WoodWorks Shearwalls Canada - Change History

 

This document provides descriptions of all new features, bug fixes, and other changes made to the Canadian version of the WoodWorks Shearwalls program since its inception.

 

The most recent major release of Shearwalls is Shearwalls 2020, released on December 22, 2020. The most recent service update is Update 2, released on April 19, 2021.

This file last updated with changes on April 22, 2021.

           

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

Shearwalls 2020, Update 2

    Shearwalls 8.4  WW 8, SR-4

Shearwalls 2020, Update 1

    Shearwalls 8.3 / 8.31 – WW 8, SR-3

Shearwalls 2020

    Shearwalls 8.2 – WW 8 SR-2

     Shearwalls 10.3 – WW 10, SR-3

    Shearwalls 8.11 – WW 8 SR-1

     Shearwalls 10.2 - WW 10, SR-2

    Shearwalls 8.0 – WW 8

     Shearwalls 10.1.1 - WW 10, SR-1a

    Shearwalls 7.22 – WW 7, SR-3

     Shearwalls 10.1 - WW 10, SR-1

    Shearwalls 7.21 – WW 7, SR-2a

     Shearwalls 10 - WW 10

    Shearwalls 7.2 – WW 7, SR-2

     Shearwalls 9.3.1 / 9.3.2 – WW9, SR-3a

    Shearwalls 7.1 - WW 7 SR-1

     Shearwalls 9.3 – WW9, SR-3

    Shearwalls 7.0 - WW 7

     Shearwalls 9.2 – WW9, SR-2

    Shearwalls 2002a – WW 2002 SR-1

     Shearwalls 9.1 – WW9, SR-1b

    Shearwalls 2002 – WW 2002

     Shearwalls 9.0.1 – WW9, SR-1a

    Shearwalls 99 – WW 99

     Shearwalls 9.0 – WW 9

    Shearwalls 97

 

Shearwalls 2020, Update 2 (Version 11.2) – April 19, 2021

1. License Server Connection Error on Startup (Bug 3642)

If the current user was not the one to install WoodWorks and had not already run WoodWorks 2020 prior to update 1, an error message stating "Unable to run WoodWorks because you are not connected to the Internet or unable to contact license server" was incorrectly being displayed on start-up preventing WoodWorks from running.   This happened to a small but significant number of users.

 

Shearwalls 2020, Update 1 (Version 11.1) – March 3, 2021

2. Crash on Design for Structures with Non-Shearwalls (Bug 3609)

Starting with version 11.0, for any structure having a non-shearwall, the program crashed upon running design. This has been corrected.

3. Crash on Accept Design for Shearwalls Combined with Non-Shearwalls (Bug 3635)

For structures that have interior non-shearwalls and shear walls on the same shearline, the program crashed when the Accept Design button was pressed, even prior to version 11.0. This has now been corrected.

Examples of this configuration are a line with exterior shear walls and interior non-shear walls, and any interior line with shear walls and non-shearwalls.

4. Crash on Generating Low-Rise Wind Loads on Variable Height Blocks (Bug 3625)

When low-rise wind loads were generated on buildings in which attached blocks have a difference of two or more in the number of levels, the program crashed. This has been corrected.

5. Plywood and OSB Wall Sheathing Materials (Change 124)

a) Sheathing Thicknesses

Published metric plywood and OSB wall sheathing thicknesses when converted to Imperial and shown in Wall Input view are now rounded in most cases to the nearest 32nd to conform with current publications and marketing. They had been shown to the closest 16th.

i. OSB

12 mm OSB is now shown as 15/32” rather than ½”. This eliminates the duplicate size ½” corresponding to 12 mm and 12.5 mm sheathing. 15 mm is now 19/32” rather than 9/16 and 18 mm is 23/32” rather than 11/16”. 18.5 mm OSB remains ¾” rather then 23/32” to distinguish it from the 18.0 mm size.

ii. Plywood

18.5 mm plywood has been changed to 23/32” from ¾”. 7.5mm plywood is still shown as 5/16”, although it is closer to 9/32”.

b) Design Thickness

When Imperial units were used, the program designed for shear resistance from both panel bending and nail strength from O86 11.6.2.2 with the nominal Imperial thickness rather than the actual metric thickness. When combined with the coarse rounding, this led to errors as much as 6% in the thickness used in these calculations. The program now uses the published metric value for design calculations even when working with Imperial units.

c) OSB Material Name

In the input list of sheathing Materials, the name OSB const has been changed to OSB.

6. Repeated Input of Non-uniform Closed Openings Category (Bug 3634)

In the Openings drop list input of the Load Generation Site Information, the second of three choices, Non-uniform, resistant, closed was repeated in place of the third choice, which should be Large, often open.  When the third choice was selected, the program generated loads for an open structure, the problem was only in the wording, which has been corrected. 

 

Previous Versions

An asterisk (*) indicates that the change was added to this record after the release of the version in which the change occurred

 

Shearwalls 2020 (Version 11.0) – December 22, 2020

The links below lead to descriptions of the features added to WoodWorks Shearwalls 2020, and other changes made to the program:

A: Update to CSA O86-19 – General 1

1. CSA O86-19. 1

2. Choice of Design Codes and Standards. 1

3. Update of Clause References. 1

4. Removal of Load Combinations from NBC. 1

5. On-line Help. 1

B: CSA O86-19 Provisions. 1

1. OSB W24 Panels (Table 9.3) 1

2. Embedment Strength for Sheathing Connection Resistance (11.6.2.2) 1

3. Modification Factors Rd and Ro and Building Categorization (11.8.1) 1

4. Nail Diameter Maxima (11.6.1.1 and 11.5.5.2) 1

5. Minimum Side Member Thickness (12.9.2.2) 1

C: Other Engineering Design. 1

1. Non-ductile Critical Design Modes (O86 11.8.1) 1

2. Intermediate Data for Bx used for Torsional Irregularity (Feature 217) 1

3. Hold-down Forces Used to Determine Displacements for Torsional Irregularities (Bug 3351) 1

4. 20% Drag Strut Increase for Low Seismic Zones (Bug 3591) 1

5. 125 mm Nail Edge Spacing (Change 99) 1

6. Minimum Nail Penetration Depth (O86 12.9.2.2) 1

7. Slow Torsional Seismic Design for Structures with Numerous Hold-downs (Bug 3602)* 1

8. Shear Results Legend. 1

9. Units in Detailed Shear Wall Design Output (Change 119) 1

D: Load Generation and Force Distribution. 1

1. Transfer of Torsional Moment Due to Variable Accidental Eccentricity (Bug 3543) 1

2. Drag Strut Display and Output (Feature 177) 1

3. Crash on Generate Loads for Multiply Indented Structures (Bug 3495) 1

4. Multi-block Low-rise Hip End Warning Message (Change 107) 1

5. Design Spectral Response Accelerations in Seismic Load Generation Details (Change 104) 1

6. Default Self-weight Units (Change 97) 1

E: Program Operation. 1

1. CAD Drawing Import Procedure (Change 89) 1

2. Options Settings and Show Menu for Elevation View (Change 57) 1

3. Menu Item for Auto-saved Files (Change 39a) 1

4. Default Size for New Openings (Change 51) 1

5. Repeating Screen Message upon Change of Gypsum Fastener Length (Bug 3529) 1

6. Crash upon Missing Wall Stud Database File (Bug 3550) 1

7. View Style in Design Results Window (Change 25) 1

 

A:  Update to CSA O86-19 – General

1. CSA O86-19

The program now implements the CSA O86-19 Engineering design in wood design standard, including Update 1, March 2020.

Although O86-19 is referenced by NBC 2020, the program continues to implement the NDS 2015 design code for the time being. 

2. Choice of Design Codes and Standards

In the Design Code drop list in the of the Design settings, the choice CSA O86-19 / NBC 2015 has been added to the existing choices.  

This selection is reflected in the Design Settings output, the About Shearwalls box accessed from the Help menu, the Welcome box and the Building Codes box accessed from Welcome box.

3. Update of Clause References

All references to O86 clauses in the program input, output, and messages were changed to refer to the clause numbers in O86-19 if CSA O86-19 is selected. Virtually all references to shear wall design provisions under 11.1-11.6 changed; those in 11.7 relating to deflection and 11.8 relating to seismic design did not. References to the structural panel tables were changed from 9.3A, 9.3B and 9.3C to 9.1, 9.2 and 9.3. and nail design clauses under 12.9.3 were changed to 12.9.4.   

4. Removal of Load Combinations from NBC

The definition of load combinations used in Shearwalls that was in O86 5.2.4.1 has been removed entirely from the design standard, which now refers to the identical load combinations listed in the NBC.  

The only reference to these load combinations, in the Hold-down Design table legend to O86 Table 5.2.4.1, has been changed to NBC Table 4.1.3.2.A.  

5. On-line Help

The On-line Help has not yet been updated where necessary to reflect changes in the O86-19 other than design code clause reference numbers.

B:  CSA O86-19 Provisions

1. OSB W24 Panels (Table 9.3)

The program now includes W24 OSB sheathing panels from O86-19 Table 9.3 (previously O86-14 Table 9.3C), which has values of for shear-through-thickness rigidity Bv for thicknesses 9.5 mm and 11 mm.

a) Input
In the Wall Input view, W24 has now been added to the Panel Mark list. When a list of thicknesses the list of thicknesses 9.5, 11.0, 12.0, and 12.5 should appear. The final two are alternative thicknesses from Table A.9 and use design values for 11.0 mm panels. 

b) Component and Cladding (C&C) Design

Because bending strength mp and planar shear strength in bending vpsb are not published in O86-19, the out-of-plane sheathing capacity for C&C design cannot be calculated.

i. Sheathing Materials by Wall Group Table

A note number “7” appears for W24 wall groups in the Notes column of the Sheathing Materials table, referring to a note saying design for C&C wind loads is not possible.

ii. C & C Results Table
In the C&C Results table, two asterisks instead of a design capacity appears for sheathing bending capacity for walls with W24 sheathing, referring to a note for materials with no sheathing capacity.   

2. Embedment Strength for Sheathing Connection Resistance (11.6.2.2)

In O86-19 11.6.2.2 a) for sheathing-to-framing connection resistance, in the calculation of Nu from 12.9.3.2, the side member embedment strength f1 is now permitted to permitted to be calculated as

f1 = 51 (1 - 0.1dF).

In 12.9.3.2 the formula is

f1 = 104 G (1 - 0.1dF),

where specific gravity G = 0.49 for DFP and 0.42 for CSP and OSB.

Effectively this says that it is permissible to use DFP strength for all plywood and OSB sheathing panels.  

a) Setting

A new Design Setting has been added, 

Use DF specific gravity G for nail embedment strength f1 in O86 12.9.3 (as per 11.6.2.2).

When selected, the program applies the DFP G = 0.49 to the calculation of f1 for Nu

b) Detailed Shear Wall Design Output

In the Detailed Shear Wall Design output,

i. Symbols Section 
The following symbol definitions have been added

f1 - Wood embedment strength                                   

G - Specific gravity of framing material                                        

ii. Equations Section
The equation

f1 = 104 G (1 - 0.1dF),

has been added to the Equations section.

iii. Parameter List

In the list of parameter values shown beneath the symbols, the value of G has been added, followed by (DF plywood) if DFP had been used in place of CSP or OSB.

iv. Calculations
The choice of calculation method shows up in the nu value in the Detailed Shear Wall Design results.

3. Modification Factors Rd and Ro and Building Categorization (11.8.1)

In 11.8.1, Seismic Design Considerations, General, 

a) Nail Failure Mode c)
Nail mode c) has been added to the list of modes from O86 clause
12.9.4.2 which must be critical for shear wall failure ensure ductility. As mode c) is a double-shear mode, this has no effect on the current Shearwalls program. Internally, the change has been made to accommodate a possible future implementation of mid-panel shear walls.

b) Critical Panel Buckling

The proviso for the use of the ductility-related and overstrength modification factors Rd and Ro values from Table 11.5 that failure is governed by sheathing-to-framing connection has been removed from the O86-19. We were informed that the removal was in error; however Shearwalls did not implement this proviso. Refer to C: 1 below for the implementation of this proviso for this version. 

c) Seismic Zone vs. IEFaSa(0.2)

The criterion from the NBC used to determine whether clauses 11.8.2 -11.8.6 are to be implemented has changed. In O86-14, these clauses they are applied if the value of IEFaSa(0.2) is equal to or greater than 0.35. In O86-19, they are applied if the Seismic Category is SC3 or SC4 rather than SC1 or SC2, these categories being determined from IES(0.2) and IES(1.0) in NBC 2020 4.1.8.5.

As the program has yet to implement NBC 2020, it still uses IEFaSa(0.2) >= 0.35 as the criterion.

i. Clauses Affected

For the higher IEFaSa values (O86-14) or SC’s (O86-19), all of 11.8.2-11.8.6 is applied as stated. These pertain to 20% hold-down force increase (11.8.2), overcapacity coefficient/ratio (11.8.3), diaphragm design force (11.8.4), diaphragms with non-wood Shearwalls (11.8.5), and 20% transfer element force increase (11.8.6).

For the lower values or categories, 11.8.7 is used, which specifies that only 11.8.6 fully applies, and that 11.8.4 and 11.8.5 apply but with overcapacity coefficient Ci = 1.0.

4. Nail Diameter Maxima (11.6.1.1 and 11.5.5.2)

The maximum nail diameter for shear wall sheathing from O86-19 11.6.1.1 has been increased from to 3.76 mm from 3.66 mm in O86-14 11.3.1.1, and the limit for walls without hold-downs (Jhd <1) from 3.25 from O86-14 11.4.5.5 to 3.33 in O86-19 11.5.5.2.

This change acknowledges the current widespread use of nails of the ASTM F1667 nail design standard rather than the obsolete B111. WoodWorks earlier received authorization to use the ASTM diameters as limits, so no there was no change to design or program operation, other than to remove a note to that effect that appears under the Sheathing Materials table when these nails are used. 

5. Minimum Side Member Thickness (12.9.2.2)

The minimum plywood or OSB side member thickness for a nailed connection from O86 12.9.2.2 has changed from 3.0 nail diameters to 2.5.

This minimum was not applied to the sheathing-to-framing nail connection in Shearwalls. Refer to C: 7 below for the new implementation.

C:  Other Engineering Design

1. Non-ductile Critical Design Modes (O86 11.8.1)

WoodWorks has clarified with the design standard authorities the meaning of the following provisos in O86 11.8.1. In both O86-19 and O86-14,  

 

The sheathing-to-framing connections shall be designed to yield in mode c), d), e), or g) shown in Clause 12.9.3.2 for nails to ensure ductility in the shearwall and diaphragm.

 

In O86-14,

 

The corresponding ductility-related seismic force modification factor, Rd, and system overstrength related force modification factor, Ro, for shearwalls are given in Table 11.8.1, provided failure is governed by sheathing-to-framing connection.

 

We have been informed that this latter statement was removed from the O86-19 in error, and we regard it as still in force.

We have also been informed that both these statements mean that when Rd and/or Ro are other than 1.0, shear walls that have brittle non-ductile critical design modes are considered to fail. These critical modes are either the nail resistance mode from O86 12.9.3.2 or when panel bending strength from 11.6.2.2.(b) governs over sheathing connection strength from 11.6.2.2.(a).

We have implemented these provisos as follows:

a)  Design Search
In the design search in which parameters defining the wall have been left unknown, the program now passes over those walls for which a non-ductile mode governs. 

b) Detailed Design Output
If a wall has a non-ductile governing mode when all parameters were selected or when the end of the design search was reached, a note appears at the bottom of the section in the Detailed Design results for that wall, saying the wall fails, giving the reason. Priority is given to panel buckling failures if both criteria are non-ductile.

c) Design Results

In the Shear Results table, for walls with governing non-ductile modes governs, a symbol appears next to the design ratio, and a warning is placed below the table saying that the wall failed either because of a critical non-ductile nail mode or because panel buckling governed. The note is followed by a list of failing walls.

d) Design Summary

If any walls have a governing non-ductile mode, a line is output in the Design Summary giving the list of such walls.  

2. Intermediate Data for Bx used for Torsional Irregularity (Feature 217)

At the end of the Torsional Analysis Details file, there is now a table showing the intermediate data used to determine Bx = δmax / δavg , from NBC 4.1.8.11 where δ is the structural displacement on extreme perimeter shear walls on each level induced by forces acting at +- 0.1Dnx from the center of mass on that level. Dnx is the building width on that level. Bx is used to determine torsional irregularity as per 4.1.8.6.

These data are shown for each level of the structure, each of the 4 force directions, and for the cases of positive accidental eccentricity and negative accidental eccentricity added to the torsional moment.

The table shows the shear line forces used to determine perimeter story drift (with Bx = 1.0 and 10% accidental eccentricity), the story drift on the extreme left and right shear lines, the average of the story drifts, and the ratio of maximum drift to average.

The table has notes explaining the meaning of the data and their consequences in the NBC provisions.

