear constant K in pounds rather than newtons was shown in the Calculations section of the Design Check output, followed by the metric symbol N. For example, K = 4.94 e06 N when it should be K = 21.97 e06 N.

This was a display issue only; the correct K was used for shear deflection calculations.   

5. Output of Additional Notch Information (Changes 186,191)

The information that appeared in the Additional Data section of the Design Check report about the factors and adjustments applied to shear design for notched members was outdated and somewhat confusing. The presentation of this information was modified for the recently added LRFD design output with Update 2, and this format has now been adapted for ASD design. Corrections to the LRFD changes were also made. The details are as follows: 

a)  ASD Factors Table (Change 191b)  

There was a column in the Factors table that said Cn for glulam and Notch for sawn lumber. Cn was our terminology for the adjustment to shear resistance Vr due to notches from NDS 3.4.3, and this nomenclature doesn’t exist in the NDS. For glulam, Notch showed the value of Cvr * Cn, where Cvr is the shear reduction factor from 5.3.10 which is 0.72 when there is a notch. This column has been removed for sawn lumber and renamed to Cvr for glulam, and now shows the value of Cvr only.

b)  Note under Factors Table (Changes 186, 191b)

The note under the factors table explaining the meaning of the Cn /  Notch column has been removed, as the remaining Cvr heading is straightforward.

For glulam, this note started with Cn = even though the table heading for glulam was Notch, and referred to notes in the NDS Supplement tables referencing Cvr rather than the main reference to Cvr in 5.3.10.

c) Calculations Section (Change 191b)

In the Calculations section, we now provide an algebraic expression, NDS reference, and value of the notch adjustment from NDS 3.4.3.2 applicable to the member, without giving it a name or symbol. The expression is derived from Eqn. 3.4-3 for tension face notches and 3.4-5 for compression face notches. It was previously presented following “Cn =”.  

d) Cvr Factor for LRFD Design (Change 191a)

When LRFD design was selected, the Cvr column in the Factors table showed 1.0 instead of 0.72 when there was a notch. The value of the adjustment for NDS 3.4.3 shown in the Calculations section was that adjustment erroneously multiplied by Cvr. These two errors cancelled when multiplying Cvr by the adjustment to arrive at the factored shear resistance Fv’.

e) Expression for Tension Face Notches (Change 191c)

In the Calculations section, the expression for the adjustment for tension face notches from NDS 3.4.3.2, Eqn. 3.4-3 was given as dn^3/d^2 when it should be (dn/d)^3. This has been corrected for both ASD and LRFD design.

The derivation of this adjustment from the unnotched shear resistance

Vr’ = 2/3 Fv’ b d.

is as follows, where Vr’,n is the notched shear resistance: 

Vr’,n = 2/3 Fv’ b dn (dn / d)2    

     = 2/3 Fv’ b d (dn / d) (dn / d)2

     = 2/3 Fv’ b d (dn / d)3    

     = Vr’ (dn / d)3    

6. Load Combination Table in Analysis Results

For Update 2, the Load Combinations table of the Analysis results was changed to accommodate LRFD design by showing LRFD combinations, adding a list of ASD deflection combinations and adding columns for the load combination numbers as listed in the ASCE 7.     

Corrections and adjustments to these changes are listed below. Note that they are just display issues and the analysis and design of the member was not affected.

a) Patterned Deflection Load Combination for LRFD (QA 10)  

When LRFD was selected for design, patterned load combinations did not appear in the list of combinations for deflection design; instead, a load combination number appeared followed by a dash. The pattern load combinations are now shown.

b) ASCE 7 ASD Load Combination Numbers for Deflection (Change 183)

When designing for LRFD, in the list of deflection load combinations, the ASCE# column was empty. It now shows the numbers as listed in the ASCE 7 for the ASD load combinations corresponding to the load combination shown in the table.

c) Formatting Changes (Change 183 a)

Changes were made to better line up table headings with data below, show blank lines, show blank lines as delimiters, change ASCE # and LC # to ASCE# and LC#, etc.

d) ASCE 7 ASD Load Combination Numbers (Change 183b)

The number shown in the ASCE# column for the ASD load combinations D + 0.75(S + 0.6W) and D + 0.75(Lr + 0.6W) was 3 when it should have been 6.

7. Time Effect Factor in Analysis Results

In the table in the Analysis results showing LRFD time effect factors:

a) Table Heading (QA 4)

The table heading has changed to TIME EFFECT FACTORS from Lambda FACTORS.

b) Factor Column Heading (QA 5)

The headings of the table column or columns showing these values referred to CD, which is the factor for is the factor for ASD design. It now says Lambda.

8. Design Code References for Load Combinations

The following errors in the references to load combinations in design codes and standards have been corrected:

a) ASD vs. LRFD in Design Summary (QA 1a)

The Design Summary output referred to the ASCE 7 and IBC clauses for ASD combinations when LRFD was selected for design.  

b) IBC ASD Reference (QA 1b)

In the Design Summary and Analysis Results, the reference to the IBC ASD load combinations was 1605.3.2, for Alternative Basic load combinations, but it should be 1605.3.1, for Basic Load combinations. 

c) IBC LRFD Reference in Design Check (QA 2a)

In the Design Check under Critical Load Combinations, when LRFD was selected, the reference was to IBC 1605.3.1, which is for ASD combinations. It has been changed to 1605.2. 

d) ASD Reference in Design Check (QA 2b)

In the Design Check under Critical Load Combinations, when ASD was selected, a blank space appeared after the words Load combinations:  It now shows the ASD references.

 


Previous Versions:

Note that an asterisk (*) beside any item in the list of previous releases below indicates that the item was added to the version history record after that version was released.

 

Sizer 2019, Update 3 (Version 12.3) – July 13, 2021 

1. Non-Dead-only Load Combinations for Columns from Version 12.1 Projects (Bugs 3660 and 3661)

When Column mode files with version 12.1 were run in version 12.2, the program created only the “Dead-only” load combination when analysing the member, although the original live, snow and wind loads appear in the load lists of the output reports. The reactions, shear forces, moments and deflections shown in the analysis and design results were those derived from dead loads only without the contribution of the other load types.

This problem also affected columns and walls created in Concept mode, they did not include non-dead loads in design nor pass them to supporting members.

This issue could be resolved if the setting is reset in the Loads Input View by pressing the Reset Original Settings then re-designing. For Concept mode, you must also press Apply Options to Concept Mode.

The problem has been corrected and version 12.1 files can be run in Version 12.3.

2. Tab Order for Load Input View (Change 181)   

The tab order for Loads Input view in beam mode was not the same for the docked view as for the pop-up view, nor was it the same as the Column mode order. For the pop-up view, it was necessary to tab through all the numerous settings and options before you got to the key fields starting with Magnitude that define the load, which was an inconvenience to those users who like to use the keyboard to enter loads rapidly.  

For the docked view, the tab order started with Name, then proceeded through Type and Distribution to get to the Magnitude fields. However, in previous versions of the program, the tab order started with Magnitude because Name is not a required field.

The tab order once again starts with the Magnitude fields, then proceeds through Location, Name, Add, Type, Distribution, the buttons for modifying the loads below the list, then all through all the options and settings, ending with the Load Duration factors that are rarely changed.

 

Sizer 2019, Update 2 (Version 12.2) – July 17, 2021

This version contains the major new features Load and Resistance Factor Design (LRFD) and Shear Deflection (Feature 203) as well as other small improvements and bug fixes.    

A. Load and Resistance Factor Design (LRFD) (Feature 94)

It is now possible to design using the Load and Resistance Factor Design (LRFD) method in the NDS. Previously the program allowed only Allowable Stress Design (ASD).

LRFD applies to all materials in Sizer (sawn, glulam, SCL, I-joists, and CLT), for all member types, and in Beam, Column and Concept mode.

1. LRFD vs ASD

LRFD is a design methodology that incorporates the variability in both loading and material resistance into design values and into separate safety factors for each, whereas ASD incorporates a factor of safety accounting for all sources of uncertainty, from both loads and resistance, into the allowable design stresses determined from the strength properties derived from the average of test samples.

a) Load Factors

LRFD loads are factored to consider the variability of each load type and to provide a margin of safety, so that for example dead loads have a factor of 1.2 and live and snow loads have a factor of 1.6 when they are the principal load in the combination.

ASD loads are essentially unfactored, except for wind loads, earthquake loads, and dead loads counteracting the effect of transient loads. Dead, live and snow loads have a factor of 1.0.

b) Load Combinations

Using LRFD, to account for the probability of loads being encountered simultaneously, separate load combinations are made with live, wind and snow as the principal load, with a high load factor, and for each of these combinations the other loads are included with a lower factor. As a result, more than one load combination is examined containing the same set of load types.  

For ASD, the probability of two load types occurring simultaneously is accounted for by a 0.75 factor applied to live, snow and wind when they occur together, and by also examining the combinations created with each load type separately with a 1.0 factor. Only one load combination is examined for each unique set of loads.

c) Resistance Factors

For LRFD, a safety factor is incorporated into the design strengths via the statistical analysis of the test samples. In addition, a factor φ accounting for size variations, workmanship, and other sources of uncertainty is included (see Resistance Factor f and Format Conversion Factor KF, below.) This factor is different for each design strength, reflecting different level of uncertainty in different applications.

Using the ASD method, all safety factors are incorporated into the reference design strengths listed in the NDS supplement and in manufacturers’ literature.

d) Design Strengths

LRFD design strengths are determined via a statistical analysis of material performance using the procedures outlined in ASTM D5457. In the absence of such an analysis, format conversion factors are used to convert ASD strengths listed in the NDS Supplement to those that correspond to the LRFD methodology. Refer to Reference Design Values, below.

