MWFRS and C&C Conceptual Question 1

[JD P.E.]

I want to make sure I'm on the right track with MWFRS/C&C concepts. I understand MWFRS are the structural elements that deal with the collected wind loads from C&C. MWFRS loads are generally distributed over larger areas while C&C loads are distributed over smaller areas and are usually higher.

When it comes to C&C, the overall goal is to evaluate strength/serviceability of parts such as girts and purlins correct? Then those wind pressures applied to those members along with other load combinations are analyzed to determine if current design members/connections are adequate?

Do structural softwares generally apply both types of wind pressure at the same time resulting in distributed loads for both MWFRS (i.e. portal or moment frame) and C&C (i.e. roof paneling, girts, purlins).

Thanks in advance...

 

[Lomarandil]

Sorry, it really depends on the software... It will apply whatever wind pressure the engineer tells it are applicable. Assuming the engineer knows the correct settings to apply.

Your overall understanding of MWFRS and C&C loads is correct.

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just call me Lo.

 

[driftLimiter]

I believe that most softwares that include Automated wind loading are using MWFRS. I would definitely get to know the specific software you are using well, so you understand what method it is using so if needed you could successfully verify the results.

ASCE 7 offers a maximum tributary area for CC components, beyond which sends you to MWFRS. Also main structural elements that are resisting loads from more than one surface of the structure (for example diaphragm gets wind pressure from exterior wall surfaces, and the top surface of the diaphragm)are generally considered MWFRS [1].

[1] Link

 

[milkshakelake]

To add to the point that most software auto calculates MWFRS, I’d say all of them do. Unless it’s a very specific software for a specialized item, which I haven’t come across. In my area, people designing C&C will not have use for MWFRS and vice versa. Design of girts is separate from main structure design, with different consultants.

 

[MotorCity]

I hope that no software on the market applies MWFRS and C&C wind loads at the same time. That would be incorrect and severely penalize the structure. Depending on the wind parameters and geometry of the building, the C&C loads can be several magnitudes larger than the MWFRS loads.