why do elevators get stuck during earthquakes?

Question

why do elevators get stuck during earthquakes?

In: 9

Answer 1

The most typical reason would be because the electricity network is damaged by the Earthquake, and without electricity, the elevator won’t be moving. The earthquake could also deform the lift shaft causing the lift cage to get stuck on its rails.

Answer 2

Well besides actual damage that renders the elevator inoperable like bent rails, or power loss, the earthquake causes some error in the elevator that the control software reads as “something has gone terribly wrong.” Bad torque readings, or position encoder readings for example. And most straightforward thing to do for safety is to lock the emergency brakes and wait for a technician to check out everything.

Newer elevators in earthquake prone areas can spend a little more money on sensors to detect earthquakes, stop the car at the nearest floor and open the doors, and lock itself there so no one is trapped. They do this in the short time you have before the quake picks up in intensity and operation is still safe. If there’s not enough time to make it to a floor before the quake picks up the elevator will still default to stopping immediately when the intensity kicks up.

And with a bit more effort the elevator can do some automatic self checks and bring itself back into service but that’s not exactly a common feature. Normally the elevator control has a limited amount of feedback, from position, speed, torque sensors, etc, and isn’t able to make a decision if the elevator is safe to run again after an earthquake forces a stop.

Answer 3

Safety.
An elevator that loses power or has an incident actually fails safe. Literally what the term fail safe means.
Most modern and safe ones will spend energy holding the brakes *off* opposed to having to use power to turn the brakes on.

A stopped elevator with brakes on is less likely to move than trying to run something up and down a tube with a complex system of pullers during an earthquake.

So stopping at a floor is the better than getting possibly stuck somewhere between, or catastrophically failing.