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I don’t get it. The Physics of it. And also how would one prevent this?
In: 6
The building have an internal structure of pillars, beams and load bearing walls. You can not see most of this structure at once as it is mostly hidden. When the ground moves and the innertia of the building cause it to stay still there is a lot of forces on the bottom pillars of the building bending them sideways. They are usually not designed to handle forces in this direction. At some point a few of the pillars might get damaged and are no longer able to support the weight of the building. Once these pillars bend or crumbles the weight of the building above is transfered through the beams between the floors into the adjasant pillars. This happens in milliseconds. The sudden increased weight on these pillars cause them to fail as well. You can see this in the very first frames of the collapse in the video as the first floor suddenly collapses and the other floors above it come crashing down on top. The collapse of the first floor is due to the pillars supporting it collapsing first.
We have lots of research showing how to prevent this. But it is expensive. When designing any structure the engineer will have to design it to handle any possible forces applied to it, including earthquakes that might occur at that site. If they had done it properly in this case they would have seen that the forces applied to the bottom pillars would have been too high. So they would have to change the design. Maybe they could have added some gussets in the form of load bearing walls supporting the pillars from horizontal forces, but then the pillars in the seconod story might experience more movement and also needed to be strengthened. And the pillars and walls themselves might not even support their own weight when shaking from side to side. Another option is to use more steel in the construction as it have different material properties then concrete. Either more rebar in the concrete or use steel pillars instead of concrete ones. Steel is more expensive then concrete to do the same work and the maintainence is a lot harder as steel rusts and even cause spauling in concrete. But the steel can actually bend and still support the load above them unlike concrete. This will allow the building to bend during an earthquake instead of breaking.
The building have an internal structure of pillars, beams and load bearing walls. You can not see most of this structure at once as it is mostly hidden. When the ground moves and the innertia of the building cause it to stay still there is a lot of forces on the bottom pillars of the building bending them sideways. They are usually not designed to handle forces in this direction. At some point a few of the pillars might get damaged and are no longer able to support the weight of the building. Once these pillars bend or crumbles the weight of the building above is transfered through the beams between the floors into the adjasant pillars. This happens in milliseconds. The sudden increased weight on these pillars cause them to fail as well. You can see this in the very first frames of the collapse in the video as the first floor suddenly collapses and the other floors above it come crashing down on top. The collapse of the first floor is due to the pillars supporting it collapsing first.
We have lots of research showing how to prevent this. But it is expensive. When designing any structure the engineer will have to design it to handle any possible forces applied to it, including earthquakes that might occur at that site. If they had done it properly in this case they would have seen that the forces applied to the bottom pillars would have been too high. So they would have to change the design. Maybe they could have added some gussets in the form of load bearing walls supporting the pillars from horizontal forces, but then the pillars in the seconod story might experience more movement and also needed to be strengthened. And the pillars and walls themselves might not even support their own weight when shaking from side to side. Another option is to use more steel in the construction as it have different material properties then concrete. Either more rebar in the concrete or use steel pillars instead of concrete ones. Steel is more expensive then concrete to do the same work and the maintainence is a lot harder as steel rusts and even cause spauling in concrete. But the steel can actually bend and still support the load above them unlike concrete. This will allow the building to bend during an earthquake instead of breaking.
Let’s say you got 4 interior walls and 4 exterior walls on each floor. You break one, and now you got a 12% more weight on the remaining ones, and given that there are conditions present that caused one to fail while supporting the normal amount of weight, the remaining ones holding the extra are even more likely to fail. Second one goes, even more weight applied to the remaining ones. Then another, and another, and boom, jet fuel/steel beams and whatnot.
The ground jiggles left to right. And the building is supposed to act like a Jello Flan. It’s supposed to wiggle and warp.
Because of the jiggles, the first 2-3 floors have soo much side to side motion that they buckle and break. And the building squashes those first couple of floors.
Once a building starts moving in one direction without a foundation… It just keeps moving.
Let’s say you got 4 interior walls and 4 exterior walls on each floor. You break one, and now you got a 12% more weight on the remaining ones, and given that there are conditions present that caused one to fail while supporting the normal amount of weight, the remaining ones holding the extra are even more likely to fail. Second one goes, even more weight applied to the remaining ones. Then another, and another, and boom, jet fuel/steel beams and whatnot.
The ground jiggles left to right. And the building is supposed to act like a Jello Flan. It’s supposed to wiggle and warp.
Because of the jiggles, the first 2-3 floors have soo much side to side motion that they buckle and break. And the building squashes those first couple of floors.
Once a building starts moving in one direction without a foundation… It just keeps moving.
Let’s say you got 4 interior walls and 4 exterior walls on each floor. You break one, and now you got a 12% more weight on the remaining ones, and given that there are conditions present that caused one to fail while supporting the normal amount of weight, the remaining ones holding the extra are even more likely to fail. Second one goes, even more weight applied to the remaining ones. Then another, and another, and boom, jet fuel/steel beams and whatnot.
The ground jiggles left to right. And the building is supposed to act like a Jello Flan. It’s supposed to wiggle and warp.
Because of the jiggles, the first 2-3 floors have soo much side to side motion that they buckle and break. And the building squashes those first couple of floors.
Once a building starts moving in one direction without a foundation… It just keeps moving.
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