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 2023, released in December 2022. Significant new features were added with Sizer 2019,Update 2,  released in June 2021. The latest service update for Sizer 2019 is Update 4 released in November 2021. For those users still using version 11, the latest update is Sizer 11.2, released in December 2019.  

 

This file last updated with changes August 31, 2013.

 

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

 

      Sizer 2023

      Sizer 11 – WW 11

      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 2023 (Version 13.0) – December 28, 2022

Use the Table of Contents to navigate to descriptions of changes below it:

 

A. Design Codes and Standards. 1

1. IBC 2021 (Change  212) 1

2. SDPWS 2021 (Change 212) 1

B. Engineering Design. 1

1. Single-ply Width b in Lateral Stability Calculations for Weak-Axis Loading (Bug 3732) 1

2. LRFD Design for Simpson Hangers (Bug 3694) 1

3. Effective Length for CLT Column Stability Factor CP (Bug 3733) 1

4. Fire Retardant Treatment Factor for Fire Design (Bug 3678) 1

5. SDPWS Repetitive Member Factor for Deflection from Wind Loads on Wall Studs (Bug 3741) 1

C. Loads Analysis. 1

1. Line loads, Concentrated Loads, and Applied Moments on CLT Panels  (Bug 3704) 1

2. Imperial Self-weight of CLT Panels Transferred to Supports in Concept Mode (Bug 3721) 1

3. Dead and Total Reactions for Net Uplift on Support with Auto Self-Weight (Bug 3731) 1

4. Fire Load Combination Factors for Live + Snow + Dead (Bug 3684) 1

5. Numerous LRFD Load Combinations from Pattern Loading or Concentrated Loads (Bug 3685) 1

D. Materials and Database. 1

1. APA PRI-405  Commercial I-joists (Change 198b) 1

2. 4”x 14” and 16” Lumber Beams (Change 169) 1

3. Concept Mode Crash due to Long Filename  (Bug 3717) 1

E. Input and Program Operation. 1

1. Saving Deflection Settings as Default for New Files (Bug 3681) 1

2. New Version Notification for Version 12.3 (Bug 3673) 1

3. Pattern Loads Default Operation (Change 202) 1

4. Startup Program Window Location (Change 203) 1

5. I-joist Inputs. 1

6. Wording of Lateral Support Design Settings (Change 194d) 1

F. Output 1

1. Design Summary Print Failure Due to Overly Wide Design Note (Bug 3722) 1

2. Simpson Hanger Selector Version Number (Change 196) 1

3. Additional Data Section of Design Check  for CLT (Bugs 3683 and 3744) 1

4. Output of Deflection for Critical Live vs. Total Load Combination or Location (Bug 3678) 1

5. Output of Stiffness EI (Change 211) 1

6. Output of Column Design Data. 1

7. NDS Reference for Shear at a Distance d (Bug 3744) 1

8. Load Distribution and Units in Loads Table for CLT Self-weight (Change 195) 1

9. Fire Retardant Treatment Factor Note for Fire Design (Bug 3678) 1

G. Graphics. 1

1. Drawing of Built-up Column Plies (Bug 3561) 1

2. Drawing of Rotated Members (Change 152) 1

3. Update of Analysis Diagram Load Combinations for Newly-entered Load Types (Bug 3675) 1

4. Load Factor for ASCE Exception Combination in Analysis Diagram Dropdown (Bug 3693) 1

 

 

A. Design Codes and Standards

1. IBC 2021 (Change  212)

The program now conforms to the International Building Code (IBC) 2021; previously it conformed to IBC 2018.

a) Program References

The updated edition year is indicated in the About Sizer box, the Welcome box, the Building Codes box, and a design note in the Design Check and Design Summary output.

b) Load Combinations

IBC 2021 no longer lists load combinations in 1605.1; it now just refers to ASCE 2.3 (Strength) and 2.4 (LRFD). The references to IBC 1605.1 have been removed from the output of load combinations in the Design Check and Analysis Results output reports. The explanation of the source of load combinations in the Building Codes box has been rephrased accordingly.

2. SDPWS 2021 (Change 212)

There is one provision (3.1.1.1 – Repetitive Member Factor for Wind Loads) implemented from the Special Design Provisions for Wind and Seismic (SDPWS). The reference to the SDPWS in the Building Codes box has been updated to SDWPS 2021 from SDPWS 2015.

