.: Ductile Frame R = 8

This past Friday, I had my friend and fellow structural engineer over for dinner. The conversations somehow veered to how destructive toddlers can be. I was telling the story of how Arya managed to almost break my spectacle frame when we were at Rajiv Chowk Metro station. Arya likes to sit on my shoulders and this time he did not want to be brought down. As I was lifting him higher to bring him down, he used his trump card. He squeezed his knees hard against my glasses, causing it to bend inwards at the nose bridge, popping one of the lenses which promptly dropped to the floor. With a toddler in one hand, the remains of the glasses in the other and partially blind, I managed to find the lens. Luckily I was also able to find Anu who was waiting in the line to buy tickets. While Arya in Anu’s custody, I got time to mend my frame. Essentially, I had to bend the nose bridging back around 60+ degrees to straighten it and fit the lens.

With the story was complete the following exchange happened over dinner, which I think is more fascinating than the story itself.
All you non-structural engineers can stop reading now.

Anantha : I am still wearing the same glasses now.
Dan : You were lucky to salvage the glasses, these must be strong.
Anantha : Yes, I think the frame is pretty ductile.
Dan : Ha ha, yes, a ductile frame *.

Being structural engineers, Dan and I laughed for a little while as the “ductile” frame sank in. It was followed by an even more hilarious discussion.

Dan : What’s do you think the R value might be?
Anantha : I would think pretty close to 8.

At this point, we were both on the floor laughing (well, almost).

* A ductile (moment) frame is a special type of structural framing to resist seismic loads, which has additional steel reinforcement detailing in order to mitigate the amount of damage it suffers during an earthquake.

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