Sizer uses only the format conversion method. Note that this method does not account for the variability in material properties as the LRFD statistical procedure would, it reflects the average values used to determine ASD strengths.

e) Design Results

For simple loading situations, it is easy to compare the design response of LRFD designs to those for ASD by the ratio of the factors that are applied when using the methods. For typical 15 psf dead and 40 psf live floor loads, for bending moment design of joists and supporting beams, LRFD is advantageous by 16%, i.e., a member loaded to capacity for ASD could be loaded 1.16 times this much before failing for LRFD.

LRFD is found to be advantageous for situations with more than one transient load type e.g., wind, snow, and live load in combination, by as much as 30%.

An exception to this is combined axial and bending design for columns subject to wind and snow loads, where LRFD can be conservative with respect to ASD by as much as 50%.

Refer to  https://www.awc.org/pdf/codes-standards/publications/archives/lrfd/AWC-ASAE984006-LRFDvsASD-9807.pdf for more details and comparisons.

2. NDS Provisions 

The following NDS provisions specific to LRFD have been implemented. Note that all other NDS provisions also apply to LRFD unless indicated as ASD-only.   

-        1.4: LRFD is given as a permitted procedure

-        1.4.4: Load combination factors are to come from the governing design code, and load combinations and time effect factors λ are from Appendix N.

-        2.1.1.2: Mandates use of LRFD adjustment factors.

-        2.3.5 and Table 2.3.5; N.3.1 and Table N1:  Specifies format conversion factor KF

-        2.3.6 and Table 2.3.6; N.3.2 and Table N2:  Specifies resistance factor φ

-        2.3.7: Mandates time effect factor λ specified in N.3.3

-        4.3.3, 5.3.2, 7.3.2, 8.3.2, 10.3.2:  Load duration factor CD indicated as ASD-only

-        4.3.14, 5.3.14, 7.3.8, 8.3.11, 10.3.10: Mandate format conversion factor KF for design criteria listed in Tables (see below)

-        4.3.15, 5.3.15, 7.3.9, 8.3.12, 10.3.11:  Mandate resistance conversion factor φ for design criteria listed in Tables (see below)

-        4.3.16, 5.3.16, 7.3.10, 8.3.13, 10.3.12: Mandate time effect factor λ specified in N.3.3 for design criteria listed in Tables (see below)

-        Tables 4.3, 5.3, 7.3, 8.3 and 10.3 – List design criteria applicable to format conversion factor KF, time effect factor λ, and resistance conversion factor φ

-        Appendix N.1.2: Loads and load combinations from applicable building code or ASCE 7

-        Appendix N.2.1: Indicates that adjusted design values are from ASTM D5457 or from NDS using N 2.2

-        N.2.2: Indicates NDS design values are to be adjusted as per Tables (see above). 

-        N.3.3 and Table N3:  Specifies time effect factor.

3. Choice of Design Procedures

An input has been added to the Design Settings allowing you to choose between Allowable Stress Design (ASD) and Load and Resistance Factor Design (LRFD).

4. Storage Live Load

Because there are different time-effect factors λ based on whether live loads are due to storage or occupancy (see item 6 below), a new load type for live loads due to storage has been added to the program.

a) Input

The load type Live storage has been added to the Type drop list in Load Input view and appears in the load lists in the output report as such. It is available regardless of whether LRFD or ASD design is chosen in the Design Settings.

b) Symbol

The load type has the symbol Ls in load combination descriptors that appear in the Design Analysis and Design Check output reports and the input list of load combinations for the Analysis diagrams. Live storage loads appear next to live loads in these descriptors, e.g. 1.4D + 1.6 L + 1.6Ls.

c) Load Combination Factor

For LRFD design, the load combination factor is the same as the factor for other live loads in the same load combination. Refer to the section on Load combinations below for more details.  

For ASD design, the load combination factor is 1.0, the same as other live loads.

d) Time Effect Factor

For LRFD load combination 2 which has principal live loads, the time-effect factor for combinations generated with live storage loads but without other live loads is 0.8, otherwise, in the absence of impact loads, it is 0.7, if there are impact loads, it is 1.25.   

For the load combinations 3,4, and 5, where live loads are secondary, the time-effect factor is unaffected by the presence of live storage loads and the factor corresponding to the principal load is used.    

Refer to the section on Time Effect Factor below for more details.

e) Load Duration Factor

The ASD load duration factor CD is unaffected by the presence of Live Storage loads, they are treated as any other live load in the determination of CD.

f) Long-term Deflection

Live storage loads are included in the long-term loads to which the creep factor KCF is applied in determining total deflection using NDS 3.5.2.

This is the only effect of live storage loads that occurs when using ASD design. It is also applied to LRFD design.  

5. Load Combinations

a) LRFD or “Strength” Load Combinations.

Load combinations to be used for LRFD or strength design are listed in table NDS Table N3 giving the time effect factor for each combination. These load combinations are derived from the numbered load combinations in IBC 1605.2 and ASCE 7 2.3. IBC designates as these being for “strength design or load and resistance factor design”, whereas ASCE 7 refers only to “strength design”. These load combinations are:

 

1.    1.4D

2.    1.2D + 1.6L + 0.5(Lr or S or R)

3.    1.2D + 1.6(Lr or S or R) + (L or 0.5W)

4.    1.2D + 1.0W + L + 0.5(Lr or S or R)

5.    1.2D + 1.0E + L + 0.2S

6.    0.9D + 1.0W

7.    0.9D + 1.0E

 

The IBC combinations also refer to hydrostatic loads H, fluid loads F, live load factors for public assembly and parking garages, and snow load factors for sawtooth roofs. The ASCE 7 separates earthquake loads into vertical and horizontal components. The load combinations listed in the NDS do not include these special situations, and they are not implemented in Sizer. 

b) Sizer Load Combinations

Sizer creates separate load types for Live Storage (Ls) and Impact (I) loads in order to apply the time-effect factors for combinations containing these loads. Live storage loads were added for LRFD impact loads already existed for ASD design.

To avoid unnecessarily complicating the list of load combinations with rarely used loads that are unlikely to govern, impact loads are incorporated only into load combination 2, where they have a different time-effect factor than other loads.

Live storage loads, however, are incorporated into all load combinations that have live loads, although the special time-effect factor is applied only to load combination 2.  

The load combinations implemented by Sizer are therefore

 

1.    1.4D

2.    1.2D + 1.6(L + Ls + I)  + 0.5(Lr or S or R)

3.    1.2D + 1.6(Lr or S or R) + (L + Ls or 0.5W)

4.    1.2D + 1.0W + L + Ls + 0.5(Lr or S or R)

5.    1.2D + 1.0E + L + Ls + 0.2S

6.    0.9D + 1.0W

7.    0.9D + 1.0E

c) Subsets of Load Combinations

As is the case with ASD load combinations, Sizer examines subsets of these load combinations if they could possibly govern for design relative to the full combination. Note they whether they can govern for design is also affected by the time-effect factor, described in CREF below. The following is a list of all subsets of the load combinations generated by Sizer for LRFD design.

 

 

Load Type

 

ASCE/NDS No.

No. in Sizer

L

Ls

Lr

S

I

W

E

Load combinations if all the loads in the combination listed exist on the member

 

Load Combination 1 (Dead only)

1.4D

1

1

 

 

 

 

 

 

 

1.4D

 

Load Combination 2 (L principal)

1.2D + 1.6 L + 0.5 (Lr or S )

 2

2

x

x

 

 

 

 

 

1.2D + 1.6(L + Ls)

2

3

 

x

 

 

 

 

 

1.2D + 1.6 Ls

2

4

x

x

x

 

 

 

 

1.2D + 1.6(L + Ls) + 0.5Lr

2

5

 

x

x

 

 

 

 

1.2D + 1.6 Ls + 0.5Lr

2

6

x

x

 

x

 

 

 

1.2D + 1.6(L + Ls) + 0.5S

2

7

 

x

 

x

 

 

 

1.2D + 1.6 Ls + 0.5S

2

8

x

x

 

x

x

 

 

1.2D + 1.6(L + Ls + I) + 0.5S

2

9

x

x

x

 

x

 

 

1.2D + 1.6 (L + Ls + I) + 0.5Lr

 

 

Load Combination 3 (Lr or S principal)

1.2D + 1.6 (Lr or S ) + ( L or 0.5W)

3

10

x

x

x

 

 

 

 

1.2D + 1.6Lr + 1.0(L + Ls)

3

11

 

 

x

 

 

 

 

1.2D + 1.6Lr

3

12

x

x

 

x

 

 

 

1.2D + 1.6 S + 1.0(L + Ls)

3

13

 

 

 

x

 

 

 

1.2D + 1.6S

3

14

 

 

x

 

 

x

 

1.2D + 1.6Lr + 0.5W

3

15

 

 

 

x

 

x

 

1.2D + 1.6S + 0.5W

 

 

Load Combination 4 (W principal)

 

4

16

x

x

x

 

 

x

 

1.2D + 1.0W + L + Ls + 0.5Lr

4

17

x

x

 

 

 

x

 

1.2D + 1.0W + L + Ls

4

18

x

x

 

x

 

x

 

1.2D + 1.0W + L + Ls + 0.5S

4

19

 

 

x

 

 

x

 

1.2D + 1.0W + 0.5Lr

4

20

 

 

 

 

 

x

 

1.2D + 1.0W

4

21

 

 

 

x

 

x

 

1.2D + 1.0W + 0.5S

Load Combination 5 (E principal)

1.2D + 1.0E +  L +  0.5 (Lr or S)

5

22

x

x

 

x

 

 

x

1.2D + 1.0E + L + Ls + 0.2S

5

23

 

 

 

x

 

 

x

1.2D + 1.0E + 0.2S

5

24

 

 

 

 

 

 

 

1.2D + 1.0E + L + Ls

5

25

 

 

 

 

 

 

x

1.2D + 1.0E 

Load Combination 6 (Counteracting W)

0.9D + 1.0W

6

26

 

 

 

x

 

 

 

0.9D + 1.0W

Load Combination 7 (Counteracting E)

0.9D + 1.0E

7

27

 

 

 

x

 

 

 

0.9D + 1.0E

 


 

d) Load Combinations for Deflection

Since LRFD combinations are intended for strength design and there is no guidance in the NDS, ASCE or IBC as to the combinations to be used for serviceability design, i.e. deflections, ASD load combinations are used to calculate deflections even if LRFD is chosen as the design procedure in the Design Settings. 

