The known bugs page was formerly hosted here and has since been moved to the MASS software documentation site:

Known Bugs in MASS

For questions about specific bugs, or to report a bug, contact mass@canadamasonrycentre.com

It’s real, and it’s spectacular! We are very excited to announce this new release, available immediately and for free to all current, active license holders.

This post originally appeared on the new MASS documentation website. Click here to view the original release notice.

If you are currently using Version 3, you can upgrade to Version 4.0 at any time (download and installation instructions are available at the end of this post).

What’s New in Version 4.0?

A 3 minute preview can be seen below with the longer 11 minute outline available here.

Those videos not enough for you? Click here for the full change log to see what else is new and exciting about the release of Version 4.0.

New Seismic Design Options

MASS has a new seismic design tab for shear walls that allows users to choose between the newer simplified approach added to the 2015 NBCC or the good old equivalent static force procedure. Ductility is now a parameter that can be specified and used for design.

Dealing with a Post-Disaster importance category? You can now specify “moderately ductile” or “ductile” in the seismic tab and let MASS handle the rest – including drift and the ductility verification!

Multi-Storey Shear Walls

Ever found yourself working through a building’s design and asked yourself “What if I could do all this work, but in fewer steps?“. Don’t let your dreams be dreams!

MASS Version 4 adds a new multi-storey module that coordinates the design of several elements to give you a result that matches unit properties and vertically aligns your reinforcement. Worried about your self-weight loads not being up to date as the design changes? Read up on our detailed design strategy and cry tears of joy because we’ve got you covered!

How to Upgrade

Anyone with a current, activated MASS license can upgrade to MASS Version 4.0 at no extra charge. New releases are included as part of keeping an active license, in addition to other benefits such as comprehensive technical support and course notifications.

To begin downloading MASS Version 4.0, click here to visit the upgrades page

Questions about the download, extraction, or installation process? Click here to view the two and a half minute video walk through that will show you how you can install MASS on your computer. There is also a full installation guide available here.

Still have Questions?

Please do not hesitate to contact myself or anyone else in CMDC with any questions or concerns regarding this upgrade.

Canada Masonry Design Centre (CMDC) is the authorized technical service provider for the MASS Software.

Version 4,0 was made possible by the support of our masonry contractor members through CMDC as well as the joint venture partnership through NMDP with CCMPA Canadian Concrete Masonry Producer’s Association – see ccmpa.ca for more information).

When software bugs are found, notifications are posted in the Known Bugs page, on the MASS welcome screen, as well as here on the CMDC website software blog in an effort to be transparent and keep all MASS users informed. This issue was found within our own office as a result of some unrelated testing on Multi-storey walls in MASS Version 4.0. As a result, the fix will be incorporated into the next software release and in the meantime, must be checked for manually by engineers who may encounter this issue.

This post outlines the conditions required to trigger this error, where the design results could have been affected, the details of the bug itself, and how to check to see if this bug is present in any MASS project.

Jump straight to:

• • Bug Summary
  • Background Information
  • What types of designs might be affected?
  • How to check if a design is affected
  • Example
  • Our Response

Bug Summary

For shear wall element designs where the web grouting pattern has not been set to “fully grouted” and the flange is fully grouted as a result of vertical reinforcement placed in each cell, the maximum allowable axial load limit is overestimated. The actual envelope curve where axial load is considered to determine moment resistance is plotted correctly and not affected by this bug. As this upper portion of the diagram tends to also correspond to lower factored bending moments, designs with any significant lateral loading would also be unlikely to be affected by this particular item of concern.

The horizontal line represents the maximum axial load, P_r, and in designs affected by the bug, that line’s location is calculated by MASS to be higher than what it should be.

Since this is only triggered for fully grouted walls with the partial grouted selection, there may be other reasons why a bar is being placed in every cell beyond needing the moment resistance. For more information regarding why MASS may be placing so much steel, click here to open this related article (opens in a new tab).

Background Information

The MASS Software has a dedicated design routine for determining Pr,max. The maximum allowable is specified by CSA S304-14: 10.4.1 is 80% of the axial load corresponding to the assemblage in full compression (where ß₁c = l_w).

This upper limit is calculated using a dedicated process which uses a particular formula based on whether the wall is hollow, fully grouted, or somewhere in between. This is done individually for the shear wall web and each flange (or boundary element in the upcoming Version 4.0 release) where the total upper limit is equal to the sum of each of the components added up.

The actual values used in MASS can be found by scrolling down the Detailed Moment Results tab, shown below:

Excerpt from the Results tab showing Pr,max components

The 1039.6 kN value seen in MASS has been incorrectly calculated using the f’_{m,hollow, flange} = 10 PMa instead of the correct f’_m,eff,flange = 7.5 MPa.

Once P_r,max has been calculated, it is can be seen on the P-M diagram (also referred to as the interaction diagram) near the top where a horizontal line is plotted. Values capped by P_r,max as well as those which extend further upward are both shown and can be selected by the user to see more exact values of the individual points.

Pro Tip: When a point is selected, the arrow keys can be used to jump to adjacent points along the envelope curve.

The actual values used along the interaction diagram curve are correctly plotted and are unaffected by this bug. This issue is specifically the height at which the upper limit on axial load has been capped.

What types of designs might be affected?

