Envelope #19: GFCI outlet and structural engineering?

Happy Thursday – This is Back of the Envelope, where I share SE-related tip bits that help you become smarter (I hope).

Today, I am going to talk about GFCI outlets.

(Wait… what?)

You know, one of those electrical outlets with two buttons in the middle. You typically find them in the bathrooms and kitchens.

“But how is that related to structural engineering?”

Well, not directly, but there are some inferences that I’d like to share. Bear with me here – it’ll be fun!

(Estimated read time = 2 minutes and 30 seconds)

What are GFCI

First, if you are unfamiliar with it, GFCI stands for “ground fault circuit interrupter.”

What’s a “ground fault”?

Basically, it means that unintentionally, the electrical current finds a pathway to the ground. This could happen when a person stands in a damp environment (e.g., bathroom or kitchen) and accidentally touches the outlet hole with his/her wet hand.

The person gets shocked, which happens very quickly (in seconds). And sometimes, this scenario could be fatal.

And that’s where GFCI comes into play – it interrupts the current when it detects a ground fault.

How does GFCI work?

The way it works is that it contains a sensor that monitors the flow of current. It knows the amount of electricity flowing into the circuit and the amount flowing out.

When it detects minor differences (i.e., think applied load not equal to reactions!), it trips to shut off the circuit within one-tenth of a second.

In other words, when a ground fault occurs due to the person-touching-outlet scenario, some currents flow through the person. This causes the amount of electricity flowing in and out of the circuit to be different.

The GFCI outlet detects that and trips to save the person from getting electrocuted.

How cool is that?

Ok ok so what does that have to do with structural engineering?

Structural Health Monitoring

Well it got me thinking, could the same concept be applied to structures to potentially help save lives?

For example, what if sensors (strain gauges?) were installed in several columns at the Surfside condominium – would it have been able to detect abnormalities over time and provide early warnings to the occupants?

What if sensors were installed during the construction of the FIU pedestrian bridge? Could the collapse have been prevented?

Apparently, there are firms out there doing exactly that – they specialize in putting sensors on structures, compiling and interpreting the data, and providing helpful information to decision-makers.

The term is “structural health monitoring (SHM).”

It’s obviously a very specialized trade and probably costs a lot of money so I assume it’s usually reserved for large infrastructure projects or maybe high-rises.

But… (now I am just thinking out loud)

What if the technology can be simplified so it’s cheaper to implement in a typical building?

Would regular structural engineers like us be able to team up with specialty firms and offer SHM services more frequently?

Would it also mean that we can productize some of what we do and turn that into a subscription-type steady revenue stream which helps increase our profit margins (i.e. higher pays)?

Anyhow, I don’t have answers to any of these questions but it is kind of interesting how looking at an outlet sent me down a rabbit hole which I thought was worth sharing.

Hopefully you also find some of this thought-provoking-ish – and if you know of anyone in the SHM field, please let me know! I’d love to get in touch.

That’s all for now. Thanks for reading and enjoy the rest of your week.

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