6. Time Effect Factor

The time effect factor λ is analogous to the load duration factor CD for ASD design. CD is not applied to LRFD design.

The time-effect factors are given in NDS Table N3 as

 

ASCE / IBC No.

Load Combination

λ

1

1.4D

0.6

2

1.2D + 1.6L + 0.5(Lr or S)

0.7 (when L is from storage)

2

1.2D + 1.6L+ 0.5(Lr or S)

0.8 (when L is from occupancy)

2

1.2D + 1.6L + 0.5(Lr or S)

1.25 (when L is from impact)

3

1.2D + 1.6(Lr or S) + (L or 0.5W)

0.8

4

1.2D + 1.0W + L + 0.5(Lr or S)

1.0

5

1.2D + 1.0E + L + 0.2S

1.0

6

0.9D + 1.0W

1.0

 

a) CD vs. λ

The main difference between CD and λ is that CD is based on the presence of load types in a combination, so that a different CD factor is applied to load combinations generated from a subset of loads than would be applied if all loads existed in the combination. λ is applied based on the combination and is the same for subsets of combinations containing fewer of the ASCE-defined types than in the full combination.

However, this is not true for load types I and Ls defined by Sizer for convenience, see below.

b) Impact and Live Storage Loads

It is possible that more than one of live occupancy, live storage, and live impact loads can be on the member. In that case, for load combination 2, the program generates the full combination and subsets of the combination not containing I, L, and/or Ls. The time effect factor is the largest for any of the loads in the combination.

For example, of live and live storage are on the member, then the combination with both has a time effect factor λ = 0.8. A combination is also generated only with live storage loads, without occupancy live loads, with a λ = 0.7.

This is analogous to the procedure used to determine the CD factor for combinations containing more than one load duration category.

c) Time Effect Factor for Sizer Load Combinations

The time effect factor for all the subsets of ASCE/NDS load combinations generated by Sizer, designating impact and live storage loads as separate load types, is shown below.

 

ASCE/NDS No.

No. Sizer

Sizer Load Combinations. 

λ

1:  Dead only - 1.4D

1

1

1.4D

0.6

2: 2D + 1.6 L + 0.5 (Lr or S)

2

2

1.2D + 1.6(L + Ls)

0.8

2

3

1.2D + 1.6 Ls

0.7

2

4

1.2D + 1.6(L + Ls) + 0.5Lr

0.8

2

5

1.2D + 1.6 Ls + 0.5Lr

0.7

2

6

1.2D + 1.6(L + Ls) + 0.5S

0.8

2

7

1.2D + 1.6 Ls + 0.5S

0.7

2

8

1.2D + 1.6(L + Ls + I) + 0.5S +

1.25

2

9

1.2D + 1.6 (L + Ls + I) + 0.5Lr

1.25

3:  1.2D + 1.6 (Lr or S) + (L or 0.5W)

3

10

1.2D + 1.6Lr + 1.0(L + Ls)

0.8

3

11

1.2D + 1.6Lr

0.8

3

12

1.2D + 1.6 S + 1.0(L + Ls)

0.8

3

13

1.2D + 1.6S

0.8

3

14

1.2D + 1.6Lr + 0.5W

0.8

3

15

1.2D + 1.6S + 0.5W

0.8

4:  1.2D + 1.0W + L + 0.5 (Lr or S)

4

16

1.2D + 1.0W + L + Ls + 0.5Lr

1.0

4

17

1.2D + 1.0W + L + Ls

1.0

4

18

1.2D + 1.0W + L + Ls + 0.5S

1.0

4

19

1.2D + 1.0W + 0.5Lr

1.0

4

20

1.2D + 1.0W

1.0

4

21

1.2D + 1.0W + 0.5S

1.0

5:  1.2D + 1.0E + L + 0.5 (Lr or S)

5

22

1.2D + 1.0E + L + Ls + 0.2S

1.0

5

23

1.2D + 1.0E + 0.2S

1.0

5

24

1.2D + 1.0E + L + Ls

1.0

5

25

1.2D + 1.0E 

1.0

6: 0.9D + 1.0W

6

26

0.9D + 1.0W

1.0

7:  0.9D + 1.0E

7

27

0.9D + 1.0E

1.0

 

d) Applicable Design Criteria

The design criteria that the time effect factor λ applies to for each material is indicated by a λ in the table below: 

 

Criterion

Sawn Glulam SCL

CLT

I-joist

Sawn, Glulam, SCL

CLT

I-joist

Bending

Fb

FbS

Mr

λ

λ

λ

Tension

Ft

FtA

n/a

λ

λ

 

Shear

Fv

Fvtv

Vr

λ

λ*

λ

Rolling shear

n/a

FsIb/Q

n/a

 

 

 

Axial compression

Fc

FcA

n/a

λ

λ

 

Compression perp. to grain

Fc^

Fc^A

R

 

 

λ*

Stiffness

E

EIeff

EI

 

 

 

Buckling stiffness

Emin

(EI)app-min

n/a

 

 

 

Shear stiffness

n/a

n/a

K

 

 

 

 

 

 

 

 

 

 

λ* - Indicates that the criterion is not implemented in generic Sizer, but may be in custom versions. 

 

e) Input of CD Factors

The inputs for CD factors for each load type in Loads View are disabled when LRFD is selected in the Design Settings.

7. Resistance Factor f and Format Conversion Factor KF

The resistance factor f from and the format conversion factor KF are applied based on the design criterion.

a) Resistance Factor f

The resistance factor is a safety factor analogous to the factor f in CSA O86. It is listed in NDS Table 2.3.5 and N2. It comes from fs in ASTM D5457 4.1.1 Table 1.

b) Format Conversion Factor KF

The format conversion factor converts from values to be used for ASD design to those to be used for LRFD design. It is listed in NDS Tables 2.3.6 and N3.  It comes from of ASTM D5457 4.1.1 Table 2.   

c) Values and Applicable Design Criteria

The values of  f and KF for each design criteria, and whether it applies for each material, are given in the table below: 

 

Criterion

Sawn Glulam SCL

CLT

I-joist

f

KF

Sawn, Glulam,

SCL

CLT

I-joist

Bending

Fb

FbS

Mr

0.85

2.54

KF, f

KF, f

KF**, f

Tension

Ft

FtA

n/a

0.80

2.70

KF, f

KF, f

 

Shear

Fv

Fvtv

Vr

0.75

2.88

KF, f

KF*, f*

KF**, f

Rolling shear

n/a

FsIb/Q

n/a

0.75

2.00

 

KF, f

 

Axial compression

Fc

FcA

n/a

0.90

2.40

KF, f

KF, f

 

Compression perp. to grain

Fc^

Fc^A

n/a

0.90

1.67

KF, f

KF, f

 

Bearing resistance

n/a

n/a

R

0.75

KF**

 

 

KF*, f*

Stiffness

E

EIeff

EI

n/a

n/a

 

 

 

Buckling stiffness

Emin

(EI)app-min

n/a

0.85

1.76

KF, f

KF, f

 

Shear stiffness

n/a

n/a

K

n/a

n/a

 

 

 

 

 

 

 

 

 

 

 

 

KF*, f* - Indicates that the criterion is not implemented in generic Sizer but may be in custom versions. 

KF** - Indicates that the value of KF is not the one listed here but must come from the manufacturer.

d) KF values for I-joists

The program uses the same KF values for I-joists that it does for other materials. According to Nordic Engineered Wood, these values are appropriate for their I-joists. It is left to a future version of the program to allow for input of proprietary KF values into the database.

8.  Reference Design Values

As per NDS N2.2 and ASTM D5457 4.1.1, the program uses the ASD design strengths and resistances published in the NDS Supplement and applies the format conversion factor KF to convert to LRFD values.

ASTM D5457 also includes a statistical analysis procedure in Section 4.2 for manufacturers and suppliers to determine the LRFD strengths empirically, without using ASD strengths or applying the KF factor. It is not currently possible in Sizer to design for material strengths determined with this method.   

Note that the using the NDS format conversion method used by Sizer does not account for variation in the strengths of materials as the statistical procedure would.

9. Deflection Design

As LRFD load combinations are intended for strength design, the program uses ASD load combinations when calculating the deflection of the member, even when the LRFD method is chosen in the Design Settings.

The LRFD KF, f, and λ factors are not applicable to the modulus of elasticity E or stiffness EI used for deflection, nor is the CD factor that is used for ASD only, so there is no other effect of the ASD vs. LRFD choice affecting deflection calculations. Deflections should be identical for ASD and LRFD.

10. Fire Design

Although there is no guidance in the NDS regarding fire design, and Table 16.2.2 for strength adjustment factors refers to ASD only, we have been informed that a future version of the NDS will indicate that these factors are applicable to LRFD as well, so LRFD is used for design of fire-reduced sections when selected in the Design Settings.      

11. Output

a) Design Notes

The design note referencing the NDS in the Design Check or Design Summary now indicates whether ASD or LFRD was used.

b) Analysis vs. Design Table

The title of the Analysis vs. Design table refers to Load and Resistance Factor Design when LRFD is selected.

c) Factors Table

In the Factors table of the Design Check output report, columns headed by KF, f, and λ appear, and the column for ASD load duration factor CD is not shown.

d) Load Combinations in Design Results

In the Design Data section of the Design Summary and in the Critical Load Combinations section of the Design Check, the existing line saying only that ASCE / IBC load combinations are used, now indicates whether they are ASD or LRFD and provides design code reference numbers.  

e) Load Combinations in Analysis Report

In the Analysis output report, separate tables are shown for the LRFD load combinations for strength design and ASD combinations for deflection.