In order to have a design result that was declared by MASS to be successful when it should not have been, there are two conditions that would have to occur:

Condition 1: The cross section and input selections would need to trigger the bug in the P_r,max calculation.

This means that shear wall flanges with the “partially grouted” selection applied with bars placed in each cell as a result of other user input values are the only types of designs that can have the incorrect P_r,max value calculated. If any one of these conditions is not met, the correct maximum axial load is calculated and even for affected cross sections where the bug is present, the plotted P-M Diagram envelope is still correct, with the exception of the height at which it is capped. Click here to jump to a full description of how to verify this condition

Condition 2: The loading needs to result in an axial factored load that exceeds what would have been the correct P_r,max value.

Load combinations with relatively low factored moments coupled with high axial loads may lie between P_r,max shown in MASS and the correct value. Click here to jump to the full description of how this can be checked in any MASS project file.

Each of these conditions is elaborated upon in the subsequent sections below. If unsure whether a previous design performed in MASS has been affected, MASS technical support is available to manually check the detailed results and confirm whether or not this bug is present in any project file.

How to tell if a design has been affected

Often times, this bug can be seen at a glance by viewing the P-M Diagram for any design. If the horizontal line drawn at P_r,max does not appear to be roughly 80% between the origin and the location where the envelope meets the vertical axis, this project file may be affected. This check is broken down into two conditions, both of which must be satisfied for a design’s results to have been impacted by this bug.

Any use of the software results for design, as well as checks, calculations, and verification described in this section and elsewhere is done at the sole discretion of the user using their own professional judgment. If you have any questions and are not 100% confident in your understanding of the material, please contact MASS support for further assistance.

Manually checking P_r,max (Condition 1)

Confirming whether this bug is present in any MASS project file is a fairly simple procedure. The most thorough approach is to manually calculate the flange contribution to P_r,max seen in the Detailed Moment Results (see example further below for demonstration), however, this can also be done by viewing the P-M Diagram drawing and locating the point of pure compression along the outer envelope curve.

Note: For shear wall designs with flanges, this will correspond to a neutral axis location of the total wall length (including flange thicknesses) divided by 0.8. Also known as the highest point with a corresponding moment resistance of zero.

Visual Inspection Method

In many cases, this issue can be identified by simply eyeballing the general height of the P_r,max limit and comparing it to where roughly 80% or 4/5ths of the height should be capped for the design. The figure below shows an example P-M diagram on the left where the bug is present and from visual inspection alone is clearly not capped at the correct height. The corresponding diagram for the same cross section is shown on the right with the flange grouting pattern changed from “Partially grouted” to “Fully grouted” and as a result, the bug is no longer present and it can be seen that the maximum axial load is capped at the correct height.

Another option is to click on the very top point on the diagram which lies on the P_f axis and multiple that by 0.80. This is less exact than verifying the calculation using the correct inputs (described further below) but can still get a result accurate to within 20kN which will be acceptable for the majority of cases.

Extreme cases like this are relatively easy to spot with a quick glance of the P-M Diagram. The example used in this article is outlined further below, here, and was purposely done using very long flanges and low masonry unit strength to highlight this issue. It is possible that this difference is less pronounced and is less obvious.

That being said, just because the bug is present in a project file does not necessarily mean that there are any issues with the design results.

Checking Load Combination Locations on the P-M Diagram (Condition 2)

If there is an issue with the incorrect P_r,max value being used, simply check the P-M Diagram and click on the load combinations with the highest factored axial load, P_f.

Any load combination can be selected in MASS by clicking on the point to reveal the exact factored moment, moment resistance, factored axial load, and neutral axis location.

The factored axial load, or P_f , can be compared to the correct P_r,max value to ensure that even if a shear wall’s envelope has not been capped at the correct location, it is still within the acceptable range.

Quick Calculation Check by Hand

If loads are in the upper region of the diagram and the P_r,max line appears roughly in the correct location, it is a good idea to quickly check the numbers by hand. This situation is covered in the section below. In the Detailed Moment Results section of the software where the P_r,max equations and formulas are found, the results can be quickly verified make sure they are correct.

Note: the f’_m value used in the P_r,max calculation can be found in the Detailed Shear Wall Properties section of the results window, along with all of the other inputs.

If any value of P_f exceeds P_r,max that was calculated manually in the subsection above, MASS has incorrectly passed these designs when they should have failed. If unsure, please do not hesitate to contact MASS support.

Example Design

To illustrate this example, a test case was chosen with many aspects that amplify this error. Consider a basic shear wall design where the web is 2210 mm long (2190 mm plus a 10 mm mortar joint on each end) with a height of 3400 mm and a total height of 24,000 mm. Disable masonry unit selections until only the 15 cm, 15 MPa unit are remaining.

Note: for typical design work, it is generally recommended to first leave several options selected before seeing an initial result and narrowing down the design from there. For purposes of demonstrating this bug, this example involves an already known cross section which is the reason for the other options being disabled.

Once the web design has been specified, click on the flange input tab and add a 2000 mm long flange to each end of the wall. Using the default offset value, specify the distance from the critical section to the top of the web as the total height value used earlier: 24,000 mm. This is a commonly missed step which will ensure that a portion of each flange is included in the cross section used for design. If this value were left at the default 0 mm, only the portions of the flanges directly adjacent to the web (140 mm in this case) would actually be used.