A change was made to the application of 3.1.1.1 (see B.5 below), but it did not arise from a change in the SDPWS.

B. Engineering Design

1. Single-ply Width b in Lateral Stability Calculations for Weak-Axis Loading (Bug 3732)

For multi-ply members loaded on the weak axis (columns loaded on the d-face and rotated beams), if the Built-up member width b for lateral stability calculations was set to Single ply, the program divided the depth d dimension by the number of plies for use in lateral stability calculations. However. the depth is unrelated to the number of plies for weak-axis loading, and the full member depth should be used.

This wrong member dimension is used for

-       the expression for slenderness ratio  RB = (le  b / d2 )0.5 from NDS 3.3.3.6. This caused a larger RB than expected, reducing the lateral stability factor CL from NDS 3.3.3.8 and often causing the member to fail because RB was greater than 50 (3.3.3.7).

-       The determination of whether d <= b so that CL = 1.0 (from 3.3.3.1),

-       The value of lu/d used to select the effective length le in Table 3.3.3,

-       The d used in the calculation for those cases with lu/d > 7.

This problem entered the program with version 11 when the single-ply vs full width setting was added, and has been corrected.

2. LRFD Design for Simpson Hangers (Bug 3694)

The program no longer allows you to select Simpson Hangers as a bearing support type when LRFD is selected as the design procedure, and if you change the Design setting to LRFD when a Simpson hanger is use, the program changes it to a generic, non-designed hanger and issues a warning.

Previously, when  LRFD was selected the program designed Simpson hangers using LRFD, or "strength-level",  load combinations, but the ASD capacities from the Simpson hanger database.

As Simpson does not provide LRFD capacities in their literature the hangers are no longer available for LRFD.

3. Effective Length for CLT Column Stability Factor CP (Bug 3733)

When calculating the column stability factor CP for CLT wall panels using NDS C3.7.1-1 to C3.7.1-4 , the program used the height of the panel rather than the effective length le = Ke ld, where ld is the distance between lateral supports. The lateral support input therefore has no effect on the calculation of CP, even if continuous is selected and CP should be 1.0.

As a consequence, the CP and thus the axial resistance for a fully supported wall panel were less than it should be for panels with intermediate supports.  For a  typical 16-foot wall panel supported by a floor at  the midpoint, the CP factor was roughly half what it should be. This has been corrected.

Note that the calculation of the slenderness ratio, which also uses the effective length le, was unaffected. The limit of 50 on the slenderness ratio from NDS 3.7.1.4 us applied correctly.

4. Fire Retardant Treatment Factor for Fire Design (Bug 3678)

The program did not apply the reduction in design strengths for fire retardant treatment required by  NDS 2.3.4  when performing fire design. AWC confirmed that this factor does apply to fire design. 

In the Factors table of the Design Check output, the user-input reduction factor was shown in the Cfrt  column for compressive axial resistance Fc and shear resistance Fv, however this factor was not used in determining the design strengths. For bending resistance Fb, a dash was shown instead of a factor.

The program now shows all these factors in the table and uses them in determining the resistances for fire design.

5. SDPWS Repetitive Member Factor for Deflection from Wind Loads on Wall Studs (Bug 3741)

Sizer now implements SDPWS 3.1.1.1, which applies special repetitive member factors Cr for only the case of wind loads on wall studs, to stiffness EI used for deflection design. Previously it was applied to bending moment design only.  

As for bending design, it is applied to sawn lumber wall studs when the checkbox in Column Input view regarding adequate sheathing is checked, and to design for W-only or D + W load combinations.  Note that the Cr factor is not ordinarily applied to E for deflection in NDS Table 4.3.1, so it is only this case that has a Cr for deflection.

The modified EI value appears in the Calculations section of the Design Check output when the D + W  combination governs for total deflection. 

Note that Cr is not applied to to the E'min value or the stiffness EImin used for buckling calculations.

C. Loads Analysis

1. Line loads, Concentrated Loads, and Applied Moments on CLT Panels  (Bug 3704)

When line loads, concentrated live loads, or applied moments were applied to CLT panels, the same load intensity was applied to both the 1-ft and 1-m design width so that the design response ratio is greater when designing with imperial units than with metric  Changing the unit system  should not influence design in this manner.

a) Line Loads

i. Previous Behaviour

The program assumed the load magnitude in kN/m or lbs/ft as entered in the input is distributed evenly over the 1-meter or 1-foot design width of the panel. When switching unit systems, the load was converted between lbs/ft and kN /m, so the same physical load is applied to a different width of resisting material.

ii. New Approach

Some users use line loads on CLT members to implement trapezoidal and triangular area snow loads on the roof, because trapezoidal and triangular loads are not available for area load input.