Titles above each table give the design code/standard reference for the tables from both ASCE and IBC. This title has been added for ASD design as well.

A column has been added giving the load combination number from the ASCE for each combination, for both LRFD and ASD combinations. 

f) Time Effect Factor in Analysis Report

When LRFD is selected, the table that shows CD factors for each combination for ASD instead shows the time effect factor λ for LRFD.

B. Shear Deflection (Feature 203)

For CLT, SCL, and I-joist materials, the program now implements rigorous shear deflection calculations based on Timoshenko beam theory, which has been incorporated in our matrix stiffness loads analysis engine.

(Sawn lumber and glulam materials do not require rigorous shear deflection analysis because the effect of shear deflection is incorporated in published modulus of elasticity E values.)

A full technical exposition of this procedure will be provided in the Online Help. The following describes the changes in program operation for this feature.

1. Previous Implementation

Previously, for CLT and I-joists, the program used an approximate method which applied an adjustment to stiffness EI based on the shear deflection of a uniformly loaded, simple span beam.

For SCL, it used an “apparent” EI that you entered in your database files as provided by the manufacturer. This EI could also be inaccurate or overly conservative compared to the True EI that manufacturers also publish.

2. Design Setting

For SCL, a setting has been added to allow you to choose between using the manufacturers published Apparent E value, and not calculate shear deflection, or use True E and calculate shear deflection. True E values have been added to all SCL database files, and Apparent E retained.

3. Design for Unknown Parameters

When searching for a passing design for unknowns, the program uses the approximate method for CLT and I-joists, and Apparent E for SCL. Then when verifying the section in the Design Check, it uses the known GA value and calculates shear deflection.

This is because in the absence of shear deflection, the program designs for unknown section size using an arbitrary stiffness EI and relies on linearity to adjust the resulting deflections once the section was known and EI can be calculated.

This is not possible with the inclusion of shear deflection, which requires the section size for shear stiffness GA for SCL or CLT, and for I-joists, for the shear constant K of the section.

It is possible, therefore, that a member which just barely passed the deflection check when searching for a design fails the Design Check, or that a section that would just barely pass the Design Check is passed over when searching for a passing section.

4. Concept Mode

In Concept Mode, if the section size of a design group is specified ahead of time, and True E is selected in the Design Settings, the program calculates the shear deflection of the member. Otherwise, it is approximated using Apparent E for SCL, and by using adjustment to EI for I-joists and SCL.

5. Output

a) Deflections

The deflections that include the effect of shear deflection can be seen in the Deflection Analysis Diagram, and in the critical deflection value shown in the Analysis vs. Design table of the Design Check results, and in the critical deflection design ratio in the Design Summary and in the Concept Mode Results by Member.

b) Calculations

The value of shear stiffness GA is output in the Calculations section of the Design Check next to bending stiffness EI. 

c) Design Notes

Design notes in the Design Check, Design Summary, and Concept Mode Design Results have been changed as follows:

A note saying that shear deflection is approximate for I-joists and CLT have been removed.

For SCL, a note has been added saying whether True E or Apparent E has been used and mentions that mentions the shear modulus G = E /16, where E is the modulus of elasticity. For Concept mode, the note indicates that calculations with True E and G = E /16 are used when the section size for a design group has been specified, and that approximation with Apparent E is used when searching for unknown sections.

C. Other Engineering Design

1. Load Duration Factor CD for CLT Rolling Shear Resistance (Bug 3631)

The program was applying a load duration factor CD to CLT rolling shear resistance Vs’ although NDS 10.3.2 and Table 10.3.1 did not include CD among the factors applicable to Fs (Ib/Q)eff  (which Sizer and APA PRG 320 call “Vs”).

The program showed a “-“ for CD in the Factors table of the Design Check as if the factor was correctly not being applied. The incorrect factor did show up in the CD Factors table of the Analysis Results.

This resulted in a resistance Vs’, as shown in the Analysis vs. Design table, that was greater than it should be for all load combinations other than those that contain only dead and live loads. For one example it was 3795 lbs instead of 3300 lbs for the D + S combination with a CD factor of 1.15.

2. CLT Rolling Shear for Transverse Layers (Bug 3649)

The CLT database contained only one rolling shear value Fs that was applied to both the transverse and longitudinal layers, but there are circumstances in which they can be different, so a value for transverse layers has been added to the database, to the Database Editor input, and to the calculation procedure for rolling shear adapted from CSA O86 8.4.4.2:

Vs’ = 2/3 Aeff Fs CD Ct

The Fs values shown in O86 Table 8.2.4 and the Vr values in PRG 320 Table A2 are the same for transverse and perpendicular layers for all stress grades listed, but this is not necessarily the case. MSR shear strength fv from NDS Supplement Table 4C can be different than those from Tables 4A and 4B for visually graded lumber, even for the same species.  Some layups are composed of MSR layers and visual layers, so the transverse layers would not have the same fs (which is roughly 1/3 fv) as longitudinal layers

3. Bending Moment Factor for Transverse Axis CLT Design (Bug 3605)

For fire design of CLT floor and roof panels, the program applied a factor of 0.85 to the transverse axis bending resistance, when it should be 1.0 as per PRG 320-2019. 0.85 is the factor for the longitudinal axis design. 

The correct 1.0 factor was being shown in the FACTORS table in the Design Check output, however internally the 0.85 factor was being used in the calculation.

This has been corrected.

4. Combined Axial and Bending Check for CLT (Bug 3632)

For CLT wall panels, in the combined axial and bending interaction formula from NDS Commentary Equation C15.4-5, the program was using lb-inches for values of maximum moment M, but lb-ft for M’, resulting in the ratio of modified moment values to be roughly 12 times higher than it should be, and the combined Analysis/Design  value much higher than it should be, often causing the member to fail when it shouldn’t. This value is shown in the Analysis vs. Design table of the Design Check output.

The interaction formula is

 

(P / Pc’)2 + (M + P D (1 + 0.234 P / PcE)) / M’ (1 – P / PcE)  £  1.0 

 

where the P is axial force Pc’ axial resistance, PcE and D is deflection. For CLT, M’ = Fb/Seff, as shown in the version of this equation in the FPInnovations CLT Handbook.

For example, for a 4-1/8” CLT wall panel, E1 grade, with 7500 plf dead and 15000 plf live axial loads, and 41.67 psf lateral wind area load, in the program was using a M value of 2812 lb-in (235 lb-ft), and M’ of 7249 lb-ft. The Analysis/Design ratio for combined axial plus bending was 1.21 but should have been 0.41.

Consistent units are now used in this equation, resulting in correct design ratios.

5. Shear Deflection Issues

The following problems with the approximate shear deflection formula for CLT and I-joists were corrected by implementing the new matrix-analysis-based shear deflection calculations (see Section B above, Shear Deflection (Feature 203).)

The approximate formula, given for CLT in NDS 10.4.1 as the expression for apparent shear stiffness EIapp, adjusted deflections for all span and loading conditions based on the shear deflection for a simple span beam with uniform loading. These corrections apply to the continued use of this formula when evaluating members with unknown section sizes. 

a) Application of I-joist Shear Deflection (Bug 3572)

Starting with version 12.1, the shear deflection using the approximate formula was no longer being added to I-joist bending deflection, resulting in deflections that were typically 10% less than they should be.

b) CLT Shear Stiffness Adjustment for Creep (Bug 3580)

The program was incorrectly reducing the CLT shear stiffness GAeff by 75% when calculating total deflection and 50% for live deflection.

These reductions were from a provision from the FPInnovations CLT Handbook implemented before CLT design was included in the NDS. It is now superseded by the creep factor of 2.0 in NDS 3.5.2.   

GAeff  is used in both the approximate formula and the new method.

c) Apparent EI for CLT Shear Deflection (Bug 3579)

The calculation of EIapp for CLT was subject to random and unpredictable errors such that it was 1% - 5% greater than the EIeff value, when it should be less. 

6. Incising Factor Ci for Compression Strength Fcp (Bug 3629)

When a sawn lumber member was incised for treatment, the program applied the input incising factor Ci for bending and shear strength, usually 0.8 from NDS Table 4.3.8 to the bearing compression strength Fcp’, whereas it should be 1.0 for that purpose.

This resulted in a bearing capacity 20% less than what should be, and a minimum required bearing length 25% more than it should be. These values are shown in the Bearing and Reactions table of the Design Check output. The Ci factor shown in the Factors table for Fcp was 1.0, despite 0.8 having been used.

The Beam View input for Ci for Strengths does not include bearing strength Fcp because it is listed as 1.0 in the NDS and assumed to always be 1.0.

A longer than expected minimum required bearing length can cause the shear and bending stresses to be slightly less than they should be due to the shortened design span. 

For example, for a 8.75’, 6 x 12” Timber beam, with Ci = 0.8, the  minimum required bearing length should be1.35” but was 1.69” and the bearing capacity should be 4383 lbs but was 3506 lbs.

D. Materials and Database

1. Element5 CLT Material (Change 162)

A proprietary CLT material called Element5 CLT has been added to the program for wall panels, floor panels and roof panels. This material includes only stress grade V2.

E. Program Operation

1. Disappearance of Load Name Input (Bug 3569)

In the Loads Input View, the load name disappeared any time you changed the load distribution. If you then entered a name again, it persisted unless the distribution was changed again. 

This has been corrected.

2. Section Depth Change for a Single Glulam Column Section (Bug 3578)

Starting with version 12.1, for only the Glulam-Balanced column, Western species, 16F-1.3E WS stress class with an 89 mm x 229 mm cross-section, when the Save or Design button in Beam View is clicked, the width changed to 79 mm from 89 mm, and the program would design with the reduced width.  This only occurred when metric units were selected and has been corrected.  

