San Francisco’s ill-fated Millennium Tower is making headlines once again for problems taking place beneath its turbulent foundation.
This time, the 58-story skyscraper is sinking even further on its vertical axis as it settles to the north and west, alarming some building scientists who feel the movement could result in significant corrosive damage despite some recent positive corrections.
Engineers say a fix that has been previously made to anchor its foundation into bedrock on the north and west sides has mostly failed to produce the 4-inch reversal their advanced data models had predicted, instead posting a correction of just a quarter-inch a year and, as outside experts surmised, causing the new directional shift that's happening in an unexpected area.
Now, the building is sinking from underneath the center of its foundation mat at a rate of one-tenth of an inch per year. The phenomenon is known as "dishing." A local geothermal engineer who is monitoring the issue told NBC Bay Area this might lead to a cycle of corrosion that would affect the concrete foundation's steel supports.
"The overall situation is very complex," Robert Pyke told the outlet. "It’s highly likely that there's been an increase in cracking for this kind of fix. That should have been obvious that there was a possibility of further increasing cracking and water intrusion into the foundation."
Ron Hamburger, the engineer in charge of the team, who had been at work correcting the tilting problem, says the soil at the site is to blame and that the remedies will nonetheless continue to yield reversals at the northwest corner. (He did not say how long or at which rate they would occur.)
The saga has played out continuously since the issue was made public by the developer in May of 2016. The retrofit enacted has since been valued at $100 million. Currently, tilting, which was first recorded at 16 inches, has advanced to slightly under 29 inches at the northwest corner.
Residents, meanwhile, are being asked to foot the $6.8 million in additional repair work that has reportedly run $20 million over budget.
16 Comments
Geez, they need to reduce the mass by 50% to safely stop the sinking. It is going to require reducing the building in height in half to 1/3 of its current height. Which is the height it should have been in the first place at that location. There isn't a solution to keep this building at its current height without it sinking AND then overturn and damage swath of other properties due to the differential soil conditions. No solid rock bedrock to tie into. The piles would need to be nearly as deep as the building is above ground to keep this from sinking or overturning. They are just pissing money down a toilet on this disaster.
the solution was end bearing piles... instead they ended up explaining to the judge why they didn't do that - the lawsuit totaled more than the initial cost to build the building
It would likely need to be something more like socketed piles. Not just end bearing on the surface of the bedrock but socketed into the bedrock to a certain amount of depth into the bedrock, but yeah, basically agree. It is nuanced differences but has engineering importance but we need not quibble on those nuance. They are too late to install such (end-bearing/socket piles) properly. Without end-bearing/socket piles, it can't support the mass. The mass has to be reduced so the piles don't continue to sink or even overturn as any soil differentials can result in pile shifting and bending. Bottom line, they f---ed up and pissing money down this toilet. I wouldn't say I am an expert on piles so much so that I wouldn't involve a geotechnical and structural engineering consultants even for a house.
The science and engineering of piles involves a lot and alot can go wrong be it a house or a high rise or anywhere in between. Personally, whenever possible, end-bearing or socketing the pile into competent bedrock is best. Simplifies some of the issues versus the issues of relying solely on friction.
I lived and worked in the USA for more than 10 years as an employed architect on the Eat coast. I then realized that the US systems and standards of construction were quite safe and improved especially when erecting high rises buildings. Now if one ship is sinking they should start evacuating it asap. And meanwhile evacuate the architects, engineers, contractors and any other liable persons of expertise who didn't foresee that disaster. I guess the insurance companies might be quite agitated by now.
I am not sure they didn't foresee the disaster. It is a mess now.
