Does changing the analysis method effect the final results?

 

The process shown here is how MASS internally performs the analysis because the design is all done at the element level. If you are interested in how Vf,seismic is determined having only the information for one element available, this page is for you!

To summarize the rest of what you are about to read [spoiler alert], there is no difference in the final result of Vs,seismic when looking at just one element, compared to the full multi-storey shear wall.

This post compares the results of just the base shear wall element to that of the multi-storey example, linked here.

Disclaimer: This post is exclusively intended to provide insight into the approach taken by the MASS design software in interpreting a CSA S304-14 code compliant seismic design. It is up to the professional discretion of the designer to input an appropriate layout, boundary and loading conditions, interpret the results, and determine how they should be incorporated into their designs. As per the end user license agreement (and also recommended within PEO’s guidelines for using engineering software), a tool cannot be considered competent and reliance on a tool does not relieve the user of responsibility.

Before reading any further, consider the two diagrams below and ask yourself how the process of determining Vf,seismic is affected when looking at the scenario on the left compared to the right.

Determining the factored moment at the base is slightly different but results in the same value.

Since the factored moment to resistance ratio is the same, the applied loads are increased by the same percentage as was done in the full multi-storey example. Be sure not to forget to also scale up the applied moment which has the same effect of scaling up the two applied loads further up the structure.

As long as you are consistent, there is no reason why looking at one element at a time should result in solutions that differ in any way from those performed looking at the structure as a whole. The important thing is to be consistent and not make mistakes along the way.

To return to the main multi-storey example post, click here.

To return to the main seismic scaling of factored shear forces, click here.

 

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Brad Crumb

Brad is a Masonry Design Engineer with CMDC. Starting in 2011, his main role with the CMDC has involved developing the masonry design software, MASS, as well as handling the engineering related technical support questions that come in on a regular basis. If you've called or emailed the CMDC office about MASS, chances are you had the pleasure of meeting Brad.

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