3. Column Input View Rearrangement (Bug 3643)

The following changes have been made to the layout of the inputs in Column View:   

a) CLT Wall Panel Layers

The CLT layup data group that appeared in the upper right corner when wall panels were selected has been removed as it contained only the Layers input, which has been moved to be at the bottom of the material and section size inputs.  

b) Modification Factors

In the Modification Factors group box:

-        The Repetitive member checkbox which had been placed awkwardly in the upper right corner has been moved down and to the left, lining up under other inputs.

-        The Treatment data group surrounding the Incising and Fire retardant inputs has been removed, and these inputs rearranged.

-        More spacing has been placed between the Modification Factors box and neighboring data groups. 

F. Output and Drawings

1. Horizontally Projected Sloped Beam Dimension Lines (Change 158)

a) Dimension Lines

The program shows each clear span, and the full span of the whole beam, joist or panel, in dimension lines above the member. These distances are measured along the slope of the member.

A Preferences setting has been added to also be able to show these as the horizontally projected values, i.e. the clear span is the actual distance between the inner edges of the supports, and the full span is the distance between the outer edges of the ends supports or cantilever end.

b) Design Check Output

In the Design Check output of the member specification underneath the drawing, the program now gives the horizontal projection, i.e., the distance between the inner edges of the supports. Previously it was showing the sloped distance between supports. The text Clear span now says Clear span (horz).

2. Sloped Beam Dimension Output (Bug 3568)

When calculating the length of a sloped beam or joist, the program was considering the total length of material needed to cut a solid member and adding a small triangular portion to each end of the member to square the ends. 

a) Dimension Lines

This distance including the extra portion was being shown on the dimension line for the full beam span even though the extension lines delineated the shorter distance between the ends cut vertically at the outer edge of each support. The correct distance is now shown on the dimension line, which is the sloped distance between the intersection of the bottom of the beam and the outer edges of the supports.

b) Design Check Output

In the Design Check output of the member specification underneath the drawing, for I-joists, the program still reports the full length of material needed, including the triangular portions.  

3. Failure Warning Note for Fire Design Shear Results (Bug 3556)

The red failure warning message In the Design Check output for the design criterion Shear(fire) that appeared whenever fire design was performed for notched members has been removed, as it could have been misconstrued as the program designing for fire but failing.

A message now appears explaining that fire design is not allowed for notched members, in the place where messages pertaining to other special circumstances are shown.

4. Unfactored Reactions for Concentric Axial Loads on Non-wood Support (Bug 3621)

In Column mode when only axial concentric loads were applied to a member resting on a non-wood or no support, the Reactions table did not appear, so that the unfactored axial reactions for each load type which ordinarily appear in this table were not shown.

5. Load Combination for Maximum Bearing Reaction in Analysis Diagram (Bug 3627)

In the Beam Analysis diagrams, for Critical Results, the load combination number for the maximum bearing reaction was from a load combination for the largest reaction on the last support rather than the one that corresponds to the largest reaction from all supports. This has been corrected.

6. Concept Mode Design Note (Change 168)

An obsolete statement about the dead load being no greater than half the live load has been removed from a Design Note in Concept mode.

 

Sizer 2019, Update 1 (Version 12.1) – May 25, 2020  

1. Slenderness Ratio in Built-up Column Axial Compression Design (Bug 3514)

The following problems regarding lateral stability calculations for built-up columns for axial compression design from NDS 15.3.1.2 were introduced with version 12.0 and have been corrected.

a) Column Width used for Slenderness Ratio Limit

The program was using the single ply width in calculating the slenderness ratio le/b  when checking against the allowable limit of 50 from NDS 15.3.2.3, although full member width should be used .

As a result, for a 10-foot column with 3-2x6 plies, the slenderness ratio was calculated as  80, causing the column to fail, when it should have been 26.7 and pass.       

When the member incorrectly failed  for this reason, a screen warning message appears, a red failure warning appears in the design check giving “Axial due to slenderness as the reason, and the axial compression line and combined axial and bending lines indicate the reason for failure. These messages refer to the identical requirement for solid columns from NDS 3.7.1.4.

Note that single-ply width is still checked to determine whether it the strength Fc’ is greater than for single ply than from multi-ply, as per 15.3.2.2 and this cannot be taken advantage of if the slenderness ratio using single-ply width is over 50. The problem was that it was indicating a design failure rather than merely not applying the advantage if it exists.

b) Slenderness Ratio for Lateral Stability Factor CP

In the calculation of the Column Stability factor CP, if the slenderness ratio was greater in the width b direction than the depth d direction, the program used the slenderness ratio calculated for the d direction, and multiplied the result by the Kf factor ordinarily applied to the b direction, instead of using the slenderness factor calculated for the b direction. This typically caused the CP factor to be greater than it should be and overestimated the strength of the column.

In the example from the previous sub-item, the Column Stability Factor CP is shown 0.351 when it should have been 0.261.

If the slenderness ratio in the d direction was greater than that in the b direction, the program behaved as expected.

2. Shutdown When Using Glulam-uniform Southern Pine Materials (Bug 3531)

The letters “SP “have been removed from all the grade combination names for Glulam-Uniform Southern Pine columns and beams, because roughly half of the names were longer than permissible in Sizer. For example, 48 1:10 (N2D10) replaces 48 1:10 (SP N2D10).

Selection of one of these combinations in any program mode would cause arcane warning messages to appear  and eventually the program would crash when running design or performing other input operations.

3. Right Cantilever and Fix-Free Column Deflections Due to Applied Moments (Bug 3545)

In the analysis of user-applied moments to right cantilever beam spans and columns with a fixed base and free top, the program was subtracting rather than adding the “fixed-end” deflection to the deflection due to rotation at supports.

As a result, downward deflections at the cantilever can be significantly lower than they should be, so that the maximum deflection that is compared to the deflection limit in the design of the member is too low. For beams that experience uplift at the cantilever, this created  larger-than-expected deflections.

For columns, this caused the deflection due to the moment to be applied on the opposite side of the column than it should, creating inaccuracies when combined with deflections from other sources.

As an example, for a beam with a 6-meter middle span and a 2-meter cantilevers on each side and 10 kN-m applied moment at each end of the beam, the cantilever deflections were 3.6 mm on the right end and 10.9 mm on the left end, although these should be the same.

The incorrect deflections could be seen in the Analysis diagrams and in the maximum deflection shown in the Design Check report,and have now been corrected.

Deflections due to applied moments on a left-end cantilever, or other column fixity conditions, were correct.

4. Simpson Hanger Database Update

The program includes the April 2020 update of the Simpson hanger database. Previously the July 2019 version was in use.

5. Load Combination Descriptors

Changes described below have been made to load combination descriptors such as D+.75(L+S) that appear in the following places

-        the main list and the table of CD factors in the Analysis Results output

-        the Critical Load Combinations section of the Design Check output

-        Analysis diagram selection controls and drawings.

a) Symbol Spacing and Formatting of Factors (Change 147)

The compressed format of the descriptors has been expanded to make them the same as they appear in the ASCE 7 and IBC design codes, by adding spaces between symbols and adding a leading zero before factors that are less than 1.0. What was formerly D+.75(L+S) now appears as D + 0.75(L + S)

The compressed descriptor still appears if it is necessary to reduce the length of a long, patterned combination in the Analysis output report, however this rarely occurs. 

b) Snow-Only Pattern Combinations (Change 146)

When a patterned snow load is the only load in a load combination, the combination was represented by the single lower-case letter “s” instead of the usual upper-case “S”. It is now S, but the lower-case s is still used in the pattern description for the half-loaded spans, so that what was previously s (pattern: sS) is now S (pattern: sS).

c)  IBC and ASCE 7 References in Load Combination List Headers (Change 148)

The program now shows the clause reference numbers 2.4 for ASCE 7 and 1604.3.2 of IBC in the headers to the lists of load combinations in the Analysis results and the Design Check. It also indicates that the ASCE combinations are “Basic” (as opposed to “Strength”).

6. Display of Data in Additional Data Section of Design Check

The following problems regarding the display of data in the Additional Data section of the Design Check output were corrected.

a) Emin when Slenderness Ratio Fails (Bug 3514)

In cases where the slenderness ratio for the calculation of the combined axial and bending check is not calculated because the slenderness ratio fails, in the Emin’ row of the Factors table , the unfactored buckling modulus Emin was was shown as 0.00 million instead of the value corresponding to the material for the member. This has been corrected.

b) Exponentiation Symbol in Weak-axis Bending Stiffness EIy (Change 149)

For members with an oblique angle, the symbol e06 representing 106 was not shown in the after the weak axis bending stiffness EIy. The major axis bending stiffness EI was shown as expected.

 

 

Sizer 2019 (Version 12.0) – December 16, 2019

WoodWorks released a Version 11.2 at the same time as version Sizer 2019 order that important corrections and other changes were  included in a version that implements the previous design codes and standards.

Most bug fixes and small changes appearing for the first time in Sizer 2019 are listed under the Version 11.2, below. Please consider both lists as the record of changes for Sizer 2019.