I am not an architect but I am a builder. IMHO I recommend cutting their losses, eating humble pie and taking the building down before it falls and takes out countless buildings and kills 1000's of people!!! Is one life not worth that, let alone 1000's!!!??? SMH
The city should simply order and do the tearing it down and bill the jerks. They can't be trusted to do the right thing for public HSW. They don't care. They care about money. City should just condemn, and immediately proceed with deconstruction of the building to the ground level. Of course with competent professionals to take it down floor by floor. Can't dynamite it. Too dangerous of a situation. It has to be done floor by floor from top, down. That is what needs to be done. Enough with these bozos. And FUCK them and their money. They can go f--- off. They tried. They failed. They don't have a solution that is satisfactory for long term safety. They have a building that will collapse in a matter of time and gambling with the lives of people in a pray that nothing goes wrong. Enough is enough. If the owners don't demolish it or block it being taken down... they should be on notice that doing so WILL result in mass murder charges if the building falls and kills people. They will be charged with murder in the FIRST degree for their actions will be treated as INTENT TO MURDER knowing if the building collapses, it WILL cost lives and they willfully intend for it to happen. Owners of this tower, YOU ARE ON NOTICE IN PUBLIC. Any attempt to not deconstruct and demolish this building before it collapses, IS and SHALL be held as INTENT to MURDER people of San Francisco in that area using the building as your murder weapon in my not so humble opinion.
I don't hate the looks of the building. I don't hate that. I would prefer you guys to deconstruct and if possible salvage material as you can and then reengineer the foundation so you can go to bedrock. If the site is not suitable, maybe you could find another site that is suitable and could build the building of that design with adjustments in the engineering as needed for that site. It isn't impossible to take that design and with appropriate adjustments, build it there. This isn't a "I hate its looks, demolish it.". I hate to see a bunch of people killed. Some others here might have more stronger opinions about the design and aesthetics of this building and would tell you their opinions as they would. I am also not saying I love the design. It's more somewhere in between, for me. I am more concern for the people and the risk they are placed in at this time.
You really can't just put in the super deep piles in AFTER the building structure is erected. The beams and joists, and slabs and all are all obstruction that prevents it. It is why it is SUPER IMPORTANT for deep foundations to be designed and engineered and installed correctly the first time. You don't typically have second chances. Failure to do this right the first time is not an option. You have to be that serious and treat it this way in that you don't have a second chance to fix this without basically deconstructing building back to foundation and redo the foundation and then build it again.
Simply emptying ten floors, then removing finished surfaces (cabinets, sinks, bathtubs, flooring), along with personal belongings, will remove Millions of pounds of material (pressure). Take off ten floors, and see if the tilting stops.
I'm think it would be more like 1/3 of the height needs to be removed. The height change would reduce weight but torsion. The issue is reducing weight may only slow down the rate in which it sinks and overturn. Ultimately, you have to reduce weight until it stops sinking. The tilting is in part a result of differential soil capacity. Since these piles are likely friction pile so its friction resistance capacity. So when there is differences in friction resistance, this would be a case for tilting.
I can support 10 floors and check and maybe up to 1/3 of the building height and see. What is important is do something about it.
I noticed the slender Maiden Lane high rise in New York is having similiar issues. Not anchored into bedrock.
I think there is some lack of wisdom and dangerous practices that are happening more, now than they used to be. Trying to do things, architects & engineers 50 years ago would never even attempt and often for good reason. Location of high rises and the importance of choosing the right locations to build. Then we have people double-down on building on the wrong sites for a such projects with buildings even taller and more overall weight and mass. Stupid double-downing on stupid. NO highrise taller than 1000 ft. should be built unless secured to solid bedrock. If they can't secure it on solid ground, they should not build at all. Without competent bedrocks, building should not be more than 250 ft. in height unless all deep foundation system are secured to bedrock. If not, they should be 250 ft. or less. Some cases the cap height may be less. This is because there is no material on the periodic table OR any alloy made of anything on the periodic table including the experimental stuff that you see on relatively few periodic tables but the most thorough ones. NONE of the materials we have access to on this planet or in the solar system is strong enough for that. They don't exist. Design with real materials and reality not fiction. Assume conditions may be worse than you may have sampled for. Soil conditions may be less ideal than your sample has. If I didn't have consolidated bedrock of granite or basalt or similar bedrock to secure foundation to, I would not even attempt such feat of stupidity.
lovely https://www.thecity.nyc/2023/05/16/stalled-condo-maiden-lane-fdny-hazard/
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