3. Hold-down Forces Used to Determine Displacements for Torsional Irregularities (Bug 3351)

In detecting Torsional Irregularities using NBC 4.1.8.11.(10) the program was using hold-down forces derived from the worst case of positive or negative accidental eccentricities to calculate the displacements used for both the positive and negative eccentricities. The effect of this was to increase the lesser of the deflections and reduce the difference in displacements that creates torsional irregularity.

This has been corrected and hold down forces are calculated for the positive and negative eccentricities independently for the purpose of calculating displacements and

4. 20% Drag Strut Increase for Low Seismic Zones (Bug 3591)

The 20% increase in seismic drag strut forces mandated by O86 11.8.6 was applied only for high seismic zones, defined in O86 11.8.1 when IaSaFa(0.2) from the NBC is greater than 0.35, however, it should have also been applied for low seismic zones as per 11.8.7.3;  i.e. the factor should have always been applied.

Furthermore, the Drag Strut Forces table legend referred to O86 11.8.2, which gave the increase for hold-downs, anchorages, etc. but should have shown 11.8.6, which is for drag struts and other lateral force transfer elements.

The Elevation view legend now shows the line Drag strut = 1.2 under Factors for low seismic zones. It correctly referred to the 11.8.6 clause number. 

The user’s file was a single block, single level structure, for which IaSaFa(0.2) = 0.33 is shown in the Irregularities table and the drag strut force could be derived directly from the shear line force, indicating that no increase had been applied. No reference to the increase appeared in Elevation view, but the reference to 11.8.2 appeared in the Drag strut table. 

When the importance factor was changed such that IaSaFa(0.2) = 0.382, then the drag strut force is 20% greater than that derived from the shear line force alone.  References appeared in both Elevation view and the Drag Strut table.

This has been corrected.

5. 125 mm Nail Edge Spacing (Change 99)

5” or 125 mm was added to the edge nail spacing choices in Wall Input view. This spacing is sometimes used in publications and occasionally in practice.

6. Minimum Nail Penetration Depth (O86 12.9.2.2)

The program now implements the minimum nail penetration depth in O86 12.9.2.2 of 5 times fastener diameter d for plywood and OSB.

The program calculates penetration by subtracting the sheathing thickness plus the gypsum underlay thickness from the nail length. If the result is less than 5 nail diameters, the shear wall design is considered to fail.

If the program is searching through unknown parameters for a design, such a wall is passed over.

If the wall has been completely specified, a failure is reported and an existing message about zero capacity walls is shown at the bottom of the Shear Results table.

It is not possible to create this condition without the use of gypsum underlay. Even with gypsum underlay it cannot occur for standard nails, and a combination of a thick, short power-driven nail is needed, for example a 2” x 3.33 mm nail with 18.5 mm sheathing plus 5/8” gypsum underlay. In that case there is 16.25” penetration but 16.65” is required.

7. Minimum Sheathing Thickness for Nail Sizes (O86 12.9.2.2)

The program now implements the minimum side member thickness for nail strength in O86 12.9.2.2 of 2.5 times fastener diameter d for plywood and OSB.

After changing the panel thickness in Wall Input View, only those nails that satisfy the 2.5d minimum thickness are included in the nail selection list, so that large diameter nails are excluded when using thin plywood. This only applies to 5/16” (7.5mm) plywood, because 3/8” (9.5 mm) plywood is more than 2.5 times as thick as the largest allowable nail diameter from O86 11.6.1.1 (3.76 mm).

8. Slow Torsional Seismic Design for Structures with Numerous Hold-downs (Bug 3602)*

For buildings with numerous hold-down locations, an internal error slowed rigid diaphragm seismic design calculations to the point that the program hanged for a long time after the design button was pushed, and eventually showed Not responding in the title bar. The slow-down was directly proportional to the number of hold-downs, so it was significant for a structure with multiple floors, numerous shearlines, and many wall segments.  

An example of a structure experiencing this problem had four levels with 11 shearlines on the first, second and third levels and nine on the fourth, with as many as six segments on a shearline on each level.   

9. Shear Results Legend

The following changes have been made to the Shear Results table legend: 

-       It is explained that Vhd is Vrs without Jhd, as Vhd is no longer defined in the O86.

-       For the sheathing connection resistance equation:

-       Equation and reference for vd based on fastener strength Nu has been added.

-       The number of shear planes, ns, was removed, as it is always 1.0.

-       Definitions and references have been added for shear wall factor JD, unblocked factor Jus and fastener spacing factor Js

-       For the panel buckling resistance equation:

-       Definitions and references have been added for the load-duration factor KD, service-condition factor KS, and treatment factor KT

-       It is indicated that KD = 1.15 and KT = 1.0

10. Units in Detailed Shear Wall Design Output (Change 119)

In the Detailed Shear Wall Design report, the words Units shown in has been added above the column headers Equation and Table. This is to clarify that one unit shown is for how it appears in the tabulated results, and the other unit is the assumption used in the list of equations.

D:  Load Generation and Force Distribution

1. Transfer of Torsional Moment Due to Variable Accidental Eccentricity (Bug 3543)

The method that was used to transfer the torsional moment for rigid diaphragm analysis downwards between levels by applying the upper-level force at the center of mass of that force to the level below, assumes that the accidental eccentricities (ae) are the same on each level, however ae's can be different due to a different building width on adjacent levels. This could lead to an inaccuracy in the torsional analysis used to distribute the seismic forces to shear lines on the lower level.

This has been corrected by applying an effective accidental eccentricity on the level below equal to (aeu*Fu + ael*Fl) / (Fu + Fl), where aeu and ael are the design code mandated ae's on the upper and lower level, and Fu and Fl are the total forces from loads applied on each level. Refer to the Online Help topics on the vertical distribution of rigid diaphragm shear force for a derivation of this adjustment.

In the Torsional Analysis Details output, when this occurs, a line is added to give the effective accidental eccentricity and the adjustment equation. The line showing the total force F used for torsional analysis on the level now shows the value of Fl, the force from loads only on that level. This appears regardless of whether differing ae's exist, as it is useful information at any time.

This issue affects seismic analysis as this is the only design case with accidental eccentricity.

To gauge the impact of the change:

Case 1 - A penthouse on the upper level, assuming that the mass per unit foot is the same as on the lower level. The maximum difference occurs when the penthouse is 41% of the lower-level width, where the effective ae is 60% of the regular ae.

Case 2 - A 6-story tower where five upper stories are narrow, supported by a podium base that is 3 times the width of the tower. The effective ae is roughly half the regular ae.

Case 3- A building shaped like an inverted pyramid. Such a building would be very non-conservative in that the additional width in two dimensions would not be accounted for on the level below. Such buildings are rare but exist.

2. Drag Strut Display and Output (Feature 177)

The following changes have been made to the display of drag strut forces in Elevation View.

a) Location of Symbol and Force

The symbol with a circle and arrow showing the drag strut force has been moved up to be just below the top of the wall. Previously the forces were shown at the top of openings. The drag strut forces are typically in the top plate of the wall, not the opening headers, and this change avoids conflict with the new force-transfer strap forces.

b) Direction of Arrow

The direction of the force arrow now indicates whether the drag strut is in tension or compression at that point. Previously the arrows always pointed away from the opening or wall end.

An arrow in the direction of the shearline force is in tension, one contrary to the shearline force is in compression. An arrow in the same direction as the shearline force pointing into an opening segment is dragging the force over the opening into the full height segment. An arrow in the opposite direction pointing into an opening segment shows the full height segment resisting force being pushed into it from over the opening.

The following change has been made to the output of drag strut forces in the Collector Forces table of the Design Results (formerly Drag Strut Forces)

c) Negative Compression forces.

The magnitude of the drag strut a force in compression is shown with a negative sign. The legend explains that positive numbers are in tension, negative ones in compression.

3. Crash on Generate Loads for Multiply Indented Structures (Bug 3495)

For a specific single block multi-level long structure with numerous small indentations, the program crashed upon generating seismic loads. This has been corrected.

4. Multi-block Low-rise Hip End Warning Message (Change 107)

In the screen message that appears when low-rise wind loads are generated with multiple blocks, the program would warn of both hip ends being treated as side panels and of unequal hip end slopes even if only one of these was true. This has been corrected.  

5. Design Spectral Response Accelerations in Seismic Load Generation Details (Change 104)

Based on the Design Setting selection for NBC 2010 and NBC 2015, the values of design spectral response accelerations that were used in the calculation of lateral seismic design force at the base from NBC 4.1.8.11 are now output in the Seismic Load Generation Details. If NBC 2010 is selected S(0.2), S(0.5), and S(5.0) are output and if NBC 2015 is selected S(0.2) and S(2.0) are output.

6. Default Self-weight Units (Change 97)

In the Default Settings, the units for self-weight have been changed from kN/m2 to kPa. These units are equivalent, but kPa is used more often in publications. 

E:  Program Operation

1. CAD Drawing Import Procedure (Change 89)

The CAD Import Wizard has been improved to make it easier and more intuitive to add drawings for multiple levels. Previously, it was unclear to some users that you had to press Start positioning to scale the CAD drawing, and the sequence between scaling and adding new levels could be confusing. The Wizard now guides you through a sequence of steps for each level.

2. Options Settings and Show Menu for Elevation View (Change 57)

The following changes have been made to the Display items in the Options Settings, and/or the corresponding items in the Show menu, which control program elements to display or output.

a) Center of Loads and Center of Rigidity

Checkboxes for Center of loads and Center of rigidity have been added under Elevation view in the Options Settings. Previously, they had only been in the Show menu. 

b) Aspect Ratio

Aspect ratio has been moved to appear below Segment numbers.

c) Nailing Information and Legend

The Nailing information used to mistakenly hide and show the legend. It has now been renamed Legend. Nailing information now is shown and hidden via the Sheathing information item.

d) Shear Force and Capacity
An item has been added to show or hide the design shear force and combined capacity information, which previously were always shown. This allows the entire material specification \to be removed if all Show menu items are turned off.

3.  Menu Item for Auto-saved Files (Change 39a)

A new menu item Open Autosaved File menu has been added under File menu to provide direct access to auto-saved backup files BackupPre.wsw and BackupPost.wsw. Refer to the On-line Help for the use of these files. Explanatory status bar messages are displayed if you hover over the menu items.

4. Default Size for New Openings (Change 51)

Now, the default size for new openings is 3 feet with an offset of 2.5 feet from bottom of the wall, approximating the size for a window. Previously the default size for a new opening was 6.75 ft approximating the size for a door.

5. Repeating Screen Message upon Change of Gypsum Fastener Length (Bug 3529)

In the Wall Input form, when fasteners less than 1-3/4” was selected for the GWB Type X material, and then you make any other action, a message pertaining to nail sizes intended for wood structural panels appeared. It kept re-appearing, making it impossible to proceed to the design stage unless you selected a larger fastener.  This has been corrected.

6. Crash upon Missing Wall Stud Database File (Bug 3550)

If a wall stud database file used in a Shearwalls project was no longer in your installation or no longer referenced by the database.ini file, the program would show a blank Framing Material in wall input view, and eventually crash upon design if an available material was not selected in its place. The program now outputs a warning and selects an available material if it detects this condition.

7. View Style in Design Results Window (Change 25)

After running design, thee Design Results are now shown in the last selected view style, Wide View or Preview.  Previously it returned to Preview each time. The program still defaults to Preview on the first design run.


Shearwalls 10.3 – Design Office 10, Service Release 3 – June 11, 2020

1. Vertical Distribution of Rigid Diaphragm Forces (Bug 2733)

a) Compounding of Accidental Eccentricity

Starting with version 10.2, the vertical distribution of rigid-diaphragm shear force amplified the effect of accidental eccentricities on lower levels, such that the total force applied to the shearlines was increasingly larger than the applied shear force F as you moved down the structure. The total shear line force should equal the applied shear force F on that level and all levels above, plus the effect of taking the worst-case of positive and negative accidental eccentricities on each level. This effect is usually small, creating shearline forces typically 10% greater than the applied shear force F, but the amplification of eccentricities created shear forces much larger than F, and an overly conservative design.

This amplification occurred because the shearline forces created using the effect of accidental eccentricity were applied to the level below and used to determine torsions on that level, so that effectively the center of mass from the upper level was shifted by the accidental eccentricity n-1 times at the base of an n-level structure, when it should only be shifted once.

This has been corrected.

b) Vertical Transfer of Rigid Diaphragm Wind Forces for Cantilevered Diaphragms (Bug 3526)

For wind loads, the program applied the shear line forces from flexible diaphragm analysis on the level above to rigid diaphragm torsional analysis on the level below. This was intended as a convenient way to apply the total loading on the level above at its center of loading to the level, but can be inaccurate in the case of cantilevered diaphragms such as occur at roof overhangs and where perimeter walls are non-shear walls.

The program now applies the total vertically accumulated load from the levels above at the centroid of these loads to the level below, for wind loads as well as seismic loads.

2. User-Defined Shearline Forces for Rigid Diaphragms (Bug 3528)

User-defined forces entered in load input view were being added to shearline forces already derived from rigid diaphragm torsional analysis of applied loads, however such forces used to model the effect of forces from adjoining structures should be included in torsional analysis. As a message that appears when load input view is invoked, giving this as a reason to add these forces, they are now treated as if they were loads on the level on which they are entered and applied to the torsional analysis.

An exception is made when there are no applied or generated loads on the level, only user-applied shear line forces. In this case we can assume that you do not want to perform rigid load distribution and wish to analyze individual shear lines with forces calculated manually.

Furthermore, for wind loads, the force was transferred to the level below only if it was defined for flexible diaphragm analysis as well as rigid. For seismic loads, it was not transferred below at all. This inconsistency has been corrected by this change, and if both loads and shearline forces are applied on a level, the effect of the forces is transferred to the level below as if they were loads. If only user-applied shear line forces are added, there is no vertical transfer. Note that flexible diaphragm user-applied forces are still transferred below in all circumstances.

3. Fundamental Period Ta for Single-Storey Buildings

When calculating the fundamental period Ta using the formula in NBC 4.1.8.11 (4) (a) for single-storey structures, Ta = 0.05 hn3/4 + .004L, the value of L, the shortest distance between shear resisting elements, was mistakenly divided by about 16.4, rendering this contribution negligible, so that the period was effectively the same as that used for multi-storey structures from 4.1.8.11 (3) (c). hn is the building height.

As the same spectral acceleration value S(Ta) is used in the generate loads for all values of Ta less than 0.2, from 4.1.8.4.(9),  this will not have an effect except for very long structures. The value of Ta for single-story structures is too low to impact other design code provisions based on Ta.

For example, for a one-storey, flat-roofed 24’ x 40’ building, the program calculated periods of 0.0994 s in the east west direction and 0.0987 s in the north-south direction, but these should be 0.127 and 0.146, respectively. These values appear as the default Ta in the Site information dialog and, rounded to 0.099, in the Seismic Load Generation details.

This problem has been corrected.

4. Storey Weight with Manually Added Building Area Masses (Bug 3537)

When manual area building masses were added to lines or walls in both the E-W and N-S directions, the story weight Wx used to generate seismic loads as per NBC 4.1.8.11 (7) was inaccurate in an unpredictable way depending on load length and the tributary width, and could be several times higher or lower than the weight of the input masses. The incorrect weights appeared in the base shear distribution table of the Seismic Load Generation Details and the Seismic Information table of the Design Results. This has been corrected.

This did not occur when manual masses were entered in just one direction.

In a typical example of a single block of 40 x 40 feet with a gable roof with 25 psf roof self- weight and 3 manually applied 30 psf area building masses with a tributary width of 5 feet on lines A, B and 1, Wx was 130,350 lbs when it should have been 62,100 lbs.

Masses are used to generate loads in both directions, so it was possible to model all building masses by adding them to shear lines in just one direction to avoid this problem, which has been corrected.

5. Flexible Distribution of Manually Applied Low-rise Shearline Forces in Windward Direction (Bug 3549)

The program was adding manually entered shear line forces in one direction only to forces created by the flexible distribution of low-rise wind loads from southeast and northwest windward corners, even though “Both” was selected as the direction when inputting these forces. The incorrect forces appeared in Plan view and the Shear Results and Deflection tables of the Design Results.

In an example project, a N->S shear line force was shown as 4153 lbs when it should be 4653 lbs. In the S->N direction, it was correctly shown as 4653 lbs.

6. Crash upon Adding Uplift or Dead Loads with Vertical Shearline Offsets (Bug 3518)

The program crashed upon adding dead or wind uplift load to shearlines that had vertical offsets between levels. However, these loads could be added to shearlines that lined up and had no vertical offsets. This has been corrected.

 

Shearwalls 10.2 – Design Office 10, Service Release 2 – July 30, 2019

1. Use of CSA O86-14 with NBC 2010 (Design Office Feature 24)

The program now allows you to select the CSA O86-14 wood design standard with the 2010 NBC building code. Although the O86-14 is referenced by NBC 2015, it is permissible to use it with the NBC 2010, which references CSA O86-14, and some jurisdictions have not yet adopted NBC 2015.