A. Design Codes and Standards

1. Update to NDS 2018 (Feature 230)

The program has been updated to conform the 2018 National Design Specification for Wood Construction, from the 2015 NDS.

a) Custom Incising Factor

NDS 4.3.8 now allows for a custom incising factor Ci based on specific incising patterns. To implement this, the Beam view data group called Modification factors has been split into two boxes, one for Service conditions containing Moisture and Temperature inputs, and one for Treatment containing Incising checkbox, and two inputs for custom MoE and Strengths. These inputs default to the values for incisions limited as in 4.3.8 but can then be changed. The default modulus of elasticity incision is 0.95 and the default for Fb, Fv, Fc and Ft is 0.80.      

b) Fire Design Char Rate vs. Char Depth

NDS 2015 Equation 16.2-1 for char rate βeff was based on a nominal one-hour char rate and exposure time and then one would multiply the char rate by the exposure time to get the char depth achar. Now, these two steps have been combined into one equation 16.2-2. Accordingly, the char rate βeff has been removed from the Calculations section of the Design Check results table.

c) SCL Tension Volume Factor

The volume factor CV stored in the database section properties is now applied to tension strength Ft for SCL members, as per NDS 2018 8.3.6.2.

d) Flat Use Factor for Beam and Stringer E and Emin

The flat use factor Cfu for beams and stringers that was previously only in Supplement table 4D are referenced from NDS 4.3.7.2.  The program had not been applying the 0.90 factor for No.1 grade members to the moduli of elasticity E and Emin This has been corrected.

e) Redwood Grades

The redwood grades that are not “open grain” have been removed from Table 4D and have been removed from the database by removing the Redwood species and renaming Redwood (o.g) to Redwood.

f) Volume Factor CV for Fb* used for Lateral Stability  

NBC 2018 includes a provision in 3.3-6 that the volume factor Cv is to be applied to the value of Fb* for lateral stability factor CL calculations if greater than 1.0 This was already implemented in Sizer 7 in 2006 as per an AWC directive.       

g) NDS Link

The link in the Help menu to the .pdf of the on-line NDS on the website has been updated to retrieve NDS 2018.

h) NDS References

The references to the edition of the NDS in the Welcome box, Building Codes box, About Sizer box, and in the Design Check output have been updated to 2018.

2. Update to IBC 2018 (Feature 230)

The program has been updated to conform to the 2018 International Building Code from the 2015 IBC.

a) IBC 1604.3 Note d

As Live roof (Lr) has been added to the load combination given in 1604.3 note d, the 0.5 factor is now applied to make the 0.5 D + Lr, and 0.5 D + 0.75 (L + Lr) combinations. Previously only the 0.5 D + Lr combination was constructed.

Note that for CLT, the dead load factor is now 1.0 rather than 0.5, so that when CLT materials are selected, the checkbox activating this item in load input view reads L + D rather than L + 0.5D and the 1.0 dead factor is applied to the above combinations rather than 0.5.

b) IBC References

The references to the edition of the IBC in the Welcome box, Building Codes box, About Sizer box, and in the Design Check output have been updated to 2018.  

3. Update to ASCE 7-16

The program has been updated to conform to the 2016 ASCE 7 Minimum Design Loads for Buildings and Other Structures from the 2010 ASCE 7. This standard is used for Sizer only for load combinations, which are also published in the IBC, and have not changed for this edition of the ASCE 7.  The reference to the ASCE 7 in the Building Codes box has been updated to ASCE 7-16.

4. Design Standard Editions in Glulam Design Note (Change 203)

In the Design Note indicating technical references for glulam materials, the edition of ANSI 117 has been updated from 2010 to 2015 and the edition of ANSI A190.1 from 2007 to 2012.

B. Beam and Joist Hanger Database and Design (Feature 226)

The program now includes a database of Simpson Strong-tie joist and beam hangers, allows you to select these hangers as the bearing support member, and automatically selects a hanger if you select Unknown.

1. Hanger Database

The hangers are selected from a database program provided by Simpson, which is incorporated into the Sizer installation.

2. Database Editor and Materials Database

The Species Dialog of database editor and/or the materials database files have been modified to account for the different resistance values for Simpson Hangers based on the material species of both the supporting member (header) and the supported one (the main member being designed by Sizer.)

a) Sawn Lumber and Glulam

For sawn lumber and glulam, the Simpson Hanger resistances are based on the specific gravity of the material. Specific gravity between .42 and .49 is considered S.P.F and above .49 it is Doug-Fir.

A disabled input called Species Group has been added, which shows one of D.Fir-L, Spruce-Pine-Fir or Northern depending on the specific gravity entered. Northern represents specific gravity less than 0.42.

No changes were necessary to the materials database for these materials.

b) Structural Composite Lumber

For structure composite lumber (SCL), the input is enabled and called SCL Type, and offers the choices LVL - DF/SP, LVL – SPF, PSL, and LSL. The existing default LVL database file has been modified to be LVL - DF/SP.  

c) I-Joists

For structure composite lumber (SCL), the input is enabled and called Flange Species with choices D.Fir-L and Spruce-Pine-Fir.  The existing default I-Joist database file has been modified to be D.Fir-L.

2. Input

All inputs for this have been added to the Supports for Bearing Design data group.

a) Type

Simpson hanger has been added to the support Type input list. The existing Hanger choice is renamed Other hanger.

Simpson hangers are not available for oblique members but are available for sloped members.

b) Applies to…

The selection of Simpson hanger applies to end supports only, and selection and design will be done only for end supports only. If All supports or any other selection that includes interior supports is selected, then then ordinary Hangers are used for the interior supports.

c) Header

The Material changes to Header when Simpson hangers are selected, shows materials from both beams and joists. Steel members are not included in the list.

d) Species

This shows the species for selected Material, as it currently does.

e) Size

The Grade field is re-tasked to show the section sizes for the selected species, in a b x d format.

f) Bearing at Support End

Bearing at support end is invisible.

g) Ledger

A checkbox indicates that the header is a ledger, which is a member assumed to be affixed to a hard material such as concrete so that nails in the face flange cannot penetrate more than the member thickness. It is active for lumber and SCL materials only.

h) Nailer

A checkbox indicates that the header is a nailer, which is a member assumed to be affixed to the top of a member of another material such as a steel I-beam, so that they lie on the flat rather than upright like other members.

i) Bearing Length

Bearing length is disabled and shows Unknown when the hanger selection is Unknown, and the hanger bearing length from the Simpson database otherwise.

j) Bearing Width

Bearing width is disabled and shows Same as beam or Same as joist.

k) Point Load Length and Width

These inputs are unaffected by the hanger selection.

l) Hanger Options

The For unknown bearing length… data group is renamed Hanger options when Simpson Hangers are selected. All existing inputs are invisible, and the inputs described below are included instead.

m) Hanger Style

An unlabelled input box has the selections All, Face mount, Top flange, used to filter the hanger list returned by the Simpson database program.

n) Model

The model input lists the available hanger models given the selections for main member and header, ordered by the cost index value supplied by Simpson.

It is headed by the choice Unknown. Only Unknown will appear if any data needed to select the hangers are not available, such as main member size or no. of plies. 

For sloped members, the program lists appropriate angled hangers, showing Simpson’s special information code like SLU5, meaning 5-degree upwards slope.

o) Fasteners

The fasteners list box used to distinguish those hanger models that have different capacities for different fasteners used on one or more of the flanges of the hanger. It is only when a hanger is selected that has this situation, to allow you to differentiate the repeated hanger model.

The fasteners are designated as Face, Side, or Top, according to which of which of these flanges have differing fastener specifications. If two or more of the flanges have different fastener selections, then the following precedence is used ­Top, Face, Side.

p) Cost Index and Resistance

The hanger resistance assuming duration factor CD = 1 and the cost index of the selected hanger are shown in text fields labelled Resistance and Cost index, respectively.

3. Design

a) Bearing Design

For each load combination, the program queries the database for the resistance corresponding to the load duration of that load combination and uses that for bearing capacity of both the main member and the supporting member. It is then compared to the factored reaction at that support.  

The Simpson database resistance includes the bearing factor CB, so Sizer does not calculate or apply a CB factor.

b) Uplift Design

For those load combinations that have an uplift reaction on one or more of the Simpson hanger supports, the program compares the uplift resistance to the factored uplift reaction. Note that it is only Simpson hangers that have uplift design; it is not otherwise incorporated in Sizer.

For load combinations including wind, earthquake, or live loads without snow loads, the program selects a resistance according to the load duration. For dead-only combinations (CD = 0.9), snow load combinations (CD = 1.25), or roof live/construction combinations (CD = 1.25), the resistance for live loads (CD = 1.0) is used then multiplied by the load duration factor. Note that except for dead-only loads, this could lead to non-conservative design; however, these load combinations rarely result in uplift loading.

c) Non-S-P-F or Doug-Fir Materials

For materials species with a specific gravity less than 0.42, the lower limit for Spruce-Pine-Fir, the resistance is multiplied by the ratio of the specific gravity to 0.42. This procedure was authorized by Simpson Strong-tie.

d) Design for Unknowns

When Unknown is selected, the program cycles through all possible fasteners in order from lowest to highest cost index, until it finds one that passes both the uplift and the bearing design criteria.

e) Min Required Bearing Length

To determine the minimum required bearing length used in determining the limits of the design span; the member is considered to be supported by a generic hanger or a “non-wood” member; i.e. as if it were supported by a steel plate, and the compressive strength of the main member is used to calculate the min. required length.

f) Effect on Beam Design

After a hanger is selected, the bearing length determined by the flange length B of the hanger and the calculated minimum required bearing are used to determine a new design span, and the beam re-analysed and designed

4. Output

a) Materials Specification

Under the beam material specification, for each support with a distinct Simpson hanger, a string of information is output giving the model number, a special information code giving for example the angle of the hanger used for sloped members, the fasteners for each flange, and, if necessary, whether backer blocks or web stiffeners are required.

b) Reactions and Bearing Table

In the Reactions and Bearing table, the fields for Cb, Cb support, and Fcp sup are irrelevant and disabled. The support resistance shows the factored resistance of the selected hanger. The Length shows the length B of the bottom flange of the hanger.

If any of the supports with a Simpson Hanger experience uplift, then rows are added for Uplift resistance and the KD factor used for the critical uplift load combination.

c) Failure Warning Message

If the program fails for uplift design, a new design criterion is added to the red failure warning message in the Design check output called Uplift restraint.

