This is a reprint of an article I wrote on Quora… It generated a lot of interest, and I think it reflects some great points of design that the general public may not be aware of… So here it is for the WordPress world to enjoy.
If there’s anything I’ve learned since I started in this field over a decade ago, it’s that in a battle between humans and Mother Nature, Mother Nature is always going to win if she really wants to.
It’s impossible to make a building completely earthquake-proof… Particularly not one that anybody would want to spend any time in. (A building that would reasonably withstand an off-the-scales earthquake would be very bunker-like.)
There are various things that we as engineers do in order to make buildings as earthquake-proof as we can… and we do those things. It really does depend upon both the particular structure that we’re building, and it depends pretty significantly upon the approach that we choose to take…
- We can make a building very flexible so that it sways like a reed in the wind.
- We can make a building incredibly rigid so that it will withstand the forces that the earthquake applies to it, just by brute force.
- We can make a building that has dampers (kind of like shock absorbers) so that it doesn’t experience as much of the force that the earthquake would otherwise apply to the building.
…but the problem with all of these approaches is that they only work up to a certain point. If the earthquake is larger than what we can possibly design a building for (without making it look like a bunker), if we can’t make it flexible enough or rigid enough or damped enough to withstand the forces, then we haven’t done a good job engineering the building.
So, we use approaches like that to a certain extent, but we always, always do something that the public doesn’t necessarily think about.We choose the manner in which we want the building to fail, and if the earthquake IS larger than what our initial approach can withstand, we design the building so that it will fail in a predictable manner. We design so that buildings will NOT undergo progressive collapse (“pancaking”). We design so that the columns are stronger than the beams, so that if anything’s going to fail and absorb energy during its failure, it’ll be the beams. That way, we will just lose part of a floor, instead of losing a column which might be supporting all the floors above it.
And so it goes, on and on, with this sort of methodology of planning out what we want to happen first during an earthquake, for any building we design in a seismically active area. We’re still in the middle of figuring out the best strategies for how to deal with earthquakes. Since they thankfully don’t occur very often, we have to wait quite a long time to prove the full-scale seismic resistance methods that we use in actual buildings, so the lag time on learning things can be pretty high… but we are still learning more every day, and we’re applying new knowledge immediately, as soon as we’re confident in that knowledge, to the new buildings that we design.
An “earthquake-proof” building may be beyond our grasp now, but it’s an ever-evolving process of learning, and while we may never be able to make our buildings withstand everything that Mother Nature throws at us engineers, we’re getting better and better at trying.