Once the flanges have been specified, click on the loads button and enter basically anything. In this example, a 1kN lateral dead load is applied simply to allow the MASS software to advance to the moment design stage. Since this bug relates to the envelope curve, exact loading is irrelevant as it only impacts where the load combination points will be drawn on the diagram.

Upon running a moment design, there should be successful results displayed with a fairly large spacing of vertical bars. Click on the PM Diagram drawing and note the location of the Pr,max line where axial load is capped.

So far in this example, the bug has not yet presented itself. Proceed by disabling all of the spacings except for 200mm, placing a vertical bar in every cell. It is these designs where you may notice a dramatic shift in Pr,max.

Breaking down the calculation of Pr,max, it is made up of three components: the left flange, the web, and the right flange. Selecting the Detailed Moment Results tab, these values can be seen in the results screen, as well as below:

Manually checking these flange values based on the inputs seen, the following is the expected (and correct) value:

Referring back to the bug summary, this issue presents itself when a shear wall web becomes fully grouted due to a vertical bar placed in every cell at 200mm spacing. The f’_m value used for the flanges is incorrect, referencing the hollow value of 10Mpa instead of the grouted 7.5MPa from Table 4.

As mentioned at the start of this subsection, the example chosen for this demonstration exercise for a few reasons. The first is that a small, low strength masonry unit was chosen because in percentage terms, there is a very large jump (33%) going from the grouted to hollow strength which diminished for higher block strengths. Shear walls with long effective flanges in relation to the web size also experience a higher discrepancy in P_r,max because the flange terms make up a higher portion of the total maximum load.

This bug ended up being very simple to find in the code and fix. It has been added to the known bugs page found here and will no longer be present in Versions 4.0 and newer.

Our Response

Bugs of this nature are taken very seriously. It was discovered in-house but not until very late in the Version 4.0 development process. As a result, the bug was investigated and a fix was added to Version 4.0. It has also been posted on our Known Bugs page where it links to this article.

If there is any question regarding the integrity of the results for a specific MASS project file, please feel free to contact CMDC directly. As the authorized MASS technical service provider, CMDC is available to help designers understand the specifics of identifying this issue, as well as any other masonry related technical questions. Click here for more information on technical assistance offered by CMDC.

As always, feel free to contact us if you have any questions at all. CMDC is the authorized service provider for the MASS software which is a joint effort of between CCMPA and CMDC.

In any windows architecture application, there is a limit of 10,000 GDI objects. Internally, there a number of these crated with every design and population of each results screen. Unfortunately, there are a number of these that are not properly “cleaned up” so using the same MASS window for an extended period of time will trigger this crash.

The release of MASS Version 4.0 has mitigated the problem but there are always residual GDI objects between every design. Our recommendation in dealing with this issue is to regularly save your work.

A full video demonstrating this and how to check your GDI object status is shown below:

This issue is most likely to occur when designing a shearline or multi-storey shear wall module as these assemblage options coordinate the creation of several shear wall elements internally, triggering the creation of additional GDI objects.

If you have any questions, please do not hesitate to contact MASS support.

As always, feel free to contact us if you have any questions at all. CMDC is the authorized service provider for the MASS software which is a joint effort of between CCMPA and CMDC.

Have you ever saved a MASS file you were working on, only to open it up a few days later to see some values that are orders of magnitude larger? If so, this post explains where the bug comes from, how to tell if a design has been affected, that you are not going crazy, and what has been done to correct it.

Bug Summary

Under some French language localization settings in the Windows operating system, project files created using MASS are reopened with values that are 10 or 100 times larger than the original numbers that had been saved. This is a result of how displayed values are saved internally, with decimals replaced by commas. MASS re-opens a saved project and does not recognize these substituted commas, resulting in values that are orders of magnitudes larger.

If the extra zero’s are manually removed from the input fields, the values will then be correctly saved with the decimal in its intended location. This bug also only applies to values that have been auto-populated by the software (meaning that you did not type them in manually). For example, if a beam length of “3000” mm is entered into MASS, the “3000” will be correctly read and re-opened.

Background Information

Numbers are not written the same way in French as they are in English. One key difference that is relevant to this issue is the French Canadian use of commas in place of decimals. For more information, click here for a summary and explanation from syllabus.com (external link will open in a new tab).

In making Windows more accessible for other languages, it seems that the numbers that show up in input fields such as side cover or yield strength are being automatically translated within MASS. With values “translated” by Windows based on number formatting preferences, the actual values within a saved .masonry14 project file are stored with the commas, shown below using the minimum clearances of a masonry beam for reference. Values that should be saved as 75.00 and 55.00 are “translated” to “75,00″ and 55,00″.

Note that this view is not accessible by the end user (or even myself) and had to be requested from the programmer who was able to see this in the debugger console within Visual Studio.

How to tell if a design is affected

The most obvious sign when encountering this issue is the loss any options of placing rebar within the masonry. After all, it is difficult to fit any steel inside of a unit if the specified side cover is 5.5 m instead of the default 55 mm! Note in the design below how MASS recognizes that it is impossible to place vertical bars so the options have been disabled as a result:

In the case of designing masonry beams, where reinforcement is required, opening these files should raise mental red flags when the yield strength jumps upward to 4000 MPa (!), making it very difficult to yield (with a yield strain that is also 10x larger than the default 0.002). This would be after dismissing all of the pop-ups that the software will prompt on the basis of the specified side cover no longer being satisfied.