To continue to accommodate this use of line loads, and to make design invariant with respect to the unit system selected, we now assume that the load is evenly distributed over the design width.

The units shown for these loads are now kN/m/m or lb/ft/ft, rather than just kN/m and lb/ft.

Note that with this approach, the width of influence of the line load on the panel changes when changing unit systems. If you have a different assumption about the width of panel over which the load acts, adjust the load intensity accordingly.

iii.  Units in Input and Output

The units shown in the Load View input and in the Loads table output for line loads are now kN/m/m or lb/ft/ft.

b) Concentrated Loads

i. Previous Behaviour

You enter a concentrated load P and the length Lc of the square area it covers. Internally, the program converts all area loads to line loads for analysis, and in this case the line load was P / Lc, so the area load was P / (b Lc) where b is the design width, and the intensity of the area load would change as the unit system changed. Equivalently, the intensity of the internal line load would not change, but the resisting width would change from 1 m to 1 ft and back again. 

ii. New Approach

For concentrated loads, we now assume that the area load intensity of the concentrated load is applied to the design width of the member, so the area load is now P / Lc2 and the internal line load is Pb / Lc2. The internal load thus changes along with the resisting design width and design responses do not change. .

This is equivalent to using a panel design width that is the same width as the concentrated load width, so it assumes that the panel outside of that width contributes nothing to the resistance to the load.

If you have different assumptions about the zone of influence of the concentrated load, then adjust the magnitude P accordingly. 

c) Applied Moments

i. Previous Behaviour

Applied moments were assumed to be concentrated at a point, as from a connection to a member, with a width of influence equal to the design width. The magnitudes were converted between kN-m and lb-ft without regard to the resisting width, so that changing unit systems changed the moment applied per unit width and thus the design response.

ii. New Approach

Applied moments are now assumed to be line moments perpendicular to the design width, as from a parapet wall in that direction. The length of the load changes when the unit system changes to reflect the wider design width, so that the moment per width remains the same and design response is unaffected. This is similar to our existing treatment of point loads (see below).

If you wish to model a point moment instead, please change the moment magnitude to reflect your assumptions about the width of influence of the moment.

iii. Units in Input and Output

The units shown in the Load View input and in the Loads table output for applied moments are now kN/m/m or lb/ft/ft.

d) Point Loads

Point loads are entered as lb/ft or kN/m and are assumed to extend the width of the design area, as from a wall perpendicular to the design width.

When converting between unit systems, the length of load changes along with the design width so design results are unaffected by the change in unit system. No change has been made to our treatment of point loads.

2. Imperial Self-weight of CLT Panels Transferred to Supports in Concept Mode (Bug 3721)

When using Imperial units, the  dead reactions due to automatic self-weight from a CLT panel  to a supporting member in Concept Mode were too large by a factor of 3.28, the ratio of a foot to a metre.

The incorrect reactions affected the design of the supporting members and anything supporting them, but not the supported CLT panel. When transferred to beam mode, the panel shows correct reactions, but the beam below did not showed the incorrect line load from those reactions. 

This problem could be circumvented by entering self-weight manually or switching to metric units, but has now been corrected.

3. Dead and Total Reactions for Net Uplift on Support with Auto Self-Weight (Bug 3731)

When a member is subject to dead loads that create net uplift on a support, and self-weight is automatically applied, the unfactored dead load reaction shown in the Reactions and Bearing table is due to the downwards dead load from self-weight only, when it should be the negative upwards load from uplift + self-weight. Furthermore, self-weight from dead load only is shown as the total factored reaction, which is meant to show reactions to net downward force on the support. The total reaction to net uplift forces is correctly shown in the Uplift column.

These problems have been corrected and the program now shows the net uplift reaction due to dead loads in the Unfactored – Dead column and a blank space in the Factored – Total column.

4. Fire Load Combination Factors for Live + Snow + Dead (Bug 3684)

For fire design, when live, snow and dead loads are all on the member, the program now uses the D + 0.75 ( L + S ) ASD combination from ASCE 2.4. Previously it was using D + L + S in accordance with the AWC  Fire Design Standard (FDS), 3.1.3.4.1, which says to use “wD + wL” and defines wL as including snow and live. According to the AWC, the intention of FDS 3.1.3.4.1 is to use the ASD 0.75 factors with the L and S loads.