C. Cross-Laminated Timber (CLT) Design (Feature 214)

The program now implements Cross-Laminated Timber (CLT) design as per NDS 2018 Chapter 10 and APA PRG 320-19. Additional sources for specific design procedures are described below. 

CLT wall, roof and floor panels are implemented in Sizer in Beam/Column modes and in Concept Mode. These panels are composed of alternating layers of softwood lumber laminations, with the laminations in one layer at a right angle to those in the adjacent layers.

1. CLT Layer Orientation and Design Axes

In what follows, the “longitudinal layers” refers to those CLT layers oriented the same way as the outermost layers, and “the transverse layers” to the other layers internal to the panel. For floor panels, roof panels, and wall panels loaded laterally, loading in the “longitudinal direction” means that support is perpendicular to the longitudinal layers.  This is also referred to as loading along the major strength axis. Loading in the “transverse direction” means support is perpendicular to the transverse layers and loading is along the minor strength axis.

Some CLT properties therefore have four values relating to the material used in the longitudinal and transverse layers, and the value of the property when loaded in the longitudinal and transverse directions.

For wall panels loaded axially, layers in the “longitudinal direction” means layers oriented vertically, and the “transverse direction” means those layers oriented horizontally. For lateral loading on wall panels, major axis design occurs when the outermost layers are vertical.    

2. Material Database

A CLT database file, uclt.cws has been created and added to the installation. This database file can be edited with Database Editor.

a) Species

The Species corresponding to those described as composing standard layups given in PRG 320 Annex A

 

S-P-F – Spruce-pine-fir

D.Fir-L – Douglas fir-Larch

Northern – Eastern Softwoods, Northern Species, or Western Woods

S. Pine – Southern Pine

 

Note that all these species correspond to layups with both the transverse and longitudinal layers the same. When making a custom CLT database file with layers of different species, you could create a new species called e.g. S-P-F/Northern.

b) Grades

These are the designations E1, E2, E3, E4, V1, V2, V3, listed as Layups in PRG 320 Annex A, Tables A1 and A2, but are technically CLT grades and appear as such in the CLT grading stamp. They specify the species and grade of lumber used in the alternating transverse and longitudinal CLT layers. Strictly speaking, a layup also specifies the thicknesses of the layers. 

c) Sections

All sections are assumed to be 12” wide, corresponding to the arbitrary design width. The depths include are from the following sources:

i. PRG 320

The sections in PRG 320 Annex A Table A2:

-        4-1/8”, 6-7/8”, and 9-5/8” (105, 175, and 245 mm) depths composed of 1-3/8“ layers throughout.

ii. Manufacturers Sizes

The following sizes produced by major CLT manufacturers are also included to provide a larger array of default choices:  

-         3-7/16”, 5-1/2”, 7-9/16”, and 9-5/8” ( 87, 139, 191, and 243 mm)  composed of  1-3/8“ longitudinal layers and 0.67” transverse layers.

-        12-3/8” (315 mm) composed of 1-3/8“ layers throughout.

Please note that the strength properties for these sizes do not correspond to those from any manufacturer; they are the strength properties for the PRG 320 grades

d) Species Properties

The only species property is weight, used for self-weight of the member, in lb/ft3.

e) Grade Properties

The following properties in are defined in psi. for each CLT grade for the materials used in the longitudinal layers and the transverse layers. They can be entered in the Grade dialog of Database Editor:

-        Bending strength Fb

-        Strength in axial compression Fc

-        Strength in axial tension Ft

-        Rolling shear strength Fs

-        Modulus of Elasticity E

These properties correspond to those in Table A1 of PRG 320. Sizer uses the Shear Analogy Model to convert them to the design capacities and (FbS)eff, (EI)eff , and Vs shown in Table A2.

Compressive strength perpendicular to the grain Fcp is also defined as a grade property for use in bearing design and is the Fcp from the lumber used in the longitudinal layers.

f) Section Properties

Section properties include:

-        actual and nominal panel depth in inches.  For the standard CLT database, these sizes are the same, although the nominal depth is expressed in fractional format and the actual depth in decimal. 

-        number of layers and thickness of transverse and longitudinal layers. Note that neither Database Editor nor Sizer verifies that the thicknesses of the layers sum to the panel thickness; it is your responsibility to ensure the data entered are consistent.

-        An option to have 2 parallel layers consecutively as the outermost layers at each side of the panel for extra strength in longitudinal loading. 

3. User Input – Panel Specification

Unless otherwise indicated, the following changes have been made to the input of materials and panel configuration in the Beam Input form, Column Input form, and Concept Mode Design Groups

a) Member Types

i. Beam and Column Modes

In Beam Mode, the member types Floor panel and Roof panel are added. For Column Mode, Wall panel has been added.

ii. Concept Mode

In Concept Mode, the Group Type box in the Joist Design Groups dialog which previously contained buttons for Roof joists and Floor joists now has four choices – Roof, Floor, Joist, Panel, of which you select two.

The Group Type box has been added to the Wall Design Groups and contains Wall panel and Wall joist.

Initial default groups have been created called Wall-Panel1, Roof_Panel1, and Floor_Panel1, and subsequent additions increment the number at the end.

b) Species and Grade

The species and grade come from the database choices described above.

c) Width

Width input is disabled and set to 1000 mm for metric and 12” for imperial. CLT design assumes a fixed strip of that width.

d) Depths

Depths are from the sections in the database. It is not possible to enter a custom depth; if you wish to have a CLT panel of a different depth than listed, it is necessary to construct a layup in Database editor.

e) Layers

In Beam and Column modes, the Plies input is renamed Layers, is disabled, and shows the number of CLT layers in the layup corresponding to the depth. 

f) Panel Orientation

A new input Panel orientation includes the choices Longitudinal and Transverse. Longitudinal means that the outermost layers are parallel to the member span; Transverse that they are perpendicular. Design using the major strength axis is performed for Longitudinal, and the minor axis for Transverse.

g) Fire-exposed Sides

Only 1 exposed side for fire design is available.

h) Fire Protection

1- or 2-ply 12.7- or 15.9-mm gypsum wallboard fire protection is available.

i) Non-structural Element Vibration Span Increase

A checkbox in Beam Input view allows you to apply the 20% vibration span increase for non-structural elements from CSA O86 A.8.5.3. It is available only for multiple spans.

j) Supporting Member Design

The following pertains to the Supports for bearing design input in Beam and Column Mode,

i. Floor and Roof Panels

CLT roof and floor panels can be supported by hangers, sill plates, beams, walls, and CLT wall panels. The bearing width input is disabled and shows the one-meter or one-foot design width. When supported by a wall panel, the list of panel depths is given as the bearing length choices. 

ii. Wall Panels

CLT wall panels can be supported by sill plates and CLT floor panels. When supported by a sill plate, the bearing length is assumed to be the panel width, i.e. continuous. When supported by a floor panel, the wall panel width or depth an be used as the bearing length. The panel width indicates continuous support.  

k) Lateral Support

The following applies to Beam and Column modes. For Concept mode, lateral support checkbox selections have no effect if not relevant to the member type. 

i. Floor and Roof Panels

Lateral support input is disabled for CLT roof and floor panels, as the panel is self-supporting laterally and there is no CP factor calculation for CLT.  

ii. Columns

For wall panels, lateral support spacing on the Width b face, i.e. the length of the wall panel, is disabled, along with the associated Ke input, as the panel is self-supporting laterally in that direction. The spacing on the d face remains enabled for calculation of the column stability factor CL.

l) Oblique angle

In Beam mode, the input for oblique angle has been disabled, so that only CLT roof panels supported by beams or walls running parallel to the roof ridge can be modelled directly by Sizer, by using the slope angle.

If the support runs from the roof to the ridge, the one-foot design width is rotated relative to the load, and Sizer’s oblique angle analysis for beams does not apply to planar panels.

If you have such a support condition, is necessary to model the roof panel as a horizontal panel and modify the input loads accordingly. In such a situation, snow loads that are assumed to be oriented vertically over the projected area of the panel should be multiplied by the cosine of the slope squared, and dead loads by the cosine of slope angle. Wind pressures that are assumed to act perpendicular to the surface need not be modified.  

m) Repetitive Member

The checkbox to indicate that the member is a repetitive member is disabled, as it does not apply to CLT.

n) Notches

In Beam View, all inputs related to Notches are disabled, as there is no design guidance for CLT notches.

o) Moisture Conditions

The Beam and Column modes, the input for Moisture Conditions is set to Dry and disabled. Refer to Modification Factors, below. In Concept mode, the Dry service checkbox selection has no effect.

p) Treatment

In Beam and Column modes, the Inputs for Incising and Fire-retardant treatment are disabled. Refer to Modification Factors, below.

3. User Input – Loads

a) Width

The Width field, when shown, is disabled and shows one foot or one meter, the arbitrary design width of the member.  

b) Area and Line Loads

Area loads are equivalent to line loads, as the line load is assumed to be distributed over the one-foot or one-meter width of the member.  The input magnitude can be equally interpreted as a plf line load along the 1-unit width, or a psf area load.

c) Point Loads

Point loads are assumed to be distributed over the one-foot or one-meter width of the member. You can show the point load as a plf line load using the existing Enter point load as UDL setting.

d) Beam Support for Area Loads

As for floor joists, the Beam Supports area load setting is disabled.

e) Column Load Face

The Load Face input is disabled and set to Width b, as the assumption is the one-meter  or one-foot design width is loaded, and there is no in-plane wall loading.

f) Default Creep Factor

The default creep factor for long-term deflection is set to 2.0 for CLT design. rather than the usual 1.5, as per NDS 3.5.2.

4. Design

Bending moment and shear design for standard CLT panels listed in PRG-320 is in accordance with PRG-320 Table A2. For custom panel lay-ups and for reduced sections for fire design, the program uses the Shear Analogy Method given in the following sources

-         FPInnovations CLT Handbook, 2013 Edition (referred to as CLT Handbook), Chapter 3, Structural and Chapter 8, Fire

-        CSA O86-14 Engineering design in wood (the Canadian design standard, referred to as O86), Chapter 8 and Appendix A8

This Shear Analogy Method also yields the results for standard sections that are shown in Table PRG 320 Table A2.  

