Envelope #21: Site Class D in ETABS and a dad joke
Happy Thursday! Andy from Back of the Envelope here. It’s been almost a month since the last email 😅 – life got busy, but it’s time to get back on it again!
In today’s email (three unrelated topics):
Why you may need to be careful when using Site Class D in ETABS
Competition vs. cooperation vs. collaboration
(Estimated reading time = 3 minutes and 24 seconds.)
“Here we go!” – Mario
1/ Site Class D & ETABS
ASCE 7-16 Section 11.4.3 introduced the concept of “Default Site Class D”. You may have seen this in various apps that calculate the seismic design parameters.
For example, ASCE 7 Hazard tool:
Basically, when you don’t have the soil properties (i.e., soil report), you shall use Site Class D as the default. But… you must bump up the “Fa” value to 1.2 per Section 11.4.4.
What does that mean?
If you look at Table 11.4-1, you’ll see that some of the values for Site Class D are lower than that of Site Class C – so conservatively, the higher value shall be used (i.e., 1.2).
For example, say that you have a site with Ss = 1.0 and you don’t have a soil report, then you are in Default Site Class D and should use Fa = 1.2.
But if the geotechnical report demonstrated that the location is a real Site Class D, then Fa = 1.1.
Hope that makes sense.
Now, if you use ETABS, you may have seen the “auto seismic loading” feature, which calculates the Sds and Sd1 for you.
Buuuut, it’s missing the option to choose “Default Site Class D” (thanks to my colleague Brandon who pointed this out).
So, potentially, the building could be under-designed if Site Class D wasn’t substantiated by a geotechnical investigation.
In other words, be careful and double-check your numbers when using a software.
2/ Competition vs. Cooperation vs. Collaboration
A couple of years ago, I was listening to a podcast called “On Purpose.” It’s hosted by a former monk named Jay Shetty (now podcaster/entrepreneur/author).
In one of the episodes, he interviewed Humble the Poet, Kanwer Singh (YouTube personality/rapper/author). Something mentioned in their conversation struck me as profound; I wrote it down so I could revisit it sometime in the future (which is now).
It went something like this:
We begin with competition, then we learn cooperation. And when we graduate to collaboration, we can accomplish things greater than ourselves.
I am still learning about this but let me elaborate on what I gathered.
This is the mindset that most of us begin with. It’s ingrained in us through evolution (survival of the fittest).
We ask questions like: “How can we do better than our competitors.”
And success means “we beat those other guys.”
Eventually, most of us understand that not everything is competition. And we begin to incorporate cooperation.
In this phase, we learn to work with others in support of another’s goals.
For example, you help your colleague or project manager to complete a project.
Or, as a structural engineer on a team, you help the architect to make sure the building is structurally sound.
Or, as a design team, you help the client/owner to fulfill their vision.
The key point is that there is some shared vision, but ultimately, it’s someone else’s stuff that you are helping to ensure it turns out good.
At some point, you graduate to collaboration.
With collaboration, you work with others to achieve a common shared goal.
You have shared ownership and interest in a specific outcome.
One example could be a non-profit like the AAa/e, where the board members and volunteers work together to raise scholarship funds to help support engineering, architecture, and construction students. The shared goal would be a bright future with talented individuals working in the industry (the organization has awarded over $400k over the years!).
In other instances, you work together to create something new -- it could be new processes, new technology, or new product…etc.
One example would be CASE, NCSEA, and SEI working together to improve our profession.
Some people call this “1+1=3”. Essentially, people working together with a shared vision and common goal will be multiple times more effective than one person working alone.
Anyhow, something in my mind tells me that this is important and there are practical uses to be applied to this whole idea, but I am not sure how to articulate it yet – stay tuned for more.
(if you have any thoughts on this – let me know also!)
3/ Dad Joke
Another colleague suggested I include a dad joke in the Back of the Envelope because, first of all, I love those (who doesn't!?). Second, if you don’t learn anything from these emails, at least you’ll get a quick laugh (I hope).
Here is the first one:
And that’s all for today – thanks for reading!
Let me know what you think of today's email?