Most important for all structures is to have some margin. That is the 10% extra money you throw in to be above the minimum of collapsing without an earthquake. If you build something that barely stands, then watch out for shaking.
You can see here that all cities carry the same 'one in a thousand' risk for a devastating earthquake. This can be understood in terms of the pgv or peak ground velocity. We can feel 1 mm/s very strongly, and everybody gets out of the buildings.
Venezuela showed us we can have very weak buildings collapsing at 20 cm/s. A good 'earthquake' building should ride through 20-40 cm/s and still be functional. This is the level for a standard frame house on a basement. Maybe some drywall cracking.
Every city has a reasonable chance of 20 cm/s. The problem with cities that haven't had that for a couple of hundred years is that they build very close to the line, perhaps putting in some wind resistance.
Although I am muddled about this, you can see that for the same earthquake New York will be Vennie. It's at the 1 in 1000 to 10000 for everywhere. Vennie was less than 1 in 100. But the East Coast cities have had big earthquakes because they have a sinking continental margin. Comparing the cost of 20 cm/s to both cities has NYC an order of magnitude greater. You think they would do something.
Nobody is putting a little bit of money in physics, and I see some horrible things in the future.
ps with that one column obviously busted, you have the whole building softened. So this is a pancaker in an earthquake.
ps with the Chile earthquake at 40 cm/s you had soft-story condos cracking and tilting. They would have had to be demolished. I think it should be the same fate for this building.


No comments:
Post a Comment