Analysis software - NBCC2020 Seismic 2

[EngDM]

Now that Manitoba apparently has earthquakes, I'm doing some research on getting software that can analyze multi-storey buildings for earthquake. So far I've landed on ETABs or RISA. ETABs appears to be more involved and is the industry standard, but I quite like the RISA gui. I'm hoping to get some perspective from the members here to see if anyone has any niche pros and cons. I like RISA because it can also do wood, and somewhat masonry as far as design, whereas ETABs won't code check for you.

 

[dik]

This is just so much government overreach horsesh*t. My understanding was that when Manitoba Hydro was researching their Nelson River Diversion project there were two below R2, and they were archaic. A current website shows:

and none of these were in Manitoba. In addition another shot of their site shows:

The government is just increasing costs to owners and businesses for no reason. I understand they were citicised for not including seismic provisions in the last code they adapted. For good reason, we are relatively safe from seismic activity in Manitoba. The professional association should be taking them to task on this.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[EngDM]

I wholeheartedly agree. I went to a seminar last Friday, the presenter of which has input on the code creation, and he basically said that the seismic code is designed for BC, and then they give some lower bounds which are still much higher than what places like Manitoba and Sask experience. He was saying Vancouver gets like 6 detectable earthquakes a day, Manitoba had 3 last years. Our seismic activity from ground forces pales in comparison to even a semi truck driving past my office.

It's ridiculous.

 

[TLHS]

The seismic provisions are going to be a mess the first half dozen times you use them because they're horribly non-user friendly and nobody in the jurisdiction is going to understand what they mean. Everyone was doing weird stuff for a few years in BC back in the day.

From a production standpoint, if it really doesn't govern in your location, it's going to be plugging two or three numbers into a spreadsheet, getting a base shear and writing down that it doesn't govern over wind. There's some connection stuff that you need to know because they can govern that part of the design even if they don't govern overall base shear, but they're really minimal for the conventional construction seismic system you'll generally use.

If you don't have it get Andy Metten's book. It's the only one I'm aware of that walks through how to do small building seismic in the straightforward way it's done in production rather than trying to deal with all the complicated parts you'd hit for a 30 floor building in Vancouver.

https://www.amazon.ca/Structural-Steel-Canadian-Buildings-Metten/dp/0994912110

I also know he's roughed out a version of his seismic worksheet thing for the new code. He's been an adamant proponent that you should be able to do the primary seismic demand calculations for a low rise building on one or two pages of a simple worksheet if they're going to be practical. I don't know where I've seen the new version though. I think in one of the code presentations. You could probably fire him an email and ask for a copy.

The 2015 version of his one page base shear worksheet is in this presentation:

https://www.caee.ca/pdf/Paper_94268.pdf

It's also in his book and includes another page that does the floor distribution

Basically, in practice, you're just going to use the short period cutoff formula for basically everything short. If things get taller, you'll just do the code assumed period formula and plug that in as well.

edit: it also looks like a bunch of manitoba for a bunch of site classes will just use the new one line simplified method. If that's the case I'd not worry too much about changing software. Manually entering values from that into whatever you're currently set up for is probably easier than transitioning to something before you've figured out a workflow for the new code.