What to do if you encounter this error

Before opening MASS, the settings in Windows can be checked to see which punctuation is used to represent the decimal point. To view the instructions on how to open the Customize Format window, click on the heading below to expand the instructions.

Once in the Customize Format window, check the selection to the right of the top drop-down menu item corresponding to Decimal symbol.The screenshot below shows the value that will be correctly recognized by MASS:

If this is anything other than a period, or “.”, MASS will not recognize the decimal in the right place and values can be shifted by orders of magnitude.

If this selection needs to be changed, make the appropriate change and click Apply or OK. The software will need to be restarted to reflect these changes and fortunately, a full machine reboot is not required.

Our Response

Bugs of this nature are taken very seriously. It was discovered in-house but not until very late in the Version 4.0 development process. As a result, the bug was investigated and a fix was added to the eventual release of Version 4.0. It has also been posted on our Known Bugs page where it links to this article.

If there is any question regarding the integrity of the results for a specific MASS project file, please feel free to contact CMDC directly. As the authorized MASS technical service provider, CMDC is available to help designers understand the specifics of identifying this issue, as well as any other masonry related technical questions. Click here for more information on technical assistance offered by CMDC.

As always, feel free to contact us if you have any questions at all. CMDC is the authorized service provider for the MASS software which is a joint effort of between CCMPA and CMDC.

Update for MASS Version 4.0 Release: Online Activation functionality has been restored.

Update (May 16th, 4:00PM EDT): The MASS website access has been restored.

Update (May 15th, 3:15PM EDT): Access to the MASS license service provider’s server has been restored and all activation support is back online. The software website is still not back online.

Earlier this week, CMDC received a notification from our hosting provider that the server used to host our software license web service has been decommissioned and everything migrated to a new server. CMDC was given no advanced warning that this migration would occur. While all information has been properly backed up and transferred intact, there are some additional network connections that must be completed before the MASS website and activation web service is back online.

As a result, the entire MASS website, where all purchases, license renewals, activations, and supplementary support material is offline while this gets sorted out. All links to the web service through our database software are also offline until IT support is able to restore the connection. As a result, all activations and activation support is unavailable until further notice and CMDC will not be able to assist. All existing copies of MASS that have already been activated will continue to function normally. In the almost nine years of developing and supporting the MASS software, this is our first significant period of downtime and we sincerely apologize for the inconvenience.

This post will be updated with any new information as it becomes available.

We appreciate your patience as we get our services back up and running. CMDC is making every effort to get things back up and running as quickly as possible. If you have any further questions, please feel free to call or email our office using the contact information at the bottom of this page.

Starting in 2010, Masonry Analysis, Structural Systems (MASS) has been available as a design tool to engineers across Canada. From day one, our mission has been to provide an effective design resource that saves significant time in the engineering design process without compromising the reliability and integrity of your design calculations. We have received a lot of feedback and always make a sincere effort to keep development costs low by only spending on areas that directly improve MASS.

As of May 15th, 2018, the price of all software renewals and purchases can be seen in the table below:

Compared to prices offered starting in 2013, this is equivalent to only a 1.9% annualized increase.

Full pricing can be found on the MASS website. With these new pricing options, there are a number of other items to keep in mind.

License revenue goes straight to improving MASS

Just to list a few examples, a new in-plane lateral load distribution module, Shearline, was created for Version 2.0 to save time on simple, single storey elevations that generally are not allocated much engineering design time. The most recent major update came in Version 3.0 where the entire scope of MASS was shifted to using the updated editions of CSA Standards for designers working in areas where the 2015 National Building Code of Canada has already been adopted. Between these major releases, minor updates have been made and released to add smaller items like fire resistance ratings, more reliable printing, and an improved launch screen. Throughout the entire process, bugs have been diagnosed, tested, and patched within each minor update to ensure that you can be confident when using MASS. The most recent example of this can be seen in Version 2.2.1 which was released after Version 3.0 which you can read more about here.

Currently, work is being done to expand the scope of MASS to include Chapter 16 seismic design requirements added in the 2014 edition of the CSA S304. This will include shear wall deflections, ductility seismic force reduction factors, ductility verification, and plastic hinge requirements. In addition to the seismic work, a new multi-storey shear wall module is under development to save time for many multi-storey structures.

Licensing revenue goes directly to improving MASS and improving it on a continuing basis.

MASS is well supported and maintained

If you have ever had any issues getting MASS running or have had technical questions about the software’s calculations and overall design approach, you have contacted MASS support. Unlike many software packages that operate using a ticketing system and involve waiting periods and escalations, anyone with a MASS license has immediate, direct access to engineering support through the Canada Masonry Design Centre. We take pride in offering excellent customer support that is knowledgeable and available for when you need it.

MASS Licenses include more than just access to the MASS Software

While the biggest part of the decision to renew MASS is based on getting access to the software, once you have a valid license, other benefits are included at no extra cost. While some programs like to nickel and dime for add-ons and features, every MASS user has access to the complete version with no fine print. When updates are released and the software is improved, you don’t have to pay an upgrade fee. Simply maintaining and renewing your MASS license entitles you to the most up to date version that is available.