If there is a conflict between CSA O86-14 and NBC 2010 provisions, the NBC 2010 provision is used to ensure compliance.

a) Input

In the Design Settings, the choice CSA O86-14 / NBC 2010 has been added to the Building code dropdown box.

b) Design

For those jurisdictions still complying with NDS 2010, this option allows for shear wall design based on nail strength and panel buckling introduced with O86-14, rather than the more conservative tabular approach used in previous editions. This and other differences with using O86-14 as opposed to O86-09 are described in Shearwalls 9.3 - CSA O86-14 Design Standard, below.

c) Program Information

The design codes and standard chosen are reflected in the Welcome box, the Help/ About Sizer box, and the Building Codes box, and in the Design Settings output.

2. Vertical Distribution of Rigid Diaphragm Shearline Forces (Bug 2733)

We have changed the way the program incorporates forces from shearlines on upper levels in the rigid diaphragm analysis on the level below.

a) Previous Procedure

In versions before Shearwalls 10.2:

i. Wind

For wind design Shearwalls included the unfactored shearline forces derived from flexible diaphragm analysis on the level immediately above and added them to the applied loads on the level for which rigid analysis was being performed. The shearline force was then factored by 1.4 for wind design.    

ii. Seismic 

For seismic design Shearwalls included the applied loads from all levels above and added them to the applied loads on the level for which rigid analysis was being performed.

b) New Procedure

For both wind and seismic design, the shearline forces arising from rigid diaphragm analysis from the level immediately above are applied to the rigid diaphragm analysis on the floor below. For each shearline, the worst case of forces from positive and negative accidental eccentricity on the level above are those which are transferred.  

c) Background and History

i. Rationale for Previous Procedure

When the rigid diaphragm procedure was implemented along with multi-story analysis in version 2002 of the program, there was concern that the torsional effect of the accidental eccentricities applied on the level above should not be carried through to the level below for two reasons:

1. Probability of Simultaneous Occurrence

It was thought that accidental eccentricity is entirely to account for inaccuracies in the distribution of mass in a structure, and that it was unlikely that these inaccuracies or variabilities would occur on each level and in the same direction.

2. Compounding of Accidental Eccentricity

There was concern that the eccentricity would unnecessarily compound, that is, the effect of eccentricity on the level above creates amplified forces that would be further amplified by the eccentricity on the level below.

ii. Implementation of Previous Procedure

1. Use of Flexible Diaphragm Forces

We received guidance at that time that it would be acceptable to apply loads derived from flexible forces on the floor above to rigid analysis on the level below. This was applied to both wind and seismic design, even though there is no requirement for accidental eccentricity for wind design.

An accidental eccentricity of 10% of building width is required for seismic design as per NBC 4.1.8.11.(11). 

2. Use of Applied Loads for Flexible Diaphragm Seismic Design

The seismic requirement for flexible diaphragms of 5% accidental eccentricity, from NBC Structural Commentary 174, was added to the program for version 8, in 2011. To avoid compounding this eccentricity, applied loads on the levels above were used in lieu of shearline forces. This was an internal change only, there is no effect on the resulting torsional moments.

d) Reason for Change

i. Probability of Simultaneous Occurrence

The USA ASCE 7 C12.8.4.2 says that it is “typically conservative to assume that the center of mass offsets of all floors and roof occur simultaneously and in the same direction.” That is, as we cannot know for certain which levels and directions the accidental eccentricities occur in, it is best practice to assume they occur on all levels.

ii. Effect of Compounding vs Flexible Diaphragm Inaccuracy

Typically, accidental eccentricity adds approximately 10% force to the shearline experiencing the greatest effect. Compounding this effect on the floor below by adding 10% of 10% = 1% is not a significant increase and is much less than the inaccuracy that arises from using the flexible diaphragm forces from the shearlines above. Flexible diaphragm analysis can result in a markedly different distribution of force than the rigid diaphragm force, and by using flexible forces, the program was not transferring the inherent torsion from the floor above to the one below.

iii. Natural Component of Accidental Eccentricity

According to NBC Structural Commentary 175, about ½ of the 10% accidental eccentricity is due to natural torsional effects such as dynamic amplification, so that component should always be transferred to the level below.

iv. Wind Loads

As there is no accidental eccentricity requirement for wind, the rationale for the previous procedure does not apply to wind design, which should use the forces that arise from rigid diaphragm analysis.

e) Consequences of New Procedure

i. Distribution of Non-torsional Direct Forces

The new procedure uses the direct forces due to shear wall stiffness on the level above, rather than those arising from flexible analysis. As we are assuming rigid diaphragms on all levels, this is a significant improvement in the accuracy of the procedure.

ii. Distribution of Inherent Torsional Forces

The new procedure transmits inherent torsional forces due to physical offset between the center of mass and center of rigidity, and these forces contribute to torsion on the level below. This is the correct procedure, as an object when subject to torque twists throughout its whole length. The old procedure did not transmit torsion between levels. 

iii. Distribution of Accidental Torsional Forces

On each line, the program transmits the maximum force from positive and negative accidental eccentricity. As such, the new procedure will transmit the increase in force due to accidental torsion but will not transmit the torsional effect of that force, as the worst case of the positive and negative accidental torsions on opposite extremities of the structure tend to cancel.

We believe this is an acceptable compromise between the conservative procedure described in ASCE 7 C12.8.4.2, and the non-conservative procedure of not including accidental eccentricities from the floor above on the floor below at all.

3. Vertical Transfer of User-applied Seismic Shearline Forces (Bug 3467)

When a seismic shearline force was added directly to a shearline using the Add as a factored force directly… input in the Add Load input form, for rigid diaphragm analysis the force affected only the level it was added on and was not being transferred below for inclusion in the torsional analysis on the level below.

This has been corrected in the course of implementing the changes in Bug 2733, above, Vertical Distribution of Rigid Diaphragm Shearline Forces.

4. Multiple Wall Selection in Load Input View (Feature 252)*

It is now possible to select multiple walls on which to apply loads in the Add Load dialog. Once walls are selected using the Control Key or Select All command, upon entering the Add Load dialog,

-       Point loads cannot be selected,

-       Apply to is disabled and shows Selected Walls,

-       The From and To locations are blank and disabled,

-       The Add as a factored force directly to the shearline is not available.

Loads are then added on all selected walls, with the Magnitude From and To being the load magnitude at the start and end of each wall. 

5. Wind Load Generation on Multiple Blocks

The following problems pertaining to the generation of wind loads on adjoining blocks have been corrected.

a) Low-Rise End Zone in Interior of a Building Face (Bug 3472)

When the wind load method for low buildings from NBC Figure 4.1.7.6.-A. is used for multiple blocks, end zones were created at the end of each block, for both walls and roofs. This would create unnecessary end zones in the interior of the structure where one block joins another.

For walls, these end zones were created on interior corners, and where the end of one block is collinear with the side of another block. For roofs, they are created when a hip roof joins a block with a side panel of the same angle, so end zone is created in the middle of a continuous compound roof panel.

End zones are no longer created in these areas, which are considered part of the building faces 1-4.

b) Low-rise End Zone for Shadowed Blocks (Bug 3464)

When a block was adjoined to another block such that there were no walls on one of the faces of the block, the end zone on both walls and roof panels on the opposite face of the block would extend the entire width of the block, rather than the end zone width specified in NBC Figure 4.1.7.6.-A. This would create larger wind loads than expected on the face.

c) Shadowed Blocks with Roof Overhangs (Bug 3465)

When a block with roof overhangs was adjoined to another block, the program would create loads on the roof the block was adjoined to in the portion shadowed by the block, even if the Exclude roof portion covered by other block checkbox in the Load Generation input was checked. This happened when using the load generation procedures for low buildings and for all other buildings.

6. Low-rise Wind Load Generation for Flat Roofed Buildings (Bug 3474)

In the case of buildings with flat roofs, the generation and distribution of low-rise loads using NBC Fig 4.1.7.6 were incorrect in several ways. In such buildings, the longest direction of the building is considered to be the direction parallel to the ridge line for buildings with roofs. The following problems were identified:

-       Case A (transverse to long direction) loads were being generated on end walls; however such walls are not loaded in the NBC model.

-       Some Case A loads were being created with the magnitude intended for Case B loads, and vice versa.

-       For torsional analysis of load Case B (wind force parallel to long direction), no force was being included parallel to the long direction.

These problems occurred on all levels of the structure and have been corrected.

7. Design Spectral Acceleration Values in Seismic Load Generation Details Output (Change 104)

The design spectral acceleration values S(T) at period T = 0.2, 0.5, and 5.0 from NBC 4.1.8.4.(9) are now output in the Seismic Load Generation Details file under the Total Design Base Shear table. These values are used to calculation the maximum base shear Vmax from 4.1.8.11.(2)(c), and the overturning reduction coefficient J and higher mode factor Mv from 4.1.8.11.(6). Their inclusion should some of the other calculations shown more transparent, such as the equivalence of Vmax and Vcalc for certain site classes and locations, because S(0.5) = S(0.2) = S(Ta) for Ta <= 0.5 for cases. Refer to NBC Commentary J-140 which shows this situation for Site Classes D and E in Vancouver.  

8.  “Getting Started” Steps (Change 103)

The instructional steps that appear when the program is run or “Getting started” is invoked from the toolbar have been revised, clarified and updated. Some of the more significant changes are:

a) Default Values

A “Step 0” has been added suggesting setting defaults for building elements, and the subsequent steps indicate how those defaults are used to create the structure.

b) Edit Walls

Explanations of the ability to change the location and size of walls via the wall input form, the selection of Standard Walls, designing for unknowns, and designing as a group have been added.

c) Edit Hold-downs

A Step 7 has been created for editing hold-down device information, by moving instructions from other steps.

d) Generate Loads

An instruction to set the Wind Load Generation Procedure has been added, and the procedure of creating seismic loads in stages with self-weights on each level explained more clearly.

e) Add or Edit Loads

The need to add dead loads to counteract overturning, and wind uplift loads, has been emphasized. An explanation of changing building masses and returning to regenerate loads has been added, as has the case of not generating loads and adding loads to check a single shearline. The unusual case of modifying generated loads has been removed.

f) Design

Several design settings have been added to the recommendation to set the Rigidity and Deflection options before designing. The mention of design processing time has been removed, as it is no longer a major issue.

g) Accept or Adjust Design

A Step 15 has been added for the Accept Design feature.

h) Detailed Results Output

The step formerly called “Log File Output” has changed to Detailed Design Results and lists the separate buttons and associated files for wind load generation, seismic load generation, and torsional analysis, that used to be in one file.

9. Force on Shearline with No Full Height Segments (Bug 3461)

Due to numerical rounding, some shearlines with numerous non-full-height sheathing segments and no full-height sheathing segments were assigned a shearline force when they shouldn’t have been. These shearlines were included in the Shear Results output table and a failure reported for them.

This problem happened infrequently and has been corrected.   

10. Drawing of Vertical Element for Offset Openings in Elevation View (Bug 3463)

When the end of an opening on an upper storey is over the interior of an opening on the floor below, the drawing in Elevation view of the vertical element extending from the bottom of the upper floor joist to the top of the opening was no longer visible because it was obscured by the gray shading over non-full-height sheathing segments that was introduced with version 10.

This has been corrected.

11. Default Imperial Snap Increment (Change 94)

The default snap increment when Shearwalls is shipped is 100 mm, so when you changed your default unit system without adjusting the snap increment and opened a new project, the snap increment would be 3.94”, which is awkward to work with. The program now uses a default of 3” in this circumstance.

If you reset to the original setting while in Imperial units, it is reset to 3” rather than 3.94”. 

12. Wind Uplift Loads on Selected Walls (Change 95)

For wind uplift loads, in the Application input of the Add a New Load dialog box, you can now add the loads to selected walls. Previously only the full wall line was available.

13. Display Control for Hold-down Design and Drag Strut Force Tables (Bug 3228)

The inclusion of the Hold-down Design and Drag Strut Forces tables in the Design Results output is now controlled by separate items in the Show menu and in the Options settings. Previously they were both controlled by a single item in the Loads and Forces settings.  

14. Colour of Selected Shearlines (Change 96)

When a wall is selected in Plan view and turns orange, the other walls on the shearline turn a darker colour of orange (or brown). Previously they were purple.

15. Order of Framing Materials in Wall Input (Change 100)

The dropdown list of in the Materials input in the Framing section of Wall Input View was mistakenly ordered alphabetically, so that proprietary SCL materials rarely used as wall studs were given first. This has been corrected and common lumber materials appear first.

 

Shearwalls 10.1.1 – Design Office 10, Service Release 1a – May 7, 2019

1. Deflection Convergence for Close to Zero Force on Segment (Change 45g)

The convergence routine for equalizing deflections along the shear wall as required by SDPWS 4.3.3.4.1 sometimes left a small residual force on a segment that should not attract any force, causing the program to report that it could not equalize deflections. The program now zeroes out the force if it is less than 0.05 plf, that is, what appears as 0.00 in the output. Note that it adds this small force back into the pot to be redistributed to other shearlines, so it isn’t leaking forces if several segments are zeroed out.

2. Missing Framing Material Crash Upon File Open (Bug 3439)

When a project file was opened opens that contained a framing material that was not amongst the materials listed in the Framing Materials drop down, starting with Version 10.1 the program crashed instead of showing you a message about the missing database file.

The message has been restored and the program now longer crashes in this situation.

Note that problem can be rectified by activating the material database file with Database Editor.

3. Standard Wall Nail Diameter Persistence (Bug 3427)

Values of power-driven nail diameters entered into Standard Walls were not being saved, so that when standard walls created with a nail diameter, are used when the program is reopened, the nail diameter used was the default diameter based on the common nail of the closest length to the power-driven nail.

This has been corrected and standard wall nail diameters now persist when a file is reopened.

 

Shearwalls 10.1 – Design Office 10, Service Release 1 – March 27, 2019

The links below lead to descriptions of the changes made for version 10.1 of WoodWorks Shearwalls.

 

A: Building Model and Shear Wall Design. 1

1. Power-Driven Nail Design Using CSA O86-09 (Bug 3406) 1

2. Design Assumptions for Weight Irregularity 2. 1

3. Constant Detection of Torsional Irregularity 7 for Seismic-only Design (Bug 3350) 1

4. Data Related to Hold-downs in Standard Wall Groups (Bug 3409) 1

5. Update of Roof Joining (Bug 3377) 1

6. Outsize Openings after Change of Wall Height (Bug 3347) 1

7. Gypsum Underlay in Sheathing Materials Table Legend (Change 43) 1

8. Deflection Settings Output when Deflection Analysis not Performed (Change 83) 1

B: Load Generation and Distribution. 1

1. Separate Wind and Seismic Details File (Change 1) 1

2. Generate Loads Dialog Update (Change 8) 1

3. Update of F(T) in Site Information. 1

4. Nonsensical Seismic Forces (Bug 3362) 1

5. Torsional Analysis Report for Flexible Diaphragm Wind Design (Change 55) 1

6. Seismic Load Generation Details Formatting. 1

7. Wind and Seismic Procedure in Site Information Table (Change 17) 1

C: Input and Program Operation. 1

1. Re-appearance of Plan View Input Forms (Change 37) 1

2. Crash on Corrupted or Empty Hold-Down Database (Bug 3375) 1

3. Log File Menu Item (Change 2) 1

4. Link to Video Tutorials in Help Menu (Change 29) 1

5. Wall and Shearline Input Form.. 1

6. Disabled Worst-Case Rigid vs Flexible Diaphragm Setting (Change 54) 1

7. Dropdown Box Style for Wall and Opening Hold-down Input (Change 82) 1

8. Tool Bar Menu Item Spelling. 1

9. Warning and Informational Messages. 1

 

A:  Building Model and Shear Wall Design

1. Power-Driven Nail Design Using CSA O86-09 (Bug 3406)

The following problems when using the CSA O86-09 design code is set, pertaining to the design of shear walls using power driven nails according to Note 5 of Table 9.5.1A, which refers to the procedure in A9.5.1, were corrected. 

a) Shear Capacity Adjustment Factor

The program was using the capacity corresponding to the standard nail in Table 9.5.1A smaller than the power-driven nail, then increasing the capacity listed in table by the square of the ratio of the power nail to the standard nail. However, A.9.5.1 says to use the standard nail size larger than the power nail size and decrease the capacity by the square of the ratio.

This created small errors in capacity for nails greater than 2.84 mm in diameter, the smallest standard nail diameter in table 9.5.1, and for known sheathing thickness, power-driven nails less than 2.84 mm diameter had zero capacity when they should have had a factored capacity.

b) 80% Diameter Rule

The program was allowing nail sizes less than 80% of the smallest size listed in Table 9.5.1 (2.84 mm) and calculating nail size adjustment factors from A9.5.1 based on that, even though A9.5.1.1 limits the allowable nails to those within 80% of the sizes listed in 9.5.1.  These factors were only applied for unknown sheathing thickness due to item a), above.     

