The Leaning Tower Of San Francisco


#101

From my Aug 8 post. It would be interesting to see whether Obayashi shares have recovered since first reported about a unit of its company being involved.


#102

It was state of the art, foolproof and over-engineered for the site,

Of course it was, that’s why we are where we are now…


#103

Like I said when I was working nobody drove piles to bedrock.
Before the Millennium project, no major building in downtown San Francisco had piles driven into bedrock. But since then, four projects under construction are being built with piles that reach bedrock — all are developments on Transbay Joint Powers Authority land: 181 Fremont, Park Tower at 250 Howard St., the Transbay Transit Center itself and the Salesforce Tower, soon to be the city’s tallest building. While transbay authority officials haven’t said the Millennium’s problems are the reason these buildings go to bedrock, they knew about the excess settling at the Millennium as early as 2009.

Funny how nobody in the press mentioned settlement for 7 years…


#104

Elt1, FYI bedrock is a layman ten :smile:

Why did the city issue certificate of occupancy? Well because the building is safe to occupy. Duh. Maybe in a few decades it will become unsafe


#105

I think it is a lawyers term…lol. …I have never been in the hole deep enough to see it…lol

We did get to test a drilled cassion in sand…It was cool…drilled two other piles and put a beam across with a jack…It didnt move .25" with 200kips of pressure on a drilled pier only 20’ deep…hard to believe a driven pile 90’ deep couldn’t hold its 200kip design load…

Obviously the building is safe…and it is hard to believe the 16 inches of settlement. .wouldnt the sidwalk collapse. …utilities break? Being 2" out of plumb in 600’ is no big deal…I had some Irish carpenters build a four story condo on California at Arguello. .It was 4" out plumb…they didnt keep aligning and bracing as they went up…couldnt get it back plumb…Still there after 34 years…I witnessed another condo building that was 2" out of square…happens all the time…I check houses for levelness all the time…2" out of level is very common. .A lot of builders cant get them within an inch of level…Code allows for a tolerance of 1" in 30 feet…so a 60’ long building with 2" of differential settlement is acceptable by code…Beside all buildings move a bit, soil settlement is a fact of life…Most houses are on shallow footings…they settle over the years…Some move seasonally…due to expansion in the clay…

I lived in a 500 year old farmhouse in England in 1966…the floor under my bed was 8" out of level…took three bricks to make the bed level…been moving around for 500 years in expansive farmland clay…still standing

BTW highrises are designed to handle lateral movement up to 1" per floor…thats up to five feet for a 600’ building…

So far the Millennium building has only moved 2"…I will buy in when they drop the prices to $100k …can still get $6000/m rent… great cap rate…


#106

The building code for SF and other areas known for earthquakes and where landfill is involved probably needs to be updated especially when it comes to extra heavy structures like the Millennium. Just because something was done for years doesn’t mean we can’t do better now. Obviously, the newer neighboring buildings were not penny wise, pound foolish. They went ahead and made their respective foundations as strong as possible and well over presumably the minimum building code. Smart. Isn’t a strong foundation of a dwelling pretty much basic house building 101? Again, I feel bad for the owners. If I am spending millions of dollars for a unit in a state of the art building the very last thing I should be worried about is whether the building would survive a major earthquake.


#107

The building has already survived dropping 16"…Looks like it can handle handle movements like those from a quake pretty well…We will see…Should be a big one in my lifetime. .Best time to buy…right after a quake…Think of all the smart investors that bought Marina properties in the early nineties…

If the bedrock only theory is correct, then should have been a lot of issuses with other highrises. .like the BoA building. …When the big one comes we will see how all the highrises perform. .They did ok in 1989


#108

I wonder how construction compares to the 101 Tower in Taipei. It’s near a fault line. There was an earthquake during construction, and they had to stop for inspections. The people there are super proud of that tower.


#109

Classic pay me now, or pay me later case study for the ages…

workers drilled a 6-inch-wide hole using a rotary drill rig that will eventually sink 260 feet into the ground. The hole will allow soil experts to drop three instruments deep into the earth below the busy intersection: an inclinometer, a piezometer and an extensometer to measure the building’s tilt, the groundwater and soil conditions, and how much the soil under the building has settled, going all the way to bedrock.


#110

I thought the bedrock was down 200’…How is this drill going to signal when it hit the bedrock? If you design for end bearing piers you have to deal with the P-delta effect…I doubt a 260’ pier would have much capacity without lateral suppport…Friction piles are the accepted standard wether in firm soils or rock…At 260’, bearing capacity is insignificant compared to the friction capacity. …Think about the relative surface area of a 14" sq pile…260×4×14/12 of skin friction compared 14×14/144 of end bearing capacity…Think about a 260 foot long pencil…very little if any bearing capacity especially if you assume the soils above have no shear capacity …Aka no friction component. …Totally wrong…Of course there is friction capacity. …that is what is holding this building and 99% of other pile structures up…

As far as I know 260’ piles don’t exist. …The biggest you can get on a truck is about 120’.
These are precast 14" sq p/t concrete piles driven by a pile driver…


#111

Reading the background it seems The Millenium was a groundbreaker in the area, not for its use of mat-pile foundation, but for its height using a reinforced concrete frame. I wonder if the builders/mgmt having a subdivision in concrete had something to do with the decision to change the initial plans for a steel frame.

It’s an interesting example because Taipei 101 has steel/concrete columns and is founded in “soft” bedrock (up to 200’ down, and yet has performed well despite regular earthquake and typhoon activity in the area…

The building is a pile through clay rich soil to bedrock 40 – 60 m below.
The plies are topped by a foundation slab which is 3m thick at the edges and up to 5m thick under the largest of columns.
There are a total of 380 1.5m dia. Tower piles.
Mega columns- 8 cm thick steel & 10,000 psi concrete infill
http://www.archinomy.com/case-studies/671/taipei-101-a-case-study


#112

Wasn’t it mentioned from the get-go that the concrete frame design was an older way of building and much heavier than with steel? To me, that says it all.


#113

I don’t remember if it was older (?), but for sure rarer for very tall high rises. Not everything can be predicted and actually the tower seems to be livable still; the silver lining is that some of the buildings which came after went to bedrock (probably after they got wind of the Millenium’s settlement). Hope the soil investigation doesn’t bring any unexpected findings which could impact the surrounding buildings.


#114

I work on the block across the street and next to one of the Salesforce towers. When they were constructing the tower we would feel the impact of the pounding next door every day. A very disconcerting and helpless feeling on the 20th floor to feel essentially earthquakes every day for awhile. Not good. I would not be sleeping well if I were living in the Millennium Tower.


#115

Wow, dare I say it, the Board of Supes actually doing something prudent…


#116

Heck, mind as well get that property tax bill reduced… but $0 value??? Come on, at least $100k…for a penthouse!!!:slight_smile:

http://www.sfexaminer.com/condo-owners-sinking-millennium-tower-estimate-homes-worth-0/


#117

#118

#119

Would she sell hers for a penny?


#120

I am in Venice…The whole city is sinking. Has been for over 1000 years…Leaning towers everywhere. .Some a few feet out of plumb…Buildings with differential settlement, leaning, bulges, cracks, decay…Once in a while they fall down. San Marco tower, over 100m high, totally collapsed in 1902…Been rebuilt a few times…No lawyers, no whinning…People just rebuild …Have no sympathy for the Millennium tower…taxpayers should not be on the hook…