MASS license holders also get notified first when a new course or seminar has been made available. The most recent iteration of the CMDC’s Engineered Masonry Design Course was announced and filled within 48 hours by MASS users who had the advantage of being the first to know about it.

Discounts are available for everyone

Everyone likes getting a deal and just because individual renewals go for $220 per person doesn’t mean that’s what you have to pay! There are many types of discounts available that you should not hesitate to take advantage of:

Early-bird Renewal Discount

Chances are, you’ve been linked here from one of our email notifications and if that is the case, you will also see that you can save 15% if you don’t put off your renewal to when your next masonry project comes along. This is available to everyone with a MASS license that needs renewing so act quickly to take advantage.

Multi-User Discount

Have more than one engineer working in your office? We have special office packages for groups of 5, 10, or more engineers that make it cheaper and more cost effective compared to purchasing individual licenses. Click here to see all of the available packages along with pricing. Note that these cannot be spread across multiple locations, which leads us to…

Discounts for Companies spread over multiple locations

If you fit this category and have at least four offices with at least one small office package, you have already been proactively contacted with a special discount offer. These are offered to try and help make up for the fact that the larger offices packages cannot be divided between engineers working from different locations.

Creating software is expensive. Period.

Everything in the software creation process takes a lot of time, energy, and money. From specifications and documentation to programming and quality assurance testing, engineering software cannot be done without significant investment both initially and on an ongoing basis. This is all before factoring in support, website maintenance, license management, and distribution.

You may have also noticed that promotion and advertising hasn’t been mentioned. The MASS software is a tool that is growing in popularity thanks to reputation and word-of-mouth alone! None of the revenue from license sales is used for anything that doesn’t go straight back in to the software you are using today.

Putting the “Not” in “Not-for-Profit”

The MASS software represents a joint venture between masonry contractors (through the not-for profit contractor association: CMDC) and masonry block producers (through the not-for-profit industry association: CCMPA). Together, the masonry industry covers over 75% of software related costs, leaving less than 25% which comes from licensing purchase and renewal fees. There is a good reason why there isn’t another masonry design software package for Canadian designers offered by a private company.

Still have questions?

Feel free to reach out to MASS support with any comments, suggestions, or other feedback regarding this change. While we understand that for many designers, masonry is a component that only comes up on projects here and there. We work very hard to make sure MASS is a product that is cost effective and pays for itself after even just one job. MASS licenses are deliberately priced and subsidized in such as way that it can be accessible to any designer in Canada using masonry in their projects.

If you have any questions, please do not hesitate to call or email the Canada Masonry Design Centre. We are here to help!

The MASS software is a product of a joint partnership between CMDC and CCMPA. CMDC is the authorized provider for MASS Technical Support.

For full details, please visit the course page, hosted on the CMDC learning platform, LearnMasonry.ca

In-class Session Schedule

Friday, April 13th

12:00pm to 6:30pm (lunch and dinner provided)

Saturday April 14th

8:30am to 5:00pm (breakfast and lunch provided)

Friday, April 27th

12:00pm to 6:30pm (lunch and dinner provided)

Saturday April 28th

8:30am to 5:00pm (breakfast and lunch provided)

Topics covered

Weekend 1

• Overview of Masonry Construction, Design and Standards
• Introduction to Masonry Materials and Assemblages
• Masonry Beams:
  • Ultimate Limit States Shear and Flexure
  • Serviceability Limit States
  • Detailing
  • Design Examples
• Masonry Shear Walls:
  • Ultimate Limit States Shear and Flexure
  • Serviceability Limit States
  • Detailing
  • Design Examples

Weekend 2

• Out-of-Plane Masonry Walls:
  • Ultimate Limit States Shear and Flexure
  • Interaction Diagram
  • Deflection, Second Order Effects, and Slenderness
  • Serviceability Limit States
  • Detailing
  • Design Examples
• Single Storey Buildings:
  • Load Calculation
  • Load Distribution around Openings and Movement Joints
  • Design Examples:
    • Individual Structural Elements
    • Full Structure Example

Online – Supplemental eLearning

In addition to the in-class component a number of lessons will be made available through our online learning platform. These additional topics are included in your fee and can be taken at anytime during the course. These added lessons will provide designers with a deeper and more nuanced understanding of masonry design and will cover topics such as:

• MASS Design Software:
  • Design of Masonry Beams
  • Design of Out-of-Plane Walls
  • Design of Masonry Shear Walls
  • Shear Wall Load Distribution with Openings and Movement Joints
• General Overview of Changes from 2004 to 2014 CSA Masonry Materials, Construction and Design Standards
• Masonry Materials:
  • Specialty Mortars, Clay Brick, Connectors and Stone Products
  • Case Studies and Diagnostics of Masonry Veneers
• Masonry Beams:
  • Design of Brick Beams, Deep Beams and Prestressed Beams
  • Modified Compression Field Theory and Shear Design of Masonry Beams using the 2014 Standard
  • Support of Masonry and Bearing Design, Using Movement Joints for Structural Applications and Arching of Masonry over Openings
• Masonry Shear Walls:
  • Unreinforced Masonry, Floor Connections and Intersecting Walls
  • Multi-Storey Shear Walls and Introduction to Seismic Design
• Masonry Out-of-Plane Walls:
  • Unreinforced Masonry
  • Intersecting Walls and Stack Pattern Masonry
  • Design Assumptions: Smeared versus Discrete Partially-Grouted Masonry

Full details can be found on the course website on CMDC’s online learning platform: LearnMasonry.ca

Masonry Analysis Structural Systems is a versatile tool that can be used to accelerate many different aspects of masonry design. While most design scenarios easily fall within the scope of the software, there are occasionally cases where extra work must be done in order to get useful results from MASS. Pilasters are one such case where their behaviour is similar in many ways out-of-plane walls. In order for the wall module to be useful, the pilaster design must be adapted to fit within the constraints of the user interface.