Note that the smallest standard nail size in Shearwalls is 2.87 mm, corresponding to the ASTM F1667 wire gauge size corresponding to 2.84 in the obsolete CSA O86 B111 nail standard. The program however limits nails to at least 80% of 2.84, or 2.272 mm.

2. Design Assumptions for Weight Irregularity 2

The following changes were made to the detection of Structural Irregularity 2 - Weight (mass) in NBC Table 4.1.8.6.

a) Definition of a Storey (Bug 3423)

The program was using the definition of a “storey”, italicized in Table 4.1.8.6 to indicate that is from the definitions in Division A, 1.4.1.2, as the distance from the top of one floor to the top of the floor above it. The roof was considered a separate storey because of the line in 4.1.8.6 saying “A roof that is lighter than the floor below need not be considered. “, implying a heavier roof need be considered as a separate storey.

However, we have received advice that the same definition of building levels used for vertical seismic force distribution should be used, that is, from the middle of the wall on one level to the middle of the walls on the level above. In this model, a roof is considered part of the upper level.

The reason for this re-evaluation is that the purpose of the weight irregularity is to make sure the structure behaves as assumed in the Equivalent Static Procedure, which is based on the first (near-linear) mode of the “lumped mass” dynamic response model that is used for vertical seismic load distribution. The linear mode assumption requires a relatively uniform mass distribution amongst the storeys. 

Furthermore, an identical irregularity provision in the USA ASCE 7 Table 12.3-2, Irregularity 2, uses the term “effective mass”, rather than the weight of a storey.

The interpretation of a storey as per the literal NBC definition caused problems with the following situations, that are eliminated by using the vertical seismic force distribution definition:

-       at the definition of a storey from a floor to a ceiling was not being applied for the case of roofs on top of cathedral ceilings

-       if buildings have trusses and you enter the mass of the whole truss system, including the ceiling, as the roof load, when the ceiling should have been part of the upper storey.  

-       when partition wall masses were incorporated into the mass of the floor load, they would be placed on a storey below where they should be

b) Inclusion of 25% of Snow Load (Bug 3422)

The storey weight for the roof did not include 25% of the snow load that is used in seismic load generation, but it should have been included, as the irregularity description in Table 4.1.8.6 includes the symbol Wi, which is defined in NBC 4.1.8.2 as a portion of W, and in the definition of W, it includes 25% of the snow load.

Therefore, the snow load is now included in the weight of the uppermost level as defined in item (a) above.  

3. Constant Detection of Torsional Irregularity 7 for Seismic-only Design (Bug 3350)

The program reported a torsional irregularity for all or most structures when only seismic loads were applied to the structure, regardless of whether this torsional irregularity existed. As a result, the Design Summary indicated that due to an irregularity, seismic design was not valid, and the Irregularities table in the Design Summary showed the irregularity 7 failing in one direction, and a red note at the top saying the Equivalent Static method is not available for that reason. This has been corrected.

4. Data Related to Hold-downs in Standard Wall Groups (Bug 3409)

Wall parameters related to hold-downs were being included in the definition of standard walls, although they are not part of the material specification intended to be part of a Standard wall: As a result, the following would occur if these were changed for a wall:

-       If Design in Group was not selected, the wall would no longer be designated as being one the Standard walls. Extra design groups would be created for all the walls affected.

-       If Design in Group was selected, the change would be propagated to all other walls that were part of the Standard wall group.

a) Hold-down Data

The following data were not available for selection in Standard Wall mode, but were being treated as Standard Wall parameters:

-        hold-down model,

-        number of brackets,

-        whether to apply the same hold-down to the openings.

b) No. of End Studs

The number of end studs, which is used only for hold-down design, has been removed from the standard wall definition for the purpose of design grouping but is retained in the Standard Wall mode of Wall Input View for the purpose of creating default walls.

Hold-down related information is no longer included in the Standard Wall definition because hold-downs are designed separately from walls, and it is desirable to group walls according to wall materials only.

5. Update of Roof Joining (Bug 3377)

For multiple blocks, the program occasionally failed to update the roofs according to the input in the data group Construction in Roof Input View in the following ways:

a) Disabled Joined Selection

If there is another block that a roof could join to, the Joined selection was sometimes disabled so the operation was impossible.  

b) Gable and Hip Selections

When roofs are joined in the N-S direction, the Gable and Hip selections sometimes had no effect and the roof remained joined when selected.

These have been corrected.

6. Outsize Openings after Change of Wall Height (Bug 3347)

When the wall height is changed in Structure input, the program now adjusts the top of any openings to ensure that they remain within the confines of the wall and removes the openings that would have no height if this is done. 

7. Gypsum Underlay in Sheathing Materials Table Legend (Change 43)

The legend entry GU - Gypsum underlay thickness is now displayed in Sheathing Materials table in the Design Results when CSA O86-14/NBC 2015 is selected. Previously it displayed only when CSA O86-09/NBC 2010 was selected.

8. Deflection Settings Output when Deflection Analysis not Performed (Change 83)

In the line saying Linearized deflection equation in the Design Settings output, if Include deflection analysis is unchecked in Design Setting, No deflection analysis is shown rather than Never or Always. The deflection equation is irrelevant if there is no deflection analysis, and the Include deflection analysis setting was not previously reported in the output.

B:  Load Generation and Distribution

1. Separate Wind and Seismic Details File (Change 1)

The program now outputs two separate files for wind and seismic load generation, rather than both in one file as before. The file extensions are .sws and .sww instead of .log. The files are accessed by two icons in the toolbar.

2. Generate Loads Dialog Update (Change 8)

In Generate Loads dialog, the following values reverted to their original values after being edited and you clicked anywhere outside the box before generating loads:

Seismic loads:

-        all self-weight text fields

-        horizontal projection check box

-        use wall self-weights…for Jhd calculations check box (Canada only)

Wind loads:

-        line/area load radio buttons

-        C&C wall loads check box

The program now retains all the inputs.

3. Update of F(T) in Site Information

The following problems regarding the update of site coefficients F(T) in the Site Information Dialog when the NBC 2015 design code setting is selected have been corrected. These values are editable when Site Class F is selected, as site specific analysis is required according to NBC 4.8.1.4.(6). Otherwise they are disabled and the values from Tables 4.1.8.4.-B-F appear.

a) Site Classes A to E (Change 16)

The program now updates the non-editable values of F(T) when Site Class A-E is selected when the peak ground elevation PGA value is changed, or the value of Sa(0.2) changes such that it switches between from being greater than or less than 0.8 PGA, as per NBC 4.1.8.4.(4). Previously the values only updated when the Site Information box was closed and reopened.

b) Upon Change of PGA for Site Class F (Change 10)

With Site Class F selected so the F(T) values are editable, after changing F(T) then the peak ground elevation value PGA, the F(T)’s reverted to their previous values.

c) Upon Return to Site Class F (Change 11)

When Site Class F is selected and F(T) values are edited, then changing to another Site class so that other non-editable values appear, and back again, the program now puts back the F(T) values that were previously entered rather than zeroes.

d) Verification upon Exit (Change 26)

If Site Class F is selected, and the F(T) values not changed from the default value of 0, the program now issues a warning message asking you to enter non-zero values. If OK is selected, you return to the input dialog; If Cancel is selected, the changes are reverted. Previously the program allowed you to save these values and generated seismic loads based on the zero F(T)’s, generating zero seismic load of all were zero.

The same functionality has been implemented for when the NBC 2010 design code setting is selected and Fa or Fv is zero when exiting the box. Previously these values defaulted to the those from the last site class selected; now zeroes appear when selecting Fa or Fv.

4. Nonsensical Seismic Forces (Bug 3362)

On rare occasions one or more shearline forces would be calculated with nonsensically high values. These values appeared in the Shear Results table and were reflected in the storey shear and diaphragm design forces in the Seismic Information table. This rarely occurring bug due to unusual values of torsional rigidity for flexible diaphragm design encountered in intermediate iterations and has been corrected.

5. Torsional Analysis Report for Flexible Diaphragm Wind Design (Change 55)

If a project is run such that torsional analysis is required, then the inputs are changed such that it is not and run again, the program retains the Torsional Analysis Details from the previous run. Torsional analysis is not required if the Rigid Analysis option is not selected in Structure Input view, and there are only wind loads on the structure, as seismic loads require flexible diaphragm torsional analysis.

6. Seismic Load Generation Details Formatting

The following minor formatting changes have been made to the Seismic Load Generation Details file. 

a) Decimal Places for Sa (5.0) (Change 15)

Four decimal places were output for the value of Sa (5.0), the 5% damped spectral response acceleration in the Seismic Load Generation Details. Now it is output with two decimal places.

b) Extra Line (Change 18)

An extra line appearing between the line reading Equations (units = N,m) and the Equations in the Seismic Load Generation Details file has been removed.  

c) Change in Subscripts for Distribution of Base Shear to Levels (Change 19)

The column headers hi, Wi and hi * Wi are now output as hx, Wx, hx * Wx in the Distribution of Base Shear to Levels table appearing in the Seismic Load Generation Details file. The change in subscript from i to x is because the subscript i is stated to be used for the level in summations in the Legend section, whereas x is for a particular level.

7. Wind and Seismic Procedure in Site Information Table (Change 17)

In the Site Information table of the Design Results, the words from and for appearing beside the NBC wind and seismic load generation procedure reference have been removed.

C:  Input and Program Operation

1. Re-appearance of Plan View Input Forms (Change 37)

When in Plan view and you close the input form, e.g. Opening Input, either by the exit button on the form window or by the Input Form icon in the toolbar, then go to another Plan view action, e.g. Roof Input, and return, the input form for the original action now re-appears. Previously it remained invisible and some users had difficulty making it reappear. 

2. Crash on Corrupted or Empty Hold-Down Database (Bug 3375)

If the hold-down database was empty or corrupted, a crash occurred on program start-up. The program now re-installs the original database if it encounters a corrupt or empty one.

It was possible to avoid the crash by deleting the corrupted hold-down database file.

3. Log File Menu Item (Change 2)

The File menu item Log File has been removed as what was previously the log file is now split into four text output files, none of which are referred to as “log files”.

The following files are now accessed from menu items in the View menu.

 

Wind Load Generation Details

Seismic Load Generation Details

Torsional Analysis Details

Detailed Shearwall Design

 

Note that they also have icons in the toolbar.    

In the View menu the word View has also been removed from Design Results View, for consistency with these menu items.

4. Link to Video Tutorials in Help Menu (Change 29)

An item Video Tutorials has been added to the Help menu for the link http://cwc.ca/woodworks-software/support-and-training/canadian-tutorials/  which goes to the WoodWorks video tutorials on the CWC website, where you will find numerous Shearwalls tutorials.

5. Wall and Shearline Input Form

The following changes were made to the operation of the Wall and Shearline Input form

a) Standard Wall Input Box Overlap (Change 5)

While in the Standard Wall mode, the dropdown box with the list of Standard Walls overlapped with the input box to the right showing the name of the Standard Wall being edited, and when dropped down it obscured part of the name of the Standard wall. There is no longer any overlap.

b) Shearline Selection in Wall Input View (Change 24)

The Shearline input is now disabled if there is no choice other than Auto. This input allows you to select the shearline a wall belongs to if the walls are within the allowable shearline offset of walls defining two or more shearlines. As the default offset in the Design Settings is only 0.15m, this rarely occurs, and the use of this input was unclear to some users.

6. Disabled Worst-Case Rigid vs Flexible Diaphragm Setting (Change 54)

In the Design Settings, the check box for Worst-Case rigid vs flexible diaphragms was disabled and showing as selected if only one of Rigid or Flexible Analysis was selected in the Structure input. Now it is shown as not selected (empty) in this case.  

7. Dropdown Box Style for Wall and Opening Hold-down Input (Change 82)

The hold-down model input in both wall and opening view has been changed from an editable drop-list to a noneditable list, as a hold-down typed into this input would not necessarily match with an existing one in the database.

8. Tool Bar Menu Item Spelling

The following spelling corrections were made in the items in toolbar dropdown menus

a) Drag Strut in Show Menu (Change 57f)

In the Show menu, under Forces, Dragstruts has been changed to Drag Struts.

b) Irregularities in Go To Table Menu (Change 87)

In the Go To Table menu under Design Results, Seismic Irregularities had the misspelling Irregulairites.

c) Storey in Go To Table Menu (Change 21)

In the Go To Table menu under Structural Data, Story Information is corrected to Storey Information.

9. Warning and Informational Messages

The following changes were made to the text in messages:

a) Warning Message for Rounded Opening Input Values (Change 48)

The warning message about opening input being rounded to the nearest snap increment, identified the input by long phrase that did not make sense in the context of the warning. It has now been abbreviated to briefly identify the input, e.g. Offset from edge. Square brackets around the input value have also been removed.

b) Loads and Forces Warning Message Misalignment (Change 4)

The warning message when Loads and Forces view for the first time had misaligned bullet points. This has been corrected.

c) Irrelevant Messages in Status Bar (Change 9)

Irrelevant messages from other part of the program operation were displayed in the status bar at the bottom of the program window upon hovering the toolbar items Go To Table, Zoom Out, Zoom in, Undo, Redo and getting Started.  These have been removed and nothing appears in the bar at this stage.

 

Shearwalls 10 –– Design Office 10 – January 31, 2018

The following major features are implemented for this version,

 

NBC 2015 – Wind Load Generation

NBC 2015 – Seismic Load Generation

5-and 6-Storey Design

Multiple Block Low-rise Loads

Improved Irregularity Detection and Design

Linearized Deflection Equation

Elevation View Improvements

 

The following is an index of links to descriptions of all the changes.

 

A: NBC 2015 and CSA O86-14 Updates - General 10

1. Choice of Design Codes and Standards. 11

2. CSA O86-14 Updates. 11

3. Synchronization of NBC and O86 Editions. 11

4. Design Code Clause References. 11

5. 5-and 6-Storey Design. 11

6. On-line Help. 12

B: NBC 2015 – Wind Load Generation. 12

1. Wind Load Generation Procedures and Methods. 12

2. Reference Height h. 13

3. Topographic Factor 14

4. Pressure Coefficients Cp for Buildings of Any Height 15

5. Pressure Coefficients CpCg for Low Buildings. 15

6. Internal Pressure Coefficient Cpi 16

C: Other Wind Load Generation. 17

1. Low-rise Wind Loads for Multiple Blocks and Eccentric Ridge Lines (Feature 26) 17

2. Low-rise Torsional Loads. 19

3. Case A Side, Case B End. 19

4. Show Menus (Bug 3240) 20

5. Partial Wind Loading Note. 20

6. Load Generation Details Output 20

7. Bug Fixes and Small Changes. 21

D: NBC 2015 – Seismic Load Generation. 22

1. Design for Low Seismic Loads. 22

2. Seismic Data. 23

3. Site Coefficients F(T) and Design Accelerations S(T) 23

4. Disallowed Irregularities for 5-6 Storey Wood Frame Construction. 24

5. Gravity-Induced Lateral Demand Irregularity Type 9. 25

6. Maximum Base Shear V. 25

7. Period Ta for Single-storey Wood Structures. 25

8. Higher Mode Effects Mv 26

9. Overturning Reduction Factors J and Jx 27

10. Base Shear Increase for User-input Ta for 5- and 6-Storey Buildings. 28

11. One-storey Buildings with Large Diaphragm Deflection. 28

E: Other Seismic Load Generation. 28

1. Period Restriction on Irregular Structures. 29

2. Vertical Stiffness Irregularity Type 1. 29

3. Weight (mass) Irregularity Type 2. 30

4. Re-evaluation of Discontinuity Irregularities Types 3, 4, and 5. 31

5. Deflection Analysis for Detection of In-Plane (stiffness) Irregularity Type 4. 32

6. Irregularity Table Changes. 33

7. Disallowed Irregularities for 5- and 6- Storey Structures. 34

8. Load Generation Details Output 34

9. Bug Fixes and Small Improvements. 35

F: Load and Force Distribution. 36

1. Sign Convention for Torsional Analysis. 36

2. Torsional Analysis Details Output 36

3. Bug Fixes and Small Improvements. 37

G: Deflection Analysis and Shearwall Design. 37

1. 3-term vs. 4-term Deflection Equation (Feature 211) 37

2. Design Results Output 39

3. Bug Fixes and Small Improvements. 41

H: Elevation View. 42

1. Zoom and View Settings (Feature 216) 42

2. Multi-storey Selected Walls (Feature 230) 42

3. Shading of Non-shear-resisting Segments (Feature 56) 43

4. Dimension Lines (Feature 79) 43

5. Display of Roof Line and Gable End (Feature 228) 44

6. Segment Numbers (Feature 77) 44

7. Bug Fixes and Small Improvements. 45

I: Plan View. 45

1. Mouse Zoom (Feature 219) 46

2. Wall Depiction in Plan View (Feature 56) 46

3. Design Case in Plan View (Feature 83) 46

4. Bug Fixes and Small Improvements. 46

J: Program Operation. 47

1. Separate Torsional Analysis and Load Generation Output 47

2. Settings. 47

3. Bug Fixes and Small Improvements. 48

 

A:  NBC 2015 and CSA O86-14 Updates 1 and 2 - General

The program now implements the 2015 National Building Code (NBC), but still retains the implementation of design with the NBC 2010 as a user option.