5. Numerous LRFD Load Combinations from Pattern Loading or Concentrated Loads (Bug 3685)

For the LRFD design procedure, when the program generated load combinations due to patterning or multi-positioned concentrated loads, if the total number of load combinations exceeded the maximum possible without patterning or concentrated loads, design of the member malfunctioned in unpredictable ways.

For one example, when concentrated live loads, wind loads, and snow loads were all present on a beam, the bearing design was reporting "******" for the factored bearing reactions and nonsensically large required bearing lengths.

In another example,  a 5-span member with full uniform live, dead, and snow loads, when either or both of the live and snow loads are patterned,  the program did not include live or snow loads in the analysis of the member for any load combination.

These problems have been corrected.

D. Materials and Database

1. APA PRI-405  Commercial I-joists (Change 198b)

Commercial I-joists from APA PRI-405  have been added as a “Species” to the I-joist  material selection and database file. Previously only the APA PRI-400 I-joists were included. Properties are from the PRI-405 Performance Standard for Commercial I-Joists. Oct 2021.

2. 4”x 14” and 16” Lumber Beams (Change 169)

4 x 14” and 4 x 16” sections were added to the Lumber database file for beams, which previously had 12” maximum depth.  The NDS Supplement Table 4A lists a size factor CF for “14” and wider” sections, and the users have reported that these beams are available and in use.  

3. Concept Mode Crash due to Long Filename  (Bug 3717)

The following database filenames were more than the 15-character limit, so that in Concept mode, the program crashed when a design using any of these materials was run:  

-        uElement5 CLT.cws (Element 5 CLT)

-        uvlcolumnbup.cwc (Versa Lam built-up columns)

-        uversalambup.cwb (Versa Lam built-up beams)

-        unorlamcolbu.cwc (Nordic built-up columns)

The filenames have been shortened and these materials can now be used in Concept mode without problems.

E. Input and Program Operation

1. Saving Deflection Settings as Default for New Files (Bug 3681)

If a new file was opened when another file was already open, the Design Settings Report interior and cantilever deflections separately and  Report dead load deflection were taken from the previously open document rather than from the last time you applied Save as default for new files for that setting. This has been corrected.

2. New Version Notification for Version 12.3 (Bug 3673)

When Sizer version 12.3 was available, the new version notification message that should have appeared upon opening version 12.2 or clicking Update Sizer from the Help menu did not appear. It appears correctly when running versions 12.1 and earlier.

The notification message when running version 12.2 works correctly to notify you that version 13.0 is available.

3. Pattern Loads Default Operation (Change 202)

If you input and place loads on a single-span beam, then add another span to the beam, the pattern loading for snow and live loads is now retroactively changed from unchecked to checked, which is the default if the loads had been entered on a multi-span beam to begin with.

4. Startup Program Window Location (Change 203)

When opening, the program now opens in full screen or window mode according to what it was when last closed, and if in window mode, the window is placed where it was when it was last closed. Previously the program always opened in full screen mode.      

5. I-joist Inputs

The following Beam View inputs were enabled when I-joists were selected, but do not apply to I-joist design.

a) Fire Retardant Treatment (Bug 3689)

The Fire retardant checkbox under Treatment  and its associated numeric input was available, however NDS 2.3.4 says the fire retardant treatment factor is applicable only to sawn lumber and glulam. This input is now disabled when I-joists are selected.

When selected, the input value appeared in the Cfrt column of the Factors table of the Design Check output, but it was not applied to any of the design resistances.  A dash now appears there for I-joists.

b) Lateral Support (Change 194b)

Sizer does not do lateral stability calculations for I-joists, but the Lateral support inputs were available. They now disappear when I-joists are selected, similar to the behaviour for CLT floor and roof panels.

6. Wording of Lateral Support Design Settings (Change 194d)

The Design settings data group previously called Lateral stability factor CL has changed to Lateral stability (NDS 3.3.3.4), and the NDS reference removed from the checkbox within that group, as it applies to both items in the group.

F. Output

1. Design Summary Print Failure Due to Overly Wide Design Note (Bug 3722)

In the Design Summary output report that lists passing sections for unknown design, and in the 'non-enhanced" (ASCII text) Design Check report, a Design Note regarding built-up members did not wrap properly and extended past the right margin of the page.