The method in this post outlined below outlines how the pilaster length can be increased to the length used for wall designs in MASS. The remaining cross section properties can be input into MASS and then all of the loads applied must be proportionally adjusted to factor in the length increase. For example, if a pilaster must be lengthened by factor of 2.5 times its original length, the loads applied must also be increased by that same factor, effectively designing a larger section for a higher load in a way such that the results obtained using MASS are useful in determining the design of the pilaster assemblage. To jump ahead to the final summary at the end of this post, click here.

Disclaimer: By using MASS to assist in the design of a pilaster, it is up to you, the engineer, to ensure that all of the differences between pilaster behaviour and that of a regular masonry wall are properly accounted for within MASS. If there is any doubt of having a complete and comprehensive understanding of how to model these differences, it is best to perform these calculations by hand.

Additionally, while the MASS software is a trusted tool in the engineering community across Canada, all of the liability regarding the results and designs is placed on the end user. If there is any uncertainty as to whether the software is being properly applied, please consult MASS support, the included help documentation, or the end user license agreement. The contents of this article are offered as a resource to be used only if the user is aware that they are no longer working within the scope of the software and do so at their own risk. That being said, the Canada Masonry Design Centre is available to answer any questions about the content of this post.

Getting Started

In order to take into account the differences between a pilaster design and a regular out-of-plane wall design using MASS, there are multiple aspects that must be considered and accounted for regarding:

1. 1. How the section is modeled (click to jump to section modelling)
   2. How the loads are applied (click to jump to load application)

This post outlines a process which helps the engineer adapt the scope of the MASS software to the design of pilasters subjected to a combination of axial loads and one-way, out-of-plane bending.

Modeling a “Pilaster” unit using MASS

In order for MASS to be useful as a design tool when dealing with pilasters, it is important to first understand the similarities to an out-of-plane wall constructed using conventional stretcher masonry units. The relevant, shared aspects include face shells with a grouted center region with up to two layers of vertical reinforcement in the middle. While the software can easily design the wall shown on the left but not on the right (below), useful results can be obtained by identifying the common characteristics and applying them within the scope of the MASS wall module.

The biggest difference and reason why pilasters cannot be modeled within MASS is that the software performs wall designs exclusively on a per metre basis. While a pilaster is an isolated element within a wall system, it must be adapted to a one metre design length to fit within the wall module. Effectively, the software can only design modules that are exactly 1m in length so the only way to obtain equivalent results is to extrapolate the pilaster length and satisfy this constraint. Displayed below is a diagram of a pilaster superimposed over its corresponding modeled assemblage using MASS:

In order to create a wall design within MASS that will be useful in the design of a pilaster element:

1. The wall must be fully grouted.
2. The masonry unit geometry must be adjusted to match that of the pilaster unit.
3. The reinforcement placement and positioning must be specified to reflect where it would be placed within a pilaster unit

Understanding these three aspects will help ensure that a wall can be created that properly represents the pilaster used for the design.

Fully Grouting the Wall

Since the entirety of a pilaster cross section is grouted, its design in MASS must also be restricted to walls that are fully grouted. This can be changed using the drop down menu along the right side of the MASS input window, shown below:

If this is left using the default selection of partially grouted, any designs that do not place a bar in every cell will have a hollow component of all compression-related calculations.

Changing the Masonry Unit Dimensions

By making use of the Masonry Unit Database, it is possible to create a custom “pilaster” unit which can be used to take into account the different unit size and face shell thickness. The Masonry Unit Database can be found along the top toolbar between the “Bearing Design” button and the “Critical Load Envelope” drop down menu, shown below:

Using this database, a masonry unit with an increased nominal thickness and corresponding face shell thickness can be created and used for design. In this example, a 390mm thick pilaster unit is created (nominal thickness of 400mm)

Once the unit has been created, it will appear in the list of suppliers and unit lines under the “Masonry unit” heading in the MASS input window.

Placement and Positioning of Reinforcement

In order to design a wall of a finite length using a MASS wall module that designs walls on a per m basis, all of the properties need to be scaled proportionally to take the different section sizes into account. For example, if designing a 0.4m long pilaster with four 20M bars arranged in a box formation, there is a total of 600mm² of steel within each layer of reinforcement (1200mm² total between all four bars). If designing the equivalent 1m section using MASS, this is equivalent to 1500mm² of steel per layer (600mm² x 1.0 m/0.4 m) and a total of 3000mm² of vertical reinforcement in the entire metre long wall.