1. Choice of Design Codes and Standards

In the Design Code drop list the Design procedures data group of the Design settings, the choice CSA O86-14/ NBC 2010 has changed to CSA O86-14/ NBC 2015. The CSA O86-09/ NBC 2010 choice remains unchanged.

This change is also reflected in the output of the design settings, the About Sizer box accessed from the Help menu and in the Building Codes box accessed from Welcome box, and the Welcome box.

2. CSA O86-14 Updates

The program now indicates in the About Sizer box and the Building Codes box that the CSA O86-14 implementation now includes Update No. 1 from May 2016 and Update No. 2 from June 2017. The latter update caused some design code clause reference numbers to change.

3. Synchronization of NBC and O86 Editions

The program now does not allow you to generate loads with 2010 NBC and design with 2014 O86, or generate with NBC and design with CSA O86-09.

If you try to do so, when Design button is pressed, the program offers a choice of cancelling design or regenerating loads.

4. Design Code Clause References

The references to the NBC design code clause numbers in the input forms and screen messages, and in warnings, design notes and other program output, have been updated to show the 2015 edition clause numbers when CSA O86-14/ NBC 2015 is chosen as the design setting. It continues to show 2010 edition numbers when CSA O86-09/ NBC 2010 is chosen.

5. 5-and 6-Storey Design

In determining which NBC provisions should be included in the program and how existing ones were to be interpreted and implemented, consideration was given to the changes in NBC which allow 5- and 6-storey design for most wood structures, instead of the previous limitation to 4 storeys.

The changed provisions relate to permissible structures of combustible construction for fire safety – 3.2.2.50 for residential use (Group C) and 3.2.2.58 for business and personal service use 9 (Group D).

Note that neither the building area limitations nor the height limits for these provisions are checked by Shearwalls and it is your responsibility to ensure that your building is within these limits.  

6. On-line Help

The on-line Help in the old Windows format containing references to the CSA O86-09 design code provisions has been removed from the program. The newer Web Help showing CSA O86-14 references is retained. It currently refers to the NBC 2010 design code and has not yet been updated for Version 10 features and changes. This will be done over time and updates posted to the web site. 

7. Building Codes Box

The reference to NBC now indicates that it is Division B, Part 4 that is used. The full name of the Structural Commentaries is now given.

Under Mid-rise Wood Construction:

-        Design code provision reference numbers to NBC and CSA O86 are now given for all the line items about what is and isn’t included in Shearwalls. 

-        The line regarding increase in base shear due to manual T value has been moved from the section about what has not been implemented.

-        The line regarding special requirements for certain shapes has been removed.

-        A line about higher mode factor Mv and overturning reduction factor J has been added.

A section about Wind Load Generation has been added indicating that partial load cases from 4.1.7.9 and intermediate exposure factors Ce for change in terrain from 4.1.7.3.(5)(c) are not in the program.

 

B:  NBC 2015 – Wind Load Generation

The changes described in this section occur when NBC 2015 is selected as the design code edition in the Design Settings, unless otherwise indicated.

1. Wind Load Generation Procedures and Methods

a) Design Setting

The Design setting for Wind load generation procedure has changed to Wind load generation method to avoid confusion with the static vs dynamic procedures, which are now so named officially.

The choices referring to Commentary Figures 1-7/8 and I-15 have changed to

NBC 4.1.7.5 – Other buildings

NBC 4.1.7.6 – Low buildings

b) Load Generation Details

i. Header

In the header to the Load Generation Details file (previously part of the Log file), now states that the Static procedure from NBC 4.1.7.3 is used (4.1.7.3) then refers to the 4.1.7.5 or NBC 4.1.7.6 method selection.

For both 2010 and 2015 NBC selections, the program now gives the C&C procedure used, as one of

2010 all-heights: NBC Commentary Figure I-15 using Cp*

2010 low rise: NBC Commentary Figure I-8

2015 all-heights: Figure A-4.1.7.5.(4)

2015 low rise: Figure 4.1.7.6.-B

ii. Code References

Throughout the report, all design code references now refer to 2015 provisions when the 2015 NBC option is selected.

c) Site Dialog

In the header section of the Site dialog, the program now refers to the Static procedure from 4.1.7.3, and that the external pressure coefficients (Cp or CpCg) and the reference height h come from 4.1.7.5 or 4.1.7.6 according to the method selected.

d) Torsional Analysis Details

In the Torsional Analysis Details file (previously part of the Log file), NBC 4.1.7.5 and NBC 4.1.7.6 are now referred to instead of I-15 and I-7.

Where it previously said   Low-rise Case A, it now says Case A (NBC Figure 4.1.7.6.-A) 

e) Wind Shear Results Table

References to NBC 4.1.7.5 and NBC 4.1.7.6 have been added to the legend to the Shear results table.

f) Dynamic vs Static Procedure

NDS 4.1.7.1 and 4.1.7.2 clarify and solidify the conditions under which the Dynamic Procedure, which is not supported by Shearwalls, must be used. However, these Articles still do not state what height is to be used in the 4:1 height to width ratio used to classify a building as dynamically sensitive: the eave height, mean roof height, or ridge height.

i. Input

This design setting giving the choice of eave, mean roof, or ridge height has been renamed to indicate that it applies only to the classification of buildings in 4.1.7.2.  All other heights have been clarified by NBC 2015.

ii. Warning

The warning message when this ratio has been exceeded has been modified to include references to 4.1.7.2.(2)(c) and 4.1.7.1.(3).

2. Reference Height h

The definition reference height h, used for the calculation of exposure factors Ce and Cei has been moved from 2010 Commentary I 7 and I 8 to 4.1.7.3.(6) and 4.1.7.3.(7), respectively. Previously it was derived using an ill-defined building height H, but this height has now been precisely given in most cases as the mid-height of the roof.

The changes listed below apply to both the NDS 2010 and NDS 2015 design code selections.

a) Criterion for Choosing Method

A literal reading of 4.1.7.3.(6)(a) could lead to using exposure factors for buildings less than 20 meters and least plan dimension, even if Low buildings is not selected as the wind generation method. However, 2010 Commentary I-7 bases the choice of reference height on the definition in I-26 of low-rise buildings, and we do not believe it was the intention of NBC to change this.

Therefore, the use of 4.1.7.3.(6)(a) is dependent on the user selection of the 4.1.7.6 – Low buildings method, and 4.1.7.3.(6)(b) on 4.1.7.5 – Other buildings, not on the actual dimensions of the building.

b) MWFRS Method – Buildings of Any Height (4.1.7.5)

i. Leeward Surfaces

Previously, the program was using ½ the eave height for all leeward surfaces (walls, roofs, and gable ends); now it uses ½ the building height, which is ½ the ridge height.  

ii. Windward Roof Surfaces and Gable Ends

NBC 4.1.7.6.(3)(a) refers only to windward walls and no guidance is given for roofs. As the adjacent clauses refer to “surfaces”, and NBC 2010 I-7 referred to windward “faces”, we have assumed that the intention was that windward roof surfaces be treated the same way as walls.

Previously, the program was using the ridge height for windward roofs and gable ends. It now evaluates the pressures at increments of height, and computes a weighted average of the pressure which takes into account the diminishing width of hip panels, gable ends, and side panels on hip roofs. The height z reported is the centroid of the force distribution, i.e., the z at which the pressure is the same as the averaged pressure. 

c) MWFRS Loads – Low Buildings (4.1.7.6)

No changes were made to the calculation of reference value h for low-rise buildings’; it is still the greater of ½ the

d) C&C Loads

i. External Pressures

There has been no change to the reference height for external pressures for C&C loads, it is still taken as the height at the top of the building level.

ii. Internal Pressures

Previously, the program was using the same reference height for internal pressures Cei as for external pressures Ce. Now it uses the greater of 6 meters or ½ the ridge height, as per 4.1.7.3.(7),

e) Load Generation Details

In the Load Generation Details output, the reference height for internal pressures is now shown above the C&C loads table, where the mean roof height was previously shown. Mean roof height has been removed as it is not relevant to C&C loads.

The definition of the reference height in the Legend has been changed to reflect the new design code reference.

3. Topographic Factor

The equations for wind pressures in NBC 2015 4.1.7.3.(1) and (3) include a new topographic factor, Ct, defined in 4.1.7.4, which is algebraically identical the procedure in 2010 NBC which uses modified exposure factor Ce* and gust effect factor Cg* in place of Ce Cg, where Ce* is defined in Commentary I-14 and Cg* in Commentary I-21.

a) Ct Calculation

The program was modified to calculate Ct independently rather than modify Cg and Ce in order to display these values in the program output when NBC 2015 design is selected.  

b) Reference Height

The NBC 2015 has made it more evident that the height used for the Ct factor is always the height above the ground, z, whereas the Ce factor may have different heights depending on the building surface and the wind load method employed. In calculating Ce* for NBC 2010, the program had been using the same reference height as used in the Ce calculation.

The program now uses the height z above the ground for both the Ct factor for NBC 2015 and Ce* in 2010.  This is the weighted average height over the surface for MWFRS loads, and the height a building element at the top of a level for C&C loads. 

c) Low-rise Loads

The procedure for determining a modified gust effect factor for low-rise combined CpCg from 2010 Commentary I-21 has been removed for 2015, as it is no longer necessary.    

d) Averaging

NBC 4.1.7.3.(2) says that pressures are to be averaged over the building surface. Previously the program had been integrating C e* /Ce over the surface then multiplying with the average Ce. then calculating the gust effect factor Cg* using average Ce* and Ce.

Now the program integrates the value Ce (z) Ct(z) over the whole surface. The difference in these two approaches can be expected to be quite small.

e) Output

In the Load Generation Details file (previously part of the Log file)

-        A definition of Ct has been added to the legend, with 4.1.7.4. reference. 

-        A definition of z for topographic factor height has been added to the legend.

-        Definitions of Lh, Hh, and x have been added to the legend.

-        The equation for the topographic factor Ct is shown in the Equations section.

-        The values of Ct for each load are shown in a column in the load table.

-        The height z corresponding to the average Ct is shown in the load table for each load.

-        The asterisks in Ce* and Cg* when there is a topographic effect have been removed from the load table headers.

f) Other Changes

For both the NBC 2010 and NBC 2015 design selections, the symbols Hh, Lh, and x have been added to the Height, Length and From crest inputs. The units (ft. or m) now appear only once in the data group title.

For the NBC 2015 selection only, 2-D Ridge will be renamed 2-D Hill, to reflect the change in the design code nomenclature.

4. Pressure Coefficients Cp for Buildings of Any Height

In NBC 2010, pressure coefficients Cp for buildings of any height were found in Commentary I-29 and Figure I-15; in NBC 2015 they are in a new section, 4.1.7.5, and shown in Figure A-4.1.7.5.(2) and (3)  for MWFRS loads and Figure A-4.1.7.5.(4) for C&C. 

Previously, the building surfaces were referred to as “walls”, not they are called “faces”, implying the projected surfaces of roofs are treated as walls.

a) H / D Ratio

Previously, the program was using the ridge height for roof loads and the eave height for walls and gable ends when determining the height-to-depth (H/D) ratio. It now uses the same building height for walls, roof panels, and gable ends on the same face of the structure.  The height used is the ridge height for faces perpendicular to the ridge, and the mean roof height for faces parallel to the ridge. For flat roofs, it is the eave height.

This change is made for both NDS 2010 and NDS 2015 design setting selections.

5. Pressure Coefficients CpCg for Low Buildings

In 2010, pressure coefficients CpCg for low-rise buildings were found in Commentary I-27 and Figure I-7 for MWFRS loads and in Commentary I-28 and Figure I-8 for C&C loads; in NBC 2015 they are in a new section, 4.1.7.6, and shown in Figure 4.1.7.6.-A, for MWFRS loads and Figure 4.1.7.6.-B for C&C loads.

There is no substantive difference in the generation of wind loads using these provisions, but the limitations on low-rise buildings given in Commentary I-26 vs 4.1.7.6.(1). NBC 2010 said that said that the coefficients are most appropriate for buildings with height/width (H/W) ratios less than 0.5, and must be used for H/W less than 1.0. NBC 4.1.7.6.(1) includes only the 1.0 H/W limitation,

a) Height used to Define Low Buildings

The extensive use of “mid-roof height” in NDS 2015 leads us to believe that is what is intended as H in the H/W ratio. Therefore, the program no longer uses the height you select in the Design Settings to determine this, and always uses the mid-roof height.

This change is made for both NDS 2010 and NDS 2015 design setting selections.

b) Width used to Define Low Buildings

For buildings with varying widths on each level, the program previously determined the width of the structure by taking the largest extent in each direction of any of the levels on the structure, then using lowest value of the NS and EW dimensions so determined. Thus, a structure with a large podium base and a narrow tower would use the base as the width of the structure.

To avoid this situation, the program now uses the average dimension of all levels on the structure in each direction, then the lesser of the two directions.

This change is made for both NDS 2010 and NDS 2015 design setting selections.

c) Warning Messages

Warning messages shown when using the low buildings for H/W ratios between 0.5 and 1.0 have been removed. Those for 1.0 and greater have been modified to show NDS 2015 references.

6. Internal Pressure Coefficient Cpi

In NBC 2010, pressure coefficients Cpi were found in Commentaries I-30 and I-31; in NBC 2015 they are in NBC 2015 4.1.7.7. The three categories for were previously called Category 1, Category 2, and Category 3, but now Table 4.1.7.7. has a column called Building Openings, with the associated Cpi values. The word “category” is no longer used.

a) Input

The Site Dialog input in the Internal Pressure data group is renamed to Openings from Category.

The choices that were previously

 

1. Exceptionally sealed

2. Ord. closed openings

3. Large open openings

 

are now

 

Uniform, small, < 0.1% area

Non-uniform, resistant, closed

Large, often open

 

This change is also reflected in the Site Info echo in the output report.

b) Load Generation Details

In the Load Generation Details report, longer descriptions are given, as follows:

 

Uniformly distributed, small, less than 0.1% of total surface area

Non-uniformly distributed; if significant, wind-resistant and closed

Large, likely to be open during storms

 

C:  Other Wind Load Generation

1. Low-rise Wind Loads for Multiple Blocks and Eccentric Ridge Lines (Feature 26) *edited extensively after first written for 10.2

The method of determining external pressure coefficients CpCg for low-rise structures from NBC 2015 4.1.7.6 and Figure 4.1.7.6.-A (or NBC 2010 Commentary Figure I-7) assumes symmetric, rectangular structures.  They are based on boundary layer wind tunnel studies of buildings of that shape, verified against full scale measurements (NBC Commentary I-20).

As relatively few low-rise structures have such a regular shape, Shearwalls now extends this method to buildings with multiple blocks and/or eccentric ridge lines.

a) Intersecting Blocks

When two blocks intersect such that the slope of a portion of a roof can be formed either by either the side panel of one block or the end panel of the other, such as one roof framing into another to form an L-shape, the manner in which the building is modelled does not affect the wind loads generated because end hip panels are treated as side panels using the other load case.

i. Walls

The area of exterior walls beneath a sloped roof are considered to “have” the slope of the roof for the purpose of Case A (transverse) load generation, which depends on roof angle. If there is a hip end in the Case B (longitudinal) direction Case A coefficients are used on the wall beneath the hip end, the same as the rest of the building face formed by the side of the other block.  

ii. Roofs

A hip end panel in the same plane as a side panel on another block has the co-efficient from the same load case as the side panel, so it is equivalent to the situation where the side panel from one block forms the roof on the entire face and the other block joins that block without forming a hip end.

b) Differing End Panels

Previously the program disallowed structures for which the hip ends on opposing ends of a block had different slopes, or there was a hip on one end and a gable on the other. Now these structures are allowed, and the coefficients used on the roof panels and the walls below the panels are based on the angle of each roof panel.

c) Eccentric Ridge Lines

Previously the program disallowed the case of an eccentric ridge line with different slopes on either side of the ridge. Now this case is allowed, and the coefficients used on the side roof panels and the walls below the panels are based on the angle of each roof panel. This applies to each roof on a structure with multiple blocks.

d) End zones

End zones are created at the ends of each roof block.  This conservatively creates higher end zones loads in areas of the building, such as interior corners and the portion of a building face where one block meets another, that should not experience higher wind loads due to end effects. These loads can be manually edited to have the same value as the non-end-zone loads on that face. It is left as a future improvement to the program to eliminate these extra end zones.

e) Height-to-Width Ratio for Building Limitations

The calculation to determine the width for the height-to-width limitations for this method in NBC 4.1.7.6.(1) considers the maximum extent of all walls on the structure rather than the extent of a single block.

f) Screen Warnings

The error messages that appeared after Generate Loads was invoked saying that load generation was not possible due to unequal hips, eccentric ridge lines, or multiple blocks, have been modified to provide warnings and suggestions for these reasons, but to indicate load generation will proceed.

g)  Load Generation Details

In the Load Generation Details output:

i. Header Note

A note in the header section of the Load Generation Details output indicates that the building does not conform to strictly to NBC 2015 Figure 4.1.7.6.-A or NBC 2010 Figure I-7 for the following reasons, included if applicable to the structure – multiple blocks, eccentric ridge lines, hip roof construction, or unequal hip or gable ends.

ii. Load Table

There are now load tables for each block for multiple block structures, where previously only one table was possible.

h) Torsional Analysis Details

If there are multiple blocks of which any two have orthogonal ridge lines, then both Case A and Case B loads can exist in the same direction on different blocks.  In this case, in the Torsional Analysis Details output where it otherwise says Low-rise Case A or Low-rise Case B, it says Low-rise Case: and then Wind Generally North-South or Wind Generally East-West.

