San Francisco’s Tilting Tower

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2022-01-14 06:30:06

Based 5% on insider information and 95% on the laws of physics, San Francisco’s 58-story Millennium Tower is in no danger of tipping over. In this age of over-stimulated media, the rabid coverage of this issue has sown doubt in the minds of ordinary citizens about the competence of those of us who develop, design, and build large things.

What actually did go wrong? The building has settled downwards, and is, in fact, tilting. Most reports say the building has settled about 17 inches, and is leaning 14 inches westward and 6 inches northward at its crown. Settlement is normal, (more about that later), but what about the tilt? Let’s do a little math: at the top, the horizontal displacement is 15.2 inches (hypotenuse of a 14:6 triangle), and the building is 645 feet tall, so the Millennium Tower is leaning 0.11 degrees to the west-northwest. How significant is this? At its most precarious, Pisa’s famous tower leaned about 5.5 degrees, but it has been stabilized in recent times to lean “only” 4.0 degrees. Right now, its apex is displaced about 13 feet. The Leaning Tower of Pisa is only 183 feet tall; if the Millennium Tower leaned 4.0 degrees, its top would be displaced 45 feet! London’s 315 foot Big Ben is also leaning, but merely 0.26 degrees, a little over twice the tilt of the Millennium Tower.

That’s enough math, but it does show that San Francisco’s tower is almost not leaning at all, especially compared to Pisa’s tower (and you probably didn’t even know about Big Ben). Yet 60 Minutes showed some San Franciscans maintaining they can clearly see the tower tilting, almost ready to tip over, and advise others to stay away. Sadly, they have fallen prey to suggestion based on the inability to distinguish between a priori truth and the opinion of anyone blurting out a tasty sound-bite.