Evaluating Bar Sizes Placed by MASS

In the case of a 0.4m long pilaster being converted to a 1m long wall section, this is fairly intuitive for a wall design with bars placed at every cell (spaced at 200mm) since this length represents two cells of a regularly constructed wall. In a case like this where the ratio of pilaster bars to bars in the MASS design equals the ratio of pilaster length to MASS wall length (always 1m), the bar size placed by MASS will match the bars used in the final pilaster design. For example, a wall designed by MASS using two 20M bars placed in every cell will contain five bars per layer within the 1m design. This will correspond to the 0.4m long pilaster design with 2 20M bars placed per layer. When the pilaster length or number of bars per reinforcement layer is changed, the math does not work out as cleanly and an added step of looking at total areas of steel is introduced.

Changing where the steel is placed

By default for designs with one bar per cell, vertical bars are placed in the middle of the wall. As soon as 2 bars are placed in each cell, they are positioned such that the cover distance between the outer edge of the bar and the outside face of the wall equals the “side cover” value in the “Minimum Clearances” section of the input window. By default, the side cover value is 55mm but this can be increased to move the reinforcement further from the face of the wall. The “Bar separation” value (by default, equal to 25mm) is checked against after the steel is placed based on the specified side cover. If the bars are too close together, such that the distance between the inside faces of each bar is less than the specified bar separation, the design will be unsuccessful.

If the symmetric option is disabled above the vertical steel section of the input window, rather than place both bars according to side cover, the first bar is placed based on side cover with the second then positioned using the bar separation input field. MASS will then check to ensure that the specified side cover is also satisfies between the second bar and the other side of the wall. Note that MASS will automatically place the steel closer to the tension face of the wall where it is most beneficial as long as the wall is subjected to loading that results in single curvature deflection for all load cases.

Fully grouting the wall, making changes to the masonry unit, and adjusting the steel positioning is the closest a MASS wall design can come to resembling that of a pilaster.

Applying Loads to a Pilaster Modeled in MASS

Once the cross section of a pilaster has been modeled within MASS, loading is the only remaining consideration needed before the software can produce helpful design results. Without making any changes to the way loads would be applied to a conventional wall design, the results created by the software are completely invalid (and likely massively under designed for the loads it will be resisting)! Starting with a quick primer on how MASS loads out-of-plane walls, this article will outline how a load can be changed to factor in the changes made to accommodate pilaster design.

Refresher on MASS Wall Loads

It is a common misconception that lateral, distributed loads are applied to wall modules in the form of pressures, rather than line loads. This mistake is often made without consequence because MASS designs walls on a per m basis so when a pressure applied in kPa or kN/m² is divided by a one metre length, the result is a line load with the same magnitude as the initial pressure. For example, an unfactored wind pressure of 1.2kPa is applied in MASS as a line load of 1.2kN/m (per m of wall).

If the wall length were not exactly one metre, there would be a difference in magnitude between the applied wind pressure and the equivalent line load applied to the wall in MASS. For example, if looking at a 0.4m long pilaster, the same 1.2 kPa unfactored wind pressure would result in a line load of only 0.48 kN/m because the pilaster is resisting a much smaller tributary area of applied wind pressure.

If the pilaster were still resisting all of the wind load applied to a one metre length then this magnitude would be the same, just like in the regular wall example, shown above the pilaster example.

When determining the loading on a pilaster section, it is likely that there is a much larger tributary area of load transferred from the walls on either side. This often results in large lateral line loads that the pilaster must be designed to resist. Consider an example where pilasters are spaced 3.2m apart along a wall with lateral and axial loads transferred to the pilaster section through the walls spanning between them. With each pilaster having a tributary width of 3.2m, the equivalent line load for a 1.2kPa unfactored wind pressure would be 3.84 kN/m applied along the height of the pilaster.

Even after accounting for tributary area, there is further adjustment needed in order for MASS to be useful for pilaster design.

Converting your Pilaster Loads for MASS

Recall the pilaster section as it is represented in MASS described earlier in this article. The unit thickness, face shell thickness, grouted area, and reinforcement positioning have been adjusted in order to model the section using MASS with the only remaining difference being the cross section length:

The length of the “wall” being designed is unable to be changed from 1m so all applied loads must be scaled up to take the additional cross section into account. Since the design in MASS is wider than the actual pilaster by factor of MASS design length to pilaster length, the loads must also be scaled by the same factor. This can be done using the expression below:

By multiplying each applied load by the ratio of MASS wall design length to the actual pilaster length, the loads are adequately scaled to ensure that the factored loading and resistances are adjusted equally. Consider the example below with a lateral, uniformly distributed load of 3.84kN/m and an axial load of 40kN applied from the roof level:

Since the section designed in MASS is 2.5 times the length of the actual pilaster being designed (1.0m/0.4m factor), the loads applied to the assemblage in MASS must also be scaled up by that same factor. This relationship holds true for all load types beyond line loads and axial loads.

Self-weight

While it is in many cases conservative to let the software include self-weight automatically, it is recommended to manually calculate and apply the magnitude of the self-weight force resting upon the critical section of the pilaster. The option to include self-weight can be disabled by un-checking the box at the bottom of the loads application window, shown below:

When applying the self-weight manually, be sure to apply it as a dead, axial load at the top of the wall. Ensure that in addition to taking into account the total area of masonry supported above the critical section, also make sure to scale this load up using the formula discussed in the previous section. While the MASS calculated value will be correct based on the modeled 1m long section, it does not include any other masonry not modeled within MASS and also makes some conservative assumptions that might be the topic of a future article. The help files can always be consulted for an explanation on how self-weight is calculated.