For orthogonal ridge lines, where the section for Case A previously had results for only one load direction, there are now results for both directions.

2. Low-rise Torsional Loads

Previously, Shearwalls analyzed low-rise wind loads from NBC 2010 Commentary Figure I-7 (NBC 2015 Figure 4.1.7.6-A) by considering pressures in the E-W and N-S directions independently and ignored the torsional forces in the orthogonal direction.

However, Note (1) to these Figures says that the building must be designed for “all wind directions”, and that Load Case A and Load Case B are the separate cases for which loads “including torsions” must be generated.

Shearwalls now includes loads due to pressures in both directions in the torsional analysis routine simultaneously, so that torsional forces from E-W loads are considered when determining N-S forces, and vice-versa.

Note that it is only Case B that has simultaneous pressures in both directions.

a) Calculations

In the torsional analysis routine, the program now calculates the torsion T in the equation

 Fti = T Ki li / (Jx + Jy)

as Tx  + Ty for both directions, when previously it Tx  was used for one direction and Ty for the other.  Refer to the Torsional Analysis Details output for the definitions of these variables.

b) Torsional Analysis Details Output

In the Torsional Analysis Details file, for load Case B

-       A note has been added to the top saying explaining the simultaneous design, referring to Note 1 in the Figures.

-       The Concentrated Load F, Center of load Cl and Eccentricity etx values are shown in a table at the top for both directions, rather than separately for each direction. F and Cl now show subscripts for direction, e.g. Fx and Cly

-       The equation of torsions has been modified to show both directions rather than one.

3. Case A Side, Case B End

The program now allows you to show in Plan View the low-rise loads for Case A in the longitudinal direction and Case B in the transverse direction, as these are the cases that will ordinarily govern for design.

a) Single vs. Multiple Block

This option is available only for single block structures, because for a particular wind direction, multiple block structures can have Case A at the end some blocks and Case B for others, and similarly for the sides.

b) Show Menu

The option Case A Side, Case B End appears after the Case A and Case B under Wind Load Case in the Show Menu.

c) Plan View Arrows

The large hollow arrow angled to show the general wind direction has been replaced by two orthogonal arrows in the N-S and E-W directions for this choice.

d) Torsional Analysis

Note that these loads are not to be considered to have been generated simultaneously, and the set of loads shown is not used to generate any torsional analysis case.

4. Show Menus (Bug 3240)

The following changes have been made to the Show menus when Wind design is selected.

a) Orientation

For wind loads, Orientation has changed to MWFRS Direction.

b) Wind Direction

When the Other buildings – 4.1.7.5 wind method is selected, Load Direction is changed to Wind Direction.

c) Wind Load Case

i. Activation When Not Relevant

When the Other buildings – 4.1.7.5 wind method is selected, the wind load case this option is now disabled. Previously the selections were available but had no effect. This happened even when seismic loads were showing.

ii. Case A and Case B Nomenclature

For single block structures, Case A or Case B appear in brackets beside the wind direction, according to the ridge direction of the structure.  

5. Load Generation Details Output

In addition to changes for new or modified features described elsewhere, numerous small formatting improvements and insertions of key information have been added to the Load Generation Details output. The following give the more important changes when NBC 2010 is selected; and the corresponding improvements made using NBC 2015 provision reference numbers when that option is selected.

a) Header and Footer

-        The title, Wind Load Generation, has been set to all capitals to make it stand out from the Seismic Load Generation section that appears later.

-        Add spaces to better delineate the start of the seismic load generation after wind load generation.

b) Site Information

-        Add internal gust factor Cgi, as it is entered in the Site information dialog.

-        Add units (m or ft.), to the hill height, length, and above crest topographic values (Change 242)

c) Legend

-        Add reference to 4.1.7.1.(4) and App. C for velocity pressure q.

-        Clarify that importance factor is ULS (ultimate limit states).

-        Correct reference for Ce from 4.1.7.1 to 4.1.7.1.(5).

-        Clarify that reference heights h come from Commentary I-7(c) as well as I-7(a) and I- 7(b).

-        Give the reference to Figures I-7 for the values of low-rise zone Zn and Windward corner WC.

-        For NDS 2015 option, there are now 2 lines for Cp, one for MWFRS loads and one for C&C loads, showing different design code references.

d) Equations

-        Clarify that C&C wind pressure is from 4.1.7.1.(1) and (3), not just (3).

-        Add the missing factor 0.7 to the equation for rough terrain exposure factor Ce.

-        Add the words “Exposure factor” before the expression for Ce.

e) Load Table

-        Add MWFRS and C&C to the header line of the tables, and remove the repetitive first columns showing these labels. (Change 233)

-        For C&C loads, the mean roof height no longer appears above the table, as it is not relevant to the calculations; instead the value of the reference height h used for Cei calculations is shown, as that had not been output anywhere previously (QA Item 12e).

-        In the low-rise C&C table, the column for internal exposure coefficients Cei was showing 1.0 regardless of the actual Cei value.  It now shows the correct Cei value (QA Item 12a).

-        In the low-rise C&C table, the CpCg column was showing the difference between external CpCg and internal Cpi * Cgi. It now shows just external CpCg as Cpi and Cgi are shown elsewhere in the table (QA Item 12d).

-        The Tributary Height column has been removed for C&C loads, as it has no meaning for these loads and showed random values. (QA Item 64)

6. Bug Fixes and Small Changes

a) Windward Low-Rise C&C Loads (QA Items 12b and 12c) 

For windward low-rise C&C loads program was using the pressure and gust co-efficient CpCg for leeward direction, and internal pressure coefficient Cpi for positive pressures when it should have been using negative pressures. The incorrect coefficients were listed in the Load Generation Details output.

This has been corrected, and different windward and leeward coefficients are created.

For out-of-plane sheathing design, the program now determines the worst case of internal positive pressure and leeward loads, and internal negative pressure and windward loads. As it is only rare cases that the windward loads govern, this had little effect on sheathing design. Nail withdrawal design is not affected.

b) Windward C&C Load Magnitudes (Change 237)

Windward C&C loads were being generated with the same magnitude as leeward ones, i.e., with differing interior and end zone magnitudes. They are now being generated with the correct magnitudes.

Windward C&C loads affect only sheathing design (not nailing), and this change has little design effect as end zone leeward (suction) loads almost always govern design. 

c) Low-Rise MWFRS Pressure/Gust Factor CpCg for Topographic Effect

For low-Rise MWFRS loads with a topographic effect, the program was not including the Cg* component from as per NBC 2010 Commentary I-21, which says you are to multiply CpCg by Cg* and divide by Cg.

It was doing this correctly for C&C loads.

Since Cg* for topographic effect is diminished relative to Cg, this was a conservative bug, and has been corrected for the NDS 2010 design code option. NDS 2015 no longer includes this calculation. 

d) End Zones Under Low-rise Hip Roofs, Case B (QA Item 90)

For walls under hip roof ends using the low-rise procedure and a longitudinal wind direction (Case B), end zones were not being created. This has been corrected.

e) End Zones Under Low-rise Hip Roofs, Case A (QA Item 90)

For walls under hip roof ends using the low-rise procedure and a parallel-to-ridge wind direction wind direction (Case B), end zones were not being created. This has been corrected.

f) End Zones Under Low-rise Hip Roofs, Case B (QA Item 91)

For walls under hip roof ends using the low-rise procedure and a perpendicular-to-ridge wind direction (Case A), end zones were created with a 1-meter width rather than 6 meters, according to 4.1.7.6.A Note 6. This has been corrected.

g) Note for Walls Under Hip Ends (QA Item 90)

The note indicating that hip ends are treated as side panels in terms of low-rise coefficients has been modified to indicate that the walls under the hip ends are also use the same load case as the roof, that is, the one for side panels. A reference to 2001 AWC Wood Frame Construction Manual, Table 2.5A has been added to explain this.

h) Saving of Height Option for b (Change 238)

The Design Setting which is now called Height for Wind Classification is now saved to the project file, it hadn’t been previously. 

i) Hip Roof Options in Load Generation Input (QA Item 43g)

The disabled options for hip roof load generation pertain to the USA version of the program and have been removed completely for Canada.

j) Topographic Factor Above / Below Crest in Site Info (Change 245)

When Below crest is selected in the Site Information dialog box, the Site Location in the Site Information of the Design Results output says Downwind of the crest.  When it is below the crest, it should be Upwind, according to Figure 4.1.7.4, and when it is above the crest, it should be Downwind. This change has been made.

k) Load Generation Log File Wind Load Header (Bug 3084)

n the Load Generation portion of the log file for the All-heights wind load generation method, the line of “------“s was printed at the tail end of the Wind Load Generation header instead of on a new line. This has been corrected for the new implementation in the Load Generation Details file.

l) Wind Direction in Loads and Forces Settings (Bug 3240)

In the Loads and Forces settings, the check boxes labelled Southwest, Northeast, Southeast, Northwest have been changed to show Wind from Southwest, Wind from Northeast, etc.

m) Partial Wind Loading Note

An explanatory note has been added to the Torsional Analysis Details output suggesting manual approaches to implementing load cases B, C, and D from NBC 2010 4.1.7.3 and NBC 2015 4.1.7.9. These cases are not generated automatically by Shearwalls, and would have an effect only on rigid diaphragm torsional forces.

n) Delay in Generating Wind Loads with Topographic Factor (Bug 3251)*

For calculation of the loads that include a topographic factor from NBC 4.1.7.4, the   program was performing the calculation of the Ce, Ce* and Cg* factors at a thousand times as many heights on the surface of the building as was intended, causing a 1-3 second delay when generating loads. This has been corrected.

D:  NBC 2015 – Seismic Load Generation

The changes described in this section occur when NBC 2015 is selected as the design code edition in the Design Settings, unless otherwise indicated.

1. Design for Low Seismic Loads

NBC 2010 4.1.8.1.(1) said that the seismic analysis using the Equivalent Static Procedure was not needed for sites with S(0.2) less than 0.12. This provision has been removed, and replaced with a method in 4.1.3.1.(3)-(15) to be used when a set of conditions for low seismic loading in 4.1.8.1.(2) is met. This method tends to create larger seismic loads than the Equivalent Static Procedure; its advantage is simplicity. It is not implemented in Shearwalls.

a) Message Box

Upon design, a message box used to appear when S(0.2) was less than 0.12, asking you if you wished to proceed with seismic load generation. This has been replaced by a message that informs you of the simplified procedure, its limitations, and that it produces higher loads. the program proceeds to design with the Equivalent Static Procedure.

2.   Seismic Data

The following pertains to the Table C-2 of Appendix C of NBC 2010 and Tables C-2 and C-3 of NBC 2015 that give climatic and seismic data for all significant Canadian towns and cities, which are selected via the default settings in Shearwalls. 

a) Peak Ground Acceleration

The program now includes the values peak ground acceleration (PGA) in the software data as the NBC 2015 Equivalent Static Force Procedure now requires them.

b) Sa(5.0)

The program now includes the spectral acceleration Sa(5.0) as it is now needed to calculate the ratio S(5.0) / S (0.2) to determine higher order factor Mv and overturning factor J. ).  It otherwise corresponds to buildings much higher than those designed in Shearwalls.

c) Spectral Acceleration Values

The values of Sa(0.2), Sa(0.5), Sa(1.0), Sa(2.0) have been changed to correspond to those in NBC 2015. Virtually every value has changed, many significantly.

3.   Site Coefficients F(T) and Design Accelerations S(T) 

This section pertains to the calculation of design spectral acceleration S(T) in 4.1.8.4 Site Properties, which is then used in the Equivalent Static Force Procedure in 4.1.8.11.(2). It is calculated by:

 

NBC 2010:  S(T) = Sa(T) * Fv (Sa(T=1.0), Site Class)

NBC 2015:  S(T) = Sa(T) * F(T, PGA, Site Class)  

 

 where

-       site coefficients F(T), Fv and F are determined from NBC tables,

-       period T is calculated by the program or entered by the user,

-       Site Class is entered by the user,

-       PGA and Sa (T) are seismic data from Appendix C stored for each city and entered either directly or by selecting a city.  

a) Input

PGA, Sa(5.0) and five values of F(T) have been added to the Site Dialog input. The fields Fa and Fv were removed. Like Fa and Fv, F(T)’s are only active for Site class F.

b) PGA ref

The calculation of PGAref = PGA * 0.8 if Sa(0.2) / PGA < 2.0 from 4.1.8.4.(4) has been added.

c) Fa and Fv

As per NBC 4.1.8.4.(7), the program now sets the value of Fa to F(0.2). Although no longer needed in the calculation of S(T), it appears in the expression IEFaSa(0.2) that is still used in many places to classify the structure for the application of various rules, particularly for irregularities.  

Fv is no longer needed by the program.

d) Calculation of S(T)

The calculation of S(T) from NBC 2015 4.1.8.4.(9) is S(T) = Sa(T) F(T), whereas for 2010 4.1.8.4.(7) it was S(T) = Sa(T) Fv

NBC 2015 Tables 4.1.8.4.-B to -E for F(T) have been entered into the program. For tables of F(T) for periods on either side of the actual period Ta, the program determines F(T) based on site class and PGAref, interpolating on intermediate values of PGAref.

Linear interpolation is then used to determine the value of F(Ta), and it is also used to determine Sa(Ta). S(Ta) is then determined via F(Ta) Sa(Ta).

For T < 0.2 s, the NBC 2015 now takes the maximum of F(0.2)Sa(0.2) and F(0.5)Sa(0.5), whereas it used to just use F(0.5)Sa(0.5). This has been implemented.

e) Load Generation Details

In the Load Generation Details output, when NBC 2015 is selected as the design option,

i. Site Information

In the Site Information section which shows the user-input data,

-        Sa(5.0) has been added

-        A line showing F(0.2), F(0.5), etc. has been added if these have been input by the user because it is Site Class F

-        Peak ground acceleration PGA has been added.

-        Fa and Fv have been removed

ii. Legend

-        The definition of Fv has been removed

-        The definition of Fa has been changed, and it is indicated that it is now used for the IEFaSa(0.2) limit

-        A definition of site coefficient F(T) has been added

-        Definitions of peak ground accelerations PGA and PGAref have been added.

iii. Equations

-        An equation for S(T) has been added, which also shows dependencies for site coefficients F

-        An equation for PGAref from NBC 4.1.8.4.(4) has been added

iv. Total Design Base Shear Table

-        A column showing F(Ta) has been added to the table

-        S(Ta) replaces S(T) in heading

4. Disallowed Irregularities for 5-6 Storey Wood Frame Construction

A new provision 4.1.8.10.(4) has been added to NBC 2015 for 5- and 6-storey wood-frame buildings. If the IEFaSa(0.2) product is equal to or greater than 0.35, then Type 4 In Plane Discontinuity and Type 5 Out-of-plane offsets irregularities are not allowed for these structures.

This was already detected and reported by the software following an identical provision in the BC Building Code, so the note under the Seismic Irregularities table has been changed to refer to NBC rather than BCBC.

5. Gravity-Induced Lateral Demand Irregularity Type 9

A new seismic irregularity, Gravity-Induced Lateral Demand, Type 9, has been added to Table 4.1.8.6, with the associated provisions 4.1.8.10.(5)-(7). Note A-4.1.8.10.(5) explains that this corresponds to such elements as inclined columns and floor cantilevers, and involve yielding mechanisms like plastic hinges. This outside the scope of the Shearwalls program and no attempt is made to detect this irregularity.    

a) Design Results Output

This irregularity has been included in the Seismic Irregularities of the Design Results output, giving the design code references, a note explaining why it is not applicable, and a description below the table.