Axial and combined axial and bending design of wall panels, bearing design, and fire design are in accordance with the NDS. Application of axial design procedures from the NDS to fire design is described in the CLT Handbook.    

a) Modification Factors

The modification factors applied to CLT design are given in NDS Table 10.3.1 – The Load Duration Factor CD, Temperature Factor Ct, Bearing Area Factor Cb, and Column Stability Factor CP 

Table 10.3.1 also includes the following factors which have no effect on CLT floor, roof, or wall panel design in Sizer:

i. Moisture Factor CM

NDS 10.3.3 says that information on moisture factors is supplied by manufacturers, and as most manufacturers do not recommend wet service, the program assumes dry moisture conditions and a CM = 1.0. 

ii. Beam Stability Factor CL

CLT floor and roof panels are continuously laterally supported on both edges, as the one-foot design width is supported by the rest of the panel. CLT wall panels are also continuously supported. Lateral support spacing is considered on the Depth d face for wall panels for the CP factor for axial compression, but this is not the direction for lateral support for out-of-plane bending design. The one-foot design width on the b face is continuously supported. 

b) Effective Stiffness

Effective stiffness (EI)eff is used bending moment resistance, calculation of panel deflection and vibration. It is calculated using the Shear Analogy Method, given in O86 8.4.3.2 and in the CLT Handbook 3.3.1, Equation 24.

 

          EIeff  = b  ( ∑ Ei ti3/12   +  Ei ti zi2 ),

 

where

-        the summation i is over all the layers for the major strength axis (longitudinal loading), and over all but the outermost layers for the minor strength axis (transverse loading).

-        ti is the thickness of the layer

-        For layers parallel to loading, Ei is the modulus of elasticity E as listed in PRG 320 Table A1

-        For layers transverse to loading, Ei  = E /30   (PRG 320, Table A1, Note d)

-        zi is the distance from the center of the layer to the neutral axis. For symmetric CLT panels, the neutral axis is the mid-point of the panel depth.

 

i. Fire-reduced sections

For fire-reduced sections, transverse layers that are the final partially charred layer and are thus the outermost layer on the charred side of the panel are not included in the summation.

The calculation of the neutral axis ỹ is given in Equation 8 of Chapter 8 of the CLT Handbook as follows

 

                      ỹ =   yi Ei ti / ∑ Ei ti

 

where yi is the distance from the unexposed side to the centre of the layer. 

As Ei in the transverse layers is effectively zero when compared to the longitudinal Ei , this reduces to Equation 9

 

ỹ =   yi ti / ∑i ti

 

where the summation is over longitudinal layers only.

ii. Double Outermost Layers

Double outermost layers are treated as a single layer in this calculation, on the assumption that the lamination between these layers is at least as strong in bending as the wood itself, and the two layers act as a unit.  

c) Bending Moment Resistance

The factored bending moment resistance for the major axis strength direction is 

 

M’ = 0.85 CD Ct (FbS)eff,f,0

 

and for the minor axis direction is  

 

M’ = CD Ct (FbS)eff,f,90,

 

where the values of (FbS)eff are those listed in table A-2 of the PRG 320. For custom CLT materials, and for fire design, (FbS) eff is calculated using O86 8.4.3.1:

 

                        (FbS) eff = α Fb Seff

 

where

 

                 Seff = 2 (EI)eff / E h

 

and

-        h is the panel depth for major axis loading, and the panel depth minus the thickness of the outermost layers for the minor axis.

-        α is 0.85 for major axis loading and 1.0 for minor axis.   

-          Fb, (EI)eff, and E are evaluated for the longitudinal layers when loading is along the major strength axis, and for the transverse layers when loading is along the minor axis. Fb and E are found in PRG 320 Table A1.

-          (EI)eff is given in the section on Deflection, below.

Note that the CLT Handbook Chapter 3, Section 2.1, Equations 1 and 2 for transverse loading uses the full panel loading depth rather then the reduced depth, and the Fb of the outermost layer rather than the transverse layers. The CSA method was used because that is the approach used to generate (FbS)eff in the current PRG 320.

i. Fire-reduced sections

(a)  Final charred layer

The depth used in the calculation of effective section modulus Seff does not include the final partially charred layer on the exposed side if is transverse to the axis of loading.

(b)  Calculation of Seff 

The calculation of Seff considers the change in the location of the neutral axis as follows, from CLT Handbook, chapter 8, section 4.1.4.1, equation 13:

 

Seff = (EI)eff /  E ( hf – ỹ)

where:

-        hf is the fire-reduced effective panel section depth

-        ỹ is the location of the neutral axis of the fire-reduced section, as described in the section on Effective Stiffness, above,

-        EIeff is also modified for fire design as described in Effective Stiffness

(c)  Adjustment Factor

The fire adjustment factor of 2.85 from Table 1.2.2 is applied.

 

d) Shear Resistance

The rolling shear resistance Vs is checked:

 

Vs’ = CD Ct Vs

 

where the values of Vs are those listed in table A-2 of the PRG. For custom CLT layups, and for fire design, Vs is adapted from O86 8.4.4.2

 

 Vs = 2/3 A Fs

 

A is the gross cross-sectional area for loading on the major axis, and for the minor axis it is the cross-sectional area minus the area of the outermost layers.

Fs is the rolling shear resistance, which is assumed to be the same for longitudinal and transverse laminations. If you have a custom CLT material with differing Fs for transverse vs. longitudinal layers, it is recommended to use the lower Fs as the material rolling shear resistance.

This method conservatively assumes that the maximum shear in the member cross section occurs in a transverse layer, where rolling shear governs, as rolling shear strength Fs is typically much lower than shear strength Fv. For custom CLT materials with higher Fs than Fv, it is recommended to enter the Fv value in the database as Fs.

i. Fire Design

The program applies an adjustment factor of 2.75 to the rolling shear strength Fs, from AWC Technical Report 10, Table 1.4.2, as it is not listed in NDS Table 16.2.2.

The calculation of the gross cross-sectional area does not include final partially charred layer if is transverse to the axis of loading.

ii. Double Outermost Layers

For the unusual case of design in the transverse direction with double outermost layers, both layers at the top and the bottom of the panel are omitted from the calculation of A.

e) Axial Design

Axial design for CLT wall panels uses considers only the layers in the longitudinal direction. Note that these layers may be the “transverse layers” in terms of defining the panel layup, if the outermost layers are horizontal.  Therefore, in what follows,

-        Aeff is the cross-sectional area of the layers oriented longitudinally (axially)

-        Ieff is the moment of inertia of the layers oriented longitudinally

-        Fc and Ft are the compressive strengths of the layers oriented longitudinally.

-        Double outermost layers are neglected for transversely oriented panels, and both are included for longitudinally oriented panels.

i. Tension

Axial design for CLT wall panels uses NDS 3.8.1 with the net section area for calculation of tensile stress ft being the cross-sectional area of the layers in the longitudinal direction multiplied by the one-foot design width.

(a)  Combined Axial and Bending

NDS Eqns. 3.9-1 and 3.9-2 are used for CLT combined axial tension and bending design, with the Fb used in determining Fb* and Fb** being for the laminations in the longitudinal (axial) direction. The 0.85 factor for conservatism that was applied to the value of (FbS)eff in PRG 320 Table A2 is also applied to Fb* and Fb** for major axis design (wall panels with outer vertical longitudinal layers).

Note that for CLT, Fb* = Fb** = Fb, as the Cv and CL factors are not applicable to CLT design in Sizer.

ii. Compression

Axial compression is design is as per NDS 3.6 with net section area for calculation of compressive stress ft being the cross-sectional area of the layers in the longitudinal (axial) direction multiplied by the one-foot design width.

(a)  Slenderness Ratio

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 = √ (I/A), so the slenderness ratio is as given in in  CLT Handbook, Chapter 8, Section 4.1.4.1, Equation 16:

 

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, for CLT it is not used in the calculations for the column or beam stability factors.

(b)  Buckling resistance PcE

The column buckling resistance PcE is required for the alternative formulations from the NDS Commentary for the column stability factor CP and for combined axial and bending design.

PcE = π2 (EI)app-min/  le2

le  is the effective length between lateral supports, which is usually KeL for wall panels, L being the panel height, and (EI) app-min is discussed in the next section.

(i)    Stiffness Used for Buckling Calculations (EI) app-min

(EI) app-min’ is the factored effective stiffness modified for shear deflection. Although the E for pure bending is used to derive Emin for other materials, NDS Commentary C10.3.7 refers to “significant shear deformation that can occur between the parallel and perpendicular CLT laminations”. 

EIapp is determined from EIeff using NDS Equation 10.4-1, then the formula from NDS Appendix Eqn. D-4 and Commentary Eqn. C4.2.4-1, is applied to get (EI) app-min. Finally the adjustment factors from NDS Table 10.3.1 (or Table 16.2.2. for fire design) are applied to get EIapp-min. 

Note that Eqn. D-4 that is ordinarily applied to E to determine Emin includes a 1.03 factor to convert to pure bending, that is, to factor out the decrease in the published E from the true E to account for shear deflection. This factor has been included in (EI)app-min even though it is intended to include shear deflection.

Examples in the CLT Handbook and the AWC Technical Report 10 for fire design include the 1.03 factor, so it is retained in Sizer as well even though it is contrary to the intention of C10.3.7.  Note that the lamination E values used to create EIeff include the 1/1.03 factor for shear deflection, so this just serves to eliminate this redundancy for buckling design.     

(ii)   Ks Factor for Column Buckling

The Ks factor in Table 10.4.1.1 used to determine EIapp for column buckling is derived using the following expression