Design Example

Looking at the elevation with 4m tall, 0.4m long pilasters spaced at 3.2m apart (referenced throughout this post), the results when calculated by hand can be compared to those of the MASS software to verify this approach. When the user has made the appropriate adjustments, the results produced by MASS can be valid for design purposes. The MASS file used to compare with hand calculations can be downloaded by clicking here. For simplicity, both the 40kN axial load and the 3.84kN/m line loads were applied as dead type loads so that there would be only one load combination, 1.4D. The exact pilaster unit created earlier was used for this exercise, having a 50mm thick face shell and the steel was placed such that layer 1 would be placed at d=290mm and layer 2 placed at d=100mm (achieved using a specified side over of 90.25mm). A summary can be seen below:

Note that nearly all of the values calculated by hand are directly proportional to their counterparts calculated using MASS. The only exceptions were measurements perpendicular to the length of the wall such as eccentricities, neutral axis locations, and deflections. While forces and moments all scaled proportionally, stress values such as v_m were the same between hand and software calculations because they are independent of length.

If there are questions about the processes or approaches used to get any of these numbers please do not hesitate to contact CMDC.

Limitations of using MASS to help with pilaster design

While the process outlined in this article can serve as a useful guide for assisting with the design of a wall containing pilasters, there are some limitations which must also be acknowledged and accepted.

Composite action with the walls on either side is not considered

In particular to cases where the flush side of the wall is also the compression face, the building can be designed such that there is composite action where the vertical reinforcement within the pilaster is coupling in tension with the compression side of the walls on either side.

There is no way to model this within MASS so any pilasters designed with the assistance of this guide will depend solely on the capacity of the pilaster element itself. If composite action is required, it is best to perform this design by hand.

Any vertical bars in compression are ignored

As specified by the CSA Standards, reinforcement in compression cannot be included when evaluating the capacity of any masonry element without being adequately tied. There is no way to tie the steel in compression within a masonry wall constructed using conventional stretcher units so it is absent from all wall designs performed by the MASS software.

Since there is no way to convey to the software that the reinforcement is tied within the wall module, there is no way to consider steel in compression.

No more than two layers of tensile reinforcement can be placed

MASS only has the ability to place up to two bars per cell and as a result there is no way to take additional layers of reinforcement within a pilaster into account. Even when there are only two layers of reinforcement in tension, there is no way to place varying areas of steel within each layer.

For example, if a pilaster were designed with reinforcement arranged in a three by three box formation, there is no way for MASS to place the area of three bars in the outermost layer and the area of two bars in the second layer. If a design requires more than two layers of tension reinforcement or a higher area of steel in the outermost layer, it is best to perform this design by hand.

…and one more thing to consider

As outlined in this post, there is considerable effort required to design a pilaster using MASS. While there are situations which warrant the use of pilasters, it may be worth considering the use of a conventional, rectangular wall constructed using a larger or stronger masonry unit. There is always the chance that it may be more economic to use a higher strength unit and resist the same loads without the need for pilaster units.

Summary

In general terms, this process can be summarized by saying that in order to model a pilaster using the wall module within MASS, the pilaster cross section can be scaled up to have a length of one metre. The loads must then be scaled upward by an equal amount to compensate for the increase in effective cross section. More specifically, the steps to accomplish this are outlines below:

The pilaster can be modeled with a longer cross section

Since the wall module in MASS only designs walls on a per metre basis, the pilaster must be modeled as having an increased length with all other properties specified accordingly.Click here to view more information on creating a pilaster section in MASS. 

Fully grout the wall

Specifying that the wall be fully grouted in MASS ensures that no hollow masonry properties are applied within the design. Placing bars spaced every cell with the partially grouted selection also accomplished this. Click here to jump back to the grout section.

Modify the masonry unit

Using the Masonry Unit Database, the geometry of the unit can be adjusted to increase the overall thickness of the masonry unit as well as the thickness of each face shell. A step by step guide on how to do this can be found by clicking here and expanding the database instructions.

Position the reinforcement

By default, MASS only places one bar in the middle of each cell. The selections can be expanded to place up to 2 bars per cell and where they are places within the unit can be adjusted by modifying the values in the minimum clearances section of the input window. Click here to jump to the steel positioning section.

All applied loads must be scaled proportionally to reflect the increase in length

Since the pilaster has been modeled as a larger section, all loads must be applied in such a way as to account for this change. Click here to read the full section on load application. 

Manually scale each load

Before any loads are applied within MASS, they must be scaled by the engineer to take the larger cross section into account. This is done by multiplying the magnitude of each load by the ratio of the length used by MASS to the length of the actual pilaster before applying them onto the wall in MASS. Click here for detailed instructions and an example to demonstrate how this can be done.

Manually calculate self-weight

While MASS can include self-weight automatically, there are limitations to how this is performed and which areas are taken into account. In particular to additional areas of masonry supported by the pilaster, it is best to manually calculate the self-weight before scaling the magnitude and applying to the wall within MASS. For more information, click here.

If you have any questions, please do not hesitate to call or email the Canada Masonry Design Centre.

The MASS software is a product of a joint partnership between CMDC and CCMPA. CMDC is the authorized provider for MASS Technical Support.