Everything new in Version 4.1 summed up in one convenient place


National Masonry Design Programs, NMDP, is proud to announce the official release of MASS Version 4.1, which addresses some important software bugs, as well as accepts serial numbers from the newly redesigned MASS website. Everyone renewing on the new website will need to replace their installation with MASS Version 4.1.

This new version is available to all current license holders at no extra charge and can be downloaded for free using the link below:

Click here to visit the Downloads page

The significant changes are itemized and explained below. If there are questions regarding any of these changes, or the philosophy behind them, please feel free to contact technical support!

Jump ahead by expanding the contents section here.

Licensing and Activation

New Serial Numbers Supported with Extendable expiration Dates

New serial numbers allow for an activated license to be extended. Note that the software will automatically check with the license server when it believes it has expired before locking the user out of the software. When the account holder pays the subscription fee, the user will automatically be able to continue using MASS for another year.

New License Transfer Option

License can now be removed from a machine, freeing it up to be used on another computer. This is subject to the MASS license transfer policy.

Formerly, this process could only be facilitated through contacting technical support and submitting additional documentation.

Technical Changes

Lambda Values for Beam Density and Shear

While the existing implementation for MASS Versions 3.0 and 4.0 is most correct to the strict S304 clause, MASS support has decided to change the implementation to better reflect realistic design scenarios.

A type C masonry unit must have a density between 1700 kN/m3 and 1800 kN/m3 to qualify. If designing using one of these units, most engineers would use the upper bound from within this range for design calculations such as self-weight, factored moment and shear in order to air on the side of conservatism.

These types of masonry units that would qualify under the Type C designation, having a density between 1700 kg/m3 and 1800 kg/m3, it in all likelihood does not have a density of exactly 1800 kg/m3. As a result should use a lower lambda value for shear calculations, taking this realistic scenario into account.

An entire post is dedicated to the decision of changing how lambda is applied, available here.

Nonloadbearing out-of-plane walls now show additional text when horizontal steel may be required

In cases where the seismic hazard index is greater than or equal to 0.75, wall designs now display additional text if horizontal steel is required to satisfy minimum seismic steel requirements.

Horizontal steel is only placed when designing shear walls so there is no way for the out-of-plane module to evaluate these criteria. For most designs where the wall is loadbearing, minimum areas of horizontal steel are placed as part of design and possibly also required to increase in-plane shear resistance. Nonloadbearing walls are seldom designed in the in-plane direction so this test was added to prevent the scenario where a user might not be warned, even though the placement of horizontal steel is not within the scope of the out-of-plane wall module.

The case where this was brought to the attention of MASS support came from an engineer who wanted to be sure they had a good understanding of what the software does and does not do for their designs, coming across this scenario. It is prudent for any practitioner to take this approach and ask for assistance when there is any uncertainty at all. MASS technical support is available and staffed by qualified, knowledgeable engineers who can easily clear up any ambiguity concerning processes and checks carried out by the software.

Seismic shear amplification now based on mechanisms at critical section

Based on a less conservative interpretation of how the CSA standards are used to amplify shear forces for multi-storey shear wall designs, all seismic amplifications are now based on the amplification and mechanism at the critical section of the wall.

For some background information covering how shear forces are scaled upward to consider seismic effects, a series of posts are available here.

Note that the amplification percentages are applied differently, based on whether developing flexural failure or not overestimating overstrength and ductility governs for a particular design (non-seismic loads are not scaled based on RdR0).

A dedicated post is available here, explaining the issue in full.

Non seismic component of in-plane shear force no longer scaled based on SFRS force modification factors

While the most earthquake related load combinations are a combination of a lateral seismic force plus a series of axial loads such as Dead, Live, and Snow type loads, there are other cases possible with companion loads applying additional non-seismic lateral loading. Previously in Version 4.0, MASS would scale up the entire lateral in-plane load rather than just the seismic component of that load. This resulted in designs where non-seismic lateral companion loads are unintentionally amplified, resulting in a higher than expected factored shear resistance requirement and overly conservative designs.

A full post explaining this change is available here.

Linear elastic deflections now used for calculating inelastic rotational demand

When performing a ductility verification, MASS currently uses drift values instead of elastic deflections in determining θid, inelastic rotational demand.

Since the expression for θid also scales up the movement similarly to the National Build Code of Canada, ductility verifications are excessively difficult to satisfy as demand before considering overstrength is higher than expected by factor of RdRo.

For normal importance category, conventional construction structures, this represents a 125% increase, resulting in excessively conservative ductility verifications.

An entire post is available here, explaining the issue in further detail, including a design example.

Change regarding maximum spacing for Seismic Reinforcement

Prior to the release of Version 4.1, any shear wall element designed within MASS would have all horizontal reinforcement checked against seismic spacings regardless of seismic hazard index when an earthquake load is applied to the wall.

An entire post is available here to further explain the issue, including all relevant CSA references as well as highlighting the issue in a design example.

This has been changed, effective for Versions 4.1 and later.


Printed Results no longer show bitmap text next to each graphic

An issue has been corrected in the printed results where graphics were accompanied with the text: “System.Drawing.Bitmap” appeared with any equation or symbol graphics.