The Call Building would remain the city's tallest for 25 years. Not to be outdone, the Chronicle's rival newspaper commissioned their own 315-foot tower in 1898. San Francisco's first skyscraper was the Chronicle Building, a 218-foot tower completed in 1890. But what the city lacks in size, it makes up for in height: San Francisco has 453 high-rise buildings, many of which are over 500 feet high. Over 835,000 people are packed into less than 47 square miles. Which I suppose says something about design being only as good as the input assumptions.San Francisco, California is a compact city. Unfortunately it didn’t help the millennium tower with this geotechnical issue. I wrote a little bit more about performance based design here : Then we do a bunch more sophisticated modelling to demonstrate the design meets the objectives. For instance, we might say no damage allowed at 30% in 50yr hazard, cracking and light damage at 10%/50yr, and no collapse at 2%/50yr hazards. It allows you to pick multiple hazards and set different objectives for them. Now industry is starting to use “performance based design” more often for seismic design of tall buildings (including the Millennium tower).
Insurance deemed them too costly and risky to repair. For instance, in the Canterbury NZ earthquake many structures performed “well” and met their design intents, but around 70% of the downtown ended up being demolished. But more recently, with ballooning recovery costs in recent earthquakes, some are starting to see its not enough. The industry has long accepted this as a good X point that balances construction cost and longevity. In the US the life safety objective corresponds to earthquake hazard of 10% probability of exceedance in 50yrs. All we can do is play with probabilities. So we need to draw a line in the sand somewhere and say “we will design for X, and detail the structure to avoid collapse if X is exceeded.” There is no such thing as an earthquake proof building, because there is always a bigger earthquake than the one considered for design. The more powerful the quake, the less frequently it occurs, and there is a long tail to this distribution. There is basically a probabilistic distribution of earthquake frequency and energy. This is something that the profession has done a terrible job in communicating with the public.īut if you think about the nature of earthquakes, it starts to make a little more sense.
#Skyscraper forum sf Pc#
It fascinated me enough to go into engineering professionally though the later PC and semiconductor revolution of the 1970s drove me to an EE degree instead of ME/CivE. At that time I was a kid and he'd "take me to work" at these sites while under construction and I got to talk to construction workers, structural engineers, etc. He was involved with most skyscrapers built in SF from 1970-1985 which includes the WF tower, Hyatt-Regency, Embarcadero Center building complex, etc. My late father was a big name in construction in the SF Bay Area. This is a legendary FU.Īnd you are seeing these New Yorkers trying to lawyer their way out of the liability they will inevitably face by doing things on-the-cheap and half-assed. And honestly, ANYTHING short of tearing the building down and starting again is at best a bandaid fix that may or may not work for long. Apparently these NYC companies did not and had zero engineering/professional intuition about the nature of earthquakes and construction in California.īecause of this the building started to both sink and tilt. Local construction companies know all about this geophysical reality. are the rocky high spots surrounded by deep valleys covered with sand from ancient water inlets). In that particular area, the rock is quite deep (all the hills you see like Nob Hill, Coit Tower, etc. SF is primarily all sand sitting atop of deeper rocks but some of that rock is very deep below the surface. The normal process is to drive piles down to bedrock. So they did NOT do any of the standard "ground work" (sic) to prepare the foundation as every other skyscraper in SF and California normally does.
#Skyscraper forum sf professional#
Part of what started this: a NYC architect and NYC construction contractor came to SF for the first time in their corporate and professional experiences and decided to build a building, cutting corners on standard local construction standards, regulations and laws because they found loopholes in all three and they thought it would save a lot of money. I find everything about this building hilarious in a dark, horrifying engineering and bureaucratic sense.
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