The architect has handed you floor plates, and you need to figure out whether a moment frame system will work for seismic resistance. The problem? You don’t have member sizes yet. You don’t know the period. And without the period, you can’t pull loads from the response spectrum. Classic chicken-and-egg.
Canadian projects see everything from heavy snowfalls to strong winds, so our designs constantly have to stand up to the elements. The National Building Code of Canada (NBCC) gives us the rulebook, but how we apply those rules can differ significantly, especially when we’re talking about Part 4 (Structural Design) versus Part 9 (Housing and Small Buildings).
The National Building Code of Canada (NBCC) gives us two primary structural design pathways that show up in everyday practice: the engineered requirements of Part 4 and the prescriptive provisions of Part 9. Deciding which one applies—and where they overlap—is a fundamental part of our work as structural engineers in Canada.
In this article we’ll be looking at seismic. Specifically, let’s chew on something that’s been a hot topic since the NBCC 2020 dropped: the growing gap in seismic design philosophies between Part 4 (Structural Design) and Part 9 (Housing and Small Buildings). If you’re juggling projects that dance on the edge of Part 9’s limits or work across different seismic zones in Canada, this is a conversation you need to be in on.
Let’s talk about something that trips up even seasoned engineers from time to time: figuring out exactly where National Building Code of Canada (NBCC) Part 9, “Housing and Small Buildings,” hands off the baton to Part 4, “Structural Design.” Get this wrong, and you could be heading for a world of compliance headaches, or worse, an under-designed structure. Get it right, and you’re setting your project up for success from day one.
You’ve got a project that, at first glance, looks like a straightforward Part 9 building – a “house or small building” as the NBCC puts it. But then you start digging into the details, the architect throws in a few “features,” or the site conditions are less than ideal, and suddenly you’re wondering if those prescriptive Part 9 solutions are going to cut it.
In our first three posts, we’ve journeyed through the “what and why” of Performance-Based Design (PBD), mapped out the typical PBD process and player lineup, and even gotten our hands dirty with the nitty-gritty of modeling, analysis, and verification. If you’ve been following along, you know PBD isn’t just a fancy buzzword; it’s a powerful approach to designing structures that meet specific, tangible performance goals.
I’m Arun Kishore, a Professional Engineer based in Vancouver, BC. I specialize in structural engineering for LNG facilities, civic water infrastructure, and advanced buildings — with a passion for automating the tedious stuff so engineers can focus on what matters.
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