6.  Maximum Base Shear V

The maximum lateral force V calculated in NBC 4.1.8.11.(2)(c) has is now derived from the maximum of two equations as opposed to just one.

a) Calculation of Base Shear

For NBC 2010, the equation is

 

2/3 S(0.2) IE W / (RdRo)

 

For NBC 2015 it is the larger of this equation and

 

S(0.5) IE W / (RdRo)

 

b) Load Generation Details

In the Load Generation Details report (formerly part of the Log file), this equation has been added to the Equations section.

For both the NDS 2010 and NDS 2015 options, the program no longer shows the notes indicating that the maximum shear has been used for design, and instead includes three base shear columns V in the Total Design Base Shear table – Vcalc, Vmax, and Vdes, giving the calculated base shear, the maximum base shear, and which of these has been chosen as the design base shear.

7. Period Ta for Single-storey Wood Structures

A new provision for single-storey wood structures, NBC 4.1.8.11.(4)(a), allows for an increase in the period Ta calculated by the empirical formula in 4.1.8.11.(3)(c) by an amount equal to .004L to where L is the shortest distance between shear resisting elements.

4.1.8.11(c) says that Ta computed using other methods but can’t be greater than 1.5 times that from using 4.1.8.11.(4)(a). This compares to a factor of 2.0 using 4.1.8.11.(3)(c).

a) Calculation of L

L is calculated as the shortest distance between any two shearlines whose extents overlap by one inch or more. The extent of the shearline is defined as the distance between the ends of the extreme shear walls on the line, disregarding gaps in between.  No attempt is made to determine whether shear resisting element extents overlap on a wall-by wall basis.

b) Calculation of Ta

For one-storey structures, the equation 0.05 hn3/4 + L is used for the approximate period Ta.

c) Restrictions on Manually Entered Period

Since this provision is “permitted” and not mandatory, the program checks whether the value input in the Site Dialog is greater than the greater of the two restrictions, that is 2.0 Ta using 4.1.8.11.(3) or 1.5 Ta using 4.1.8.11.(4).

d) Load Generation Details Output

In the Load Generation Details report, for one storey structures,

-        the equation for Ta in the Equations section includes .004L where applicable

-        The expression for Tmax shows the maximum of the two equations

-        A definition of L is given in the Legend.

8.   Higher Mode Effects Mv

The program now includes a calculation of higher mode effects Mv from NBC 4.1.8.11.(6), which is used in the calculation of base shear in 4.1.8.11.(2).

In previous editions of the NBC, all Mv = 1 for all values of period T equal to 1.0 or less, so that no building in Shearwalls could have a non-unity Mv. Table 4.1.8.11 of NDS 2015 has non-unity Mv values for T= 1.0 and values of S(0.2)/S(5.0) > 20. Because a new column bas been added with values of 1.0 for T = 0.5, due to linear interpolation, non-unity values exist for these ratios whenever the period is greater than 0.5.

Since a period of twice the one calculated by empirical formula 4.1.8.11.(3)(c) is allowed by 4.1.8.11.(3)(d)(iii), any height above that corresponding to T = 0.25 using the formula could have a significant Mv. Since that height is 8.5 meters, well below the highest allowable structure in Shearwalls the calculation of Mv in the program is now required. In practice, values of Mv greater than 1.0- will come into play primarily for 5- and 6-storey structures that are newly permitted by NBC.

Note too that ratios of S(0.2)/S(5.0) > 20 for which Mv > 1 occur in numerous locations in Canada.

a) Determination of Mv

The values of Mv are taken from the section for Walls, Wall Frames SRFS from Table 4.1.8.11. Within the range of structures allowed in Shearwalls, these values are identical to those for Other systems.

A separate Mv is determined for each orthogonal force direction, using period Ta and the ratio S(0.2)/S(5.0) to index Table 4.1.8.11. 

i. Interpolation

According to Notes 1 and 2 of Table 4.1.8.11, interpolation should be done on Sa(0.2)/Sa(5.0) first, then on Ta, and Note 2 says to interpolate on S(Ta) Mv, not just Mv(Ta).  So, if we define Sr as the ratio of Sa(0.2)/Sa(5.0), for a Ta between 0.5 and 1.0, we

-        use interpolation on Sr to find Mv( Sr, 0.5 ) and Mv( Sr,1.0 ).

-        calculate the values S(0.5) Mv( Sr, 0.5 ), and S( 1.0 ) Mv( Sr, 1.0 ).

-        interpolate between them to find [S Mv ] ( Sr, Ta ).

-        interpolate S between 0.5 and 1.0 to find S( Ta  ),

-        Mv ( Sr, Ta ) = [ S Mv  ] ( Sr, Ta ) / S ( Ta ).

b)  Load Generation Details Output

Mv had always been in the Total Design Base Shear table, showing 1.0. The value is now shown to 3 digits precision.

An expression showing the dependencies of Mv has been added to the Equations section, for both NBC 2010 and NBC 2015

9.   Overturning Reduction Factors J and Jx

Although values of overturning reduction factor Jx less than 1.0 were possible for previous editions of NBC, through interpolating between the value of 1.0 for T=0.5  and the non-unity values for T = 1.0, such structures would largely be 5- and 6-storey buildings not previously permitted by NBC. Furthermore, as per NDS 2015 Commentary J-165, J is intended as a corrective to the overestimation of higher mode effects Mv as regards overturning, and Mv was not in previous versions of Shearwalls.

With the introduction of Mv in this version of the software, the overturning effect factors J and Jx have also been implemented.  

As with Mv, non-unity J values occur only for Ta between 0.5 and 1.0, but unlike Mv, the occur for any value of the ratio S(0.2)/S(5.0).

a) Determination of J for Whole Structure

The values of J are taken from the section for Walls, Wall Frames SRFS from Table 4.1.8.11. Within the range of structures allowed in Shearwalls, these values are identical to those for Other systems.

A separate J is determined for each orthogonal force direction, using period Ta and the ratio S(0.2)/S(5.0) to index the table.   

As per to Notes 1 and 3 below the table, interpolation is done on Sa(0.2)/Sa(5.0)  first, then on Ta.

b) Storey Factor Jx

For each level, and in each direction, a story factor Jx is determined using NBC 4.1.8.11.(8):

 

Jx = 1.0 when hx >= 0.6 hn

                   Jx = J + (1 – J) hx / 0.6 hn when hx < 0.6 hn

hx is the height at the top of level x, and hn is the mean roof height.

c) Hold-down Forces

All hold-down forces on a particular level and direction are multiplied by the factor Jx for that level and direction. This is because hold-down forces in Shearwalls are derived from the formula Mx / L, where Mx is defined as in 4.1.8.11.(8) and L is the wall segment length.  

d) Output

i. Load Generation Details

In the Load Generation Details report:

-        definitions J and Jx have been added to the legend

-        an expression showing the dependencies for J has been added to the Equations section

-        The formula for Jx has been added to the Equations section

-        A column for J has been added to the Total Design Base Shear table

-        Columns for Jx in each direction have been added to the Distribution of Base Shear to Levels

ii. Hold-down Design Table

The value of Jx is shown for each shearline in the Hold-down Design table. A definition appears in the legend beneath the table.

iii. Elevation View

Jx is shown in the Factors section of the legend in Elevation view.

10. Base Shear Increase for User-input Ta for 5- and 6-Storey Buildings

A new provision in NBC, 4.1.8.11.(12), calls for a 20% increase in base shear for 5 and 6 storey structures for periods determined using 4.1.8.11.(3)(d), i.e., “other established methods of mechanics using a structural model”, most commonly Rayleigh analysis.

As an increase in T results in reduced base shear, we assume that whenever you over-ride the period determined using the empirical equation 4.1.8.11.(3)(c) by entering a larger one in the Site Dialog input, 4.1.8.11.(3)(d) is being used and the 20% surcharge is applied.

A decrease in the period is assumed to mean that you are just adjusting the height used in 4.1.8.11.(3)(c), as no advantage is accrued.

a) Calculation

For each orthogonal direction independently, if the period Ta is greater than that calculated by the empirical equation 4.1.8.11.(3)(c), a factor 1.2 is applied to the calculation of base shear V in     

b) Load Generation Details Output

When applied, the equation for V shown in the Equations section of the Load Generation Details Output includes the 1.2 factor. In the unusual case that it is applied in only one orthogonal direction, two equations are shown for V, one for each direction.

11. One-storey Buildings with Large Diaphragm Deflection

A new provision in NBC, 4.1.8.15.(4) for single-storey structures with a wood roof diaphragm and with Rd greater than 1.5, requires magnification of deflections and/or design forces if the diaphragm deflection exceeds ½ the storey drift of the adjoining shear walls. This affects only large structures with a large sufficient distance between shearlines to create large diaphragm deflection.

As Shearwalls does not currently calculate diaphragm deflections, a warning is displayed for structures of a size that is susceptible to this condition.

a) Detection of Condition

The check for this condition is made before loads are generated. For single-storey structures only, if the Rd value is greater than 1.5, the program will determine, in both directions, the shortest distance between shear-resisting elements, using the same algorithm as given above. For imperial units, if the distance is greater than 100 feet, and for metric, 30 metres, the building is considered susceptible. 

b) Warning Message

If the condition is detected, a Yes, No, Cancel message box asks you whether you want to change Rd to 1.5. The actions taken are

Yes – Change Rd to 1.5 and generate seismic loads.

No – Continue to use the existing Rd and generate seismic loads

Cancel – Don’t generate seismic loads  

E:  Other Seismic Load Generation

1. Period Restriction on Irregular Structures

The program previously assumed that there would be no periods greater than 0.5, so the program did not check for the condition Ta > 0.5 or disallow irregularities of Type 1-6 as per 4.1.8.7.(1)(c).

However, a period of twice the one calculated by empirical formula 4.1.8.11.(3)(c) is allowed by 4.1.8.11.(3)(d)(iii), so any height above that corresponding to T = 0.25 using the formula, or 8.5 meters, could have a Ta > 0.5. In practice, 5- and 6-storey structures now supported by Shearwalls often do have periods in this range when calculated using methods such as the Rayleigh quotient.

The following applies if Irregularities Type 1, 2 ,3, 4, 5, or 6 exist and if IEFaSa(0.2) >= 0.35:

a) Irregularity Table Failure Column

if T >= 0.5 in the direction(s) for which the irregularity exists, the shearlines and direction(s)s that have these irregularities appear in the “Fails for” column.

b) Table Warning

If T >= 0.5 in at least one direction for which the irregularity exists, a red warning message appears above the table indicating that design has failed due to the irregularity.  The message saying that the program does not check for T > 0.5 has been removed.

c) Screen Warning

If T >= 0.5 in at least one direction for which the irregularity exists, a screen warning message appears indicating that design results are not valid.

d) Notes

Notes appear below the table indexed to the irregularities saying that seismic design is not allowed using the Equivalent Static Procedure when T > 0.5, and it is if it is less than or equal to 0.5. 

e) Design Summary

If T >= 0.5 in at least one direction for which the irregularity exists, it triggers the note in the Design Summary saying that at least one irregularity violates design code provisions.

2. Vertical Stiffness Irregularity Type 1

The program now detects the Type 1 Irregularity – Vertical Stiffness, which occurs when the lateral stiffness of a storey’s SFRS less than 70% of that of an adjacent storey, or 80% of the average of the three storeys above and below.   

a) Detection

In each direction, for both rigid and flexible diaphragms, the program determines the stiffness of all wall segments on the level using the same procedure by which it determines the stiffness for Irregularity 4 – In Plane Discontinuity. It will then sum all those stiffness values.

If the stiffness on any level is less than 70% of the stiffness on the level above or below, than the irregularity exists.

For those levels with 3 storeys either above or below (levels 1 and 4 in a 4- storey structure; 1, 2, 4, and 5 in a 5-storey structure, and any level in a 6-storey structure), the program determines average of the 3 storeys either above or below the level, and if stiffness on the level under consideration is less than 80% of that value, the irregularity exists.

b) Irregular for..

For the adjacent level stiffness, the Irregular for… column in the Seismic Irregularity Table shows the level with the reduced stiffness followed by the stiffer level e.g. 3,4.

For the average of 3 levels, it shows the reduced stiffness followed by the stiffer levels as e.g.  4,1-3

The Direction shows E-W, N-S, Both, or None. 

c) Fails for…

If there is a weight irregularity and T>=0.5 for at least one direction, and IaFaSa(0.2) >= 0.35, the storeys appear in the Fails for column

d) Notes

The note saying it is irregularity detection is not required for because it is not a post-disaster building has been removed.

The existing notes about the relevance of IEFaSa(0.2) >=  0.35 or < 0.5 and T < 0.5 are included when irregular. If T >= 0.5 a new note says that Equivalent Static Procedure is not allowed.

e) Design Not Valid Warnings,

If irregular, T >= 0.5 in at least one direction, and IEFaSa(0.2) >=  0.35, a screen warning message appears indicating that design results are not valid, a red warning message appears above the Irregularities table, and the Design Summary says that at least one irregularity violates design code provisions.

f) Description

The description of the irregularity below the table gives the 70% rule and 80% rules and explains the table columns.

3. Weight (mass) Irregularity Type 2

The program now detects the Type 2 Irregularity – Weight (mass), which occurs when a level is 1.5 x more massive than an adjacent non-roof level, or a roof is 1.5 x as massive as its adjacent level.

a) Detection

Table 4.1.8.6 refers to a storey, which is defined in NBC Division A, 1.4.1.2 as the distance from the top of one floor to the top of the floor above it. The roof is considered a separate storey.

On the other hand, the levels that are defined for apportioning seismic load are defined from the middle of the wall on one level to the middle of the walls on the level above. A roof is considered part of the upper level.

For irregularity detection, the program collects all the masses that are tagged as being on level 2, for example, but come from the lower portion of level 3, and includes them as storey 3 loads. It excludes masses from the roof and gable ends, which are on the uppermost level, from the upper storey, and creates a separate storey for these. 

For multi-block structures, for mass from roofs on blocks with fewer levels than the highest block, the roof is added to the mass of the level above the highest storey on the block. For example, if Block 1 has 2 storeys and block 2 has 4 storeys, a roof on block 1 will is part of level 3.

Flat roofs and ceilings are part of the uppermost storey of the block they are on, not the roof level. 

Snow masses are not included among the weights for this purpose.

b) Irregular for…

The Irregular for… column in the Seismic Irregularity table shows the heavier storey followed by the light storey, e.g., 3,4. The direction is always Both. If a heavy roof is one of the storeys, the word “Roof” is used.

c) Fails for…

If there is a weight irregularity and T>=0.5 for at least one direction, and IaFaSa(0.2) >= 0.35, the storeys appear in the Fails for column

d) Notes

The note saying it is irregularity detection is not required for Ta less than 0.5 has been removed. The existing notes about the relevance of IEFaSa(0.2) >=  0.35 or < 0.5 and T < 0.5 are included when irregular. If T >= 0.5 a new note says that Equivalent Static Procedure is not allowed.

e) Design Not Valid Warnings,

If irregular, T >= 0.5 in at least one direction, and IEFaSa(0.2) >=  0.35, a screen warning message appears indicating that design results are not valid, a red warning message appears above the Irregularities table, and the Design Summary says that at least one irregularity violates design code provisions.

f) Description

The description of the irregularity below the table gives the 150% rule, defines a storey, and explains the table columns.

4. Re-evaluation of Discontinuity Irregularities Types 3, 4, and 5

Research into the intention of NBC 2015 4.1.8.15.(5) (NDS 2010 4.1.8.15.(4)) has inspired a re-evaluation of the approach taken by Shearwalls to this provision. This clause states that elements supporting a discontinuous wall are to be designed for forces equal to the lateral capacity of the SFRS components they support rather than calculated forces. The intention is to protect the gravity force resisting system from forces due to lateral loading, for example a lintel above an opening that supports vertical element such as a column carrying a hold-down force at the end of a discontinuous shear wall on the level above the opening. In such a case, the column, lintel, hold-down, and other connections are to be designed using the capacity of the discontinuous wall.

a)  Relevant Irregularities

Shearwalls previously applied this irregularity for Irregularities Type 3 - Vertical geometric, Type 4 - In-Plane Discontinuity (offset), Type 4 - In-Plane Discontinuity (stiffness) and Type 5 - Out-of-plane Offsets,  The rationale for Types 3 and 5 was that a discontinuity must exist somewhere for these irregularities to exist, and for Type 4 - In-Plane discontinuity (stiffness) that the NBC 2010 Commentary J-205 (NBC 2015 J-208) referred to Type 4 irregularities in general.

Shearwalls now applies this provision only for Type 4 - In-Plane Discontinuity (offset) and Type 5 - Out-of-plane Offsets. Shearwalls detects an in-plane offset whenever wall ends do not line up on adjacent floors, which is exactly the type of discontinuity this provision is meant to address. Type 5 discontinuities occur when there is no wall below a wall on the level above, which also creates a discontinuity at wall ends.

