NBCC2020 - Seismic Loads on Drawings

[EngDM]

Hey all,

With the NBCC2020 coming into effect January of next year for me, I was hoping to get some input from you guys. There is a clause 4.1.8.1 sentence 12) that states that certain items are to be designed for 33% extra loading. When preparing drawings, we typically show unfactored braced loads for wind. Earthquake typically doesn't govern where I am located, however I am not sure what to do in the case that, for brace loads the 1.4Wind factor would govern, but for the connection itself earthquake loading may govern.

Would the best and most accomodating approach to be to provide both the earthquake tension loading and the wind loading, and let the connection designer figure it out from there.

Now from the connections designer point of view, I have seen drawings call for the design to full member strength. So, if there are no loads provided do you design for 33% above the member strength now?

 

[jayrod12]

I believe the plan at our firm is to provide the importance category, site classification and Sa(0.2) in our general notes and indicate that all components designed by others must be designed to meet clause 4.1.8 in it's entirety.

For the first while we're expecting additional reviews being required of shop drawings etc to ensure that the loading is being applied correctly. I believe it's specifically this sort of issue that resulted in the high seismic areas to stop delegating design of those types of connections so they had better control over the methodology used during the design.

 

[canwesteng]

If connections and members have different forces, I would put both on the drawing if you are delegating connection design. In your case specifically, I don't see why you would need two sets of forces. This doesn't apply to diagonal braces. Which element are you delegating specifically? Because for most of what is shown in sentence 12, I would show only one force, the force governing for connection design

 

[EngDM]

all components designed by others must be designed to meet clause 4.1.8 in it's entirety

So the connection designer is to run their own earthquake analysis in this case to determine loads on the braces?

 

[EngDM]

Which element are you delegating specifically?

Typically we provide the horizontal unfactored force at the top of the brace, and with this the connection designer can figure out the tension in their brace, since it semi depends on their work points and connection type. I guess providing the load and specifying if it earthquake or wind may be required so they know what to factor it by (1.4 or 1.33 depending).

 

[jayrod12]

We've always provided factored forces on the bracing aspects. Actually always factored loads when it comes to connections.

Now that I think about it, we'll need to clarify that somehow in the notes. I'm of the opinion that we should provide the factored load we expect the designer to use. Would make reviewing the details far easier knowing that even if they only designed for the number on the page we're covered.