This caused a warning message to appear when printing, and if you chose to print anyway, a few centimeters of text were cut off at the left of the page, rendering the report unusable.

This did not occur for the enhanced Design Check that is usually output, or for the same note in the Concept Mode output.

2. Simpson Hanger Selector Version Number (Change 196)

The program now outputs the Simpson Hanger Selector database version number in the Design Note that appears in the Design Check report when the hangers are used, and in the Building Codes box that is accessed from the Welcome box. The current version is 2020.4.22.

3. Additional Data Section of Design Check  for CLT (Bugs 3683 and 3744)

The following changes have been made to the Additional Data section of the Design Check output for CLT wall, floor and roof panels.  

a) Removal of EIapp

EIapp has been removed from the Factors table and from the Calculations section because it has no direct design consequences. EIeff is used for deflection with rigorous shear deflection calculations, and EIapp-min is used for buckling calculations.

Since rigorous shear deflection was implemented, the value shown as EIapp was in fact EIeff. EIeff’ was also shown in the Calculations, and continues to be.   

b) Addition of EIapp-min

For wall panels, EIapp-min’ used for buckling calculations is now shown in the Calculations section.

c) Vs’ and M’ vs Fs and Fb

In the Factors table, the allowable rolling shear force Vs' is now shown instead of allowable rolling shear Fs, and allowable moment M'  is shown instead of allowable bending stress Fb. Vs has been removed from the Calculations section and Fb and Fs have been added.

For CLT, Fs, and Fb have only an indirect effect on the member resistance, and the factors shown in the table are applied to M and V, not Fb and Fs.

d) Alignment of Factors Table

The alignment of the Factors table headers with the rows below has been improved.

4. Output of Deflection for Critical Live vs. Total Load Combination or Location (Bug 3678)

In the Analysis vs Design table of the Design Check output, the program very occasionally showed live or total deflection corresponding to the load combination or beam location that was critical for the other deflection criterion of live and total. This occurred for the less critical of the live and total deflection criteria, i.e. the one that had the lower maximum design response ratio, and only occurred when the critical load combination or location for that criterion comes before the critical load combination or location for the more critical of the two deflection criteria.

For example, if load combination 3 was critical for live deflection, and load combination 5 was critical for total deflection, and total deflection had a higher response ratio than live deflection, the live deflection shown was the lower value for load combination 5 rather than the critical value for load combination 3.

Similarly, if the point 3 feet was critical for total deflection, and 5 feet for live deflection, and live deflection had a higher response ratio than the total, then the total deflection shown was at 5 feet rather than 3 feet.

The output also showed the design response ratio corresponding to the incorrect deflection, which is less than the actual design ratio, i.e., non-conservative. However, the problem could not cause a failing member to show a passing design, because it affects the less critical of the two design criteria. For example, it could show a passing live deflection ratio when both live and total fail, however the failure message would correctly include both live and total among the failing criteria.

This problem also had no effect the deflection used in determining whether the member passed or failed when cycling through the possibilities for unknown parameters.

This problem rarely occurred because later load combinations have more load types and are more likely to be critical, and because it is unusual for critical live and total deflections to be at different points on the beam. It has been corrected nonetheless.  

5. Output of Stiffness EI (Change 211)

The following problems with the output of the bending stiffness EI in the Calculations section of the Design Check output were corrected.

a) Weak Axis Symbol Always Shown (Change 211a)

The  symbol EIy for weak-axis is design was shown regardless of whether the loading is strong-axis or weak axis, however the EI value shown was correct. For rotated beams, both EI values shown were given as EIy.

Strong-axis values are now shown as just EI.

b) Exponentiation (Change 211b)

The exponentiation symbol e06 was not appearing after the EIy value.