Stiffness irregularities are irrelevant to the intent of this item so Type 4 - In-Plane discontinuity (stiffness) is no longer included. And although Type 3 - Vertical geometric implies a discontinuity must exist somewhere, it is a general, statistical check which cannot be used to identify where action must be taken. If Type 3 exists, then a Type 4 or Type 5 must also exist somewhere, so the situation will be handled without the need to include Type 3 in the solution.  

b) Weak Storey

The program previously reported a failure due to these irregularities if the capacity of the entire SRFS on the floor below the one with the discontinuity was less than the capacity of one with the discontinuity. This was based on a misconception and has been removed from the program.

The program no longer includes discontinuous shearlines in the Fails for column of the Seismic Irregularities table for this reason, nor does it issue screen warnings for this failure or place a red failure message above the table. The notes below the table have also been modified. 

c) Strengthening of Hold-downs

When an irregularity was detected, the program automatically used shear wall capacity as the design hold-down force on all shear walls on both the level with the irregularity and the level below. This is an overly conservative approach, and this automatic procedure has been removed from the program until we can develop an algorithm to identify and strengthen only those hold-downs that require it.

d) Strengthening of Drag Struts

When an irregularity was detected, the program automatically used shear wall capacity as the design drag strut force on all shear walls on the level below. Instead, the program should add the additional force due to capacity-based design on the floor above as a surcharge to the diaphragm shear force used to calculate drag struts on the floor below. The automatic strengthening of drag struts has been removed until we can develop such a procedure.

e) Design Iterations

The need to identify irregularities to apply the automatic strengthening of hold-downs and drag struts necessitated an additional iteration of force distribution and design in Shearwalls. This has been removed, which should lead to somewhat faster design results.

f) Warnings and Notes

All screen warnings have been modified to indicate that you must manually strengthen hold-downs and drag struts at specific locations, rather than informing you that the program has done so. The notes below the Irregularities table have been similarly modified. 

g) Design Settings

The asterisk beside the Design Settings Drag strut / Hold-down forces based on … Applied loads has been removed, along with the note saying that shear wall capacity is used for discontinuities as per 4.1.8.15.(4).

5.   Deflection Analysis for Detection of In-Plane (stiffness) Irregularity Type 4

Due to the non-linearity in the nail deformation term of the equation for deflection for shear wall deflection from 11.7.1.2, shear wall stiffness decreases as applied force increases. As a result, Shearwalls previously identified a Type 4 In-Plane Discontinuity (stiffness) in NBC 4.1.8.6 based on a lower-storey shear resisting element having less stiffness than an upper storey one even when walls on the two storeys had identical construction.

As structural analysis for most materials assumes a linear stiffness relation v = K δ, where v are forces, δ deflection, and K a constant stiffness matrix, we do not believe it was the intention of NBC 4.1.8.6 to consider identically constructed storeys as having differing stiffness. The program therefore uses the 3-term linearization of the deflection equation introduced in this version (see G: 1 below), to determine the deflections for Type 1 - Vertical Stiffness and Type 4 – In-plane Discontinuity (stiffness) irregularity detection. It does so even when the non-linear 4-term equation is used for deflection analysis for force distribution and storey drift.

a)  Design Iterations

If you have selected the 4-term deflection equation option in the design settings (the default), an additional design iteration will be inserted before the existing iterations, using the 3-term deflection equation, for the purpose of detecting Type 1 and Type 4 (stiffness) irregularities. Another iteration is then performed for final design of the shear walls using the non-linear 4 term equation, during which all other irregularities are detected.

b) Tolerance

Testing revealed that small, unwanted differences in stiffness still occurred for identical shear walls on adjacent levels. A comparison tolerance of 1% was added which eliminated these occurrences.

c) Description of Irregularity

The description of the Type 4 – In-plane Discontinuity (stiffness) irregularity beneath the Irregularity table has been modified to reflect this procedure.

6. Irregularity Table Changes

a) Irregularity Names

Irregularity names in the Irregularity table have been modified to conform more closely to the nomenclature in Table 4.1.8.6.  In screen messages they have been expanded to show a less abbreviated name, and in the descriptions below the Irregularities table, the full name as it appears in Table 4.1.8.6 is shown.

b) Format of References

The format of references to NBC provisions in the table has been modified to conform to NBC protocol, e.g., 7-1c is now 7(1)(c).  Compound references change from e.g. 10-1,2b to 10(1),(2)(b).

Also changed comma between two Sentence references to a semi-colon, to distinguish from comma between Clauses.

c) Detected by Column

The Detected by column has been removed as all relevant irregularities are now detected by the program. 

d) Type 6 Irregularity Message (QA Item 52)

The screen message indicating an Irregularity 8 was detected referred to an IESaFa(0.2) value of 2.0 when it should have been 0.2. This has been corrected.

e) Weak Storey Irregularity 6 Notes (QA Item 78n)

The notes pertaining to Weak Storey Irregularity Type 6 have been reorganized and improved, giving references to NBC 4.1.8.10.(1) and 4.1.8.10.(2)(b).

f) Post Disaster Note (QA Item 78o)

A reference to NBC 4.1.8.10.(2)(a) has been added to the note about post-disaster buildings.

g) NBC References for IEFaSa (QA Item 78l)

The notes that include IEFaSa(0.2) >= 0.35  or < 0.35 N now include references to NBC 4.1.8.7.(1)(a), 4.1.8.6.(3) and Commentary J-122.

h) Commentary Reference for Type 7 Irregularity (QA Item 78d)

NDS 2010 Commentary J-156 (NBC 2015 J-150) has been added for Type 7 Irregularities. 

i) Commentary Reference for Type 7 Irregularity (QA Item 78e)

NDS 2010 Commentary J-207 was a mistake; it has been changed to J-205.  

j) Commentary Reference for Type 7 Irregularity (QA Item 78h)

NDS 2010 Commentary J-127 was a mistake; it has been changed to J-128. 

k) Commentary Reference for Type 7 Irregularity (QA Item 78i)

NDS 2010 Commentary J-177-9 was a mistake; it has been changed to J-171-3. 

7.   Disallowed Irregularities for 5- and 6- Storey Structures

A new provision 4.1.8.10.(4) has been added to the NBC disallowing Irregularities Type 4 In Plane Discontinuity and Type 5 Out-of-plane offsets for 5- and 6-storey structures when IEFaSa(0.2) >= 0.35.

This had already been implemented in Shearwalls based on an identical provision in the British Columbia Building Code (BCBC). The note at the bottom of the Irregularities table and the screen message that appears for this condition have been updated to refer to the NBC and remove references to British Columbia.

8.   Load Generation Details Output

In addition to the changes to the Load Generation Details output described elsewhere due to new or changed features, numerous small formatting improvements and insertions of key information have been made. The following gives the more important changes:

i. Header

-        The title, Seismic Load Generation, has been set to all capitals to make it stand out from the Wind Load Generation section that appears earlier.

ii. Site Information

-        Removed the words Regular Structure. This was not intended to be in the Canadian version and appeared even when the structure is irregular

-        The spectral accelerations Sa(0.2), Sa(0.50), etc., have been placed on one line for compactness, rather than each one occupying its own line.

-        Similarly, for the NBC 2010 option the Fa and Fv values have been placed on one line, and they are now shown only for site class F (when they are input by the user).

-        The importance factor Ie is now shown only when input by user for hazardous category.

iii. Legend

-        Reorganize table to put long descriptions all on left side so that the table fits within a printed page.

-        The definition for T now says it is in seconds (s).

-        Remove SRFS from the definition for Rd

-        The definition of hn now says that it is the top level, not just “level n

-        For subscripts x, “level analyzed” is used instead of “level x

-        For subscripts i, the word “levels in sum” is used instead of “level i

iv. Equations

-        The units, (N, m) have been added to the title of the Equations section indicating the assumptions used when calculating the equations. These units are always metric regardless of what is used to display the output values. 

-        Removed the unit reference for the height hn used for T, as units have been added to the table heading

-        Design code reference numbers have been added for all the equations

-        An equation for Vmax has been added (NBC 4.1.8.11.(2)(c))

-        For the NBC 2010 option, an expression showing the dependencies of S(Ta) has been added

-        An expression showing the dependencies for RdRo has been added (NBC 4.1.8.9)

-        An expression for Ta max has been added (NBC 4.1.8.11.(3)(d)(iii))

-        The maximum Ft value is now indicated (0.25 V)

v. Total Design Base Shear Table

-        The table has been renamed Total Design Base Shear, from Calculation of the total design base shear:

-        The data are now displayed in a tabular format with headings, rather than as repeated symbols, equal signs, and values.

-        Units have been added to the title of the table showing the system used for the data displayed, which unlike the units for the Equations table can be metric or imperial and show kN rather than N.

-        Fa and Fv values are now shown beneath the table, as they are ordinarily calculated by the program and not user input. Fv appears only for the NBC 2010 option

-        The importance factor Ie is now shown beneath the table, as it contributes to the calculation and is not ordinarily input by the user.

-        Removed information about distribution of loads to the levels from note about manually entered seismic loads and forces.

vi. Distribution of Base Shear to Levels Table

-        Distribution of total design base shear to Levels has been changed to Distribution of Base Shear to Levels

-        In the table heading, the words Height and Weight have been changed to the symbols hi and Wi, which are defined in the legend

-        The information about top level Ft has been moved from a note at the top of the table to be a separate line in the table

-        Numbers are now right-justified so decimal places line up, and trailing zeros are no longer truncated.

-        Added note about distribution of manually entered seismic loads and forces.

9. Bug Fixes and Small Improvements

a) Importance Factor Input for Hazardous Category (Bug 2718)

The Importance factor in the Site Information dialog for Hazardous importance category, which is a value you can override due to Commentary J-110, would revert to the default value of 1.3 when the Site Parameters Dialog was re-opened. This value was then used for design unless it is changed.

This has been corrected and the input of importance factor now persists.

b) Seismic Irregularity Type 6 Failure Criterion (QA Item 65)

The program was basing the failure criterion of Seismic Irregularity Type 6 – Weak Storey on a value of IEFaSa(0.2) > 0.12 when it should have been 0.20 as per 4.1.8.10.(1). 

c) Seismic Irregularity Type 7 for Post-Disaster Buildings (QA Item 69)

Seismic Irregularity Type 7 was not amongst the irregularities that provoked a failure due to NBC 4.1.8.10.(2).(a) for post-disaster structures, but it should be. This has been corrected.

d) Show Menus (Bug 3240)

i. Wind Load Cases

When seismic loads are selected, the Wind Load Case options are now disabled. Previously the selections were available but had no effect.

ii. Force / SFRS Direction

The Force Direction item has been renamed SFRS Direction, for consistency with the change to MWFRS for wind. SFRS stands for Seismic Force Resistance System

iii. Load / Force Direction

The Load Direction input has been renamed Force Direction, as the shearline and hold-down forces are the only things that could potentially change when an opposing direction is selected. Note that it is very rare that seismic forces differ in opposing directions and this set of options usually has no effect.

 

F:  Load and Force Distribution

1. Sign Convention for Torsional Analysis

In the Torsional Analysis Details file, distances such as center of load, center of mass, shearline location and eccentricity have been based on a fixed co-ordinate system with its origin in the southwest corner of the structure. S->N distances are positive, and N->S are negative.

 The forces F, however, are based on the direction of applied force; for N->S applied force, all values in the N->S direction are positive; for S->N applied force, they are negative.

Some users find this confusing and wish to see all values relative to the same fixed co-ordinate system. Other users, however, wish to see positive shearline forces when they are in the direction of the applied force, and this corresponds to the way they are presented in the Plan view drawing. 

Accordingly, we now offer a choice in the Options settings of showing forces based on a fixed co-ordinate system, or relative to the applied force.

2. Torsional Analysis Details Output

In the Torsional Analysis Details output report (previously part of the Log file)

a) Accidental Eccentricity References

In the Torsional Analysis Details, the references to accidental eccentricities have changed:

-        For flexible diaphragm seismic, it was J 178 from a previous design code edition, and is now J-172 for J NBC 2010 and J-178 for NBC 2015.

-        For rigid diaphragm seismic, it mistakenly showed a wind reference, and now shows NBC 4.1.8.11.(11) for 2015 and NBC 4.1.8.11.(10) for 2010.

-        For rigid diaphragm all heights wind, it said just 37 for 2010, now it is I-37. For low rise wind for 2015 it refers to NBC 4.1.7.9.(1)(a) and A-4.1.7.9.(1) Case A      

b) Headers

i. Repeated Header Line (Change 236)

When wind loads only were on the structure, the torsional analysis section of the log file output had a repeated header line. The new Torsional Analysis Details file shows only one header in this case.

ii. Wind Load Subheading Under Flexible Seismic (Change 240)

A sub-heading for wind loads mistakenly appeared under flexible seismic design. It has been removed.

c) Flexible Seismic Explanation (QA Item 3a)

It has been made clear that the explanation of the Fti calculation is an example in one direction only.

d) USA ASD Reference (Change 239)

A note referred to ASD load factors, which is a USA term. This has been corrected.

e) Concentrated Load Terminology (QA Item 45a)

The term Concentrated Load F has been changed to Total Load F, as the load is not concentrated at a location. 

3. Bug Fixes and Small Improvements

a) Nonsensical Hold-down Forces under Monoslope Gable End (Bug 3217)

When a wall was underneath a gable end from a monoslope roof, the hold-down forces calculated were nonsensically large. This has been corrected.

a) Shearwalls have Equal Rigidity Setting

The Design setting under Shearwall rigidity per unit length…  for Shearwalls have equal rigidity has been removed from the program, as it does not correspond to any physical situation. It is a vestige of the original, less sophisticated implementation of torsional force distribution and is no longer needed. 

a) Force Distribution due to Unsorted Openings (Bug 2099) 

Occasionally, after a complex set of user interface operations, wall openings could become unsorted internally and skew the distribution of forces on the shearline, also affecting shearwall design. This has been corrected.

b) Nonsensical Output of Diaphragm Force (Bug 3185)

Occasionally, one of the diaphragm force Fpx values in the Seismic Information table would show a nonsensically high number. This was a rarely occurring bug due to unusual configurations of program memory, and has been corrected.

c) Show Menu Items for Center of Load and Center of Rigidity (Change 251)

The show menu items for center of load and center of rigidity were always disabled in Loads and Forces view, only becoming active in Load Generation view. This has been corrected and they are active in both views.

d) Center of Loads for No-load Cases (Change 251)

When there are no loads in a direction, such as for low-rise wind load Case A, the program showed the Center of Load in the direction without loads at the zero location, making it difficult to notice. In this case, it has now been moved to where the Center of Rigidity is located.

e) Overlapping Center of Load and Rigidity Symbols (Change 251)*

When the center of loads and center of rigidity are in the same place or close to it, the symbols CL and CR now longer overlap.

 

G:  Deflection Analysis and Shear Wall Design

1. 3-term Linearized Deflection Equation (Feature 211)

Shearwalls now offers the choice of using the 4-term deflection equation in CSA O86 11.7.1.2 and a 3-term linearization of this equation. The linearization follows a formulation in the AWC Special Design Provisions for Wind and Seismic, equation 4.2-1, for shear wall deflection analysis in the United States.

a) Background

The 3-term equation is a linearization of the 4-term equation, arrived at by combining the shear and nail slip equations in the 4-term equation using an “apparent” shear stiffness Ga.  The linearization is achieved by setting the non-linear occurrences of shear force v to the shear capacity of the shear wall to render them constant. It is therefore identical to the 4-term equation when the shear wall is at capacity, conservative when below capacity, and non-conservative for shear walls that are overstressed for design anyway.

The 3-term equation can be preferable because the process of equalizing deflections on the shear wall segments by adjusting the forces apportioned to each segment sometimes does not converge due to the non-linearity of the 4-term equation, whereas the 3-term equation always converges to a solution. Furthermore, using the 4-term equation, Irregularity Type 4 – In Plane Discontinuity (stiffness) from NBC 4.1.8.6 is detected for adjacent storeys even if they are constructed of identical materials (see E: 5 above). 

b) Design Setting

A Design Setting called Linearize deflection equation has been added to allow you to choose between these two methods It is recommended to choose Never, but switch to Always if using the deflection-based force distribution method and one or more of the shearlines do not show the same deflections on each loaded shear wall segment in the line.

Note that the choices of Always and Never have been chosen to allow the future implementation of a hybrid design for which we allow the program to automatically change from 4-term to 3-term on individual shearlines if non-convergence is detected, especially using flexible distribution; however, for Version 10, the switch must be made manually and for all shearlines in the structure.

Mixing the two methods in the same design could adversely influence force distribution based on relative stiffness. This is true within a line, and possibly distribution to shearlines if the rigid distribution method is used, so further research is needed before a hybrid approach is attempted.

c) Deflection Calculation

The following terms in the two-term equation

 

  

 

are replaced by

 

i. Ga Calculation

The calculation of Ga for wind design uses the formula

 

 

 

0.75 is the serviceability (SLS) importance factor for wind design, and 1.4 is the load combination factor f