Envelope #26: Structural Irregularities “Cheat Sheet”
Andy Lin
March 30, 2023
Happy Thursday! This is Back of the Envelope – the place to learn structural engineering in tiny bites 🍪.
Today I am going to share a “cheat sheet” I created to help myself with ASCE 7 structural irregularities (actually, they are more like small notes added to the margin – you’ll see).
Let’s dive in.
(Estimated read time = 1 minute and 20 seconds)
The Challenge
A little bit ago, some questions came up while a colleague was developing the fee proposal for a project:
“How do we know if a building needs dynamic analysis?”
“And how do we know if it needs a 3d model?”
Good questions.
Simple: Just look at “Table 12.3-1 Horizontal structural Irregularities” and “Table 12.3-2 Vertical Structural Irregularities.”
…Right?
Well, yes, but not really.
Here’s what the tables look like: (for illustration purposes only – don’t actually read it right now)
For me, it wasn’t easy to tell, at a glance, which requires dynamic analysis and which requires 3d modeling…etc.
The Solution
If you look closely (figuratively speaking), here are the pertinent sections:
1/ “Table 12.6-1”: This is where ASCE 7 talks about when ‘equivalent lateral force procedure’ is permitted and not permitted (therefore requires dynamic).
2/ “Section 12.7.3”: This section discusses when a 3D model is required.
So I thought – hey, what if I highlight them on the table with different colors and add a quick note to remind me what they are.
Here is the result:
That should help me avoid flipping back and forth between the pages.
I would also be able to quickly tell the implications of each irregularity by glancing at the table.
If you think this is helpful, I recommend you do the same: read through each section; create your own notes and highlights to add flairs to the table.
(Or you can download mine here – sharing is caring 😊)
And this is all for now; time for a quick engineering joke:
Before studying engineering, if someone asked me what 1+1 is, I would have said “2”.
Now, I’d say, “I’m pretty sure it’s 2, but we’d better make it 3 just to be safe.”
The end. Hope you like it – have a good day!
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