I’m not sure quite how they do it but architects and engineers seem to know when the Leaning Tower of Pisa and the Millennium Tower in San Francisco are relatively stable. They’ve held up this long so far.
But maybe, just maybe they are BS-ing it and they know that leaning towers last a long while before finally crumbling or tilting completely over. No matter the deal, I know I would never take a unit in the Millennium Tower as my home. I also never want to go on a tour up the Leaning Tower of Pisa. Although some are willing to risk these things.
Major earthquakes have struck Pisa since the tower was built. It was a mystery how it held up during these crises. Dynamic soil-structure interaction is the theory of why it still stands. It would seem that the same soft soil that causes it to lean also protects it during earthquakes.
San Francisco also suffers from earthquakes. But its leaning has more complex causes as it has to do with at least three layers of different soils. My takeaway is that it might not survive earthquakes as well as the Leaning Tower of Pisa.
With both towers, attempts have been made to shore them up. The Leaning Tower of Pisa once had a tilt of 5.5 degrees. That is down to 3.9 degrees. The Millennium Tower now leans 29 inches which isn’t nearly as much as the Leaning Tower of Pisa. But there is concern it is sinking further.
I think it would be fantastic if they could predict to the day when each tower finally crumbles. Imagine that, you could build a tower with an expiration date. You could move out a few weeks before the fall, taking all the stuff that could foul the air like it did to ground zero of 9/11.
Earthquakes do of course complicate these predictions. With the Leaning Tower of Pisa, they might not be a factor because of the dynamic soil-structure interaction. So someone might indeed be capable of predicting when the tower finally falls.
If the same is not true of the Millennium Tower, likely an earthquake will take it out. As much as I wish all leaning towers had a definite expiration date, we aren’t there yet.
Maybe at a future time we could build towers on soft soil like Pisa and live in them for a guaranteed amount of years before moving out. Then we could watch them fall as one by one they got destroyed. Don’t we love footage of buildings being demolished? This would be nature’s way of demolishing these towers.