6. Output of Column Design Data

The following changes have been made to the output of column design data in the Design Check report.

a) Output of Slenderness Ratio for Columns (Change 144)

The slenderness ratios le/b and le/d for column axial compression design from NDS 3.7.1 are now output in the Calculations section of the Design Check report. For built-up columns, ratios for full column width and for single-ply width are shown.

b) NDS Reference in Warnings for Built-up Slenderness Ratio Limit (Change 154)

Both the screen warning message and the line in  the Analysis vs Design table indicating that built-up columns cannot be designed for axial compression because they have a slenderness ratio greater than 50 referred to the NDS clause 3.7.1.4 for solid columns for rather than 15.3.2.3. for built-up columns. This has been corrected.

c) Output of Emin’ Factors for Columns Loaded on Wide d-Face (Change 177)

When columns are loaded on the d-face when it is the wider face or on a square section, the row for the buckling modulus Emin’ was not being output in the Factors table of the Design Check. It appeared for b-face loading, for narrow d-face loading , and for d-face loading on wall studs.  It now appears for narrow d-face loading on columns.

d) Combined Axial and Bending Data (Change 204)

Previously, in the design data for combined axial and bending appeared in the Critical load Combinations section of the Design Check report as follows,

Combined: LC #2  = D + L  fb= 232, Fb’ = 725

          FcE= 564  Pxe/S=fc(6xe/d)= 72

fb is the bending stress due only to lateral loading; Fb’ is the factored bending resistance; the expression Pxe/S=fc(6xe/d) gives the bending stress due to eccentric loads, and FcE is a parameter used in buckling calculations from NDS 3.9.2.

The following changes have been made:

i. Location of Data (Change 204d) 

These data have been moved to the Calculations section of the report where other similar data have been shown.

ii. Format of Eccentric fb Expression Change 204b)

The expression Pxe/S=fc(6xe/d) has been changed to

 fbe = (P x e)/S = fc(6e/d)

 to make it apparent that the expression represents bending stress due to eccentric loading and that fb does not include eccentric bending.

iii. Eccentric fb for Weak Axis Loads (change 204a)

In the expression (P x e)/S = fc(6e/d)for columns loaded on the d-face, the program now output the symbol “b” rather than “d”, as it is the dimension in the direction of the load that is used in the calculation. This is especially beneficial for multi-ply design, as it indicates that the distance used is just the single ply b and not the full member width.

iv. fb for Eccentric-only Loading (Change 204c)

The program now shows fb = 0 when there are no lateral loads. Previously it was not shown.

v. Organization of Data (Change 204d) 

The data have been reorganized to fit on one line as follows:

Combined: Fb’ = 200; fb = 100; fbe = (P x e)/S = fc(6e/d) = 72; FcE = 564

7.  NDS Reference for Shear at a Distance d (Bug 3744)

For beams and joists, a reference to NDS 3.4.3.1(a) has been placed after V design in the Calculations section of the Design Check output. This provision gives the calculation of design shear by neglecting loads within a distance d of the support. This reference already appeared for CLT panels.

8. Load Distribution and Units in Loads Table for CLT Self-weight (Change 195)

In the Loads table of the Analysis, Design Check, and Design Summary output reports, for CLT floor and roof panels, self-weight was shown as a Full UDL with units plf or kN. It is now shown as an area load Area load with units psf or kN/m2.

9. Fire Retardant Treatment Factor Note for Fire Design (Bug 3678)

When fire design is active, the note appearing under the Factors table of the Design Check output was shown twice. This has been corrected.  

G. Graphics 

1. Drawing of Built-up Column Plies (Bug 3561)

In the drawing beside the material input of the depth (d) face of a built-up column, and in the load view when loading on depth face is selected, the program now shows the individual plies. Previously it showed the undivided width of the column as if it was a solid member.

2. Drawing of Rotated Members (Change 152)

When an oblique angle is entered, the Beam drawing in Beam and Loads views now shows both the top face and the side face of the rotated member, delineated by a line. 

For 90-degree rotated members, i.e. planks, the drawing now shows the b-dimension of the member. Previously the d-dimension was shown as if it was not rotated. For multi-ply members, the individual plies are shown.   

3. Update of Analysis Diagram Load Combinations for Newly-entered Load Types (Bug 3675)

After adding loads to a previously designed member and then re-running the design, the Load combinations dropdown menu above the Analysis diagrams did not always show the new load combinations made necessary by the new loads. This has been corrected.

4. Load Factor for ASCE Exception Combination in Analysis Diagram Dropdown (Bug 3693)

For 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, the 0.5 factor was not displayed in the load combinations dropdown box in the  Analysis Diagrams view, instead just “L”  is shown, i.e.  “1.2D + 1.0W + L” . The correct combination,  “1.2D + 1.0W + 0.5L”, is now shown. This combination always appeared in the list of load combinations in the Analysis Results output. 

 

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 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.

 

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

 

λ

 

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

 

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